In Orbit
It is quite alarming to discover how many people think that a "Satellite" is a dish-shaped object to be found on the side of a house; just like a "microwave" is a device for heating pies rather than a range of electromagnetic wavelengths. This is one of the effects of progress; technical terms pass into common usage until their precise meaning becomes blurred.
Correctly speaking, a body that is held in an orbital path around another is termed a satellite. Even this is an oversimplification, since the two objects in fact orbit a common point, though in the case of artificial satellites, the gravitational effect of the satellite on planet Earth is rather slight - so much so that there is no noticeable perturbation of Earth’s orbit.
Our one and only natural satellite, the Moon, is sufficiently massive to have a noticeable effect on Earth. Nothing humans have ever managed to put in orbit has enough mass to cause any measurable effects, but each and every object - space stations, weather satellites, debris jettisoned from space vehicles, even the occasional dropped spanner, is technically a satellite.
However, in order to make a useful distinction, we will refer to a satellite as an artificial object deliberately placed in orbit to carry out some function (e.g., scientific experiments, weather observation or communications). Space Stations are those satellites designed to support a human crew for an extended period. Manned vehicles carrying out various missions are not considered to be satellites here, and neither is the vast assortment of space junk orbiting our planet.
Correctly speaking, a body that is held in an orbital path around another is termed a satellite. Even this is an oversimplification, since the two objects in fact orbit a common point, though in the case of artificial satellites, the gravitational effect of the satellite on planet Earth is rather slight - so much so that there is no noticeable perturbation of Earth’s orbit.
Our one and only natural satellite, the Moon, is sufficiently massive to have a noticeable effect on Earth. Nothing humans have ever managed to put in orbit has enough mass to cause any measurable effects, but each and every object - space stations, weather satellites, debris jettisoned from space vehicles, even the occasional dropped spanner, is technically a satellite.
However, in order to make a useful distinction, we will refer to a satellite as an artificial object deliberately placed in orbit to carry out some function (e.g., scientific experiments, weather observation or communications). Space Stations are those satellites designed to support a human crew for an extended period. Manned vehicles carrying out various missions are not considered to be satellites here, and neither is the vast assortment of space junk orbiting our planet.
Satellites
Many of the early missions – manned and unmanned – were simply "space lobs" in which an object reached sub-orbital height for a brief period in order to conduct an experiment. Now that orbital insertion is commonplace – how many successful satellite launches make the news? – sub-orbital missions are less common. While it is a little cheaper to dispense with an unnecessary insertion manoeuvre, the far longer life span of a satellite in a stable orbit makes multiple experiments and long-term deployments more economically viable.
There are many reasons for wanting to send an object into orbit. So many, in fact, that commercial satellite launches are common. No longer are orbital launches the exclusive province of the great world power; private corporations now offer a launch service to any company wishing to purchase space on a launch vehicle.
Treaties banning certain military applications of space technology also have implications for commercial activity in space, but for the most past the "high frontier" is a marketplace like any other. There is really no difference between a 1999 firm paying Sea Launch to place a TV satellite in orbit and a 1700 firm paying a shipping firm to fetch tea from India. The technology is different; the principle is the same.
Of course, just as India is not one place – our 1700 firm would do well to specify which of India’s many ports the tea was to be picked up from – and neither is "orbit". Orbit is any stable path outside the atmosphere, within Earth’s gravity well. If a satellite is to be any use, its position must be precisely defined. Several factors determine a satellite’s orbital characteristics.
Altitude
The altitude of an orbit determines the speed at which an object must travel to maintain that orbit. If the object is travelling faster than the required speed for a particular orbit, it will rise into a higher one or leave orbit entirely. Slower, and the satellite drops to a lower orbit or falls back to earth. Velocity changes of just a few metres per second cause large changes in orbital altitude, so orbital corrections are done slowly and carefully to avoid expensive satellites shooting off into deep space or burning up in the atmosphere.
An orbital path can be more or less circular about a central point, or can take the form of an elongated ellipse. Assuming for a moment a perfectly circular path, the distance a satellite must travel to complete a 360° revolution is thus determined by the formula 2p R, where R is the radius of the circle (the distance of the satellite from the centre of the earth). Given that a particular velocity must be maintained in order to keep the satellite in orbit at a particular altitude, it can be seen that the orbital period (i.e. the time taken to make a complete 360° circuit) is defined by the altitude of the satellite. If a particular orbital period is required for the satellite to carry out its mission, then the altitude of the satellite must be appropriate. Likewise, if a particular altitude is required then the orbital period is also fixed.
Of course, the Earth is spinning on its axis while the satellite is orbiting above, so the orbital period is not relative to a point on the ground but to an imaginary fixed point in space. The same point on the Earth’s surface will not be beneath the satellite each time it completes an orbit, except in one very special case.
A satellite placed in an orbit such that it is always above the same point on the earth’s surface – a Geostationary orbit – must orbit at such a height that its orbital velocity is the same as the rate at which the Earth rotates on its axis. This occurs at an altitude of about 33,000 km – quite a high orbit. This application is most useful for communications satellites, which must of course orbit in the same direction as the Earth’s rotation.
An object in a higher orbit will orbit will be "outrun" by the Earth’s surface, while in a lower orbit the satellite will race ahead of an observer on the ground.
Inclination
Orbital inclination is an important factor. A satellite launched due East on the equator will go into a true geostationary orbit if placed at the correct height – it will remain above exactly the same point on the Earth’s surface. If launched from a point, say, 23° north of the equator, the satellite’s path will describe a path which seems to wander between 23° North and 23° South. A satellite placed in a 33,000km orbit which is not directly above the Equator will seem to describe a figure-8 as observed from the ground. Such an orbit is termed Geosynchronous rather than Geostationary. The period is the same; only the orbital inclination differs.
Eccentricity
Orbital paths vary from almost circular to extremely elliptical. It is not possible to place an object into a completely circular orbit, though it is possible to come very close. Minor irregularities in the shape and mass distribution of planet earth cause small fluctuations in the gravity force experienced by the satellite, causing minor orbital irregularities which must be compensated for periodically.
The eccentricity of an orbit is a measure of how elliptical the orbital path is – how far it varies from a perfect circle. An object in an elliptical orbit will pass through a low point – Perigee - at its closest approach to Earth and a high point – Apogee – at its most distant.
An eccentric orbit is sometimes desirable. Operators of a spy or communications satellite can maximise time over the target area by having the satellite reach apogee over the target and perigee on the opposite side of the planet. Thus the satellite seems to "hang in the sky" over the target and is thus available for longer periods before apparently plunging around the back of the planet in minimal time.
Direction
Satellites and other space vehicles are generally launched due east, in the direction of earth’s rotation. This is because an object on the surface of the planet is by definition moving at the same velocity as the planet. This velocity provides a sizeable component of the speed required to reach orbital velocity – at the equator this "free velocity" is about 0.47km/sec out of a required 8 km/sec. Farther from the Equator, the amount of velocity thus gained is reduced.
