Exploration of the Solar System
When the first astronomers decided that there was a difference between stars and planets, our exploration of the solar system could be said to have begun. Their only means of exploration was a rather crude form of remote sensing – standing around looking up at the night sky.
Remote sensing is still our main method of gathering data. The development of huge optical telescopes, then sophisticated radio telescopes, has allowed us to gather data from ever more distant sources – or to gather more detailed information from nearby objects such as our neighbouring planets.
Our best efforts in the remote sensing department take the form of unmanned probes, launched to fly by, land on or crash into the other worlds of our solar system. The various probe programmes have gathered and sent back a wealth of data despite numerous technical problems.
Of course, if we really want to know about the worlds of our system, it will be necessary to go there and take a look for ourselves. To date we have visited only one extraterrestrial body – our own Moon – and that for only brief periods. No human has set foot on another world for many years, and at times it has appeared that we will never do so again.
The original moon missions were as much about political and national prestige as about getting to another world. It is time we reached out for the sake of reaching out, not as part of a political agenda. For if we would learn the secrets of our neighbour worlds, we must visit them.
And who knows what else we will learn along the way?
Remote sensing is still our main method of gathering data. The development of huge optical telescopes, then sophisticated radio telescopes, has allowed us to gather data from ever more distant sources – or to gather more detailed information from nearby objects such as our neighbouring planets.
Our best efforts in the remote sensing department take the form of unmanned probes, launched to fly by, land on or crash into the other worlds of our solar system. The various probe programmes have gathered and sent back a wealth of data despite numerous technical problems.
Of course, if we really want to know about the worlds of our system, it will be necessary to go there and take a look for ourselves. To date we have visited only one extraterrestrial body – our own Moon – and that for only brief periods. No human has set foot on another world for many years, and at times it has appeared that we will never do so again.
The original moon missions were as much about political and national prestige as about getting to another world. It is time we reached out for the sake of reaching out, not as part of a political agenda. For if we would learn the secrets of our neighbour worlds, we must visit them.
And who knows what else we will learn along the way?
Observation and Calculation
Often forgotten about, but just as important as the observation tools themselves, is the intellect. There is only so much that can be observed about our system with the naked eye or a simple telescope, yet from this basic data a great deal can be calculated, predicted or inferred.
Several of the planets were predicted long before they were observed. An astronomer could spend a whole lifetime searching the skies for a new planet by simply looking through a telescope – space is vast and planets are tiny by comparison. The planets, and everything else in the framework, are subject to relative motion so it is not merely a case of quartering the sky.
Knowing where to look simplifies this process to the point where there is a realistic chance of spotting the object – planet, moon, or comet – though this is still by no means an easy task.
Many of the bodies in our system were found by studying perturbations in the movements of known bodies. This is a lengthy and painstaking process, involving large amounts of observed data.
The various bodies in our system obey certain known laws. Their position at any time can be predicted because their orbit has been mapped and a mathematical model of it created. However, all physical masses exert some gravitational attraction on other bodies. This causes small variations in orbital path, referred to as perturbations.
Mostly this effect is too small to measure – a small asteroid has insufficient mass to alter the orbit of Jupiter by any measurable amount. However, in every orbit there are known perturbations due to the gravity of planets and other large bodies. These known perturbations are built into the model, which becomes more complex and accurate as each one is added.
If a body is observed to vary from its predicted path, the most likely reason is that the model is incomplete or incorrect. It may simply be that somebody got his or her sums wrong. If, once the mathematics have been proven correct, the real (observed) position of the body is still different to its predicted position, then clearly there is some factor affecting the orbital path which has not been built into the model.
More observation and calculation is needed at this point, to find any known bodies which might have been overlooked in the original calculation. Once this is ruled out then there is only one answer left – the orbit is being affected by something as yet undetected.
This mysterious object might be quite small and close by, or distant and massive. Yet more work is required to narrow down the possibilities. Fortunately, everything in the solar system affects everything else (to a greater or lesser degree) so it is possible to cross-reference the effects on several known bodies.
By this method it is possible to determine that a given perturbation is being caused by a body of a certain mass, within a certain area. A careful search of the area with telescopes might yield a visual identification of the body, or it may remain hidden for the time being. Either way, the newly-discovered body is built into the orbital models for the bodies it affects, and becomes a known component of our solar system.
Most of the exploration of our solar system has thus far been done by this painstaking method. A great many bodies remain undiscovered – the very existence of Near Earth Asteroids was not suspected until quite recently – and while the calculations are assisted by computer, the process of finding new bodies is still a long and painstaking one.
Once a body is found, it can be studied with telescopes and other instruments on the Earth’ surface or in orbit aboard satellites. However, to really find out what is out there, a manned or probe mission is required.
Several of the planets were predicted long before they were observed. An astronomer could spend a whole lifetime searching the skies for a new planet by simply looking through a telescope – space is vast and planets are tiny by comparison. The planets, and everything else in the framework, are subject to relative motion so it is not merely a case of quartering the sky.
Knowing where to look simplifies this process to the point where there is a realistic chance of spotting the object – planet, moon, or comet – though this is still by no means an easy task.
Many of the bodies in our system were found by studying perturbations in the movements of known bodies. This is a lengthy and painstaking process, involving large amounts of observed data.
The various bodies in our system obey certain known laws. Their position at any time can be predicted because their orbit has been mapped and a mathematical model of it created. However, all physical masses exert some gravitational attraction on other bodies. This causes small variations in orbital path, referred to as perturbations.
Mostly this effect is too small to measure – a small asteroid has insufficient mass to alter the orbit of Jupiter by any measurable amount. However, in every orbit there are known perturbations due to the gravity of planets and other large bodies. These known perturbations are built into the model, which becomes more complex and accurate as each one is added.
If a body is observed to vary from its predicted path, the most likely reason is that the model is incomplete or incorrect. It may simply be that somebody got his or her sums wrong. If, once the mathematics have been proven correct, the real (observed) position of the body is still different to its predicted position, then clearly there is some factor affecting the orbital path which has not been built into the model.
More observation and calculation is needed at this point, to find any known bodies which might have been overlooked in the original calculation. Once this is ruled out then there is only one answer left – the orbit is being affected by something as yet undetected.
This mysterious object might be quite small and close by, or distant and massive. Yet more work is required to narrow down the possibilities. Fortunately, everything in the solar system affects everything else (to a greater or lesser degree) so it is possible to cross-reference the effects on several known bodies.
By this method it is possible to determine that a given perturbation is being caused by a body of a certain mass, within a certain area. A careful search of the area with telescopes might yield a visual identification of the body, or it may remain hidden for the time being. Either way, the newly-discovered body is built into the orbital models for the bodies it affects, and becomes a known component of our solar system.
Most of the exploration of our solar system has thus far been done by this painstaking method. A great many bodies remain undiscovered – the very existence of Near Earth Asteroids was not suspected until quite recently – and while the calculations are assisted by computer, the process of finding new bodies is still a long and painstaking one.
Once a body is found, it can be studied with telescopes and other instruments on the Earth’ surface or in orbit aboard satellites. However, to really find out what is out there, a manned or probe mission is required.
Probes
A probe is an unmanned device designed to collect data from an inaccessible place. By this definition, orbital telescopes and some satellites are also "probes" but the distinction is drawn here to differentiate between objects placed in Earth orbit to collect data and those sent to perform their task close to the target.
Since probes do not have to provide space and life-support for a crew, they can be much smaller and lighter than a manned vessel. They can also be considered disposable, and sent to crash into their target rather than make a careful touchdown – and of course probes are not recovered, so there is no need for fuel or engines to make a return trip.
All of this means that probes are many times cheaper than manned space missions. Despite their limitations, probes can collect an immense amount of data and relay it by radio, for a fraction of the cost of sending a team of astronauts to perform the same task.
Probes go wrong, of course. Some fail partially or completely, and without personnel on hand to perform repairs the mission may have to be written off simply because a receiver circuit failed. On the other hand, it is relatively easy to fund another probe mission, and of course no lives are lost.
Probes are becoming increasingly sophisticated and reliable, and will remain our main means of obtaining data on the other bodies of our system for some time.
Lunar Probes
The logical first target for probe missions was our Moon. A mere quarter of a million miles away, humans had never seen the far side. The early probes were somewhat primitive, so studying a nearby target was a necessary learning experience if more powerful probes were to be launched to the more distant planets.
Solar Probes
Our Sun gives out so much energy that it can be effectively studied by satellites in Earth orbit. However, probes have been launched to study our nearest star close-up. The probe series used for this purpose include NASA’s Pioneer and the ESA Helios and Ulysses probes.
Mercury Probes
The Mariner 10 mission was altered to include a Mercury flyby after the primary objective of a Venus encounter.
Venus Probes
Many probes have been launched to study the planet Venus or have collected data there as part of a greater mission. These include the Soviet Venus (Venera) and Zond, NASA’s Mariner, Magellan, Pioneer and Gallileo probes.
Mars Probes
Mars probes have been launched by several space agencies. NASA has deployed part of the Mariner series, Viking, Mars Observer and Surveyor, Pathfinder and Sojourner. The Soviet Union has launched the troubled Mars series and part of the Zond series. The Japanese Planet B probe also has Mars as its objective.
Probes to the Outer Planets
Sending probes to the outer planets and their moons presents an even greater challenge to the space agencies. Outer-Planet probes have to contend with the intense radiation around Jupiter, the risk of collision with micrometeoroids or even asteroids, and the chance of equipment failure during the journey, all in addition to the usual risks inherent in launching a vehicle into space.
Just creating a probe capable of surviving the epic voyage is a prodigious feat, let alone one capable of gathering and transmitting useful data from its destination. Nevertheless, several probes have been successfully deployed to the outer planets. These include: Voyager, Galileo, Cassini, Pioneer 10 and 11.
Other Probes
Probes have been launched to bodies other than planets. The two Soviet Vega probes were launched to Halley’s Comet, as was NASA’s ISEE 2, the Japanese Sakigake and Suisei and the European Giotto. Phobos 1 and 2 studied the moon of that name in addition to their Mars objectives. NEAR (Near-Earth Asteroid Rendezvous) was launched to discover more about the near-Earth asteroids.
Since probes do not have to provide space and life-support for a crew, they can be much smaller and lighter than a manned vessel. They can also be considered disposable, and sent to crash into their target rather than make a careful touchdown – and of course probes are not recovered, so there is no need for fuel or engines to make a return trip.
All of this means that probes are many times cheaper than manned space missions. Despite their limitations, probes can collect an immense amount of data and relay it by radio, for a fraction of the cost of sending a team of astronauts to perform the same task.
Probes go wrong, of course. Some fail partially or completely, and without personnel on hand to perform repairs the mission may have to be written off simply because a receiver circuit failed. On the other hand, it is relatively easy to fund another probe mission, and of course no lives are lost.
Probes are becoming increasingly sophisticated and reliable, and will remain our main means of obtaining data on the other bodies of our system for some time.
Lunar Probes
The logical first target for probe missions was our Moon. A mere quarter of a million miles away, humans had never seen the far side. The early probes were somewhat primitive, so studying a nearby target was a necessary learning experience if more powerful probes were to be launched to the more distant planets.
Solar Probes
Our Sun gives out so much energy that it can be effectively studied by satellites in Earth orbit. However, probes have been launched to study our nearest star close-up. The probe series used for this purpose include NASA’s Pioneer and the ESA Helios and Ulysses probes.
Mercury Probes
The Mariner 10 mission was altered to include a Mercury flyby after the primary objective of a Venus encounter.
Venus Probes
Many probes have been launched to study the planet Venus or have collected data there as part of a greater mission. These include the Soviet Venus (Venera) and Zond, NASA’s Mariner, Magellan, Pioneer and Gallileo probes.
Mars Probes
Mars probes have been launched by several space agencies. NASA has deployed part of the Mariner series, Viking, Mars Observer and Surveyor, Pathfinder and Sojourner. The Soviet Union has launched the troubled Mars series and part of the Zond series. The Japanese Planet B probe also has Mars as its objective.
Probes to the Outer Planets
Sending probes to the outer planets and their moons presents an even greater challenge to the space agencies. Outer-Planet probes have to contend with the intense radiation around Jupiter, the risk of collision with micrometeoroids or even asteroids, and the chance of equipment failure during the journey, all in addition to the usual risks inherent in launching a vehicle into space.
Just creating a probe capable of surviving the epic voyage is a prodigious feat, let alone one capable of gathering and transmitting useful data from its destination. Nevertheless, several probes have been successfully deployed to the outer planets. These include: Voyager, Galileo, Cassini, Pioneer 10 and 11.
Other Probes
Probes have been launched to bodies other than planets. The two Soviet Vega probes were launched to Halley’s Comet, as was NASA’s ISEE 2, the Japanese Sakigake and Suisei and the European Giotto. Phobos 1 and 2 studied the moon of that name in addition to their Mars objectives. NEAR (Near-Earth Asteroid Rendezvous) was launched to discover more about the near-Earth asteroids.
Probes and Probe Series
Clementine
The Clementine probe was intended to study the Moon and Near-Earth asteroid 1620 Geographos. After a successful Moon-mapping operation the probe went out of control, preventing the flyby of 1620 Geographos. The secondary mission goal of testing components in space was successful despite the malfunction.
Cassini
The single probe Cassini will study Saturn and its moons. Launched on a complex trajectory involving a gravity-assist orbit of Venus and another of Earth, the probe should arrive in the region of Saturn in 2004. There, it will carry out a detailed investigation of Titan, using radar surface mapping and the Huygens lander probe. The other Saturninan moons and the ring system will be studied by remote survey.
Deep Space 1 and 2
Deep Space 1 was a technology demonstrator for future programmes, but still had a strong scientific content to its mission. Launched in October 1998, the probe made a flyby of a near-Earth asteroid as planned and is now on course for a flyby of the comet Borrely.
Deep Space 2 (AKA the Mars Microprobe project) should have penetrated the Martian surface and relayed data on its composition, with a particular objecting of finding evidence of water. Contact was lost in December 1999.
Galileo
The Galileo probe was launched to Jupiter by way of the asteroid belt, conducting flybys of the major asteroids Gaspra and Ida. Having reached Jupiter in 1995, Galileo deployed an instrument package into the Jovian atmosphere and entered orbit to collect further data.
Giotto
Launched in July 1985, Giotto made a close pass of the comet Halley in March 1986, suffering damage from dust particles, which rendered several instruments inoperable. Despite the damage, enough of Giotto’s instrumentation remained functional that the Halley encounter and the extended mission (an encounter with comet P/Grigg-Skjellerup) both yielded a great deal of information.
Luna Series
The first probe missions to the Moon began in 1959 with the Soviet Luna probes. Luna 1 (January 1959) trialled the vehicle, and proved the rather important concept that it was possible to escape from Earth orbit. Luna 2 followed in September, crossing the gulf of space to become the first human-made object to reach another world.
This achievement was followed up a few weeks later by Luna 3, which sent back the first pictures of the far side of the moon.
Luna 4 (April 1963) was the first of a series of craft intended to investigate soft-landing techniques, a programme beset with difficulties. Radio contact with Luna 4 was lost close to the Moon. Luna 5 (May 1965), 7 (October 1965) and 8 (December 1963) suffered retro-rocket malfunctions and crashed on the Lunar surface, while Luna 6’s manoeuvre engine ran wild during a course correction, causing the probe to miss the moon entirely.
Lunar 9 (Jan 1966) finally succeeded, making the first-ever soft-landing. It sent back many pictures over the next 3 days.
The next batch of Luna probes were orbiters designed to study the Moon. Luna 10 (March 1966) orbited for 2 months, collecting data on the Moon’s magnetic field and surface gravity.
Luna 11 (August 1966) and 12 (October 1966) continued this process
More soft-landers followed. Luna 13 (December 1966) studied Lunar soil density and radiation, while 14 (April 1968) studied the Moon’s gravitational field.
Luna 15 was an attempt to gather samples from the Moon and return them to Earth. The fact that it was launched just a few days before the Apollo 11 mission is probably not a coincidence. The probe made a successful insertion to Lunar orbit but did not descend to the surface immediately. Concerned about radio interference between the two missions, NASA contacted the Soviet space administration, who assured NASA that there would be none. Thus Luna 15 did not begin its Lunar descent until just before Apollo 11 was to lift off from the Moon. This first attempt at automatic descent failed, and Luna 15 crashed.
Luna 16 (September 1970) succeeded in soft-landing and deployed an automatic drilling device, which collected samples of Lunar soil. These were launched in a capsule back to Earth and were successfully recovered.
Luna 17 (November 1970) soft-landed, and achieved a new first in space exploration. Lunokhod 1, a remotely-controlled vehicle, was deployed onto the Lunar surface and began collecting samples and data.
Luna 18 (September 1971) was less successful, crashing while making a difficult landing in highland terrain.
Luna 19 (September 1971) was an orbiter. It studied the Moon’s Mass Concentrations and surface gravity field and took pictures of the surface.
Luna 20 (February 1972) was a second soil-recovery device and succeeded in returning its samples to Earth.
Luna 21 (January 1973) carried a second Lunokhod rover. The mission was an uphill struggle, but despite difficulties with the rover and the Luna vehicle carrying it, Lunokhod 2 was successfully deployed.
Luna 22 (June 1974) was another orbiter.
Luna 23 (October 1974) and Luna 24 (August 1976) were successful landers. Luna 24 returned samples to Earth.
Lunar Orbiter
The orbiter missions were carried out in parallel with early Apollo flights. While the Apollo missions tested out the craft that would hopefully take humans to the moon and bring them home again, the Orbiter probes were searching for landing sites on the Lunar surface. 5 Orbiter missions were launched in 1966-7.
All the Orbiter missions were highly successful, allowing a comprehensive map of the Lunar surface to be built up from photographs taken from orbits as low as 40km. As well as providing the first pictures of the South Lunar Pole, the Orbiters discovered a dozen or so "Mascons" – mass concentrations, which caused gravitational effects on orbiting craft.
The Orbiters were deliberately crashed on the Lunar surface when their missions ended.