If a due-East launch is not desired, the amount of "free velocity" falls off as the angle between the launch direction and due East increases. A satellite launched at right angles to the Earth’s direction of rotation – directly North or South – gains no benefit from the Earth’s rotation and must gain the whole of its orbital velocity from thrust. Such an orbit is described as a Polar Orbit and might be useful for a survey satellite as the groundtrack – the points directly beneath the satellite – covers all latitudes and moves over the entire surface of the Earth due to the planet’s rotation.
A satellite launched in a westerly direction enters what is known as a Retrograde orbit. Since the planet is spinning in the opposite direction, such a satellite seems to zip around the planet very quickly. Launching a satellite into a retrograde orbit carries a velocity "penalty" in the same manner as launching Eastwards gains a bonus. Since the launcher is moving at about 0.47km/sec in an easterly direction, and the satellite needs to attain a velocity of 8km/sec in a Westerly direction, it in fact needs to gain nearly a whole 1km/sec more than a satellite launched in the opposite direction – about 12% more velocity. This translates to increases in the power of engines and the amount of fuel needed, and in turn to an increase in cost.
There are many reasons for wanting to send an object into orbit. So many, in fact, that commercial satellite launches are common. No longer are orbital launches the exclusive province of the great world power; private corporations now offer a launch service to any company wishing to purchase space on a launch vehicle.
Treaties banning certain military applications of space technology also have implications for commercial activity in space, but for the most past the "high frontier" is a marketplace like any other. There is really no difference between a 1999 firm paying Sea Launch to place a TV satellite in orbit and a 1700 firm paying a shipping firm to fetch tea from India. The technology is different; the principle is the same.
Of course, just as India is not one place – our 1700 firm would do well to specify which of India’s many ports the tea was to be picked up from – and neither is "orbit". Orbit is any stable path outside the atmosphere, within Earth’s gravity well. If a satellite is to be any use, its position must be precisely defined. Several factors determine a satellite’s orbital characteristics.
Altitude
The altitude of an orbit determines the speed at which an object must travel to maintain that orbit. If the object is travelling faster than the required speed for a particular orbit, it will rise into a higher one or leave orbit entirely. Slower, and the satellite drops to a lower orbit or falls back to earth. Velocity changes of just a few metres per second cause large changes in orbital altitude, so orbital corrections are done slowly and carefully to avoid expensive satellites shooting off into deep space or burning up in the atmosphere.
An orbital path can be more or less circular about a central point, or can take the form of an elongated ellipse. Assuming for a moment a perfectly circular path, the distance a satellite must travel to complete a 360° revolution is thus determined by the formula 2p R, where R is the radius of the circle (the distance of the satellite from the centre of the earth). Given that a particular velocity must be maintained in order to keep the satellite in orbit at a particular altitude, it can be seen that the orbital period (i.e. the time taken to make a complete 360° circuit) is defined by the altitude of the satellite. If a particular orbital period is required for the satellite to carry out its mission, then the altitude of the satellite must be appropriate. Likewise, if a particular altitude is required then the orbital period is also fixed.
Of course, the Earth is spinning on its axis while the satellite is orbiting above, so the orbital period is not relative to a point on the ground but to an imaginary fixed point in space. The same point on the Earth’s surface will not be beneath the satellite each time it completes an orbit, except in one very special case.
A satellite placed in an orbit such that it is always above the same point on the earth’s surface – a Geostationary orbit – must orbit at such a height that its orbital velocity is the same as the rate at which the Earth rotates on its axis. This occurs at an altitude of about 33,000 km – quite a high orbit. This application is most useful for communications satellites, which must of course orbit in the same direction as the Earth’s rotation.
An object in a higher orbit will orbit will be "outrun" by the Earth’s surface, while in a lower orbit the satellite will race ahead of an observer on the ground.
Inclination
Orbital inclination is an important factor. A satellite launched due East on the equator will go into a true geostationary orbit if placed at the correct height – it will remain above exactly the same point on the Earth’s surface. If launched from a point, say, 23° north of the equator, the satellite’s path will describe a path which seems to wander between 23° North and 23° South. A satellite placed in a 33,000km orbit which is not directly above the Equator will seem to describe a figure-8 as observed from the ground. Such an orbit is termed Geosynchronous rather than Geostationary. The period is the same; only the orbital inclination differs.
Eccentricity
Orbital paths vary from almost circular to extremely elliptical. It is not possible to place an object into a completely circular orbit, though it is possible to come very close. Minor irregularities in the shape and mass distribution of planet earth cause small fluctuations in the gravity force experienced by the satellite, causing minor orbital irregularities which must be compensated for periodically.
The eccentricity of an orbit is a measure of how elliptical the orbital path is – how far it varies from a perfect circle. An object in an elliptical orbit will pass through a low point – Perigee - at its closest approach to Earth and a high point – Apogee – at its most distant.
An eccentric orbit is sometimes desirable. Operators of a spy or communications satellite can maximise time over the target area by having the satellite reach apogee over the target and perigee on the opposite side of the planet. Thus the satellite seems to "hang in the sky" over the target and is thus available for longer periods before apparently plunging around the back of the planet in minimal time.
Direction
Satellites and other space vehicles are generally launched due east, in the direction of earth’s rotation. This is because an object on the surface of the planet is by definition moving at the same velocity as the planet. This velocity provides a sizeable component of the speed required to reach orbital velocity – at the equator this "free velocity" is about 0.47km/sec out of a required 8 km/sec. Farther from the Equator, the amount of velocity thus gained is reduced.
If a due-East launch is not desired, the amount of "free velocity" falls off as the angle between the launch direction and due East increases. A satellite launched at right angles to the Earth’s direction of rotation – directly North or South – gains no benefit from the Earth’s rotation and must gain the whole of its orbital velocity from thrust. Such an orbit is described as a Polar Orbit and might be useful for a survey satellite as the groundtrack – the points directly beneath the satellite – covers all latitudes and moves over the entire surface of the Earth due to the planet’s rotation.
A satellite launched in a westerly direction enters what is known as a Retrograde orbit. Since the planet is spinning in the opposite direction, such a satellite seems to zip around the planet very quickly. Launching a satellite into a retrograde orbit carries a velocity "penalty" in the same manner as launching Eastwards gains a bonus. Since the launcher is moving at about 0.47km/sec in an easterly direction, and the satellite needs to attain a velocity of 8km/sec in a Westerly direction, it in fact needs to gain nearly a whole 1km/sec more than a satellite launched in the opposite direction – about 12% more velocity. This translates to increases in the power of engines and the amount of fuel needed, and in turn to an increase in cost.
Satellite Operations
There are numerous reasons to place satellites in orbit. These reasons break down into several distinct operational areas.
Civilian Satellites
Communications Satellites
The range of a radio-frequency signal is limited by the fact that radio (and by definition, TV) signals are electromagnetic radiation and therefore travel in straight lines. Therefore the practical range of radio should be from the top of a high tower to the horizon – and no further, unless a repeater transmitter is used. This is impracticable across foreign countries and oceans, and expensive in any case.