Lunar Prospector
Lunar Prospector was an attempt to find water ice on the Moon. After a study of the surface, the probe was crashed into a crater in July 1999, to throw up a dust cloud, which could then be analysed for traces of water ice. No such traces were found.
Lunokhod
Designed specifically for conditions on the Moon, the Lunokhod vehicle had an 8-wheel motive section using electric power and an instrument compartment. Remotely controlled from Earth by a 5-man team (this was a very tiring exercise involving great teamwork), Lunokhod also had automatic systems to override commands from the ground station in the event that the vehicle is on unstable terrain. This was necessary since the communication lag between vehicle and ground station could result in a crash, however skilled the operators.
Lunokhod I (Landed November 1970) was operational for nearly a year, taking thousands of photographs and making hundreds of soil analyses at various points. Eventually, with its stock of fuel for the warming device exhausted (this device kept the cameras and other equipment functional in the -150° C Lunar night), Lunokhod 1 froze and ceased operations. Even then, the laser-reflector on its topside remained positioned so that it could be used in future ranging experiments.
Lunokhod 2 (Landed January 1973) remained operational for 4 months and covered more ground that its predecessor. This rover collected more data about Lunar surface conditions and took thousands more photographs during an ambitious programme of manoeuvres which included scrambling up a 400m Lunar mountain.
Magellan
The Magellan probe spent four years in orbit around Venus, collecting data for relay back to Earth. This data includes a detailed radar map of the surface. Late in 1994, its mission was completed when the probe entered the Venusian atmosphere upon command, collecting data until its destruction.
Mariner
Mariner craft were launched by NASA to both Venus and Mars. The missions were mostly conducted in pairs of launches. In July 1962, Mariner 1 suffered a malfunction just after takeoff and was destroyed, but Mariner 2 (launched August 1962) successfully made a fly-by of Venus, registering the surface temperature of the planet at over 400° C.
Launched in November 1964, Mariner 3 was intended to make a fly-by and send back pictures of the Martian surface. It suffered a motor failure and did not reach Mars. The Mariner 4 mission, launched 3 weeks later, overcame guidance problems and succeeded in sending back pictures of the Martian surface. The craft entered solar orbit and remained functional.
Mariner 5 (June 1967) was something of a bonus. Originally a backup vehicle for the Mars missions, it was modified for and successfully made a close flyby of Venus. Mariner 5 recorded surface temperatures of 250° C. The vehicle also detected the planet’s weak magnetic field.
Mariner 6 (February 1969) and its sister, Mariner 7 (March 1969) were intended to study the atmosphere of Mars as well as sending back pictures of the surface. Another objective of the mission was to prove technology for an eventual manned mission to Mars. Mariner 6 studied the equatorial region, while Mariner 7 (Still functioning despite sustaining damage from a micrometeoroid impact) targeted the south pole.
Mariner 8 and 9 (May 1971) were to orbit and map the surface of Mars. Mariner 8 crashed on takeoff, but 9 exceeded expectations, succeeding in mapping the entire planetary surface. This was the first human-made object to orbit another planet. The mission also photographed both the moons of Mars and studied the Martian seasons. Other discoveries from the Mariner 9 mission included the fact that Mars is geologically active, and studies of a vast dust storm provided clues as to the effects of pollution on Earth.
The mission objective of Mariner 10 (November 1973) was altered as a result of the success of earlier probes. The made the planned fly-by of Venus, then used the planet’s gravity field to accelerate for a close approach to the planet Mercury. This was the first "slingshot orbit" carried out by a spacecraft. By entering a solar orbit, Mariner 10 was able to make 3 encounters with Mercury, detecting a trace atmosphere and taking photographs of the sunward side of the planet.
Mars
After preliminary experiments conducted in 1962 with Sputniks 22 and 24, the Soviets embarked upon the Mars series of probes. Several of the missions failed, but following standard Soviet practice, only those which reached their destination were named as part of the Mars series. For example the vehicle which would have been Mars 2 failed to achieve separation from its 4th stage launcher and fell back to Earth. This mission was redesignated Cosmos 419 (probably its launch designation) and the next probe became Mars 2.
Mars 1 (November 1962) contained, orbital and planetary components. After 100 million kilometres, the probe’s orientation system developed a fault, preventing the antenna from being aligned correctly and contact with the probe was lost.
Mars 2 followed much later, in May 1971. This attempt reached Mars and detached the planetary component. This failed to soft-land and was destroyed on impact. The orbital component of the probe entered orbit and began a study of the Martian atmosphere.
Mars 3 (May 1971) successfully reached Mars and detached its planetary module. This made a heavy landing in the middle of a dust storm. The planetary probe functioned for about 2 minutes, transmitting a few seconds of video, but then succumbed to a combination of landing and local conditions. The orbital section of the probe functioned for 3 months.
Mars 4 and 5 were launched as a pair in July 1973. Mars 6 and 7 followed 2 weeks later, using information from Mariner 9 to assist in choosing a landing site.
Mars 96 Orbiter
The Mars 96 probe mission included two lander units, two penetrators and an orbiter unit based on the Phobos probes. The probe reached Earth orbit but suffered a malfunction and re-entered.
Mars Global Surveyor
Launched in 1996 as the first of a new series of Mars probes, the MGS mission is in some ways a repeat of the Mars Surveyor mission, studying the planet from orbit throughout the Martian year. Additionally, the craft functions as a radio relay beacon for future missions.
Mars Observer
Mars Observer was designed to study Mars from orbit over a whole Martian year, collecting a variety of data. Contact was lost as the craft entered Mars orbit.
Mars Pathfinder
Mars Pathfinder was launched in December 1996 and landed on Mars six months later. It collected data on the Martian atmosphere and surface.
NEAR (Near-Earth Asteroid Rendezvous)
As part of a programme to study the Near-Earth Asteroids, NEAR was launched in February 1996 to 433 Eros.
Nozomi
The Nozomi or Planet B probe is a Japanese craft launched in 1998. The craft did not attain sufficient speed to reach Mars on schedule, and was placed on a longer trajectory, which will encounter Mars in late 2003. Once in orbit, Nozomi will study the effects of solar wind on the Martian atmosphere.
Phobos
The two Soviet Phobos probes were intended to study the interplanetary environment on their way to Mars, then to make a detailed observation of the moon Phobos. Several other nations contributed to the project, which failed due to malfunctions in both craft. Phobos 1 lost contact in September 1988 while Phobos 2 fulfilled many of its mission objectives. A computer malfunction caused the craft to be lost in Mars orbit in March 1989.
Pioneer
The Pioneer series of missions has covered a wide range of objectives, and has been fraught with difficulties. Pioneer I was NASA’s first spacecraft, the project having been handed over from the USAF.
Pioneer 1-4 (1958-9) were intended as Lunar probes. Pioneer 1-3 failed to reach the moon due to various malfunctions. Pioneer 4 made a fly-by but failed to enter Lunar orbit.
The next objective of the Pioneer series was Solar observation. Pioneer 5 (March 1960) studied solar flares and the "solar wind". Pioneer 6 (December 1965) and 7 (August 1966) collected data on the solar atmosphere. Pioneer 8 (December 1967) and 9 (November 1968) continued this observation programme and additionally studied Earth’s magnetosphere.
The mission that was to be Pioneer 10, another Solar probe, crashed in the Atlantic.
The next Pioneer mission, renamed Pioneer 10 (March 1972), was launched to Jupiter. Pioneer 11 (May 1973) followed in the footsteps of its predecessor but went to Saturn by way of Jupiter. Both probes acted as scouts for the Voyager missions and proved that a craft could survive the asteroid-belt passage.
Pioneer 12 looked inward once again, to Venus. Entering orbit in 1978, Pioneer 12 radar-mapped the surface and studied the Venusian atmosphere in addition to studying comets as the opportunity arose.
Pioneer 13 (1978) was another Venus probe, which deployed four packages into the Venusian atmosphere to measure its composition and temperature.
Ranger
The Ranger probes were part of a programme to gather data for the planned Apollo Moon landings. Ranger 1-6 (1961-4) were all failures, suffering various malfunctions and system failures.
Ranger 7 (July 1965) was able to transmit the long-awaited Lunar close-ups before it crashed into the surface of the Moon. Ranger 8 (February 1965) and 9 (March 1965) contributed more spectacular close-up footage from the Moon and helped make the Apollo landings possible.
Sakigake
A Japanese vehicle, Sakigake made a flyby of comet Halley in 1986 and a study of the solar wind. The craft remained functional until November 1995, having made three Earth flybys.
Stardust
Launched in February 1999, Stardust is a sample-collection probe intended to gather dust samples from interplanetary space and from the comet P/Wild 2. The probe is currently operational.
Suisei
The Suisei vehicle was identical to Sakigake, though it carried a different instrument package. The mission aim to gather further data on comet Halley was a success, but propellant depletion forced the abandonment of and extended mission.
Surveyor
Another Programme deployed in support of the Apollo landings, the Surveyor series was more successful than its predecessor, Ranger. All probes in this series were intended to soft-land on the Lunar surface at sites around the equator.
Surveyor 1 (June 1966) landed successfully and photographed the Lunar landscape. Surveyor 2 (September 1966) crashed and 3 (April 1967) bounced heavily but survived.
Surveyor 4 (July 1967) lost radio contact just before touchdown and crashed, but 5 (September 1968) overcame technical problems to make a chemical analysis of the Lunar soil.
Surveyor 6 (November 1967) not only landed successfully but took off again. This second flight lasted a few seconds and moved the probe all of 8 feet – but it proved that the Lunar surface was firm enough for a manned landing.
Surveyor 7 (January 1968) was not involved with seeking a landing site for the Apollo missions. Instead it studied debris in the Tycho crater, which was not considered as a possible Apollo landing site.
Vega 1 and 2
Combining a flyby of Venus and of comet Halley, the two Vega missions were launched in December 1984. After deploying a descent module into the Venusian atmosphere, the probes used a gravity-assist orbit to place them on course for the comet.
Venus (Venera) Series
In 1961, the Soviets achieved another first – the launching of a probe to Venus from a vehicle in orbit. Venus I was deployed into orbit by Sputnik 8 in February 1961, from where it made a fly-by of Venus, collecting the first close-up data to be gathered from another planet.
Venus 2 (November 1965) passed close to the planet but suffered a malfunction and returned no data.
Venus 3 (November 1965) was the first vehicle to reach the surface of another planet ("land on" is too grand a title for what Venus 3 did). The probe failed to return any data, though.
Venus 4 (June 1967) successfully penetrated the Venusian atmosphere and transmitted a wealth of data throughout its descent. It ceased transmission upon colliding with a mountain range.
Venus 5 and 6 (Both January 1969) entered the Venusian atmosphere within a day of one another. Both survived nearly an hour in the hostile environment and penetrated to a depth of over 35km, transmitting more data until they were destroyed.
Venus 7 (August 1970) reached the surface of the planet, where it suffered antenna damage from the impact . Nevertheless the probe managed to transmit data back to earth for just over 20 minutes before conditions (including atmospheric pressure 60 times greater than surface pressure on Earth) destroyed it.
Venus 8 (March 1972) also reached the Venusian surface, and recorded temperatures hot enough to melt lead.
Venus 9 and 10 (1975) made use of a fluid cooling system to allow the probe to survive for nearly an hour in the hostile Venusian environment. Venus 9 transmitted pictures and data back from the surface, including atmospheric analysis and a recorded surface temperature of 485° C. Venus 10 recorded similar data.
Venus 11 and 12 (1978) made soft landings on the surface and studied the atmosphere and clouds of Venus.
Venus 13 (1978) survived for over 2 hours on the surface and carried out a variety of measurements, including chemical analyses and studies of electrical discharges in the atmosphere. Venus 14 (1981) repeated these experiments.
Venus 15 and 16 were a pair of identical craft launched in 1983 to radar-map the surface of Venus from orbit. Both craft were placed in polar orbit to facilitate mapping.
Viking
The two Viking probes were launched to Mars in 1975. Each comprised an orbiter and a landing module.
The orbiters entered different orbits – Viking 1 an equatorial orbit and Viking 2 a more inclined one to study the poles. Viking 2 also photographed Deimos from close up. The lander modules made an analysis of the surface composition, finding evidence of iron but no signs that Mars even had life.
Voyager
The two Voyager craft – Voyager 1 and 2 – were a development of an earlier project, the Grand Tour. This ambitious project would have taken advantage of fortunate alignment of planets to send a probe on a "grand tour" of the outer system. The project was cancelled in 1972 for lack of funding and a general disinterest in space exploration. It was replaced by Mariner Jupiter Saturn, a more modest mission based on the proven Mariner probes. This project was renamed Voyager, and kept some of the spirit of the Grand Tour alive. While the probe had a design life of five years, long enough to reach Saturn but not much more. However, both craft were launched on trajectories calculated for the Grand Tour missions. If they happened to survive long enough, the probes might be able to visit the outer planets after all.
Of course, they did survive. They still do.
The Voyager probes weighed in and measured about the same as a small car (though with a rather different shape) Voyager 1 was launched in August 1977, somewhat after Voyager 2 but on a faster trajectory. It is powered by heat generated from the decay of a small amount of radioactive Plutonium. Solar cells were not appropriate to provide power so far out in the solar system, though the Sun does serve one very important function. Along with the star Canopus, our Sun is used by instruments aboard the probe to calculate its position and to keep the dish antenna aimed at Earth.
Voyager has three computers, each with a backup. These are very primitive by today’s standards but have functioned in deep space for over 20 years. The vehicle also carries a variety of instruments including magnetometers, cosmic ray detectors and charged particle detectors. Choosing the instruments proved to be a problem, as scientists did not know what to expect on any of the worlds Voyager would visit. A wide range of devices was settled upon, along with general-purpose equipment such as TV cameras and spectrometers, which it was hoped would be useful under almost any conditions.
Despite the increasing time lag as Voyager moves further out from Earth, getting signals to the craft is not much of a problem – providing the on-board systems keep the dish antenna properly aligned. It is not difficult to produce a sufficiently powerful radio signal to reach Voyager intelligibly. Signals from Voyager are something of a problem, however. With limited on-board power available (transmissions are less powerful than a decent household torch) the problem must be solved on Earth. This is accomplished by using arrays of dish antenna linked into a huge system rather than a single receiver.
Voyager 1 made a flyby of Jupiter during the period late 1978-early 1979. Scientists studying the photographs sent back to Earth found that the atmosphere had changed in appearance since the Pioneer flybys in 1974. Voyager also studied the Jovian moons. Despite slight damage to the electronics from Jupiter’s radiation, Voyager continued to function well, discovering a thin ring around Jupiter and evidence that Io was volcanically active. As Voyager 1 pulled away, Voyager 2 began its approach, sending back yet more photographs and instrument data.
The Voyager 2 probe had suffered a fault early in the journey, before it had even cleared the asteroid belt. The primary receiver had died completely and the backup was suffering from a fault limiting the frequencies it could receive on. This was a problem, since the rotation of the Earth caused a Doppler shift in transmission frequencies. Scientists were able to invent a method of compensating for the Doppler shift and restored some control over Voyager 2. Just in case, they sent it a set of instructions for limited data collection and transmission in case contact was lost again. At least they would get something from Voyager 2, even if direct control was lost.
Voyager 2 was able to collect more data on volcanic Io and the other Jovian moons, including Europa, which had not been clearly visible during the Voyager 1 flyby.
Following in the footsteps of Pioneer 11, Voyager 1 passed Saturn in 1980 and sent back spectacular photographs of the ring system plus data on Saturnian weather and of course the ring system. This was found to be more complex and baffling than previously thought. A completely new discovery was the existence of co-orbitals – satellites in the same orbit. It was discovered that these moons were actually closing at about 10m/s. Scientists theorised that when they were close enough, their gravity would cause the co-orbitals to swap position and pull apart again.
Voyager also found evidence that the rings were being kept in place by "shepherd moons" whose gravity helps maintain the ring system.
Voyager 2 followed its sister craft closely, giving scientists on Earth a chance to further investigate the phenomena observed by the first probe.
After Saturn, the Voyager craft passed Uranus, studying the moons and discovering several new ones as well as collecting data on the atmosphere and ring system of the planet itself.
Leaving Uranus, Voyager lived up to it auspicious name by leaping the huge gulf to Neptune. There, further amazing discoveries awaited. In order to receive weak signals from Voyager at this huge range, the antennae of the Deep Space Network were rebuilt with larger dishes and linked with other large receivers.
It was worth it. Many unexpected discoveries were made. Uranus was found to be a deep blue colour. The atmosphere was far more turbulent than expected, displaying superhurricanes and great dark spots reminiscent of Jupiter’s Red Spot.
After studies of the ring system and moons of Neptune and a final set of incredible photographs, Voyager left the solar system, bound for the great mysteries of deep space. Despite not being designed to last beyond Saturn, the instruments aboard the craft are still in use, sending back data on the solar wind and other deep-space phenomena. The craft should have power to last until about 2020, so perhaps there are a few discoveries still to be made by these awesome interplanetary – interstellar – travellers.
Zond
The Soviet Zond series of probes began with Zond 1 in April 1964, and beset with problems from the start. A Venus probe, Zond 1 suffered a communications failure and sent back no useful data. Zond 2 (November 1964) was similarly unsuccessful. This time launched at Mars, Zond 2 returned no data.
Zond 3, a Lunar probe launched in July 1965, was more successful, sending back pictures of the far side of the moon.
The remaining Zond missions were all Lunar probes. Although Zond 4 (March 1968) failed to leave Earth orbit, Zond 5-8 (September 1968 to October 1970) made successful circumlunar flights and returned to Earth for recovery.
The Clementine probe was intended to study the Moon and Near-Earth asteroid 1620 Geographos. After a successful Moon-mapping operation the probe went out of control, preventing the flyby of 1620 Geographos. The secondary mission goal of testing components in space was successful despite the malfunction.
Cassini
The single probe Cassini will study Saturn and its moons. Launched on a complex trajectory involving a gravity-assist orbit of Venus and another of Earth, the probe should arrive in the region of Saturn in 2004. There, it will carry out a detailed investigation of Titan, using radar surface mapping and the Huygens lander probe. The other Saturninan moons and the ring system will be studied by remote survey.
Deep Space 1 and 2
Deep Space 1 was a technology demonstrator for future programmes, but still had a strong scientific content to its mission. Launched in October 1998, the probe made a flyby of a near-Earth asteroid as planned and is now on course for a flyby of the comet Borrely.
Deep Space 2 (AKA the Mars Microprobe project) should have penetrated the Martian surface and relayed data on its composition, with a particular objecting of finding evidence of water. Contact was lost in December 1999.
Galileo
The Galileo probe was launched to Jupiter by way of the asteroid belt, conducting flybys of the major asteroids Gaspra and Ida. Having reached Jupiter in 1995, Galileo deployed an instrument package into the Jovian atmosphere and entered orbit to collect further data.
Giotto
Launched in July 1985, Giotto made a close pass of the comet Halley in March 1986, suffering damage from dust particles, which rendered several instruments inoperable. Despite the damage, enough of Giotto’s instrumentation remained functional that the Halley encounter and the extended mission (an encounter with comet P/Grigg-Skjellerup) both yielded a great deal of information.
Luna Series
The first probe missions to the Moon began in 1959 with the Soviet Luna probes. Luna 1 (January 1959) trialled the vehicle, and proved the rather important concept that it was possible to escape from Earth orbit. Luna 2 followed in September, crossing the gulf of space to become the first human-made object to reach another world.
This achievement was followed up a few weeks later by Luna 3, which sent back the first pictures of the far side of the moon.
Luna 4 (April 1963) was the first of a series of craft intended to investigate soft-landing techniques, a programme beset with difficulties. Radio contact with Luna 4 was lost close to the Moon. Luna 5 (May 1965), 7 (October 1965) and 8 (December 1963) suffered retro-rocket malfunctions and crashed on the Lunar surface, while Luna 6’s manoeuvre engine ran wild during a course correction, causing the probe to miss the moon entirely.
Lunar 9 (Jan 1966) finally succeeded, making the first-ever soft-landing. It sent back many pictures over the next 3 days.
The next batch of Luna probes were orbiters designed to study the Moon. Luna 10 (March 1966) orbited for 2 months, collecting data on the Moon’s magnetic field and surface gravity.
Luna 11 (August 1966) and 12 (October 1966) continued this process
More soft-landers followed. Luna 13 (December 1966) studied Lunar soil density and radiation, while 14 (April 1968) studied the Moon’s gravitational field.
Luna 15 was an attempt to gather samples from the Moon and return them to Earth. The fact that it was launched just a few days before the Apollo 11 mission is probably not a coincidence. The probe made a successful insertion to Lunar orbit but did not descend to the surface immediately. Concerned about radio interference between the two missions, NASA contacted the Soviet space administration, who assured NASA that there would be none. Thus Luna 15 did not begin its Lunar descent until just before Apollo 11 was to lift off from the Moon. This first attempt at automatic descent failed, and Luna 15 crashed.
Luna 16 (September 1970) succeeded in soft-landing and deployed an automatic drilling device, which collected samples of Lunar soil. These were launched in a capsule back to Earth and were successfully recovered.
Luna 17 (November 1970) soft-landed, and achieved a new first in space exploration. Lunokhod 1, a remotely-controlled vehicle, was deployed onto the Lunar surface and began collecting samples and data.
Luna 18 (September 1971) was less successful, crashing while making a difficult landing in highland terrain.
Luna 19 (September 1971) was an orbiter. It studied the Moon’s Mass Concentrations and surface gravity field and took pictures of the surface.
Luna 20 (February 1972) was a second soil-recovery device and succeeded in returning its samples to Earth.
Luna 21 (January 1973) carried a second Lunokhod rover. The mission was an uphill struggle, but despite difficulties with the rover and the Luna vehicle carrying it, Lunokhod 2 was successfully deployed.
Luna 22 (June 1974) was another orbiter.
Luna 23 (October 1974) and Luna 24 (August 1976) were successful landers. Luna 24 returned samples to Earth.
Lunar Orbiter
The orbiter missions were carried out in parallel with early Apollo flights. While the Apollo missions tested out the craft that would hopefully take humans to the moon and bring them home again, the Orbiter probes were searching for landing sites on the Lunar surface. 5 Orbiter missions were launched in 1966-7.
All the Orbiter missions were highly successful, allowing a comprehensive map of the Lunar surface to be built up from photographs taken from orbits as low as 40km. As well as providing the first pictures of the South Lunar Pole, the Orbiters discovered a dozen or so "Mascons" – mass concentrations, which caused gravitational effects on orbiting craft.
The Orbiters were deliberately crashed on the Lunar surface when their missions ended.
Lunar Prospector
Lunar Prospector was an attempt to find water ice on the Moon. After a study of the surface, the probe was crashed into a crater in July 1999, to throw up a dust cloud, which could then be analysed for traces of water ice. No such traces were found.
Lunokhod
Designed specifically for conditions on the Moon, the Lunokhod vehicle had an 8-wheel motive section using electric power and an instrument compartment. Remotely controlled from Earth by a 5-man team (this was a very tiring exercise involving great teamwork), Lunokhod also had automatic systems to override commands from the ground station in the event that the vehicle is on unstable terrain. This was necessary since the communication lag between vehicle and ground station could result in a crash, however skilled the operators.
Lunokhod I (Landed November 1970) was operational for nearly a year, taking thousands of photographs and making hundreds of soil analyses at various points. Eventually, with its stock of fuel for the warming device exhausted (this device kept the cameras and other equipment functional in the -150° C Lunar night), Lunokhod 1 froze and ceased operations. Even then, the laser-reflector on its topside remained positioned so that it could be used in future ranging experiments.
Lunokhod 2 (Landed January 1973) remained operational for 4 months and covered more ground that its predecessor. This rover collected more data about Lunar surface conditions and took thousands more photographs during an ambitious programme of manoeuvres which included scrambling up a 400m Lunar mountain.
Magellan
The Magellan probe spent four years in orbit around Venus, collecting data for relay back to Earth. This data includes a detailed radar map of the surface. Late in 1994, its mission was completed when the probe entered the Venusian atmosphere upon command, collecting data until its destruction.
Mariner
Mariner craft were launched by NASA to both Venus and Mars. The missions were mostly conducted in pairs of launches. In July 1962, Mariner 1 suffered a malfunction just after takeoff and was destroyed, but Mariner 2 (launched August 1962) successfully made a fly-by of Venus, registering the surface temperature of the planet at over 400° C.
Launched in November 1964, Mariner 3 was intended to make a fly-by and send back pictures of the Martian surface. It suffered a motor failure and did not reach Mars. The Mariner 4 mission, launched 3 weeks later, overcame guidance problems and succeeded in sending back pictures of the Martian surface. The craft entered solar orbit and remained functional.
Mariner 5 (June 1967) was something of a bonus. Originally a backup vehicle for the Mars missions, it was modified for and successfully made a close flyby of Venus. Mariner 5 recorded surface temperatures of 250° C. The vehicle also detected the planet’s weak magnetic field.
Mariner 6 (February 1969) and its sister, Mariner 7 (March 1969) were intended to study the atmosphere of Mars as well as sending back pictures of the surface. Another objective of the mission was to prove technology for an eventual manned mission to Mars. Mariner 6 studied the equatorial region, while Mariner 7 (Still functioning despite sustaining damage from a micrometeoroid impact) targeted the south pole.
Mariner 8 and 9 (May 1971) were to orbit and map the surface of Mars. Mariner 8 crashed on takeoff, but 9 exceeded expectations, succeeding in mapping the entire planetary surface. This was the first human-made object to orbit another planet. The mission also photographed both the moons of Mars and studied the Martian seasons. Other discoveries from the Mariner 9 mission included the fact that Mars is geologically active, and studies of a vast dust storm provided clues as to the effects of pollution on Earth.
The mission objective of Mariner 10 (November 1973) was altered as a result of the success of earlier probes. The made the planned fly-by of Venus, then used the planet’s gravity field to accelerate for a close approach to the planet Mercury. This was the first "slingshot orbit" carried out by a spacecraft. By entering a solar orbit, Mariner 10 was able to make 3 encounters with Mercury, detecting a trace atmosphere and taking photographs of the sunward side of the planet.
Mars
After preliminary experiments conducted in 1962 with Sputniks 22 and 24, the Soviets embarked upon the Mars series of probes. Several of the missions failed, but following standard Soviet practice, only those which reached their destination were named as part of the Mars series. For example the vehicle which would have been Mars 2 failed to achieve separation from its 4th stage launcher and fell back to Earth. This mission was redesignated Cosmos 419 (probably its launch designation) and the next probe became Mars 2.
Mars 1 (November 1962) contained, orbital and planetary components. After 100 million kilometres, the probe’s orientation system developed a fault, preventing the antenna from being aligned correctly and contact with the probe was lost.
Mars 2 followed much later, in May 1971. This attempt reached Mars and detached the planetary component. This failed to soft-land and was destroyed on impact. The orbital component of the probe entered orbit and began a study of the Martian atmosphere.
Mars 3 (May 1971) successfully reached Mars and detached its planetary module. This made a heavy landing in the middle of a dust storm. The planetary probe functioned for about 2 minutes, transmitting a few seconds of video, but then succumbed to a combination of landing and local conditions. The orbital section of the probe functioned for 3 months.
Mars 4 and 5 were launched as a pair in July 1973. Mars 6 and 7 followed 2 weeks later, using information from Mariner 9 to assist in choosing a landing site.
Mars 96 Orbiter
The Mars 96 probe mission included two lander units, two penetrators and an orbiter unit based on the Phobos probes. The probe reached Earth orbit but suffered a malfunction and re-entered.
Mars Global Surveyor
Launched in 1996 as the first of a new series of Mars probes, the MGS mission is in some ways a repeat of the Mars Surveyor mission, studying the planet from orbit throughout the Martian year. Additionally, the craft functions as a radio relay beacon for future missions.
Mars Observer
Mars Observer was designed to study Mars from orbit over a whole Martian year, collecting a variety of data. Contact was lost as the craft entered Mars orbit.
Mars Pathfinder
Mars Pathfinder was launched in December 1996 and landed on Mars six months later. It collected data on the Martian atmosphere and surface.
NEAR (Near-Earth Asteroid Rendezvous)
As part of a programme to study the Near-Earth Asteroids, NEAR was launched in February 1996 to 433 Eros.
Nozomi
The Nozomi or Planet B probe is a Japanese craft launched in 1998. The craft did not attain sufficient speed to reach Mars on schedule, and was placed on a longer trajectory, which will encounter Mars in late 2003. Once in orbit, Nozomi will study the effects of solar wind on the Martian atmosphere.
Phobos
The two Soviet Phobos probes were intended to study the interplanetary environment on their way to Mars, then to make a detailed observation of the moon Phobos. Several other nations contributed to the project, which failed due to malfunctions in both craft. Phobos 1 lost contact in September 1988 while Phobos 2 fulfilled many of its mission objectives. A computer malfunction caused the craft to be lost in Mars orbit in March 1989.
Pioneer
The Pioneer series of missions has covered a wide range of objectives, and has been fraught with difficulties. Pioneer I was NASA’s first spacecraft, the project having been handed over from the USAF.
Pioneer 1-4 (1958-9) were intended as Lunar probes. Pioneer 1-3 failed to reach the moon due to various malfunctions. Pioneer 4 made a fly-by but failed to enter Lunar orbit.
The next objective of the Pioneer series was Solar observation. Pioneer 5 (March 1960) studied solar flares and the "solar wind". Pioneer 6 (December 1965) and 7 (August 1966) collected data on the solar atmosphere. Pioneer 8 (December 1967) and 9 (November 1968) continued this observation programme and additionally studied Earth’s magnetosphere.
The mission that was to be Pioneer 10, another Solar probe, crashed in the Atlantic.
The next Pioneer mission, renamed Pioneer 10 (March 1972), was launched to Jupiter. Pioneer 11 (May 1973) followed in the footsteps of its predecessor but went to Saturn by way of Jupiter. Both probes acted as scouts for the Voyager missions and proved that a craft could survive the asteroid-belt passage.
Pioneer 12 looked inward once again, to Venus. Entering orbit in 1978, Pioneer 12 radar-mapped the surface and studied the Venusian atmosphere in addition to studying comets as the opportunity arose.
Pioneer 13 (1978) was another Venus probe, which deployed four packages into the Venusian atmosphere to measure its composition and temperature.
Ranger
The Ranger probes were part of a programme to gather data for the planned Apollo Moon landings. Ranger 1-6 (1961-4) were all failures, suffering various malfunctions and system failures.
Ranger 7 (July 1965) was able to transmit the long-awaited Lunar close-ups before it crashed into the surface of the Moon. Ranger 8 (February 1965) and 9 (March 1965) contributed more spectacular close-up footage from the Moon and helped make the Apollo landings possible.
Sakigake
A Japanese vehicle, Sakigake made a flyby of comet Halley in 1986 and a study of the solar wind. The craft remained functional until November 1995, having made three Earth flybys.
Stardust
Launched in February 1999, Stardust is a sample-collection probe intended to gather dust samples from interplanetary space and from the comet P/Wild 2. The probe is currently operational.
Suisei
The Suisei vehicle was identical to Sakigake, though it carried a different instrument package. The mission aim to gather further data on comet Halley was a success, but propellant depletion forced the abandonment of and extended mission.
Surveyor
Another Programme deployed in support of the Apollo landings, the Surveyor series was more successful than its predecessor, Ranger. All probes in this series were intended to soft-land on the Lunar surface at sites around the equator.
Surveyor 1 (June 1966) landed successfully and photographed the Lunar landscape. Surveyor 2 (September 1966) crashed and 3 (April 1967) bounced heavily but survived.
Surveyor 4 (July 1967) lost radio contact just before touchdown and crashed, but 5 (September 1968) overcame technical problems to make a chemical analysis of the Lunar soil.
Surveyor 6 (November 1967) not only landed successfully but took off again. This second flight lasted a few seconds and moved the probe all of 8 feet – but it proved that the Lunar surface was firm enough for a manned landing.
Surveyor 7 (January 1968) was not involved with seeking a landing site for the Apollo missions. Instead it studied debris in the Tycho crater, which was not considered as a possible Apollo landing site.
Vega 1 and 2
Combining a flyby of Venus and of comet Halley, the two Vega missions were launched in December 1984. After deploying a descent module into the Venusian atmosphere, the probes used a gravity-assist orbit to place them on course for the comet.
Venus (Venera) Series
In 1961, the Soviets achieved another first – the launching of a probe to Venus from a vehicle in orbit. Venus I was deployed into orbit by Sputnik 8 in February 1961, from where it made a fly-by of Venus, collecting the first close-up data to be gathered from another planet.
Venus 2 (November 1965) passed close to the planet but suffered a malfunction and returned no data.
Venus 3 (November 1965) was the first vehicle to reach the surface of another planet ("land on" is too grand a title for what Venus 3 did). The probe failed to return any data, though.
Venus 4 (June 1967) successfully penetrated the Venusian atmosphere and transmitted a wealth of data throughout its descent. It ceased transmission upon colliding with a mountain range.
Venus 5 and 6 (Both January 1969) entered the Venusian atmosphere within a day of one another. Both survived nearly an hour in the hostile environment and penetrated to a depth of over 35km, transmitting more data until they were destroyed.
Venus 7 (August 1970) reached the surface of the planet, where it suffered antenna damage from the impact . Nevertheless the probe managed to transmit data back to earth for just over 20 minutes before conditions (including atmospheric pressure 60 times greater than surface pressure on Earth) destroyed it.
Venus 8 (March 1972) also reached the Venusian surface, and recorded temperatures hot enough to melt lead.
Venus 9 and 10 (1975) made use of a fluid cooling system to allow the probe to survive for nearly an hour in the hostile Venusian environment. Venus 9 transmitted pictures and data back from the surface, including atmospheric analysis and a recorded surface temperature of 485° C. Venus 10 recorded similar data.
Venus 11 and 12 (1978) made soft landings on the surface and studied the atmosphere and clouds of Venus.
Venus 13 (1978) survived for over 2 hours on the surface and carried out a variety of measurements, including chemical analyses and studies of electrical discharges in the atmosphere. Venus 14 (1981) repeated these experiments.
Venus 15 and 16 were a pair of identical craft launched in 1983 to radar-map the surface of Venus from orbit. Both craft were placed in polar orbit to facilitate mapping.
Viking
The two Viking probes were launched to Mars in 1975. Each comprised an orbiter and a landing module.
The orbiters entered different orbits – Viking 1 an equatorial orbit and Viking 2 a more inclined one to study the poles. Viking 2 also photographed Deimos from close up. The lander modules made an analysis of the surface composition, finding evidence of iron but no signs that Mars even had life.
Voyager
The two Voyager craft – Voyager 1 and 2 – were a development of an earlier project, the Grand Tour. This ambitious project would have taken advantage of fortunate alignment of planets to send a probe on a "grand tour" of the outer system. The project was cancelled in 1972 for lack of funding and a general disinterest in space exploration. It was replaced by Mariner Jupiter Saturn, a more modest mission based on the proven Mariner probes. This project was renamed Voyager, and kept some of the spirit of the Grand Tour alive. While the probe had a design life of five years, long enough to reach Saturn but not much more. However, both craft were launched on trajectories calculated for the Grand Tour missions. If they happened to survive long enough, the probes might be able to visit the outer planets after all.
Of course, they did survive. They still do.
The Voyager probes weighed in and measured about the same as a small car (though with a rather different shape) Voyager 1 was launched in August 1977, somewhat after Voyager 2 but on a faster trajectory. It is powered by heat generated from the decay of a small amount of radioactive Plutonium. Solar cells were not appropriate to provide power so far out in the solar system, though the Sun does serve one very important function. Along with the star Canopus, our Sun is used by instruments aboard the probe to calculate its position and to keep the dish antenna aimed at Earth.
Voyager has three computers, each with a backup. These are very primitive by today’s standards but have functioned in deep space for over 20 years. The vehicle also carries a variety of instruments including magnetometers, cosmic ray detectors and charged particle detectors. Choosing the instruments proved to be a problem, as scientists did not know what to expect on any of the worlds Voyager would visit. A wide range of devices was settled upon, along with general-purpose equipment such as TV cameras and spectrometers, which it was hoped would be useful under almost any conditions.