By using the electromagnetic effects caused by the ionosphere, it is possible to "bounce" a signal so that it gains greater range – in effect the ionosphere acts as a mirror to allow the radio signal to reach "around the corner" of the horizon. However, atmospheric conditions are such that the ionosphere is not reliable, and even at best the signal is somewhat scattered. This not only means that the intended recipient receives a weak or fuzzy signal, but also that the signal may be picked up by unintended recipients, either as interference on a desired signal or perhaps by someone deliberately listening for things they were not intended to hear.
Communications satellites do away with some of these problems. A tight-beam signal can be sent to a satellite (which will normally be in a geostationary or geosynchronous orbit to give reliable coverage) from where it can be retransmitted to a ground receiver very distant from the original transmitter. The satellite can also retransmit the signal to another satellite, enabling contact to be made with a ground station on the other side of the planet.
Because the signal is retransmitted, it does not become scattered, so reception and security are both greatly improved. In addition, the signal can be scrambled so that only a receiver with the correct decryption equipment can make sense of the contents. Thus pay-to-view boxing matches, private telephone conversations and sensitive military information can all be sent directly to the recipient anywhere in the world.
There are a vast number of communications satellites in orbit, operated by television and telephone companies, governments and military forces. The number of useful orbits is somewhat limited, and in some cases (such as Satellite TV) ground receivers may be insufficiently precise in locating satellites and can experience interference.
Another use for Communications satellites is navigation. For example the Global Positioning System can give a ship or vehicle’s computer a location fix accurate to within a few metres, anywhere in the surface of the planet.
Microsatellites for communications http://www.sstl.co.uk/services/subpage_services.html
Observation Satellites
Satellite observation of the earth’s surface has many peaceful and beneficial applications. Satellites can be used to search for mineral resources, detect geological fault lines, monitor changing climatic conditions or improve maps.
An early example of Earth observation by satellite for peaceful means was the Earth Resources Technology Satellite (ERTS) programme. This endeavour involved researchers from 50 nations. The ERTS satellite (two were planned but only one was launched, into a near-polar orbit) sent back a stream of false-colour pictures of the Earth’s surface. Detailed information on water pollution, crop health, geological faults and mapping inaccuracies became available allowing improved land use and cultivation, pest control and improved navigation. All of the ERTS data was unclassified and publicly available, and benefited many nations.
Microsatellites for Earth Observation http://www.sstl.co.uk/services/subpage_services.html
Research Satellites
Many satellites are launched with the aim of furthering scientific knowledge. Some are simple one-experiment payloads which ascend to the edge of space, gather and transmit their data, and fall back to Earth. Others are more sophisticated and will remain in orbit for thousands of years after their useful lives (themselves measured in years) are over.
Early research satellites conducted one-off experiments such as carrying a live animal into space to see if humans could survive there. Others began experimental programmes which are still ongoing to this day. Investigations carried out by satellites include: Investigation of the Van Allen Belt (a region of intense radiation beginning about 1000km from Earth’s surface); Data collection on Cosmic Gamma rays, orbital temperatures, atmospheric limits; star mapping and observation of neutron stars and pulsars; measurement of background radiation; testing of propulsion systems; studies of micrometeoroids, comets and Near-Earth Asteroids… the list gets longer with every launch.
Orbital research devices such as the Hubble Space telescope are large and expensive satellites, but satellites nonetheless. The Hubble telescope can achieve a resolution far better than any achievable by Earthbound observatories, because light reaching the telescope has not been scattered by Earth’s atmosphere.
The Hubble is an amazing resource, so good that time on it is at a premium – booked years in advance. To provide for the need for space-based observation of a lower level of sophistication, the Humble Space Telescope has been devised. Rather less complex and expensive – humbler in all ways – than the Hubble, the Humble Space telescope is far more accessible. Its observations are available on the Internet.
The Humble Space telescope http://www.sil.com/humble.htm
(Yes, that's supposed to say 'humble')
Weather Satellites
Humans have tried to predict the weather for as long as they have been capable of thought. We have been getting it wrong for just as long. In the latter half of the 20th Century, weather prediction became more accurate and reliable through the use of satellites. Not only did it become possible to directly observe cloud patterns and identify extreme weather, plot the course of hurricanes and so forth, but perhaps more importantly it became possible to constantly gather data for comparison purposes. Air temperature and humidity can be measured by satellite, and storms brewing in inaccessible places can be observed and tracked. . By comparing the satellite pictures of today’s cloud formations with those taken in other years, it is possible to match a probable outcome with a particular set of weather parameters. Satellite weather prediction has saved countless lives by providing timely warnings of severe weather. Less tangibly, it has made agriculture a less chancy business and improved the safety of shipping and aircraft.
Military Satellites
Killer Satellites
Given the vast number of military applications for satellite technology, it is no surprise that the armed forces of the world have developed the means to kill or disable satellites in orbit. In wartime, the benefits of orbital reconnaissance, ballistic missile launch detection or just taken-for-granted long-range communications are such that the enemy cannot be allowed to retain them – though there is a strong argument for leaving missile detection satellites in position, to avoid the risk of uncontrolled escalation.
There are many means to put out an enemy’s eyes in the sky. US reconnaissance satellites have reportedly been blinded on some passes by some sort of ground-based system (thought to be an infrared beam) since the 1970s. Another approach is to launch missiles at the satellites; either large ground-based missiles or a smaller air-launched type. This type of anti-satellite missile is carried to high altitude by a high-performance interceptor aircraft such as the F-15 Eagle and then launched to climb to orbit under its own power. Sending a manned mission to physically smash or steal the satellites is expensive and probably not feasible.
However, the best weapon to use against satellites seems to be another satellite. A small device can be placed in orbit to lie dormant for years, then be controlled to manoeuvre close to its target before taking offensive action. This "killersat" then launches a small projectile or is detonated by an internal explosive charge, shredding the target with fragments of its own casing. Using satellites to kill satellites is expensive but quite workable. A large number of killersats could be placed in orbit ready for use in a massed anti-satellite campaign against enemy satellites – including opposing killer-sats if they could be located and identified - or even against manned stations or spacecraft.
Reconnaissance Satellites
Once it became apparent that high-flying reconnaissance aircraft such as the U-2 were no longer able to overfly enemy territory with impunity, the appeal of placing a camera on a satellite became apparent. This spy-sat could then conduct aerial photo-reconnaissance from low orbit, penetrating deep into foreign territory to seek out secrets and expose them.
As with much space technology, international law was somewhat behind the space race – and has not to date caught up. Thus while nations were free to use lethal force to defend their airspace (the area of atmosphere directly above that nation’s territory and coastal waters), there was nothing in international law to prevent overflight above the atmosphere.
This situation continues to this day. While nations consider satellite reconnaissance to be an unfriendly act, it has not been considered desirable to ban it, nor truly practicable to enforce such a ban. Besides, the implications of allowing the legal destruction of orbital devices are not pleasant.
The earliest spy satellites were somewhat clumsy affairs, mounting a camera with an extremely long focal length whose film was quickly used up. Once this had occurred, either the whole satellite was recovered or the film package was ejected to descend to Earth. Ingenious capture devices were at installed in aircraft, to pluck the falling film package from the air. This tricky operation was successfully conducted on a routine basis – eventually, after much experimentation.