Despite the increasing time lag as Voyager moves further out from Earth, getting signals to the craft is not much of a problem – providing the on-board systems keep the dish antenna properly aligned. It is not difficult to produce a sufficiently powerful radio signal to reach Voyager intelligibly. Signals from Voyager are something of a problem, however. With limited on-board power available (transmissions are less powerful than a decent household torch) the problem must be solved on Earth. This is accomplished by using arrays of dish antenna linked into a huge system rather than a single receiver.
Voyager 1 made a flyby of Jupiter during the period late 1978-early 1979. Scientists studying the photographs sent back to Earth found that the atmosphere had changed in appearance since the Pioneer flybys in 1974. Voyager also studied the Jovian moons. Despite slight damage to the electronics from Jupiter’s radiation, Voyager continued to function well, discovering a thin ring around Jupiter and evidence that Io was volcanically active. As Voyager 1 pulled away, Voyager 2 began its approach, sending back yet more photographs and instrument data.
The Voyager 2 probe had suffered a fault early in the journey, before it had even cleared the asteroid belt. The primary receiver had died completely and the backup was suffering from a fault limiting the frequencies it could receive on. This was a problem, since the rotation of the Earth caused a Doppler shift in transmission frequencies. Scientists were able to invent a method of compensating for the Doppler shift and restored some control over Voyager 2. Just in case, they sent it a set of instructions for limited data collection and transmission in case contact was lost again. At least they would get something from Voyager 2, even if direct control was lost.
Voyager 2 was able to collect more data on volcanic Io and the other Jovian moons, including Europa, which had not been clearly visible during the Voyager 1 flyby.
Following in the footsteps of Pioneer 11, Voyager 1 passed Saturn in 1980 and sent back spectacular photographs of the ring system plus data on Saturnian weather and of course the ring system. This was found to be more complex and baffling than previously thought. A completely new discovery was the existence of co-orbitals – satellites in the same orbit. It was discovered that these moons were actually closing at about 10m/s. Scientists theorised that when they were close enough, their gravity would cause the co-orbitals to swap position and pull apart again.
Voyager also found evidence that the rings were being kept in place by "shepherd moons" whose gravity helps maintain the ring system.
Voyager 2 followed its sister craft closely, giving scientists on Earth a chance to further investigate the phenomena observed by the first probe.
After Saturn, the Voyager craft passed Uranus, studying the moons and discovering several new ones as well as collecting data on the atmosphere and ring system of the planet itself.
Leaving Uranus, Voyager lived up to it auspicious name by leaping the huge gulf to Neptune. There, further amazing discoveries awaited. In order to receive weak signals from Voyager at this huge range, the antennae of the Deep Space Network were rebuilt with larger dishes and linked with other large receivers.
It was worth it. Many unexpected discoveries were made. Uranus was found to be a deep blue colour. The atmosphere was far more turbulent than expected, displaying superhurricanes and great dark spots reminiscent of Jupiter’s Red Spot.
After studies of the ring system and moons of Neptune and a final set of incredible photographs, Voyager left the solar system, bound for the great mysteries of deep space. Despite not being designed to last beyond Saturn, the instruments aboard the craft are still in use, sending back data on the solar wind and other deep-space phenomena. The craft should have power to last until about 2020, so perhaps there are a few discoveries still to be made by these awesome interplanetary – interstellar – travellers.
Zond
The Soviet Zond series of probes began with Zond 1 in April 1964, and beset with problems from the start. A Venus probe, Zond 1 suffered a communications failure and sent back no useful data. Zond 2 (November 1964) was similarly unsuccessful. This time launched at Mars, Zond 2 returned no data.
Zond 3, a Lunar probe launched in July 1965, was more successful, sending back pictures of the far side of the moon.
The remaining Zond missions were all Lunar probes. Although Zond 4 (March 1968) failed to leave Earth orbit, Zond 5-8 (September 1968 to October 1970) made successful circumlunar flights and returned to Earth for recovery.
Manned Missions
Lunar Missions
Humans have visited only one body beyond our own Earth, and that for brief periods only. But the story of manned space exploration is far from over, and people from Earth may yet set foot on other worlds, perhaps even worlds in other solar systems.
Those few small steps onto the Lunar surface were the culmination of several programmes intended to develop the technologies and techniques to be used in the Lunar landing missions. While unmanned probes collected necessary data about the destination, manned missions tested the equipment that would carry the Astronauts on their epic journey. These support missions deserve as much attention as the "main event", for without them we would never have set foot on another world.
Apollo 1
In 1967, it seemed like the goal of placing men on the Moon by the decade’s end was in sight. The Gemini programme had reached a successful conclusion, and despite numerous accidents, malfunctions and the explosion of several unmannned rockets on the launch pad, there had been no fatalities during space missions by any nation.
Tragically, that was about to change during the final checks on Spacecraft 12, the prototype Apollo capsule. After a day fraught with difficulties, Astronauts Grissom, White and Chaffee were coming to the end of a series of checks on the craft when telemetry indicated an electrical short in the capsule. Ten seconds later Chaffee reported smelling fire, and the crew initiated the emergency escape procedure.
The flames spread quickly in the pure oxygen atmosphere of the capsule, and despite the best efforts of White on the inside and the pad personnel outside the capsule, the hatch could not be opened. Only 16 seconds after the first warning the cabin was split by an explosion, which caused extensive damage and started fires in the support area around the capsule.
Despite the intense heat, heroic rescue attempts continued. Staff worked in blinding smoke without masks to find the outer hatch release bolts. A technician lifted the middle hatch off and carried it out of the entryway – a task normally requiring the efforts of two men.
Finally the rescuers forced the inner hatchway, to find the bodies of the three Astronauts within. They had all been killed as the cabin ruptured, incinerated by the heat that melted their suits and destroyed the craft around them.
The first humans to die in a spacecraft had not even left the ground.
Apollo 4-6: Unmanned Tests
There was no attempt at a cover-up after the Apollo 1 disaster. Instead, NASA was determined to learn from the tragedy and build a new, safer space vehicle. Between November 1967 and October 1968 unmanned tests were carried out with various components of the Lunar craft.
Apollo 4 was the proving flight for the immense Saturn V launch vehicle and the Apollo craft. Apollo 5 tested Lunar module systems operation in Earth orbit. Apollo 6 was to have been a repeat of the Apollo 4 mission, but failed due to oscillations of the Saturn V first stage during the launch.
Apollo 7
After a tragic year in which five astronauts and one cosmonaut lost their lives in air crashes and Cosmonaut Komarov became the first casualty during a space mission – he was killed when his re-entry system failed - a team of astronauts prepared to make a manned trial of the new Block 2 Apollo capsule. This team was headed by the veteran Schirra and comprised Astronauts Eisele and Cunningham. Their mission was designated Apollo 7.
In defiance of the ghosts hanging around the launch pad, Apollo 7 made a perfect takeoff and reached orbit without major incident. Despite Schirra developing a cold, the mission was a complete success. The separation, turnaround and redocking manoeuvre necessary to withdraw the lunar module from its housing was carried out without incident.
The entire mission was a success, though the Astronauts became increasingly bad-tempered as demands for extra tests and experiments came in from the ground staff. These strained relations were kept hidden while the crew made the first ever series of live broadcasts from orbit.
After 11 days, Apollo 7 returned triumphantly to Earth, and put the moon landings back on course.
Apollo 8
Late in 1968, two Soviets Zond spacecraft completed circumlunar flights with a variety of living things aboard. The possibility existed that a Zond craft could carry a lone Cosmonaut on a similar journey. NASA decided to make sure the first manned circumlunar flight was an American achievement, and accordingly swapped the mission goals of Apollo 8 and 9 around.
Thus it was that Astronauts Borman, Lovell and Anders found their mission brought forward to December 1968. On the 21st they blasted off atop the huge Saturn V rocket and made history by breaking Earth orbit - going where only some flies, meal worms and a couple of turtles had gone before.
The Apollo 8 crew carried out a number of important experiments during their historic flight, including a simulation of the manoeuvre required to orient the Command Service module with the Lunar module, using the third-stage booster as a dummy.
Borman, the mission commander, suffered a brief period of illness suffered which was at first thought to be ‘flu. It was finally blamed on a sleeping pill he had taken. Despite Borman’s slight illness the mission proceeded so well that the decision was taken to enter into Lunar orbit rather than to simply swing around in the Moon’s gravitational field and make a direct return to Earth. This was the default option, built into the flight plan in case of disaster.
The redesigned Apollo Command Service module performed admirably as manoeuvres were carried out to alter its elliptical Lunar orbit to a circular one, and later on the return journey. Despite an accident with the vessel’s computer which erased much of its memory, Apollo 8 succeeded in bring its crew home safely from what was at that time the longest journey ever made by humans.
Apollo 9
Tests with the Lunar Module formed the most vital part of the Apollo 9 mission. The vehicle had been tested on the ground and had made an unmanned flight aboard Apollo 5, but this mission was critical. If the module failed the series of tests planned for it, the 1969 Moon landing goal would be unattainable.
The mission personnel comprised McDivitt (commander), Scott (Navigation specialist) and Schweikart (Lunar Module Pilot).
Despite carrying the largest load to date, the Saturn V launch vehicle placed the mission in orbit flawlessly. The Lunar module was activated and the tricky undock-rotate-redock manoeuvre completed successfully.
On the second and third days of the mission, the crew suffered space sickness but were able to carry out intensive trials with the Lunar Module, including drills for emergency procedures for use if the tunnel between the craft and the Command Service module became blocked. The crew also trialled the backpack life support system to be used by Lunar explorers, as well as an overgarment designed to protect against radiation and micrometeorites.
The climax of the mission was a dry run of the Lunar landing and takeoff evolutions. The Lunar Module was separated and moved into an orbit that would carry the two craft apart. Once a suitable separation was achieved, a simulated Lunar takeoff was carried out. The descent stage was jettisoned and the ascent engine fired to catch up with the Command Service module.
Docking proved difficult for the Lunar Module pilot, whose view was restricted. In future, docking would be the responsibility of the Command Service Module Pilot.
Despite a scare when the Command Service module engine failed to fire, the remaining five days of the mission were something of an anti-climax, ending in a perfect re-entry and splashdown. The entire Apollo 9 mission was characterised by hard work and well-planned success rather than seat-of-the-pants heroics.
Apollo 10
The final mission to be flown before the planned Moon landings, Apollo 10 carried on the work of earlier missions rather than breaking new ground. The crew comprised Stafford (Commander), Young (Command Service Module Pilot) and Cernan (Lunar Module Pilot).
After the climb to orbit and a burn to set their craft on a Lunar trajectory, the crew carried out the tricky undock-rotate-redock manoeuvre to link Lunar and Command Service modules in the correct configuration.
En route to the moon, the crew carried out a series of broadcasts (not all of them scheduled) and performed minor experiments. A major feature of this mission was that the food was better and drinking water was spun to get rid of hydrogen gas, which was thought to have caused space sickness in previous crews.
After four days in space, Apollo 10 entered Lunar orbit and rotated to orbit tail-first. But before the experimental lander flight could be undertaken, the astronauts were forced to engage in a little spring-cleaning. At some point during the mission, parts of the mylar insulation in the docking tunnel had flaked off. When the tunnel was opened, the Command Service module was invaded by small particles, which had to be dealt with before the mission could continue. Ever ready to meet the challenge, specialists at ground control improvised a spacecraft-cleaning procedure using fans and wet towels.
The lander mission suffered further problems. The insulation flakes had blocked the docking-tunnel vents, requiring another backup procedure to depressurise the tunnel so that separation could be achieved. Then, it was discovered that the lander and Command Service modules had slipped out of alignment. Undocking might destroy the clamps and make redocking impossible.
Just before the craft disappeared behind the Moon and lost radio contact, ground control informed the crew that the misalignment was not enough to damage the docking clamps.
Probably.
After an anxious 35 minutes, contact was re-established with not one but two craft. The modules had achieved separation and were flying in close formation. 25 minutes later the Lunar module with Cernan and Stafford aboard began to move away from parent craft, leaving Young very alone in a Command Service module that suddenly seemed very much larger.
The Lunar module descended as planned to within 9 miles of the Lunar surface, photographing the prospective landing sites and most importantly demonstrating that the lunar module could function in its intended environment. Finally the time came to jettison the descent stage and return to the Command Service module. This was an anxious moment. If the ascent engine failed, Cernan and Stafford would become the first men to visit the moon, arriving in a spectacular and fatal manner.
With this unpleasant thought in mind, the crew made to jettison the descent stage. At first, nothing happened. Then the ascent stage shot free and began to run wild. Its rampage lasted less than ten seconds before Stafford brought the craft under manual control, but it caused intense anxiety aboard both craft and at ground control too.
Investigation later showed that the secondary guidance system had been left switched on due to an omission in the checklist. When the ascent stage came free, the guidance system had begun swivelling the craft to look for the Command Service module, causing the frantic moments experienced aboard.
Docking with the Command Service module was achieved almost three hours later, this time conducted by Young rather than the Lunar module crew. After placing the Lander in a safe orbit around the Sun, the three astronauts began the journey home. During this leg of the mission the crew of Apollo 10 achieved another first in space exploration. They shaved off their week’s worth of beard in space before making a perfect splashdown. Their return to Earth set a new record for re-entry speed – 40,000 kph.
With Apollo 10 safely back on Earth, the preliminaries were complete. The equipment worked, the procedures had been shaken down, the crews were ready.
The time had come for humans to walk on another world.
Apollo 11
The crew of the historic Apollo 11 mission comprised Neil Armstrong (Commander), Edwin Aldrin (Lunar Module Pilot) and Collins (Command Service Module Pilot). Collins had missed his slot aboard Apollo 8 due to a loose disc in his neck, which was affecting his reflexes. Choosing to undergo risky surgery to correct the problem, Collins made an amazing recovery, a testimony to his determination to be on the Lunar missions. In fact he might even have been fit in time to fly aboard Apollo 8, but schedules and training were set well in advance. By this curious mix of fortunes, Collins was assigned to "The" mission, though he would not set foot upon the Moon.
Apollo 11 lifted off without incident, despite the risks inherent in launching a vehicle with 12 million working parts into orbit, and after navigation checks the third stage engine fired to boost the craft out of Earth orbit and on course for the Moon.
After performing the tricky flip-over to withdraw the landing module from its housing, the crew settled down for the journey. Many of their tasks during this period were unglamorous "housekeeping" necessary for correct operation of a space vessel. Several TV broadcasts were also made, one of which demonstrated the vast improvement in living conditions enjoyed by the astronauts, especially their food. Aldrin explained a feature of weightlessness to the world, saying that it was great fun to float around but eventually you grow tired of bouncing off the walls and ceiling. He added that jamming yourself into a corner feels more natural.
During the Apollo 11 flight the Soviet Luna 15 robot mission was launched. The Soviets supplied data on the orbit of their probe and assured NASA that their craft would not interfere with radio traffic between ground control and the Apollo mission, which was carrying medals commemorating the dead cosmonauts Gagarin and Komarov. These were to be left on the surface of the Moon in remembrance.
Despite a scare when a small piece of space debris collided with the Command Service module, the mission was proceeding according to plan as Apollo 11 went out of radio contact behind the Moon. The burn to slow the craft and establish Lunar orbit must be carried out during this period of no contact. If anything went wrong, the crew were going to have to deal with it alone.
Apollo 11 came out of radio shadow exactly on time and perfectly on course.
After circularising the orbit and carrying out checks on both craft, Armstrong and Aldrin said farewell to Collins and manned the Lander module, named Eagle. Despite intermittent communications problems, the lander crew were given the green light to begin their descent.
The descent was not without difficulties. The flight computer began registering an overload and the lander looked like overshooting the target area. Warning lights came on, showing less that 5% of the descent fuel remained. If the Eagle did not land in the next 90 seconds, the crew would have to make a dangerous low-level abort.
As the intended moment of touchdown approached, the lander made a series of manoeuvres that worried ground control. It later transpired that the auto-targeting was aiming the craft at a crater filled with huge boulders. Armstrong took over manual control and with Aldrin offering advice attempted to reach a safe landing site with the last of the fuel.
With 20 seconds to abort, the Lunar module touched down in the Sea of Tranquility, the first manned craft to reach the surface of another world.
The Eagle had drifted somewhat from the intended landing site, and the crew were at first unable to give a precise location. Despite this minor glitch, Aldrin and Armstrong prepared for the first moonwalk, donning their bulky pressure suits and life-support backpacks.
Finally, more than six hours after touchdown, the astronauts were ready for their historic first steps onto an alien world. After depressurising the lander module, Armstrong deployed the remote camera and stepped out onto the "porch" of the lander module. The remote camera relayed his image to the waiting world as he stepped onto the Lunar surface.
After accepting a camera from Aldrin, Armstrong made an inspection of the landing site and collected "contingency samples" – a few rocks and some dust – in case the mission had to be terminated early.
Armstrong was joined on the Lunar surface by Aldrin shortly afterward. Together they planted a plaque and a United States flag in the Lunar soil, collected samples and practiced moving around in the low gravity. Among the experiments they deployed was a lunar seismometer and a laser reflector for use in measuring the distance between Earth and Moon.
The EVA finally over (after nearly 3 hours on the Lunar surface), the two astronauts still had to place their samples aboard Eagle, remove their suits and collect all the dead weight – the life-support backpacks and other items which were no longer needed. This was left behind on the Moon to save weight in the ascent module. After briefing Houston about their discoveries, the astronauts were finally able to settle down to sleep.
After a little under 22 hours on the Lunar surface, the Eagle prepared to lift off. This was another critical stage of the mission. No manned craft had ever taken off from the surface of another world. There was one chance to get it right, or Armstrong and Aldrin would become permanent Lunar residents.
The liftoff was flawless. The Ascent Module rose smoothly into the Lunar sky, leaving behind, along with its lower stage and a heap of trash, an Apollo shoulder patch in memory of the three Apollo 1 casualties, and medals commemorating the two dead cosmonauts.