Modern spy satellites are no longer short-lived cameras in the sky. They mount a variety of sophisticated sensors including infrared cameras and equipment to monitor electromagnetic emissions from foreign installations.
National Recon office http://www.nro.odci.gov/
US Space Command http://www.peterson.af.mil/usspace/index.htm
Space Command satellite catalogue http://www.peterson.af.mil/usspace/satcat.htm
Army Space Command http://www.peterson.af.mil/usspacearmy/index.htm
US Military satellite programs: http://www.schriever.af.mil/satellite_programs/index.htm
Space Warfare centre http://www.schriever.af.mil/swc/
21st Space Wing http://www.peterson.af.mil/21sw/index.htm
Civilian Satellites
Communications Satellites
The range of a radio-frequency signal is limited by the fact that radio (and by definition, TV) signals are electromagnetic radiation and therefore travel in straight lines. Therefore the practical range of radio should be from the top of a high tower to the horizon – and no further, unless a repeater transmitter is used. This is impracticable across foreign countries and oceans, and expensive in any case.
By using the electromagnetic effects caused by the ionosphere, it is possible to "bounce" a signal so that it gains greater range – in effect the ionosphere acts as a mirror to allow the radio signal to reach "around the corner" of the horizon. However, atmospheric conditions are such that the ionosphere is not reliable, and even at best the signal is somewhat scattered. This not only means that the intended recipient receives a weak or fuzzy signal, but also that the signal may be picked up by unintended recipients, either as interference on a desired signal or perhaps by someone deliberately listening for things they were not intended to hear.
Communications satellites do away with some of these problems. A tight-beam signal can be sent to a satellite (which will normally be in a geostationary or geosynchronous orbit to give reliable coverage) from where it can be retransmitted to a ground receiver very distant from the original transmitter. The satellite can also retransmit the signal to another satellite, enabling contact to be made with a ground station on the other side of the planet.
Because the signal is retransmitted, it does not become scattered, so reception and security are both greatly improved. In addition, the signal can be scrambled so that only a receiver with the correct decryption equipment can make sense of the contents. Thus pay-to-view boxing matches, private telephone conversations and sensitive military information can all be sent directly to the recipient anywhere in the world.
There are a vast number of communications satellites in orbit, operated by television and telephone companies, governments and military forces. The number of useful orbits is somewhat limited, and in some cases (such as Satellite TV) ground receivers may be insufficiently precise in locating satellites and can experience interference.
Another use for Communications satellites is navigation. For example the Global Positioning System can give a ship or vehicle’s computer a location fix accurate to within a few metres, anywhere in the surface of the planet.
Microsatellites for communications http://www.sstl.co.uk/services/subpage_services.html
Observation Satellites
Satellite observation of the earth’s surface has many peaceful and beneficial applications. Satellites can be used to search for mineral resources, detect geological fault lines, monitor changing climatic conditions or improve maps.
An early example of Earth observation by satellite for peaceful means was the Earth Resources Technology Satellite (ERTS) programme. This endeavour involved researchers from 50 nations. The ERTS satellite (two were planned but only one was launched, into a near-polar orbit) sent back a stream of false-colour pictures of the Earth’s surface. Detailed information on water pollution, crop health, geological faults and mapping inaccuracies became available allowing improved land use and cultivation, pest control and improved navigation. All of the ERTS data was unclassified and publicly available, and benefited many nations.
Microsatellites for Earth Observation http://www.sstl.co.uk/services/subpage_services.html
Research Satellites
Many satellites are launched with the aim of furthering scientific knowledge. Some are simple one-experiment payloads which ascend to the edge of space, gather and transmit their data, and fall back to Earth. Others are more sophisticated and will remain in orbit for thousands of years after their useful lives (themselves measured in years) are over.
Early research satellites conducted one-off experiments such as carrying a live animal into space to see if humans could survive there. Others began experimental programmes which are still ongoing to this day. Investigations carried out by satellites include: Investigation of the Van Allen Belt (a region of intense radiation beginning about 1000km from Earth’s surface); Data collection on Cosmic Gamma rays, orbital temperatures, atmospheric limits; star mapping and observation of neutron stars and pulsars; measurement of background radiation; testing of propulsion systems; studies of micrometeoroids, comets and Near-Earth Asteroids… the list gets longer with every launch.
Orbital research devices such as the Hubble Space telescope are large and expensive satellites, but satellites nonetheless. The Hubble telescope can achieve a resolution far better than any achievable by Earthbound observatories, because light reaching the telescope has not been scattered by Earth’s atmosphere.
The Hubble is an amazing resource, so good that time on it is at a premium – booked years in advance. To provide for the need for space-based observation of a lower level of sophistication, the Humble Space Telescope has been devised. Rather less complex and expensive – humbler in all ways – than the Hubble, the Humble Space telescope is far more accessible. Its observations are available on the Internet.
The Humble Space telescope http://www.sil.com/humble.htm
(Yes, that's supposed to say 'humble')
Weather Satellites
Humans have tried to predict the weather for as long as they have been capable of thought. We have been getting it wrong for just as long. In the latter half of the 20th Century, weather prediction became more accurate and reliable through the use of satellites. Not only did it become possible to directly observe cloud patterns and identify extreme weather, plot the course of hurricanes and so forth, but perhaps more importantly it became possible to constantly gather data for comparison purposes. Air temperature and humidity can be measured by satellite, and storms brewing in inaccessible places can be observed and tracked. . By comparing the satellite pictures of today’s cloud formations with those taken in other years, it is possible to match a probable outcome with a particular set of weather parameters. Satellite weather prediction has saved countless lives by providing timely warnings of severe weather. Less tangibly, it has made agriculture a less chancy business and improved the safety of shipping and aircraft.
Military Satellites
Killer Satellites
Given the vast number of military applications for satellite technology, it is no surprise that the armed forces of the world have developed the means to kill or disable satellites in orbit. In wartime, the benefits of orbital reconnaissance, ballistic missile launch detection or just taken-for-granted long-range communications are such that the enemy cannot be allowed to retain them – though there is a strong argument for leaving missile detection satellites in position, to avoid the risk of uncontrolled escalation.
There are many means to put out an enemy’s eyes in the sky. US reconnaissance satellites have reportedly been blinded on some passes by some sort of ground-based system (thought to be an infrared beam) since the 1970s. Another approach is to launch missiles at the satellites; either large ground-based missiles or a smaller air-launched type. This type of anti-satellite missile is carried to high altitude by a high-performance interceptor aircraft such as the F-15 Eagle and then launched to climb to orbit under its own power. Sending a manned mission to physically smash or steal the satellites is expensive and probably not feasible.
However, the best weapon to use against satellites seems to be another satellite. A small device can be placed in orbit to lie dormant for years, then be controlled to manoeuvre close to its target before taking offensive action. This "killersat" then launches a small projectile or is detonated by an internal explosive charge, shredding the target with fragments of its own casing. Using satellites to kill satellites is expensive but quite workable. A large number of killersats could be placed in orbit ready for use in a massed anti-satellite campaign against enemy satellites – including opposing killer-sats if they could be located and identified - or even against manned stations or spacecraft.
Reconnaissance Satellites
Once it became apparent that high-flying reconnaissance aircraft such as the U-2 were no longer able to overfly enemy territory with impunity, the appeal of placing a camera on a satellite became apparent. This spy-sat could then conduct aerial photo-reconnaissance from low orbit, penetrating deep into foreign territory to seek out secrets and expose them.
As with much space technology, international law was somewhat behind the space race – and has not to date caught up. Thus while nations were free to use lethal force to defend their airspace (the area of atmosphere directly above that nation’s territory and coastal waters), there was nothing in international law to prevent overflight above the atmosphere.
This situation continues to this day. While nations consider satellite reconnaissance to be an unfriendly act, it has not been considered desirable to ban it, nor truly practicable to enforce such a ban. Besides, the implications of allowing the legal destruction of orbital devices are not pleasant.
The earliest spy satellites were somewhat clumsy affairs, mounting a camera with an extremely long focal length whose film was quickly used up. Once this had occurred, either the whole satellite was recovered or the film package was ejected to descend to Earth. Ingenious capture devices were at installed in aircraft, to pluck the falling film package from the air. This tricky operation was successfully conducted on a routine basis – eventually, after much experimentation.
Modern spy satellites are no longer short-lived cameras in the sky. They mount a variety of sophisticated sensors including infrared cameras and equipment to monitor electromagnetic emissions from foreign installations.
National Recon office http://www.nro.odci.gov/
US Space Command http://www.peterson.af.mil/usspace/index.htm
Space Command satellite catalogue http://www.peterson.af.mil/usspace/satcat.htm
Army Space Command http://www.peterson.af.mil/usspacearmy/index.htm
US Military satellite programs: http://www.schriever.af.mil/satellite_programs/index.htm
Space Warfare centre http://www.schriever.af.mil/swc/
21st Space Wing http://www.peterson.af.mil/21sw/index.htm
Space Stations
The need for a manned orbital station has long been perceived. In order to investigate whether humans can survive in space for any length of time, astronauts must remain in orbit for weeks or even months. This is not feasible in the cramped confines of a spacecraft. A larger, permanent (or semi-permanent) orbital station is required.
An orbital station also allows the crew to conduct lengthy experiments and can be better equipped with scientific equipment than a space capsule.
Skylab
The US space station Skylab was launched on May 14, 1973. Among other missions – solar observation and early-warning of natural disasters on earth - it was intended to demonstrate that humans could live and work in space for extended periods. Three teams of astronauts spent a total of 171 days aboard the station, conducting a number of experiments while they themselves were participating in the beginnings of a greater experiment – to see if humans could survive in space long enough to make a journey to the other planets.
Skylab comprised an Orbital Workshop (OWS), which was the main living quarters for the crew and contained most of the station’s equipment, the Instrument Unit, Airlock Module, the Multiple Docking Adapter and a large telescope mount. The crew ascended to the station in an Apollo Command Service Module and returned to Earth by the same means. While aboard the station they lived and worked aboard the OWS with its larger quarters.
Skylab was beset by problems – indeed its operational life came to resemble an ongoing damage-control exercise. Launch vibration tore away part of the thermal shield and damaged one of the solar wings intended to provide power to the station. Debris jammed the other. With only a little power available from the solar panels on the Telescope Array, environmental control was almost impossible and the internal temperature of the station became dangerously high.
Initially it was planned to send the first crew up to Skylab immediately, but the mission was postponed while options were explored. The first mission to Skylab attempted to repair the station by extending the jammed solar wing and attaching a solar shade to the station. Despite docking problems the mission was a success. The astronauts were able to enter the station and by heroic efforts during an extremely hazardous spacewalk, to effect some repairs to the damaged solar panels. The station became operational, though at less than anticipated efficiency. The astronauts were even able to complete most of their planned experiments and further repair Skylab. Among the sophisticated repair techniques employed was a battery repair conducted by thumping it with a hammer.
The second Skylab mission started badly but achieved a successful docking. A form of motion sickness caused by weightlessness afflicted all three crew, and in addition the Command Service Module developed a leak of manoeuvring gas. Despite these problems the mission was a success; experiments with spiders (to see of they can spin a web while weightless) and with astronaut personal manoeuvring units were conducted, among others. After further repairs to the station, the Astronauts made a safe return to Earth despite their faulty Command Service Module.
One of the goals of the third Skylab mission was the observation of the Comet Kohoutek. The crew also conducted further repairs to the station, including the repair of a damaged antenna while working outside the station.
During this mission, the Soviet Soyuz 13 began its own flight, and for the first time Astronauts and Cosmonauts were in space at the same time. When the third and final crew left Skylab, the station was depressurised. A little later it was boosted into a higher orbit to extend its time to re-entry.
Eventually the station fell into the Earth’s atmosphere and was destroyed – burned up or crashed – but Skylab remains a significant milestone in the history of humanity in Space.
Salyut
The Soviet Salyut space stations were individually less impressive than Skylab, but were deployed in a series rather than a single station. The stations were of different types, used for distinct civilian and military purposes. Operational periods of the early Salyut stations were just a few months, but their crews set a series of records for extended stays in space. Another Salyut "First" was resupply by an unmanned Soyuz vehicle. Like Skylab, the Salyut stations were launched unmanned, intended to be visited by several crews over an extended period.
Running repairs were a feature of the Salyut programme, just as with Skylab. Perhaps they will be a feature of any operation involving a device as complex as a space station. Certainly the Salyut missions were fraught with difficulties; the stuff of space adventure rather than coldly technical operations.
The Salyut stations were subject to a process of evolution, but can be said to comprise: A docked Soyuz capsule (generally considered to be a component of the station), a transfer tunnel between Salyut and Soyuz, and a main habitable area. This had three sections: a large main cylinder, a smaller cylinder and a cone connecting them. All Soyuz stations deployed a number of solar panels and various external systems such as heat regulators and manoeuvring thrusters.
Launched in April 1971, Salyut 1 was placed in a very low orbit, possibly due to the weight of the payload and the limitations of available rocket technology. The station lasted almost 6 months in orbit, but required repeated boosts to avoid re-entry. The crew of Soyuz 10 (the first mission to the station) docked with the Salyut 1 but did not enter – perhaps they were unable to do so. After about 16 hours the crew returned to Earth. Soyuz 11 succeeded in docking and the 3-man crew set a record by spending 23 days working aboard the station. All three Cosmonauts were killed by depressurisation caused by a defective valve during re-entry. Although more missions were planned and the Salyut 1 station was maintained in a ready state, Soviet planners decided that modifications to the station would be needed for future operations. No further Soyuz missions were made to Salyut 1.
Launched April 1973, Salyut 2 was, according to Soviet sources, "similar in design and purpose" to Skylab. A series of problems with the station’s orientation were reportedly overcome a week after launch and the station was boosted into a higher orbit to commence its operational life. However, Salyut 2 became unstable and broke up, the main fragments re-entering by the end of May.