After docking, the crew transferred their samples to the Command Service module and ran checks on their craft. The Lander module was then jettisoned and Apollo 11 broke Lunar orbit, headed homeward.
After splashdown and recovery by the aircraft carrier Hornet, the crew of Apollo 11 and their craft were placed in quarantine in case any harmful organisms had been brought back from the Moon. The samples were taken to the Lunar Receiving Laboratory at Houston, and in due course the astronauts were pronounced free from contamination.
All the work and preparation – and the sacrifices – had not been in vain. Humans had walked on the face of another world, and brought back samples to investigate.
In retrospect, the first Moon landing was achieved more for reasons of international prestige than scientific endeavor. It was a hurried affair of there-and-back. Two men had landed, wandered around for a couple of hours and rushed home with a box of rocks.
Had anything really been achieved by the Apollo 11 mission?
What had been achieved was to prove that humans could reach another world and survive there.
If it could be done, it could be done again.
There was more to come.
Apollo 12
Having achieved President Kennedy’s goal of a Moon landing by the end of the decade, the Apollo programme could slow down a little and take the time to make Apollo 12 a more scientific expedition than its predecessor. Had Apollo 11 failed, there were plans to launch 12 in September 1969. Instead, the mission blasted off in November.
The crew of Apollo 12 comprised three US Navy officers, all holding the rank of Commander: Conrad (Commander), Gordon (Command Service Module Pilot) and Bean (Lunar Module Pilot)
Apollo 12 lifted into a heavy rainstorm, and almost immediately the mission went awry. The craft was struck by lightning. The power surge caused the main electrical system to shut down and the entire warning panel to light up.
As the rocket continued to accelerate out over the Atlantic, the crew struggled to bring their systems back on-line using battery power. Meanwhile the first stage dropped away as the automatic guidance system performed correctly despite the damage.
Amazingly, Apollo 12 reached orbit and after some damage control operations blasted out of orbit en route for the Moon. Despite the damage, the craft’s trajectory was so good that a planned course correction was cancelled.
The detection of a tumbling object following the craft caused some worry, but this was eventually identified as the third stage booster. Otherwise, the next three days passed in relative calm and on 18th November, Conrad and Bean manned the Landing module, named Intrepid. Their target was Surveyor Crater, landing site of one of the Surveyor probes.
Making a perfect landing right on target, the astronauts discovered that their landing site was a great deal dustier than the Apollo 11 site. Conrad descended to the Lunar surface first, collecting contingency samples in case of an early abort. He excitedly pointed out the Surveyor probe just 200m from Intrepid before handing up the samples to Bean.
The astronauts then set up a series of experiments, all powered by a small nuclear generator. These experiments were intended to determine whether the Moon had any atmosphere, ionosphere or magnetic field and to study moonquakes. The dust proved to be a problem, though it also came in handy for weighing down the skirt of the seismometer.
After collecting rock samples and a core sample, the dusty astronauts returned to Intrepid after four hours on the surface. They struggled in vain to get rid of the dust that coated everything, and Conrad suffered an unexpected hazard of planetary exploration – wet feet, resulting from water from his suit cooling system pooling in his boots.
The second EVA started early, as the excited astronauts were unable to sleep for more than a few hours. This excursion involved more geology and a visit to the old Surveyor. Conrad fell over several times while collecting samples, but did not report this to Houston. Fortunately he did not damage his suit.
The Surveyor probe, which had been resting on the Lunar surface for two and a half years, had apparently bounced on touchdown but appeared to be in good shape when the astronauts visited it. They cut off some samples before making their final visit of the EVA, taking samples and photographs of Block Crater.
After clearing the ascent module of dead weight (all except the dust, which the astronauts were unable to get rid of), the landing was at an end and there only remained to return to orbit. After nearly 32 hours on the surface, Intrepid lifted off and made rendezvous with the Command Service Module.
After unloading the samples from the Intrepid (the dust-covered pressure suits were left inside the ascent stage to reduce the amount of lunar dust floating about in the Command Service module), the Lander was jettisoned and allowed to crash on the Moon. The astronauts spent another day continuing the work carried out by Gordon in photographing the Moon.
Even before Apollo 12 began her trans-Earth injection burn, the experimental results were coming in. The seismometer registered a moonquake lasting 55 minutes – an unheard-of duration on Earth.
The astronauts had a final treat in store on the way home; their flight path put the Earth between them and the Sun, causing a total eclipse. Soon after witnessing this incredible sight the Command module plunged into the atmosphere to make splashdown in the Pacific Ocean.
Recovered by the aircraft carrier Hornet, the crew spent 16 days in quarantine but suffered no ill effects from breathing Lunar dust all the way home. The mission also brought home the only living things ever found on the Moon. These were microorganisms found in the Surveyor equipment salvaged by the astronauts, which had originated on Earth and amazingly survived the journey and long isolation on the Moon. They had of course got in while Surveyor was being constructed.
The Apollo 12 mission was an incredible achievement from a mission that started so badly. The scientific data was of incalculable value, and the precision landing beside Surveyor showed that missions could be sent to more scientifically interesting, but rugged, areas.
The stage was set for even greater things.
Apparently.
Apollo 13
The climate was changing as Apollo 13 readied for launch. The public were losing interest in Moon missions, budget cuts were beginning to bite, and enthusiasm for space exploration was waning fast.
Against this backdrop, preparations for the mission went ahead with a greater than usual amount of problems. One of the two Command Service module oxygen tanks would not drain properly, but was retained as this would not affect the mission. Other relatively minor glitches were fixed as fast as they cropped up as the engineers struggled to meet the launch date of April 11th 1970.
Less than a week before launch it became necessary to drop Mattingly (Command Service Module Pilot) from the crew after it became apparent that he had been in contact with German Measles, to which he had no resistance. Rather than swap the prime and backup crews, it was decided that Swigert (the backup crew pilot) would take his place. The last few days before launch saw the crew undertaking a hurried series of simulations to establish the effective teamwork so vital to a successful space mission.
Along with newcomer Swigert, the crew of Apollo 13 comprised the experienced Lovell as Commander and Haise as Lunar Module Pilot. The team shook down satisfactorily despite the rush. Apollo 13 blasted off on April 11th, heading for the Fra Mauro uplands. The launch attracted far less public interest that the two previous Moon landing missions.
Apollo 13’s troubled voyage began during launch, when the second stage cut out two minutes early. By firing the other engines for an extra few seconds the situation was returned to normal. The astronauts made a TV broadcast and prepared to continue with the mission.
There was no real cause for concern. The mission was less than a minute behind schedule and had not used up an excessive amount of fuel. No space mission is without technical difficulties, and if this was as bad as Apollo 13 was going to get, it would be a fine mission.
With docking and extraction of the Lunar module completed, the mission proceeded well for 3 days. Public interest was limited, even during the critical manoeuvres. The biggest worry aboard was over Swigert’s income tax forms, which he had forgotten to file in the hurry to join the mission.
Minor problems presented themselves as the mission continued, and on one occasion the master alarm early in a sleep period brought all three crewmen hurrying to the cockpit searching for the cause. But so far, so good – it was a false alarm. Another TV broadcast showed the crew in good spirits, making jokes about the drinking bags they would use inside their helmets during the moonwalk and warning viewers about "funny noises" that might result.
Ten minutes after the broadcast ended, disaster struck and one of humanity’s greatest adventure stories began to unfold.
A warning light came on at Mission Control, showing low pressure in a hydrogen tank. There had been intermittent problems with the tanks throughout the mission, and the solution was simple. Swigert was instructed to switch on the fans that would stir the tanks.
Unknown to the crew or Mission Control, the insulation on some of the fan wiring was very thin. This was due to overheating during the drainage problems encountered weeks before. Sixteen seconds after the fans were switched on, an arc jumped between the wires, causing a fire in the oxygen tank. This rapidly spread throughout the bay before escaping oxygen and fumes from the burning insulation blew out the outer hull panel. This allowed the gas to vent into space and probably saved Apollo 13 from immolation.
However, it also threw the craft off course and caused a power drop in main bus B (one of the two major power circuits). With the master alarm sounding and no real idea of what had happened, Swigert informed Mission Control with the now-immortal words, "OK, Houston, we’ve had a problem."
At first it was unclear what had happened, or how serious the problem was. Instruments were reading a range of faults and unsafe levels of pressure and temperature. It was not even clear what had caused the power drop. At this time, the main concern was whether the moon landing was still possible.
Then Lovell reported that oxygen tank 2 was reading zero pressure and 1 was dropping. This oxygen was needed not for the crew to breathe but also for water and to power the fuel cells that supplied electricity to the craft. It became apparent that not only were the astronauts not going to be landing on the Moon, they might well not be going home, either.
Lovell then reported that the craft was venting gas, which was causing vibration and sending the vessel off course despite the manual control being applied.
Still trying to determine the nature of the problem, ground control began looking for anything that seemed to be normal among Apollo 13’s system readouts. There was nothing. Two of the three vital fuel cells were dead and the output of the other one was dropping, communications were patchy and the oxygen level in the remaining tank was falling.
The crew began powering down systems in the Command Service module, saving what power remained for vital systems. They also connected main bus A to the re-entry battery to boost the available power, but were told by ground control to disconnect it. If it became discharged the crew would certainly die during re-entry – assuming they made it that far.
It was by now clear that the only chance for the three astronauts was to use the Lunar module as a liferaft. There was no chance of simply reversing direction, so the crippled spacecraft would have to be put back on a free-return trajectory and allowed to swing around the Moon to commence its homeward journey. With the Command Service module out of action, the life support systems and descent engine of the Lander offered the only hope. The posed a new problem. The Lander was designed to support two occupants for perhaps 50 hours. It would have to sustain three for nearly 100.
To meet this challenge, experts from the firms contracted to supply components of the spacecraft were placed on constant call. An analysis team was set up at Mission Control to come up with solutions to technical problems – hopefully before they occurred.
The crew of Apollo 13 powered up the Lunar module and calibrated its guidance system. They were now totally dependent upon the Lander to keep them alive and get them home – they would only re-power the dark and silent Command Service module for re-entry.
Six hours after the crisis began, Lovell manually fired the descent engine in the first of two burns. This one was to place the craft on a return trajectory around the back of the Moon. The second would accelerate the craft enough to make it home before the air ran out.
Spirits rose a little among the crew. They might burn up in the atmosphere or die of suffocation along the way, but at least Apollo 13 would bring them home. Better that than being lost forever in the deeps of space.
As Apollo 13 cleared the Moon and prepared for the second burn, experts at ground control were still debating the how to make the best use of the available resources. Ideas such as jettisoning the Service Module component of the craft, leaving only the mass of the Lander and the Command module, then burning the available lander fuel at full throttle were rejected as too risky. In the end a slower, steady acceleration was settled upon, which would make the journey a whole day longer but left more margin for error.
With severe damage and only half a set of thrusters, plus most of the instruments powered down, controlling the craft was extremely difficult. Just keeping the craft stable long enough for a position sighting to be taken was a major undertaking, but eventually the burn was completed. However, ground control were dismayed to notice that Apollo 13 was still drifting off course.
Conditions were becoming worse in the craft, too. The temperature was down to 10° C and carbon dioxide levels were very high. The latter problem was solved with a jury-rigged device made from a hose and one of the Command Service module’s lithium hydroxide canisters.
As Apollo 13 approached Earth, it became necessary to correct the drift and place the craft on a trajectory that would hit the narrow re-entry window. Even a slight variation in speed or angle of approach would prove fatal as the craft skipped off the atmosphere into deep space or burned up.
The tricky deceleration burn was handled as a three-man operation. Lovell kept the craft aligned correctly using a set of cross-hairs and the few working thrusters. Swigert timed the burn and Haise fired the Lander engine. All three astronauts were so fatigued by this time that they became confused as to whether they were seeing the Earth or the Moon out of the cockpit window.
They were also suffering from the cold and damp – it was down to 3° C in the Command Service module, and were so short of water that they had only 20% of the normal minimum requirement to drink each day. Despite their suffering, the crew continued with the mission as best they could, transferring the film they had shot while passing the Moon to the Command Service module and stowing non-essential items in the Lander.
Final preparations continued. The Command Service module batteries were charged from the Lander and Mattingly, who had not developed German Measles, worked through the re-entry in the simulator and read the checklist up to his colleagues. There were worries that the separation of the Command Service and Lunar modules might cause another course shift, and a final correction was planned accordingly.
With less than ten hours to re-entry, the crew powered up the Lander and began to defrost the thrusters. The Service module was then jettisoned, leaving only the tiny Command module linked to the Lander. The astronauts were able to view the damage to their Service module as it broke away, and expressed amazement that the craft had survived at all.
The extent and nature of the damage raised a new question – had the heat shield been damaged by the explosion? If it had, the crew would not survive re-entry.
Finally, there only remained to check orientation – it was perfect – and jettison the Lander. The crew took photographs of their life-saving craft until it disappeared from view.
90 minutes later, Apollo 13 re-entered Earth’s atmosphere. A final message from the crew thanked the staff and advisors on the ground for all their efforts and then there was nothing to do but hope or pray. Either the heat shield would hold or it would fail.
Millions of people – less blasé about Moon missions now – were glued to their TV or radio sets as Apollo 13 entered the radio blackout phase of descent. The blackout seemed to go on forever. The expected moment of contact passed with no sign of the astronauts. Another half minute crawled by. Hope began to turn to despair. To have come so close….
Then Apollo 13 came out of radio blackout, giving the world a final piece of theatre as she opened her parachutes in full view of the rescue carrier. It was the most accurate splashdown to date.
The Apollo 13 mission was a failure in that it did not achieve its goal of landing men on the Moon to conduct more experiments. However, in another way it was a monumental success. Lessons were learned about survivability of spacecraft, resulting in design changes to future craft. A public grown complacent about space missions were given some new drama to provoke interest.
But most of all, against all the odds, Lovell, Haise and Swigert came home.
Apollo 14
The crew of the Apollo 14 mission was headed by Shepard, America’s first man in space, accompanied by Lunar Module Pilot Mitchell and Command Service Module Pilot Roosa. Theirs was the first of a new series of Lunar missions aimed at exploring more of the surface and developing a greater understanding of the nature of our satellite. This mission was aimed at the Fra Mauro uplands, destination of the ill-fated Apollo 13.
It was an improved Apollo vehicle that blasted off in January 1971. Not only was the craft itself redesigned with safety in mind but launch procedures had been tightened too. A 40-minute hold was required to allow the weather to clear – another lightning strike was not desirable. In the event the rocket functioned perfectly.
The docking of Command Service module and Lunar module proved to be a problem, but after several frustrating attempts Roosa was able to complete the manoeuvre. Ground control theorised that ice might have formed on the docking clamps during the launch, preventing them from latching. The mission was soon back on course, though a series of minor faults and problems kept the crew from becoming complacent.
Apollo 14 entered a lower Lunar orbit than had previously been used, in order to conserve Lander fuel. As Lunar mountains appeared on the horizon, they appeared to be higher than the orbiting craft, a disconcerting sight which was fortunately only an optical illusion.
Shortly after the Command Service and Lunar modules separated, a computer fault triggered the Abort sequence aboard the Lander. Mission Control was eventually able to bypass this system, allowing the mission to proceed. Them, during the descent, the landing radar ceased to function, leaving Shepard and Mitchell with no means of determining their altitude. After some frantic work by Mitchell, the radar began to work again and the Lander touched down safely close to the target area.
On the Lunar surface, Shepard and Mitchell deployed a main package of six instruments plus several minor ones, including a set of geophones and explosive charges intended to study the Lunar crust. This package failed to work properly, causing frustration.
A second moonwalk was aimed at exploration. The astronauts visited several prominent landmarks and craters around the landing site, wheeling a specially-designed handcart with them to carry tools and samples. This device caused an unexpected problem. During the bumpy ride over the surface, items would be bounced off it and the wheels began to stick in the dust. Eventually the astronauts resorted to carrying the cart and its contents.
As the astronauts returned to the Lander module, Shepard produced a six iron and several golf balls. Despite the bulky suit he succeeded in sending golf balls for a considerable distance over the rocky Lunar surface. The longest shot travelled about 400 yards.
The Lander then returned without incident to the Command Service Module, where Roosa had been conducting a number of experiments. These were continued after the return of Shepard and Mitchell. NASA was interested in the manufacturing possibilities inherent in weightless conditions.
Apollo 14 returned home for recovery, and the crew were found to be in good physical condition as they entered the quarantine facility. They were the last Apollo crew to do so. The facility was dispensed with on future missions as unnecessary. There was nothing living, harmful or otherwise, on the surface of the Moon.
Apollo 15
The Apollo 15 mission, comprising Scott (Commander), Irwin (Lunar Module Pilot) and Worden (Command Service Module Pilot), was a geological field trip intended to discover the nature of the Moon’s core – was it still active, like Earth’s, or solid? The astronauts underwent intensive training as geologists in addition to their mission preparation.
The public remained uninterested in Moon missions, despite the fact that this one was the largest yet. Among the equipment aboard the Lander was a new device, the "moon buggy" or Lunar Rover. This battery-powered vehicle folded for transport and used a similar motive system to the Soviet Lunokhod rovers. It was hoped that the vehicle, combined with a less bulky pressure suit, would facilitate greater mobility on the surface.
Although the launch site was struck several times by lightning in the days preceding the launch, the liftoff itself was without problems. The Saturn V rocket, which had been upgraded to handle the extra weight, functioned flawlessly. This good fortune continued as Apollo 15 entered its trans-lunar phase. This course was slightly different from that of the other Apollo missions as the destination was far from the Lunar equator. It was also a no-return orbit, meaning that if the engines failed to fire the craft would not swing around the Moon and return unpowered to Earth orbit but would instead wander off to be lost in deep space.
No space mission is complete without a few malfunctions and minor crises. In Apollo 15 it was the electrical system that provided most of the drama. A short-circuit threatened to activate the main engine and later a false master alarm caused grave concern. The astronauts also had to turn plumber to fix a water leak, but otherwise Apollo 15 proceeded smoothly.