Salyut 3 was launched in June 1974. Its operations included research into the effectiveness of manned reconnaissance craft. This was carried out by the crew of Soyuz 14, who photographed and reported upon a number of targets laid out in Soviet territory. The station was set up for automatic operation before the Soyuz 14 crew departed. The Soyuz 15 mission failed to dock with the station when the automatic docking system (which was being tested with a view to automatic resupply operations) twice malfunctioned and sent the Soyuz capsule out of control while close to the station. After dealing with the crisis the Soyuz crew, which included the first grandparent (aged 48) in space, made an emergency return to Earth and landed safely.
Salyut 4 reached low orbit in December 1974, and was boosted into a higher orbit 11 days after launch. The first crew, aboard Soyuz 17, made a manual docking after an automatic approach, apparently without difficulties. Salyut 4 tested a water recycling system for use in space, and conducted observations of the Sun, the Earth and other planets of the solar system. The two cosmonauts returned safely to Earth after just under 30 days.
The next mission to Salyut 4 should have been Soyuz 18 with a planned duration of nearly 60 days. In the event, this mission lasted just a few minutes. The 3rd-satge rocket malfunctioned and the vehicle went off course. An automatic system fired the escape mechanism to detach the crew capsule and abort the mission. Despite pulling 14-15gs and expressing concern that the escape mechanism was functioning incorrectly, the Cosmonauts were safely recovered. This was the first time any manned mission was aborted between lift-off and orbital insertion, and proved both the value and workability of escape mechanisms.
The next mission to Salyut 4 was the re-named Soyuz 18. The crew boarded the station, which had been running automatically, and began a long stay of 61 days. Experiments continued, including growing onions aboard the station. After Soyuz 18, the station ran on automatic for many months, during which time the unmanned Soyuz 20 vessel automatically docked with the station and demonstrated that a station could be resupplied by automated vehicles. Salyut 4 re-entered in February 1977.
Salyut 5 was launched in June 1976, while Salyut 4 was still in orbit. Salyut 5’s mission was mainly military in purpose, though many scientific experiments were conducted. Observations were carried out of the military exercises in Siberia, to investigate the role an orbital station might have in monitoring and even participating in military operations. The crew were forced to make an early return to Earth due to environmental problems aboard the station. The second mission to Salyut 5, Soyuz 23, was unable to dock with the station and made an emergency return to Earth, landing off course in Lake Tengiz. This was the first water landing by a Soviet spacecraft. The final mission to Salyut 5, Soyuz 24, was of short duration - 17 days – and relatively routine.
Salyut 6, launched in September 1977, was a move towards a permanently manned station. Improvements in habitability and automatic station-keeping, some of which had been trialled in earlier stations, were incorporated. The first mission to Salyut 6, Soyuz 25, failed to dock and returned to Earth. Soyuz 26 achieved docking with Salyut 6’s secondary port without difficulties and the crew began a record-breaking stay of 84 days. EVA operations included inspection of the main docking port for damage caused by collision with Soyuz 25, and provided a few scares when an instrument fault incorrectly reported that Cosmonaut Grechko would not be able to return to the station due to a repressurisation valve failure. In the event there was no failure and Grechko was able to re-enter Salyut 6. In January 1978, the Cosmonauts aboard Salyut 6 were joined by the crew of Soyuz 27; scenes of their historic and emotional link-up were seen around the world on TV. After 5 days the Soyuz 27 crew returned to Earth, leaving the original inhabitants still aboard the station.
Later in January 1978, Salyut 6 was resupplied by an automated freighter named Progress 1. The refuelling operation was long and arduous, but was completed without a hitch. Progress 1’s engines were used to raise Salyut 6’s orbit, and then the freighter returned to Earth as a spacegoing dustbin filled with used air filters, containers and such like. The crew of Soyuz 26, still aboard, were joined by the Soyuz 28 mission. Various experiments were carried out, including metallurgical research, and in March 1978 the crew left the station running on automatic as they descended to a hero’s welcome on Earth.
In February 1979 Soyuz 32 carried a new crew to rendezvous with Salyut 6. Cosmonauts Lyakhov and Ryumin carried out vital maintenance work on the station, repairing or replacing components that had been designed for neither. Their workload was considerable, and continued after the first Progress resupply mission. The Progress unit was used to boost Salyut 6’s orbit after it had contributed to the hazardous and difficult repair of a fuel tank aboard the Salyut station. It was then discarded.
Soyuz 33 lifted off in April 1979, carrying the first civilian commander of a space mission. Despite the hazards of foul weather – the worst conditions under which a manned launch had been undertaken to date – the mission made a successful rendezvous with the station. However, during the docking approach the Soyuz engine malfunctioned and the mission had to be aborted using the emergency backup engine. The crew made an 8-g ballistic descent at night, but were found unharmed if shaken beside their overturned capsule.
While engineers tried to determine what had happened to Soyuz 33, the crew still aboard Salut 6 carried on their programme of experiments, resupplied by Progress 6 and the unmanned Soyuz 34. Soyuz 34 was sent to replace Soyuz 32 which it was thought might deteriorate to an unsafe condition during the long period in space. Normally visitors swapped ships with the crew to ensure that a relatively new vessel was available for them to leave the station at need.
In June 1979, Progress 7 brought a new radiotelescope to be fitted to the station. This was correctly fitted by the Cosmonauts, but fouled the aft docking port when the antenna was stowed. Try as they might, the crew could not free the antenna from inside the station, so in order to clear the docking port the Cosmonauts volunteered to undertake – insisted upon undertaking - an unplanned, hazardous EVA at the rear of the station where no Cosmonaut had previously worked. Despite the difficulties he encountered, Cosmonaut Ryumin was able to free the antenna and kick it away from the port. A few weeks later the two-man-crew returned to Earth after nearly 6 months in space.
In April 1980, Ryumin returned to Salyut 6 after a late personnel switch. During the period of automatic operation, a new unmanned craft, Soyuz T-1, had docked with the station. As soon as it left, Progress 8 arrived and required unloading. More experimentation was carried out using supplies delivered by Progress 9, and the first visitors arrived aboard Soyuz 36.
The first manned Soyuz T ferry arrived in June 1980. This mission was in part a proving flight for the new automatic docking systems. While the new craft was being evaluated, Soyuz 36 and 37 arrived with more visitors. The station was resupplied by Progress 11 in September, in the hope that the station could be used again even though it had exceeded its intended lifespan. The station was placed in a safe orbit and the Cosmonauts departed in October.
Soyuz T-3 docked with the venerable Salyut 6 station in November 1980, carrying the first 3-man Soyuz crew since the Soyuz 11 mission, where all 3 Cosmonauts had been killed during re-entry. This new crew carried out the most complex repair programme yet, and even managed to complete some scientific experiments.
After a resupply mission by Progress 12, yet another crew was launched aboard Soyuz T-4 in March 1981. Cosmonaut Viktor Savinykh became the 100th human in space and the 50th Cosmonaut during this mission, which included more repairs and scientific experiments. More visitors joined the crew for a short time, arriving aboard Soyuz 39. Soyuz 40, last of its kind, delivered the last visitors to the station a few weeks later, and in May 1981 the standing crew closed up shop for the last time and departed the station.
Salyut 6 demonstrated that humans could live and work in space for months at a time – or even longer - at need, and to conduct the most difficult and complex tasks within a space vehicle or during EVA. In addition to the immense amount of data gathered in many experiments, the station was the proving ground for automated capsules and systems. And it still had one final part to play.
In June 1982 Cosmos 1267, an unmanned vessel as large as the Salyut station, was launched to rendezvous with Salyut 6. Cosmos 1267 was used as a tug to propel the station through a series of manoeuvres designed to investigate its stability under power. The mission completed, both craft re-entered in July 1982 having proven that space station modules could be manoeuvred by orbital tugs and thus helped pave the way for a new generation of orbital stations.
Salyut 7 was placed in orbit in April 1982, before Salyut 6 had re-entered. Very similar to its predecessor, Salyut 7 boasted improved docking and navigation systems and solar panels.
The first crew arrived aboard Soyuz T-5 in May 1982. After some docking problems the crew checked over the station and got down to work. After resupply by Progress 13, the first visitors arrived in June aboard Soyuz T-6, including a Frenchman. While many of the visitor missions had been "international" in that they included personnel from allied countries, Soyuz T-6 was unique in that Jean-Loup Chretien was the first Westerner aboard a Soviet station. More docking problems ensued, but the crew – for the first time five men aboard the Salyut station – got quickly down to work, including experiments on the use of antibiotics in weightless conditions. Soyuz T-7 arrived in August 1982 with the second woman in space aboard. This week-long mission concentrated mainly on microbiological experiments.
The crew of Salyut 7 returned to Earth in December 1982, having travelled 80 million miles and spent half a year in space. They had conducted over 300 experiments and made many valuable observations of the Earth. The capsule came down in a blizzard and rolled over on a slope. Despite their traumatic landing, the Cosmonauts recovered well.
In March 1983 Cosmos 1443, an updated version of Cosmos 1267, conducted an automatic docking. This vessel carried a far greater payload than the Progress ships, and could also function as an orbital tug. It was used to lower Salyut 7’s orbit in preparation for a new manned launch.
The expected launch came in April 1983, when Soyuz T-8 attempted delivery of a 3-man crew to the station. Discovering that the docking-control radar had failed, the crew made numerous attempts to fix the fault, and then even began a manual docking operation using only a searchlight mounted on the Soyuz capsule. Despite their courage and best efforts, the mission had to be abandoned as fuel stocks ran low. The Cosmonauts made a safe if hasty re-entry.
Soyuz T-9 docked with Salyut 7 (which itself was still mated to Cosmos 1443) in June 1983, bringing aboard a new 2-man crew. While practising a station evacuation drill, the crew were alarmed by a micrometeorite impact against a station window. It was too small to cause serious damage but sharply illustrated the dangers faced by personnel working in space.
In August, the Cosmos module undocked and returned to Earth after conducting its own tests. Its place was taken by Progress 17, which marked a new innovation in resupply. Among its cargo of mission supplies, mail and spares was a consignment of fresh food loaded only hours before launch. Previously fresh food had been sent up to the orbital station but was loaded days in advance and lost some of its appeal.
After refuelling in September, things began to go badly wrong for Salyut 7. A fuel leak and other problems put most of the station’s attitude thrusters out of action and with the backup motor also out of commission the station was reported in the US as being "dead in the water".
Reports also began to emerge of a launch mishap during a hurried operation to get Soyuz T-10 to the station ahead of the expected October launch window. Two Cosmonauts had a narrow escape when a fuel leak less than two minutes before launch caused a huge fireball to engulf their craft. The automatic escape mechanism was destroyed by the fire and had to be triggered from launch control. Both Cosmonauts survived unharmed despite coming within seconds of incineration.
Suspecting that the Soyuz T-9 capsule was out of commission, some US analysts speculated that the crew were in dire straits and unable to leave their station – even if Soyuz T-10 and its 2-man crew had reached the station, there was no way to bring 4 Cosmonauts home in a 3-man ship. A rescue mission by the Space Shuttle was postulated while the press ran features on the two Cosmonauts with dire headlines such as "Marooned In Space".
In fact the station was in trouble, though things were not as bad as some thought. The fuel leak was less serious than imagined, but the corrosive fuel had caused environmental problems and reduced the station’s available power. As a result, cabin temperature was unpleasantly low and high humidity caused damp conditions on top of everything else.
The Soyuz T-10 mission (redesignated Soyuz T-10A) had been initiated in response to this situation. The crew were to have assembled the extra solar panels brought aboard by Cosmos 1443, to augment the station’s power and allow continued operations. The panels were already aboard the station, so the two men aboard were forced to attempt assembly despite never having trained for the operation. Their two difficult EVA missions were a success and, having saved the station, the crew resupplied from Progress 18, mothballed the station and returned safely to earth aboard the supposedly-defunct Soyuz T-9.
The next mission to Salyut 7, blasting off aboard Soyuz T-10 (the aborted mission had been redesignated T-10A) in February 1984, brought 3 Cosmonauts to the station for a new long-duration mission. Their number included a doctor who had been sent to study the effects of long periods in space first-hand.
The first visitors to Salyut 7 on this mission arrived in April aboard Soyuz T-11, including an Indian guest Cosmonaut who practised Yoga instead of the standard exercises. The station was a little crowded with six personnel aboard, and shortly after the guests’ arrival, space was more populated than ever before as five Shuttle Astronauts were in orbit at the same time.
After the guests’ departure, Salyut 7 received a shipment of spares for the repair of the main propulsion unit. This ambitious task was aided by a folding work platform and framework developed specially for the mission. The repairs were difficult in the extreme – on their second EVA the crew spent a whole hour trying to unjam a single nut. This pushed their EVA to five hours. Their first, at four hours, had set a new Soviet record.
The repairs were a complete success, and by comparison the EVA operation the Cosmonauts had trained for, adding more solar panels to the station, proved straightforward. This evolution was completed in a single 3-hour EVA.
More visitors arrived in July, a stay which set another record – the first EVA by a woman, who was also the first woman to twice reach space. EVA experiments with a hand-held electron-beam cutter/welder proved to be a success.
The crew continued their work after the guests had left, setting a new endurance record, and returned to Earth in October 1984.
Salyut 7 continued to orbit under the control of its automatic systems for some time. At some point, ground control lost contact with the station and it became clear that the station was unstable and in a decaying orbit, headed for an inglorious end after 3 years off stalwart service.
Nine months after the departure of the previous crew, a 2-man mission to Salyut 7 blasted off. The Cosmonauts had been training for a routine occupation of the station. Now they were to undertake a risky salvage operation under unknown circumstances. Making a seat-of-the-pants manual approach to the station, which was tumbling out of control, the crew achieved docking and boarded Salyut 7.
The station was in a sorry state. With the temperature so low that the drinking water had frozen and frost had formed on the walls, no power in the batteries and the air still and lifeless, there seemed little hope. But for the determination of the Cosmonauts and the ingenuity displayed at every turn by space explorers of all nations, the mission would have failed utterly.
With advice from their ground controllers the Cosmonauts began working to restore some power to the station, which was so cold that they had to frequently retire to their Soyuz capsule where they had jury-rigged a stove to heat food and drinks. The capsule was not designed nor equipped for this role but with nothing better the Cosmonauts made do or adapted what they had.
Amazingly, they succeeded in bringing Salyut 7 painfully back to life, and late in June a resupply ship arrived, bringing vital spares to restore the station to operational life. The Cosmonauts performed much work outside the station, benefiting from recent improvements in EVA suits, incorporating lessons learned in earlier Salyut missions.
By September, Salyut 7 was ready to receive visitors and a crew changeover. Normal operations continued, including an ambitious experimental programme. However, by November it was apparent that something was wrong aboard the station and shortly afterward it was announced that the Cosmonauts had returned early to Earth due to the illness of one of their number. Western analysts have interpreted the "illness" as psychological rather than physical.
Despite this downbeat ending to the last Salyut mission, the stations had proved beyond doubt that not only could humans live and work in space for extended periods of time but could conduct repairs and alterations to a space station or vessel far beyond what the designers had expected. The wealth of scientific data and experience with space operations gathered in the course of the Salyut missions prepared humans to take another step down the road to the stars.
And when the time came to take that step, Salyut 7 had a final part to play.
Spacelab
The International Spacelab project, an orbital laboratory, was a rather different concept to Skylab or Salyut. Rather than a semi-permanent station to which crews ascended, Spacelab was conceived as a payload unit to be carried into orbit and returned to Earth in the payload bay of the US Space Shuttle.
In November 1983 a crew of six Astronauts under the veteran John Young made a perfect takeoff aboard the shuttle Columbia and reached orbit before the inevitable space-station troubles began. The door connecting the crew compartment of Columbia to the pressurised Spacelab bay jammed and required the efforts of the entire crew to free.
After this setback, Spacelab was deployed successfully and operations began on a three crew on/three off basis to maximise returns from the station. After a few days, however, the strain of the awesome workload placed on the crew began to tell. After a sharp exchange with Mission Control, the schedule was adjusted to a more humanly-possible one.
Later in the mission three of the six astronauts held a press conference while the others staged a memorable – but silent – protest at the staged and scripted nature of the supposedly open conference.
At the very end of the longest Shuttle mission to date, Columbia, which had performed perfectly so far, developed a number of faults caused by a vibration – itself caused by a fault with the manoeuvring thrusters. After a fraught 4-orbit period spent trying to find the fault, Columbia made a clean re-entry and touchdown at Edwards Airforce Base. More drama ensued just after landing as smoke was observed coming from one of the Orbital Manoeuvring System pods. A fuel leak had caused a fire which destroyed nearby equipment which included power-generating units. Valuable lessons were learned from the incident, which almost ended in tragedy.
Spacelab 3 flew ahead of Spacelab 2, in April 1985. As with Spacelab 1, the orbital laboratory was pressurised and habitable "in shirtsleeves" while the Astronauts conducted their research. Two dozen rats and two squirrel monkeys accompanied the human personnel on the mission, which was to include research in four major fields including life sciences.
Shuttle Challenger blasted off after a slight delay caused by a problem at Mission Control, to make a perfect orbital insertion. The shuttle performed flawlessly for a week, with only a minor problem with a water dispenser. The scientific equipment was less co-operative, however. The usual orbital-operation problems began when a satellite antenna jammed the launch unit and could not be freed. Two of the five atmospheric experiments failed, and monkey faeces drifted into the shuttle’s flight deck, causing some aggravation among the flight crew. Several repairs were improvised by the crew or directed by Mission Control, allowing most of the experiments to be conducted.
Despite a problem with the payload bay door latches, Challenger made a safe landing to conclude a mission judged to be an overall success despite the problems with various equipment.
Spacelab 2 blasted off in July 1985 aboard the shuttle Challenger, carrying a variety of experiments in several fields. The configuration of the lab was different this time, an open load carried in a shuttle pallet rather than a self-contained laboratory unit. Indeed, the Shuttle itself was to be an integral part of the experimental sequence, using its OMS engines to create a temporary "hole" in the ionosphere for ground instruments to use.
An earlier launch attempt had been aborted on the pad due to technical problems but this time the launch went flawlessly until booster separation, when the temperature of a high-pressure fuel pump began to climb. An abort at this stage would require a most hazardous manoeuvre, but Challenger managed to clear the danger zone before the pump exceeded safety limits and automatically shut down. After several anxious moments it became clear that the shuttle would be able to limp into a safe abort orbit on her two remaining engines and make a textbook return to base.
Then a second gauge began to show excess temperature, which quickly reached dangerous levels. Losing a second engine at this point would probably mean a crash-landing in the Atlantic. Suspicious that two engines would suffer identical failures, Mission Control cross-checked with other systems and deduced an instrument failure. The decision to override the sensor was a weighty one, but as Challenger lit her OMS engines to augment the thrust of her remaining two main motors and struggled into orbit it became clear that the courageous decision to continue the mission was the right one.
With much of her OMS fuel used up in reaching orbit and an engine gone, Challenger was not able to reach the planned orbital height, yet the Astronauts succeeded in completing a reduced experimental package which included important experiments to detect cosmic "background noise" and ionospheric disruptions. The lower orbit proved to be an ideal height for the plasma physics experiments.
After completing 90% of the intended experiments, Challenger and Spacelab 2 returned to Earth for a perfect landing.
The fourth and final Spacelab mission was flown with a pressurised laboratory module similar to Spacelab 1 and 3, designated Spacelab D-1. Experiments from several nations were carried, of which many came from Germany (D stood for Deutsche). The mission comprised a record-breaking eight personnel aboard the shuttle Challenger. Liftoff and orbital insertion took place in late October 1985, and proceeded without flaw. The workload was as usual intense, with the lab manned in two shifts by teams of three. Despite the fact that the mission was jointly controlled from the US and Germany, excellent teamwork resulted in a smooth mission which conducted many experiments including extensive research into weightlessness adaptation.
After a near-perfect mission, Challenger and Spacelab D-1 made a textbook touchdown and conducted some manoeuvres during roll-out to test modifications to the landing gear.
Spacelab D-1 was a total success.
Mir
Launched in February 1986, the Russian station Mir ("World") was a direct descendant of the Salyut stations, and benefited from experience gained in Salyut operations. Constructed on a modular basis, Mir has five docking ports at the "front" end and an aft port used by Progress resupply vessels in much the same manner as the Salyut stations.
The first module added to Mir was Kvant (Quantum) I, in March 1987. Kvant II joined the station in 1989. The station was fully operational long before this, being designed to take additional modules at any time.
The interior of the station was designed with Salyut experience in mind. Crew comfort and habitability were greatly improved, as would be expected with a station intended to be permanently manned. By moving much of the experimental equipment into modules and thus creating a main habitation area, it was possible to create small individual cabins for each crewmember and a gymnasium area. In addition, much of the station’s running was automated, increasing the amount of time available for Cosmonauts to spend on experimentation rather than housekeeping.
It should be no surprise to anyone familiar with space station operations that