In Lunar orbit, the crew deployed an extensive instrument package including a laser altimeter and spectrometer. Worden was to continue collecting data using these devices during the Landing phase of the mission.
A loose power connection caused problems as the Lander and Command Service modules separated, but only a few minutes behind schedule Worden boosted the Command Service module into a higher orbit as Scott and Irwin began their descent.
The landing was a little rough. Lunar dust blinded the craft, forcing Scott to make an instrument touchdown with one landing foot in a small crater. After a preliminary look around, the astronauts began describing the features nearby for the benefit of the geologists back home.
After a few hours’ rest the astronauts ventured outside and unfolded the moon buggy. This proved top be quite a struggle, and even when the job was completed the front-wheel steering would not work. Scott began the drive using only the rear-wheel steering. Despite the rough ride, the buggy made it possible to cover a lot of ground, albeit in bouncy and uncomfortable fashion.
After collecting many geological samples, the astronauts returned to the Lander and deployed the Experiment Package. Attempts to sink tow heat-flow probes 10 feet into the Lunar soil failed. The ground was so dense that the drill would only penetrate to a little over five halfway. In the end they stuck the probes in and hoped for the best.
The second moonwalk began late, as the astronauts had to mop up spilled water from a leak and repair Irwin’s suit antenna before beginning. It was a welcome surprise to find that the front-end steering on the moon buggy had spontaneously decided to work. The buggy carried Scott and Irwin to a new site where they collected more samples. Some of these were pale green glass thought to be Lunar core fragments. After another attempt to drill holes for the heat-flow probes, the astronauts returned to their craft.
The third and final moonwalk took Scott and Irwin to the top of Hadley Rille after a strenuous battle to extract a sample core drilled on the first day. From the top of the rille they were able to film and sample the lava flows and bedrock nearby, delighting the geologists at mission control.
Shortly before takeoff Scott franked the first stamps of a new issue commemorating the US space programme and demonstrated that Galileo had indeed been correct when he theorised that a hammer and a feather would fall at the same rate without air resistance to slow them.
After parking the moon buggy where its camera could film their takeoff, the astronauts placed a plaque commemorating the 14 Astronauts and Cosmonauts who had died since the beginning of the space programme.
The Command Service module remained in orbit for two more days to complete the orbital experimentation programme carried out by Worden. After launching a small satellite into Lunar orbit, the Command Service Module began the voyage home. During the trip Worden stepped into the limelight to make an EVA, retrieving film cassettes from the instrument bay.
Apollo 15 returned to Earth without further incident after a highly successful mission.
Apollo 16
The Apollo 16 mission suffered several accidents during the preparation phase, then had its launch postponed due to the illness of the Lunar Module Pilot, Duke. Finally, on April 16th 1972, the mission blasted off under the command of the veteran Young, accompanied by Duke and Command Module Pilot Mattingly, who had missed Apollo 13 due to suspected illness.
As usual, there were problems. Twice the master alarm sounded as the navigation platform locked up due to a short circuit. Despite this, Apollo 16 entered Lunar orbit and conducted a survey from orbit as Young became the first man to orbit the Moon on two missions.
The Lander caused more problems during preparation, but finally the two craft moved apart. As Mattingly prepared to move the Command Service module into a higher orbit, a fault in the engine nozzle motor manifested itself. With the craft in Lunar orbit, there was no way to get home if the engine was not controllable. The landing was postponed, leaving Young and Duke waiting helplessly aboard the Lander while the engineers at ground control tried to sort out the problem.
Finally the decision was taken to proceed with the landing. The main engine should still function correctly, the engineers thought. Young and Duke began their descent from the highest altitude to date, with an antenna that functioned only intermittently.
Despite their difficulties, the astronauts made a flawless landing on the Descartes plateau. Overhead, Mattingly nudged the Command Service module into a higher orbit. So far, the engine was performing well, but the engineers were still concerned.
On the Lunar surface, Duke and Young rested before commencing their moonwalk. Duke’s drinking bag began to leak, giving him an orange-juice shampoo inside his helmet, but the astronauts pressed on. They set up the moon buggy and cameras and deployed the experiment package.
Unlike Apollo 15, there was no problem obtaining a core sample or in drilling a deep enough shaft to deploy the heat flow probes, but Young tripped over the power cables for the probes and broke them. Unable to repair the damage, the astronauts were forced to abandon the experiment.
Next, Young and Duke boarded the moon buggy for a sample-collection trip and Young played rally-driver, sliding the rover around and generally enjoying himself. Normally laconic, in his exuberance he was even moved to parody Neil Armstrong’s famous speech. Indicating Charles Duke (who was much taller than Young) he announced to the world, "One small step for Charlie is a giant leap for me!"
The second moonwalk too place some hours later. This time Duke drove, and he too was possessed with a desire to throw the rover around. His driving was so violent that Young complained and some of the rover instruments broke, but the vehicle continued to function.
This trip allowed the astronauts to collect a large amount of rock samples and measure the Lunar magnetic field. After 71/2 hours they returned to the Lander and gave the world an insider view of space exploration as they discussed digestive problems caused by potassium in their drinks in front of a mike they thought was turned off.
A third moonwalk collected more samples but could not find any evidence of volcanic activity, which had been predicted in the region. The astronauts returned to the Lander to perform for the cameras one last time, jumping around and throwing objects in the low gravity. Duke fell on his back but did not damage his suit.
As Mattingly fired the Command Service module engine again to lower his orbit for pickup, ground control watched anxiously, but the rendezvous went according to plan. Houston had decided to shorten the post-landing phase of the mission, and asked the crew to jettison the lander before resting. The tired astronauts incorrectly set the controls. Instead of descending to crash on the Lunar surface (providing a shock for the seismographs to pick up) like all the other ascent modules, the Lander almost collided with the Command Service module forcing Mattingly to fire the suspect main engine in an emergency manoeuvre. The ascent module eventually crashed on the Moon.
After deploying a small satellite, Apollo 16 broke orbit for home. The engine continued to function correctly and two days into the flight Mattingly repeated Worden’s EVA to retrieve instrument-bay film cassettes. At the same time the crew conducted an experiment involving the exposure of biological samples to cosmic rays.
Apollo 16 made a good re-entry and an extremely accurate touchdown.
The mission continued to be a success even after the astronauts returned to Earth. A remote-controlled device left behind on the Moon caused and registered several shocks, allowing further study of the Moon’s crust.
Apollo 17
Data collected by the earlier Apollo missions suggested that the Lunar highlands were where answers would be found as to the nature of the Moon’s core and its history. For this reason the destination of the final Apollo mission was chosen as the region between the Littrow crater and the Taurus mountains. It was also decided to send a scientist on this mission in the place of one of the astronauts.
The crew of Apollo 17 comprised Cernan as commander, making his second Lunar mission, and Evans as Command Service module pilot. The Lunar Module pilot’s berth was taken by Dr Schmitt, a geologist.
The mission ran into trouble on the launch pad. With just 30 seconds to go the third stage oxygen tank refused to pressurise. Ground crews struggled to overcome the problem and finally the huge rocket blasted off.
In order to make up time, Apollo 17 was boosted onto a no-return trans-Lunar course. Engine failure would mean slow death in deep space for the crew, but despite a series of false master alarms the rocket functioned perfectly.
While Evans raised the Command Service module into a higher orbit, Cernan and Schmitt made the descent to the Lunar surface without incident. They unfolded the moon buggy then Cernan deployed a US flag. This one had hung in the Mission Operations Control Room since the first Lunar landing mission, and now Cernan placed it on the Lunar surface in memory of the hard work and ingenuity that had made the missions possible.
Cernan and Schmitt then deployed the instrument package, which included more heat flow probes and advanced seismic sensors. Drilling the probe shafts and obtaining a core sample was hard work and took longer than expected. Ground control thus made some changes to the EVA schedule. Samples were collected from Steno crater, then the astronauts made their way back to the Lander for a rest. Both were filthy – Schmitt had fallen over several times and a broken fender on the moon buggy allowed dust to spray over the passengers.
On the second day, the rover was repaired with a makeshift fender. This was constructed from lunar maps, emergency lighting clips and some tape. It worked, even if it wasn’t pretty.
Making a long drive to the South Massif, Cernan and Schmitt collected samples and studied the debris of a landslide. Stopping at Lara and Shorty craters on the way back, searched for evidence that either had ever been a volcanic vent, which some scientists believed likely. Orange soil around Shorty crater provoked a flurry of scientific interest – it might be evidence of water or volcanic activity. After taking samples the astronauts made their way back to the Lander. These samples later yielded the truth about the orange soil. The colour was due to concentrations of titanium, the position due to a meteorite impact. Scientists were disappointed with the answer, but thanks to Apollo 17 at least they had one.
The third EVA was in the direction of the North Massif. The rugged terrain caused some damage to the rover, but the astronauts were able to reach their goal. They were not able to find evidence of any volcanic activity despite an exhausting search.
With a huge amount of samples aboard, the Ascent module was above her takeoff weight. Despite the extra load, the craft made a perfect rendezvous and docked with the Command Service module on the second attempt. Communications became patchy during the ascent, requiring Evans aboard the Command Service module with only five mice for company (they were part of a cosmic ray experiment) to act as a relay.
After two more days conducting experiments in orbit, the three men and five mice that formed the crew of Apollo 17 began the journey home. Evans performed his EVA to retrieve the film cassettes. Despite worries over a pair of scissors lost somewhere in the craft and potentially presenting a hazard, the Command module made a perfect re-entry with Evans trying out a special pair of trousers designed to prevent blood pooling in the legs.
As Apollo 17 hit the Pacific, the Moon Landings came to an end.
Retrospect: The Manned Moon Landings
We went to the Moon and we came back. The planned follow-on orbital laboratory failed to materialise and there have been no more manned missions to other worlds.
Was there really any point to all the expense and risk to human lives? Was the Apollo programme nothing more than a political football, an expensive round of golf and a course in low-g rally driving? What is there to show for it all beyond a few rocks lying in glass cases around the world?
Was anything really achieved by the Apollo programme besides international prestige?
From the surface of the Moon, Scott said, "… there’s a fundamental truth to our nature. Man must explore. And this is exploration at its greatest." And so it was.
Disregarding the advances in technology that spun off the Apollo programme, the Lunar landings proved that Humans can weather adversity to survive in space. It proved that we can reach other worlds, land on them and return safely. Most of all, it proved that we can meet seemingly impossible goals through ingenuity, courage and dedication.
The greatest part of overcoming any challenge is realising that it can be done.
We now know that we can reach other worlds. There only remains to do it.
That is the legacy of the Apollo missions.
Humans have visited only one body beyond our own Earth, and that for brief periods only. But the story of manned space exploration is far from over, and people from Earth may yet set foot on other worlds, perhaps even worlds in other solar systems.
Those few small steps onto the Lunar surface were the culmination of several programmes intended to develop the technologies and techniques to be used in the Lunar landing missions. While unmanned probes collected necessary data about the destination, manned missions tested the equipment that would carry the Astronauts on their epic journey. These support missions deserve as much attention as the "main event", for without them we would never have set foot on another world.
Apollo 1
In 1967, it seemed like the goal of placing men on the Moon by the decade’s end was in sight. The Gemini programme had reached a successful conclusion, and despite numerous accidents, malfunctions and the explosion of several unmannned rockets on the launch pad, there had been no fatalities during space missions by any nation.
Tragically, that was about to change during the final checks on Spacecraft 12, the prototype Apollo capsule. After a day fraught with difficulties, Astronauts Grissom, White and Chaffee were coming to the end of a series of checks on the craft when telemetry indicated an electrical short in the capsule. Ten seconds later Chaffee reported smelling fire, and the crew initiated the emergency escape procedure.
The flames spread quickly in the pure oxygen atmosphere of the capsule, and despite the best efforts of White on the inside and the pad personnel outside the capsule, the hatch could not be opened. Only 16 seconds after the first warning the cabin was split by an explosion, which caused extensive damage and started fires in the support area around the capsule.
Despite the intense heat, heroic rescue attempts continued. Staff worked in blinding smoke without masks to find the outer hatch release bolts. A technician lifted the middle hatch off and carried it out of the entryway – a task normally requiring the efforts of two men.
Finally the rescuers forced the inner hatchway, to find the bodies of the three Astronauts within. They had all been killed as the cabin ruptured, incinerated by the heat that melted their suits and destroyed the craft around them.
The first humans to die in a spacecraft had not even left the ground.
Apollo 4-6: Unmanned Tests
There was no attempt at a cover-up after the Apollo 1 disaster. Instead, NASA was determined to learn from the tragedy and build a new, safer space vehicle. Between November 1967 and October 1968 unmanned tests were carried out with various components of the Lunar craft.
Apollo 4 was the proving flight for the immense Saturn V launch vehicle and the Apollo craft. Apollo 5 tested Lunar module systems operation in Earth orbit. Apollo 6 was to have been a repeat of the Apollo 4 mission, but failed due to oscillations of the Saturn V first stage during the launch.
Apollo 7
After a tragic year in which five astronauts and one cosmonaut lost their lives in air crashes and Cosmonaut Komarov became the first casualty during a space mission – he was killed when his re-entry system failed - a team of astronauts prepared to make a manned trial of the new Block 2 Apollo capsule. This team was headed by the veteran Schirra and comprised Astronauts Eisele and Cunningham. Their mission was designated Apollo 7.
In defiance of the ghosts hanging around the launch pad, Apollo 7 made a perfect takeoff and reached orbit without major incident. Despite Schirra developing a cold, the mission was a complete success. The separation, turnaround and redocking manoeuvre necessary to withdraw the lunar module from its housing was carried out without incident.
The entire mission was a success, though the Astronauts became increasingly bad-tempered as demands for extra tests and experiments came in from the ground staff. These strained relations were kept hidden while the crew made the first ever series of live broadcasts from orbit.
After 11 days, Apollo 7 returned triumphantly to Earth, and put the moon landings back on course.
Apollo 8
Late in 1968, two Soviets Zond spacecraft completed circumlunar flights with a variety of living things aboard. The possibility existed that a Zond craft could carry a lone Cosmonaut on a similar journey. NASA decided to make sure the first manned circumlunar flight was an American achievement, and accordingly swapped the mission goals of Apollo 8 and 9 around.
Thus it was that Astronauts Borman, Lovell and Anders found their mission brought forward to December 1968. On the 21st they blasted off atop the huge Saturn V rocket and made history by breaking Earth orbit - going where only some flies, meal worms and a couple of turtles had gone before.
The Apollo 8 crew carried out a number of important experiments during their historic flight, including a simulation of the manoeuvre required to orient the Command Service module with the Lunar module, using the third-stage booster as a dummy.
Borman, the mission commander, suffered a brief period of illness suffered which was at first thought to be ‘flu. It was finally blamed on a sleeping pill he had taken. Despite Borman’s slight illness the mission proceeded so well that the decision was taken to enter into Lunar orbit rather than to simply swing around in the Moon’s gravitational field and make a direct return to Earth. This was the default option, built into the flight plan in case of disaster.
The redesigned Apollo Command Service module performed admirably as manoeuvres were carried out to alter its elliptical Lunar orbit to a circular one, and later on the return journey. Despite an accident with the vessel’s computer which erased much of its memory, Apollo 8 succeeded in bring its crew home safely from what was at that time the longest journey ever made by humans.
Apollo 9
Tests with the Lunar Module formed the most vital part of the Apollo 9 mission. The vehicle had been tested on the ground and had made an unmanned flight aboard Apollo 5, but this mission was critical. If the module failed the series of tests planned for it, the 1969 Moon landing goal would be unattainable.
The mission personnel comprised McDivitt (commander), Scott (Navigation specialist) and Schweikart (Lunar Module Pilot).
Despite carrying the largest load to date, the Saturn V launch vehicle placed the mission in orbit flawlessly. The Lunar module was activated and the tricky undock-rotate-redock manoeuvre completed successfully.
On the second and third days of the mission, the crew suffered space sickness but were able to carry out intensive trials with the Lunar Module, including drills for emergency procedures for use if the tunnel between the craft and the Command Service module became blocked. The crew also trialled the backpack life support system to be used by Lunar explorers, as well as an overgarment designed to protect against radiation and micrometeorites.
The climax of the mission was a dry run of the Lunar landing and takeoff evolutions. The Lunar Module was separated and moved into an orbit that would carry the two craft apart. Once a suitable separation was achieved, a simulated Lunar takeoff was carried out. The descent stage was jettisoned and the ascent engine fired to catch up with the Command Service module.
Docking proved difficult for the Lunar Module pilot, whose view was restricted. In future, docking would be the responsibility of the Command Service Module Pilot.
Despite a scare when the Command Service module engine failed to fire, the remaining five days of the mission were something of an anti-climax, ending in a perfect re-entry and splashdown. The entire Apollo 9 mission was characterised by hard work and well-planned success rather than seat-of-the-pants heroics.
Apollo 10
The final mission to be flown before the planned Moon landings, Apollo 10 carried on the work of earlier missions rather than breaking new ground. The crew comprised Stafford (Commander), Young (Command Service Module Pilot) and Cernan (Lunar Module Pilot).
After the climb to orbit and a burn to set their craft on a Lunar trajectory, the crew carried out the tricky undock-rotate-redock manoeuvre to link Lunar and Command Service modules in the correct configuration.
En route to the moon, the crew carried out a series of broadcasts (not all of them scheduled) and performed minor experiments. A major feature of this mission was that the food was better and drinking water was spun to get rid of hydrogen gas, which was thought to have caused space sickness in previous crews.
After four days in space, Apollo 10 entered Lunar orbit and rotated to orbit tail-first. But before the experimental lander flight could be undertaken, the astronauts were forced to engage in a little spring-cleaning. At some point during the mission, parts of the mylar insulation in the docking tunnel had flaked off. When the tunnel was opened, the Command Service module was invaded by small particles, which had to be dealt with before the mission could continue. Ever ready to meet the challenge, specialists at ground control improvised a spacecraft-cleaning procedure using fans and wet towels.
The lander mission suffered further problems. The insulation flakes had blocked the docking-tunnel vents, requiring another backup procedure to depressurise the tunnel so that separation could be achieved. Then, it was discovered that the lander and Command Service modules had slipped out of alignment. Undocking might destroy the clamps and make redocking impossible.
Just before the craft disappeared behind the Moon and lost radio contact, ground control informed the crew that the misalignment was not enough to damage the docking clamps.
Probably.
After an anxious 35 minutes, contact was re-established with not one but two craft. The modules had achieved separation and were flying in close formation. 25 minutes later the Lunar module with Cernan and Stafford aboard began to move away from parent craft, leaving Young very alone in a Command Service module that suddenly seemed very much larger.
The Lunar module descended as planned to within 9 miles of the Lunar surface, photographing the prospective landing sites and most importantly demonstrating that the lunar module could function in its intended environment. Finally the time came to jettison the descent stage and return to the Command Service module. This was an anxious moment. If the ascent engine failed, Cernan and Stafford would become the first men to visit the moon, arriving in a spectacular and fatal manner.
With this unpleasant thought in mind, the crew made to jettison the descent stage. At first, nothing happened. Then the ascent stage shot free and began to run wild. Its rampage lasted less than ten seconds before Stafford brought the craft under manual control, but it caused intense anxiety aboard both craft and at ground control too.
Investigation later showed that the secondary guidance system had been left switched on due to an omission in the checklist. When the ascent stage came free, the guidance system had begun swivelling the craft to look for the Command Service module, causing the frantic moments experienced aboard.
Docking with the Command Service module was achieved almost three hours later, this time conducted by Young rather than the Lunar module crew. After placing the Lander in a safe orbit around the Sun, the three astronauts began the journey home. During this leg of the mission the crew of Apollo 10 achieved another first in space exploration. They shaved off their week’s worth of beard in space before making a perfect splashdown. Their return to Earth set a new record for re-entry speed – 40,000 kph.
With Apollo 10 safely back on Earth, the preliminaries were complete. The equipment worked, the procedures had been shaken down, the crews were ready.
The time had come for humans to walk on another world.
Apollo 11
The crew of the historic Apollo 11 mission comprised Neil Armstrong (Commander), Edwin Aldrin (Lunar Module Pilot) and Collins (Command Service Module Pilot). Collins had missed his slot aboard Apollo 8 due to a loose disc in his neck, which was affecting his reflexes. Choosing to undergo risky surgery to correct the problem, Collins made an amazing recovery, a testimony to his determination to be on the Lunar missions. In fact he might even have been fit in time to fly aboard Apollo 8, but schedules and training were set well in advance. By this curious mix of fortunes, Collins was assigned to "The" mission, though he would not set foot upon the Moon.
Apollo 11 lifted off without incident, despite the risks inherent in launching a vehicle with 12 million working parts into orbit, and after navigation checks the third stage engine fired to boost the craft out of Earth orbit and on course for the Moon.
After performing the tricky flip-over to withdraw the landing module from its housing, the crew settled down for the journey. Many of their tasks during this period were unglamorous "housekeeping" necessary for correct operation of a space vessel. Several TV broadcasts were also made, one of which demonstrated the vast improvement in living conditions enjoyed by the astronauts, especially their food. Aldrin explained a feature of weightlessness to the world, saying that it was great fun to float around but eventually you grow tired of bouncing off the walls and ceiling. He added that jamming yourself into a corner feels more natural.
During the Apollo 11 flight the Soviet Luna 15 robot mission was launched. The Soviets supplied data on the orbit of their probe and assured NASA that their craft would not interfere with radio traffic between ground control and the Apollo mission, which was carrying medals commemorating the dead cosmonauts Gagarin and Komarov. These were to be left on the surface of the Moon in remembrance.
Despite a scare when a small piece of space debris collided with the Command Service module, the mission was proceeding according to plan as Apollo 11 went out of radio contact behind the Moon. The burn to slow the craft and establish Lunar orbit must be carried out during this period of no contact. If anything went wrong, the crew were going to have to deal with it alone.
Apollo 11 came out of radio shadow exactly on time and perfectly on course.
After circularising the orbit and carrying out checks on both craft, Armstrong and Aldrin said farewell to Collins and manned the Lander module, named Eagle. Despite intermittent communications problems, the lander crew were given the green light to begin their descent.
The descent was not without difficulties. The flight computer began registering an overload and the lander looked like overshooting the target area. Warning lights came on, showing less that 5% of the descent fuel remained. If the Eagle did not land in the next 90 seconds, the crew would have to make a dangerous low-level abort.
As the intended moment of touchdown approached, the lander made a series of manoeuvres that worried ground control. It later transpired that the auto-targeting was aiming the craft at a crater filled with huge boulders. Armstrong took over manual control and with Aldrin offering advice attempted to reach a safe landing site with the last of the fuel.
With 20 seconds to abort, the Lunar module touched down in the Sea of Tranquility, the first manned craft to reach the surface of another world.
The Eagle had drifted somewhat from the intended landing site, and the crew were at first unable to give a precise location. Despite this minor glitch, Aldrin and Armstrong prepared for the first moonwalk, donning their bulky pressure suits and life-support backpacks.
Finally, more than six hours after touchdown, the astronauts were ready for their historic first steps onto an alien world. After depressurising the lander module, Armstrong deployed the remote camera and stepped out onto the "porch" of the lander module. The remote camera relayed his image to the waiting world as he stepped onto the Lunar surface.
After accepting a camera from Aldrin, Armstrong made an inspection of the landing site and collected "contingency samples" – a few rocks and some dust – in case the mission had to be terminated early.
Armstrong was joined on the Lunar surface by Aldrin shortly afterward. Together they planted a plaque and a United States flag in the Lunar soil, collected samples and practiced moving around in the low gravity. Among the experiments they deployed was a lunar seismometer and a laser reflector for use in measuring the distance between Earth and Moon.
The EVA finally over (after nearly 3 hours on the Lunar surface), the two astronauts still had to place their samples aboard Eagle, remove their suits and collect all the dead weight – the life-support backpacks and other items which were no longer needed. This was left behind on the Moon to save weight in the ascent module. After briefing Houston about their discoveries, the astronauts were finally able to settle down to sleep.
After a little under 22 hours on the Lunar surface, the Eagle prepared to lift off. This was another critical stage of the mission. No manned craft had ever taken off from the surface of another world. There was one chance to get it right, or Armstrong and Aldrin would become permanent Lunar residents.
The liftoff was flawless. The Ascent Module rose smoothly into the Lunar sky, leaving behind, along with its lower stage and a heap of trash, an Apollo shoulder patch in memory of the three Apollo 1 casualties, and medals commemorating the two dead cosmonauts.
After docking, the crew transferred their samples to the Command Service module and ran checks on their craft. The Lander module was then jettisoned and Apollo 11 broke Lunar orbit, headed homeward.
After splashdown and recovery by the aircraft carrier Hornet, the crew of Apollo 11 and their craft were placed in quarantine in case any harmful organisms had been brought back from the Moon. The samples were taken to the Lunar Receiving Laboratory at Houston, and in due course the astronauts were pronounced free from contamination.
All the work and preparation – and the sacrifices – had not been in vain. Humans had walked on the face of another world, and brought back samples to investigate.
In retrospect, the first Moon landing was achieved more for reasons of international prestige than scientific endeavor. It was a hurried affair of there-and-back. Two men had landed, wandered around for a couple of hours and rushed home with a box of rocks.
Had anything really been achieved by the Apollo 11 mission?
What had been achieved was to prove that humans could reach another world and survive there.
If it could be done, it could be done again.
There was more to come.
Apollo 12
Having achieved President Kennedy’s goal of a Moon landing by the end of the decade, the Apollo programme could slow down a little and take the time to make Apollo 12 a more scientific expedition than its predecessor. Had Apollo 11 failed, there were plans to launch 12 in September 1969. Instead, the mission blasted off in November.
The crew of Apollo 12 comprised three US Navy officers, all holding the rank of Commander: Conrad (Commander), Gordon (Command Service Module Pilot) and Bean (Lunar Module Pilot)
Apollo 12 lifted into a heavy rainstorm, and almost immediately the mission went awry. The craft was struck by lightning. The power surge caused the main electrical system to shut down and the entire warning panel to light up.
As the rocket continued to accelerate out over the Atlantic, the crew struggled to bring their systems back on-line using battery power. Meanwhile the first stage dropped away as the automatic guidance system performed correctly despite the damage.
Amazingly, Apollo 12 reached orbit and after some damage control operations blasted out of orbit en route for the Moon. Despite the damage, the craft’s trajectory was so good that a planned course correction was cancelled.
The detection of a tumbling object following the craft caused some worry, but this was eventually identified as the third stage booster. Otherwise, the next three days passed in relative calm and on 18th November, Conrad and Bean manned the Landing module, named Intrepid. Their target was Surveyor Crater, landing site of one of the Surveyor probes.
Making a perfect landing right on target, the astronauts discovered that their landing site was a great deal dustier than the Apollo 11 site. Conrad descended to the Lunar surface first, collecting contingency samples in case of an early abort. He excitedly pointed out the Surveyor probe just 200m from Intrepid before handing up the samples to Bean.
The astronauts then set up a series of experiments, all powered by a small nuclear generator. These experiments were intended to determine whether the Moon had any atmosphere, ionosphere or magnetic field and to study moonquakes. The dust proved to be a problem, though it also came in handy for weighing down the skirt of the seismometer.
After collecting rock samples and a core sample, the dusty astronauts returned to Intrepid after four hours on the surface. They struggled in vain to get rid of the dust that coated everything, and Conrad suffered an unexpected hazard of planetary exploration – wet feet, resulting from water from his suit cooling system pooling in his boots.
The second EVA started early, as the excited astronauts were unable to sleep for more than a few hours. This excursion involved more geology and a visit to the old Surveyor. Conrad fell over several times while collecting samples, but did not report this to Houston. Fortunately he did not damage his suit.
The Surveyor probe, which had been resting on the Lunar surface for two and a half years, had apparently bounced on touchdown but appeared to be in good shape when the astronauts visited it. They cut off some samples before making their final visit of the EVA, taking samples and photographs of Block Crater.
After clearing the ascent module of dead weight (all except the dust, which the astronauts were unable to get rid of), the landing was at an end and there only remained to return to orbit. After nearly 32 hours on the surface, Intrepid lifted off and made rendezvous with the Command Service Module.
After unloading the samples from the Intrepid (the dust-covered pressure suits were left inside the ascent stage to reduce the amount of lunar dust floating about in the Command Service module), the Lander was jettisoned and allowed to crash on the Moon. The astronauts spent another day continuing the work carried out by Gordon in photographing the Moon.
Even before Apollo 12 began her trans-Earth injection burn, the experimental results were coming in. The seismometer registered a moonquake lasting 55 minutes – an unheard-of duration on Earth.
The astronauts had a final treat in store on the way home; their flight path put the Earth between them and the Sun, causing a total eclipse. Soon after witnessing this incredible sight the Command module plunged into the atmosphere to make splashdown in the Pacific Ocean.
Recovered by the aircraft carrier Hornet, the crew spent 16 days in quarantine but suffered no ill effects from breathing Lunar dust all the way home. The mission also brought home the only living things ever found on the Moon. These were microorganisms found in the Surveyor equipment salvaged by the astronauts, which had originated on Earth and amazingly survived the journey and long isolation on the Moon. They had of course got in while Surveyor was being constructed.
The Apollo 12 mission was an incredible achievement from a mission that started so badly. The scientific data was of incalculable value, and the precision landing beside Surveyor showed that missions could be sent to more scientifically interesting, but rugged, areas.
The stage was set for even greater things.
Apparently.
Apollo 13
The climate was changing as Apollo 13 readied for launch. The public were losing interest in Moon missions, budget cuts were beginning to bite, and enthusiasm for space exploration was waning fast.
Against this backdrop, preparations for the mission went ahead with a greater than usual amount of problems. One of the two Command Service module oxygen tanks would not drain properly, but was retained as this would not affect the mission. Other relatively minor glitches were fixed as fast as they cropped up as the engineers struggled to meet the launch date of April 11th 1970.
Less than a week before launch it became necessary to drop Mattingly (Command Service Module Pilot) from the crew after it became apparent that he had been in contact with German Measles, to which he had no resistance. Rather than swap the prime and backup crews, it was decided that Swigert (the backup crew pilot) would take his place. The last few days before launch saw the crew undertaking a hurried series of simulations to establish the effective teamwork so vital to a successful space mission.
Along with newcomer Swigert, the crew of Apollo 13 comprised the experienced Lovell as Commander and Haise as Lunar Module Pilot. The team shook down satisfactorily despite the rush. Apollo 13 blasted off on April 11th, heading for the Fra Mauro uplands. The launch attracted far less public interest that the two previous Moon landing missions.
Apollo 13’s troubled voyage began during launch, when the second stage cut out two minutes early. By firing the other engines for an extra few seconds the situation was returned to normal. The astronauts made a TV broadcast and prepared to continue with the mission.
There was no real cause for concern. The mission was less than a minute behind schedule and had not used up an excessive amount of fuel. No space mission is without technical difficulties, and if this was as bad as Apollo 13 was going to get, it would be a fine mission.
With docking and extraction of the Lunar module completed, the mission proceeded well for 3 days. Public interest was limited, even during the critical manoeuvres. The biggest worry aboard was over Swigert’s income tax forms, which he had forgotten to file in the hurry to join the mission.
Minor problems presented themselves as the mission continued, and on one occasion the master alarm early in a sleep period brought all three crewmen hurrying to the cockpit searching for the cause. But so far, so good – it was a false alarm. Another TV broadcast showed the crew in good spirits, making jokes about the drinking bags they would use inside their helmets during the moonwalk and warning viewers about "funny noises" that might result.
Ten minutes after the broadcast ended, disaster struck and one of humanity’s greatest adventure stories began to unfold.
A warning light came on at Mission Control, showing low pressure in a hydrogen tank. There had been intermittent problems with the tanks throughout the mission, and the solution was simple. Swigert was instructed to switch on the fans that would stir the tanks.
Unknown to the crew or Mission Control, the insulation on some of the fan wiring was very thin. This was due to overheating during the drainage problems encountered weeks before. Sixteen seconds after the fans were switched on, an arc jumped between the wires, causing a fire in the oxygen tank. This rapidly spread throughout the bay before escaping oxygen and fumes from the burning insulation blew out the outer hull panel. This allowed the gas to vent into space and probably saved Apollo 13 from immolation.
However, it also threw the craft off course and caused a power drop in main bus B (one of the two major power circuits). With the master alarm sounding and no real idea of what had happened, Swigert informed Mission Control with the now-immortal words, "OK, Houston, we’ve had a problem."
At first it was unclear what had happened, or how serious the problem was. Instruments were reading a range of faults and unsafe levels of pressure and temperature. It was not even clear what had caused the power drop. At this time, the main concern was whether the moon landing was still possible.
Then Lovell reported that oxygen tank 2 was reading zero pressure and 1 was dropping. This oxygen was needed not for the crew to breathe but also for water and to power the fuel cells that supplied electricity to the craft. It became apparent that not only were the astronauts not going to be landing on the Moon, they might well not be going home, either.
Lovell then reported that the craft was venting gas, which was causing vibration and sending the vessel off course despite the manual control being applied.
Still trying to determine the nature of the problem, ground control began looking for anything that seemed to be normal among Apollo 13’s system readouts. There was nothing. Two of the three vital fuel cells were dead and the output of the other one was dropping, communications were patchy and the oxygen level in the remaining tank was falling.
The crew began powering down systems in the Command Service module, saving what power remained for vital systems. They also connected main bus A to the re-entry battery to boost the available power, but were told by ground control to disconnect it. If it became discharged the crew would certainly die during re-entry – assuming they made it that far.
It was by now clear that the only chance for the three astronauts was to use the Lunar module as a liferaft. There was no chance of simply reversing direction, so the crippled spacecraft would have to be put back on a free-return trajectory and allowed to swing around the Moon to commence its homeward journey. With the Command Service module out of action, the life support systems and descent engine of the Lander offered the only hope. The posed a new problem. The Lander was designed to support two occupants for perhaps 50 hours. It would have to sustain three for nearly 100.
To meet this challenge, experts from the firms contracted to supply components of the spacecraft were placed on constant call. An analysis team was set up at Mission Control to come up with solutions to technical problems – hopefully before they occurred.
The crew of Apollo 13 powered up the Lunar module and calibrated its guidance system. They were now totally dependent upon the Lander to keep them alive and get them home – they would only re-power the dark and silent Command Service module for re-entry.
Six hours after the crisis began, Lovell manually fired the descent engine in the first of two burns. This one was to place the craft on a return trajectory around the back of the Moon. The second would accelerate the craft enough to make it home before the air ran out.
Spirits rose a little among the crew. They might burn up in the atmosphere or die of suffocation along the way, but at least Apollo 13 would bring them home. Better that than being lost forever in the deeps of space.
As Apollo 13 cleared the Moon and prepared for the second burn, experts at ground control were still debating the how to make the best use of the available resources. Ideas such as jettisoning the Service Module component of the craft, leaving only the mass of the Lander and the Command module, then burning the available lander fuel at full throttle were rejected as too risky. In the end a slower, steady acceleration was settled upon, which would make the journey a whole day longer but left more margin for error.
With severe damage and only half a set of thrusters, plus most of the instruments powered down, controlling the craft was extremely difficult. Just keeping the craft stable long enough for a position sighting to be taken was a major undertaking, but eventually the burn was completed. However, ground control were dismayed to notice that Apollo 13 was still drifting off course.
Conditions were becoming worse in the craft, too. The temperature was down to 10° C and carbon dioxide levels were very high. The latter problem was solved with a jury-rigged device made from a hose and one of the Command Service module’s lithium hydroxide canisters.
As Apollo 13 approached Earth, it became necessary to correct the drift and place the craft on a trajectory that would hit the narrow re-entry window. Even a slight variation in speed or angle of approach would prove fatal as the craft skipped off the atmosphere into deep space or burned up.
The tricky deceleration burn was handled as a three-man operation. Lovell kept the craft aligned correctly using a set of cross-hairs and the few working thrusters. Swigert timed the burn and Haise fired the Lander engine. All three astronauts were so fatigued by this time that they became confused as to whether they were seeing the Earth or the Moon out of the cockpit window.
They were also suffering from the cold and damp – it was down to 3° C in the Command Service module, and were so short of water that they had only 20% of the normal minimum requirement to drink each day. Despite their suffering, the crew continued with the mission as best they could, transferring the film they had shot while passing the Moon to the Command Service module and stowing non-essential items in the Lander.
Final preparations continued. The Command Service module batteries were charged from the Lander and Mattingly, who had not developed German Measles, worked through the re-entry in the simulator and read the checklist up to his colleagues. There were worries that the separation of the Command Service and Lunar modules might cause another course shift, and a final correction was planned accordingly.
With less than ten hours to re-entry, the crew powered up the Lander and began to defrost the thrusters. The Service module was then jettisoned, leaving only the tiny Command module linked to the Lander. The astronauts were able to view the damage to their Service module as it broke away, and expressed amazement that the craft had survived at all.
The extent and nature of the damage raised a new question – had the heat shield been damaged by the explosion? If it had, the crew would not survive re-entry.
Finally, there only remained to check orientation – it was perfect – and jettison the Lander. The crew took photographs of their life-saving craft until it disappeared from view.
90 minutes later, Apollo 13 re-entered Earth’s atmosphere. A final message from the crew thanked the staff and advisors on the ground for all their efforts and then there was nothing to do but hope or pray. Either the heat shield would hold or it would fail.
Millions of people – less blasé about Moon missions now – were glued to their TV or radio sets as Apollo 13 entered the radio blackout phase of descent. The blackout seemed to go on forever. The expected moment of contact passed with no sign of the astronauts. Another half minute crawled by. Hope began to turn to despair. To have come so close….
Then Apollo 13 came out of radio blackout, giving the world a final piece of theatre as she opened her parachutes in full view of the rescue carrier. It was the most accurate splashdown to date.
The Apollo 13 mission was a failure in that it did not achieve its goal of landing men on the Moon to conduct more experiments. However, in another way it was a monumental success. Lessons were learned about survivability of spacecraft, resulting in design changes to future craft. A public grown complacent about space missions were given some new drama to provoke interest.
But most of all, against all the odds, Lovell, Haise and Swigert came home.
Apollo 14
The crew of the Apollo 14 mission was headed by Shepard, America’s first man in space, accompanied by Lunar Module Pilot Mitchell and Command Service Module Pilot Roosa. Theirs was the first of a new series of Lunar missions aimed at exploring more of the surface and developing a greater understanding of the nature of our satellite. This mission was aimed at the Fra Mauro uplands, destination of the ill-fated Apollo 13.
It was an improved Apollo vehicle that blasted off in January 1971. Not only was the craft itself redesigned with safety in mind but launch procedures had been tightened too. A 40-minute hold was required to allow the weather to clear – another lightning strike was not desirable. In the event the rocket functioned perfectly.
The docking of Command Service module and Lunar module proved to be a problem, but after several frustrating attempts Roosa was able to complete the manoeuvre. Ground control theorised that ice might have formed on the docking clamps during the launch, preventing them from latching. The mission was soon back on course, though a series of minor faults and problems kept the crew from becoming complacent.
Apollo 14 entered a lower Lunar orbit than had previously been used, in order to conserve Lander fuel. As Lunar mountains appeared on the horizon, they appeared to be higher than the orbiting craft, a disconcerting sight which was fortunately only an optical illusion.
Shortly after the Command Service and Lunar modules separated, a computer fault triggered the Abort sequence aboard the Lander. Mission Control was eventually able to bypass this system, allowing the mission to proceed. Them, during the descent, the landing radar ceased to function, leaving Shepard and Mitchell with no means of determining their altitude. After some frantic work by Mitchell, the radar began to work again and the Lander touched down safely close to the target area.
On the Lunar surface, Shepard and Mitchell deployed a main package of six instruments plus several minor ones, including a set of geophones and explosive charges intended to study the Lunar crust. This package failed to work properly, causing frustration.
A second moonwalk was aimed at exploration. The astronauts visited several prominent landmarks and craters around the landing site, wheeling a specially-designed handcart with them to carry tools and samples. This device caused an unexpected problem. During the bumpy ride over the surface, items would be bounced off it and the wheels began to stick in the dust. Eventually the astronauts resorted to carrying the cart and its contents.
As the astronauts returned to the Lander module, Shepard produced a six iron and several golf balls. Despite the bulky suit he succeeded in sending golf balls for a considerable distance over the rocky Lunar surface. The longest shot travelled about 400 yards.
The Lander then returned without incident to the Command Service Module, where Roosa had been conducting a number of experiments. These were continued after the return of Shepard and Mitchell. NASA was interested in the manufacturing possibilities inherent in weightless conditions.
Apollo 14 returned home for recovery, and the crew were found to be in good physical condition as they entered the quarantine facility. They were the last Apollo crew to do so. The facility was dispensed with on future missions as unnecessary. There was nothing living, harmful or otherwise, on the surface of the Moon.
Apollo 15
The Apollo 15 mission, comprising Scott (Commander), Irwin (Lunar Module Pilot) and Worden (Command Service Module Pilot), was a geological field trip intended to discover the nature of the Moon’s core – was it still active, like Earth’s, or solid? The astronauts underwent intensive training as geologists in addition to their mission preparation.
The public remained uninterested in Moon missions, despite the fact that this one was the largest yet. Among the equipment aboard the Lander was a new device, the "moon buggy" or Lunar Rover. This battery-powered vehicle folded for transport and used a similar motive system to the Soviet Lunokhod rovers. It was hoped that the vehicle, combined with a less bulky pressure suit, would facilitate greater mobility on the surface.
Although the launch site was struck several times by lightning in the days preceding the launch, the liftoff itself was without problems. The Saturn V rocket, which had been upgraded to handle the extra weight, functioned flawlessly. This good fortune continued as Apollo 15 entered its trans-lunar phase. This course was slightly different from that of the other Apollo missions as the destination was far from the Lunar equator. It was also a no-return orbit, meaning that if the engines failed to fire the craft would not swing around the Moon and return unpowered to Earth orbit but would instead wander off to be lost in deep space.
No space mission is complete without a few malfunctions and minor crises. In Apollo 15 it was the electrical system that provided most of the drama. A short-circuit threatened to activate the main engine and later a false master alarm caused grave concern. The astronauts also had to turn plumber to fix a water leak, but otherwise Apollo 15 proceeded smoothly.
In Lunar orbit, the crew deployed an extensive instrument package including a laser altimeter and spectrometer. Worden was to continue collecting data using these devices during the Landing phase of the mission.
A loose power connection caused problems as the Lander and Command Service modules separated, but only a few minutes behind schedule Worden boosted the Command Service module into a higher orbit as Scott and Irwin began their descent.
The landing was a little rough. Lunar dust blinded the craft, forcing Scott to make an instrument touchdown with one landing foot in a small crater. After a preliminary look around, the astronauts began describing the features nearby for the benefit of the geologists back home.
After a few hours’ rest the astronauts ventured outside and unfolded the moon buggy. This proved top be quite a struggle, and even when the job was completed the front-wheel steering would not work. Scott began the drive using only the rear-wheel steering. Despite the rough ride, the buggy made it possible to cover a lot of ground, albeit in bouncy and uncomfortable fashion.
After collecting many geological samples, the astronauts returned to the Lander and deployed the Experiment Package. Attempts to sink tow heat-flow probes 10 feet into the Lunar soil failed. The ground was so dense that the drill would only penetrate to a little over five halfway. In the end they stuck the probes in and hoped for the best.
The second moonwalk began late, as the astronauts had to mop up spilled water from a leak and repair Irwin’s suit antenna before beginning. It was a welcome surprise to find that the front-end steering on the moon buggy had spontaneously decided to work. The buggy carried Scott and Irwin to a new site where they collected more samples. Some of these were pale green glass thought to be Lunar core fragments. After another attempt to drill holes for the heat-flow probes, the astronauts returned to their craft.
The third and final moonwalk took Scott and Irwin to the top of Hadley Rille after a strenuous battle to extract a sample core drilled on the first day. From the top of the rille they were able to film and sample the lava flows and bedrock nearby, delighting the geologists at mission control.
Shortly before takeoff Scott franked the first stamps of a new issue commemorating the US space programme and demonstrated that Galileo had indeed been correct when he theorised that a hammer and a feather would fall at the same rate without air resistance to slow them.
After parking the moon buggy where its camera could film their takeoff, the astronauts placed a plaque commemorating the 14 Astronauts and Cosmonauts who had died since the beginning of the space programme.
The Command Service module remained in orbit for two more days to complete the orbital experimentation programme carried out by Worden. After launching a small satellite into Lunar orbit, the Command Service Module began the voyage home. During the trip Worden stepped into the limelight to make an EVA, retrieving film cassettes from the instrument bay.
Apollo 15 returned to Earth without further incident after a highly successful mission.
Apollo 16
The Apollo 16 mission suffered several accidents during the preparation phase, then had its launch postponed due to the illness of the Lunar Module Pilot, Duke. Finally, on April 16th 1972, the mission blasted off under the command of the veteran Young, accompanied by Duke and Command Module Pilot Mattingly, who had missed Apollo 13 due to suspected illness.
As usual, there were problems. Twice the master alarm sounded as the navigation platform locked up due to a short circuit. Despite this, Apollo 16 entered Lunar orbit and conducted a survey from orbit as Young became the first man to orbit the Moon on two missions.
The Lander caused more problems during preparation, but finally the two craft moved apart. As Mattingly prepared to move the Command Service module into a higher orbit, a fault in the engine nozzle motor manifested itself. With the craft in Lunar orbit, there was no way to get home if the engine was not controllable. The landing was postponed, leaving Young and Duke waiting helplessly aboard the Lander while the engineers at ground control tried to sort out the problem.
Finally the decision was taken to proceed with the landing. The main engine should still function correctly, the engineers thought. Young and Duke began their descent from the highest altitude to date, with an antenna that functioned only intermittently.
Despite their difficulties, the astronauts made a flawless landing on the Descartes plateau. Overhead, Mattingly nudged the Command Service module into a higher orbit. So far, the engine was performing well, but the engineers were still concerned.
On the Lunar surface, Duke and Young rested before commencing their moonwalk. Duke’s drinking bag began to leak, giving him an orange-juice shampoo inside his helmet, but the astronauts pressed on. They set up the moon buggy and cameras and deployed the experiment package.
Unlike Apollo 15, there was no problem obtaining a core sample or in drilling a deep enough shaft to deploy the heat flow probes, but Young tripped over the power cables for the probes and broke them. Unable to repair the damage, the astronauts were forced to abandon the experiment.
Next, Young and Duke boarded the moon buggy for a sample-collection trip and Young played rally-driver, sliding the rover around and generally enjoying himself. Normally laconic, in his exuberance he was even moved to parody Neil Armstrong’s famous speech. Indicating Charles Duke (who was much taller than Young) he announced to the world, "One small step for Charlie is a giant leap for me!"
The second moonwalk too place some hours later. This time Duke drove, and he too was possessed with a desire to throw the rover around. His driving was so violent that Young complained and some of the rover instruments broke, but the vehicle continued to function.
This trip allowed the astronauts to collect a large amount of rock samples and measure the Lunar magnetic field. After 71/2 hours they returned to the Lander and gave the world an insider view of space exploration as they discussed digestive problems caused by potassium in their drinks in front of a mike they thought was turned off.
A third moonwalk collected more samples but could not find any evidence of volcanic activity, which had been predicted in the region. The astronauts returned to the Lander to perform for the cameras one last time, jumping around and throwing objects in the low gravity. Duke fell on his back but did not damage his suit.
As Mattingly fired the Command Service module engine again to lower his orbit for pickup, ground control watched anxiously, but the rendezvous went according to plan. Houston had decided to shorten the post-landing phase of the mission, and asked the crew to jettison the lander before resting. The tired astronauts incorrectly set the controls. Instead of descending to crash on the Lunar surface (providing a shock for the seismographs to pick up) like all the other ascent modules, the Lander almost collided with the Command Service module forcing Mattingly to fire the suspect main engine in an emergency manoeuvre. The ascent module eventually crashed on the Moon.
After deploying a small satellite, Apollo 16 broke orbit for home. The engine continued to function correctly and two days into the flight Mattingly repeated Worden’s EVA to retrieve instrument-bay film cassettes. At the same time the crew conducted an experiment involving the exposure of biological samples to cosmic rays.
Apollo 16 made a good re-entry and an extremely accurate touchdown.
The mission continued to be a success even after the astronauts returned to Earth. A remote-controlled device left behind on the Moon caused and registered several shocks, allowing further study of the Moon’s crust.
Apollo 17
Data collected by the earlier Apollo missions suggested that the Lunar highlands were where answers would be found as to the nature of the Moon’s core and its history. For this reason the destination of the final Apollo mission was chosen as the region between the Littrow crater and the Taurus mountains. It was also decided to send a scientist on this mission in the place of one of the astronauts.
The crew of Apollo 17 comprised Cernan as commander, making his second Lunar mission, and Evans as Command Service module pilot. The Lunar Module pilot’s berth was taken by Dr Schmitt, a geologist.
The mission ran into trouble on the launch pad. With just 30 seconds to go the third stage oxygen tank refused to pressurise. Ground crews struggled to overcome the problem and finally the huge rocket blasted off.
In order to make up time, Apollo 17 was boosted onto a no-return trans-Lunar course. Engine failure would mean slow death in deep space for the crew, but despite a series of false master alarms the rocket functioned perfectly.
While Evans raised the Command Service module into a higher orbit, Cernan and Schmitt made the descent to the Lunar surface without incident. They unfolded the moon buggy then Cernan deployed a US flag. This one had hung in the Mission Operations Control Room since the first Lunar landing mission, and now Cernan placed it on the Lunar surface in memory of the hard work and ingenuity that had made the missions possible.
Cernan and Schmitt then deployed the instrument package, which included more heat flow probes and advanced seismic sensors. Drilling the probe shafts and obtaining a core sample was hard work and took longer than expected. Ground control thus made some changes to the EVA schedule. Samples were collected from Steno crater, then the astronauts made their way back to the Lander for a rest. Both were filthy – Schmitt had fallen over several times and a broken fender on the moon buggy allowed dust to spray over the passengers.
On the second day, the rover was repaired with a makeshift fender. This was constructed from lunar maps, emergency lighting clips and some tape. It worked, even if it wasn’t pretty.
Making a long drive to the South Massif, Cernan and Schmitt collected samples and studied the debris of a landslide. Stopping at Lara and Shorty craters on the way back, searched for evidence that either had ever been a volcanic vent, which some scientists believed likely. Orange soil around Shorty crater provoked a flurry of scientific interest – it might be evidence of water or volcanic activity. After taking samples the astronauts made their way back to the Lander. These samples later yielded the truth about the orange soil. The colour was due to concentrations of titanium, the position due to a meteorite impact. Scientists were disappointed with the answer, but thanks to Apollo 17 at least they had one.
The third EVA was in the direction of the North Massif. The rugged terrain caused some damage to the rover, but the astronauts were able to reach their goal. They were not able to find evidence of any volcanic activity despite an exhausting search.
With a huge amount of samples aboard, the Ascent module was above her takeoff weight. Despite the extra load, the craft made a perfect rendezvous and docked with the Command Service module on the second attempt. Communications became patchy during the ascent, requiring Evans aboard the Command Service module with only five mice for company (they were part of a cosmic ray experiment) to act as a relay.
After two more days conducting experiments in orbit, the three men and five mice that formed the crew of Apollo 17 began the journey home. Evans performed his EVA to retrieve the film cassettes. Despite worries over a pair of scissors lost somewhere in the craft and potentially presenting a hazard, the Command module made a perfect re-entry with Evans trying out a special pair of trousers designed to prevent blood pooling in the legs.
As Apollo 17 hit the Pacific, the Moon Landings came to an end.
Retrospect: The Manned Moon Landings
We went to the Moon and we came back. The planned follow-on orbital laboratory failed to materialise and there have been no more manned missions to other worlds.
Was there really any point to all the expense and risk to human lives? Was the Apollo programme nothing more than a political football, an expensive round of golf and a course in low-g rally driving? What is there to show for it all beyond a few rocks lying in glass cases around the world?
Was anything really achieved by the Apollo programme besides international prestige?
From the surface of the Moon, Scott said, "… there’s a fundamental truth to our nature. Man must explore. And this is exploration at its greatest." And so it was.
Disregarding the advances in technology that spun off the Apollo programme, the Lunar landings proved that Humans can weather adversity to survive in space. It proved that we can reach other worlds, land on them and return safely. Most of all, it proved that we can meet seemingly impossible goals through ingenuity, courage and dedication.
The greatest part of overcoming any challenge is realising that it can be done.
We now know that we can reach other worlds. There only remains to do it.
That is the legacy of the Apollo missions.
Commercial Space Exploration
The future is reasonably encouraging. The national space agencies are continuing with probe investigations of Mars and the Moon, which may lead someday to Lunar colonies and bases in the outsystem.
But the real future of space exploration lies in the corporate world. Numerous corporations are involved in space launches or component fabrication for the space industry. Without massive national budgets to spend, these private organisations have a strong incentive to make their operations cost-effective and efficient.
It may be that this drive towards cost-effectiveness will show that space exploration and exploitation is economically viable. The opportunities in space are limitless. Weightless fabrication, asteroid mining, rare-materials prospecting… even orbital hotels. It remains for a visionary company to show that big money can be made in space.
And once that is proven, business will lead the way to the stars.
But the real future of space exploration lies in the corporate world. Numerous corporations are involved in space launches or component fabrication for the space industry. Without massive national budgets to spend, these private organisations have a strong incentive to make their operations cost-effective and efficient.
It may be that this drive towards cost-effectiveness will show that space exploration and exploitation is economically viable. The opportunities in space are limitless. Weightless fabrication, asteroid mining, rare-materials prospecting… even orbital hotels. It remains for a visionary company to show that big money can be made in space.
And once that is proven, business will lead the way to the stars.
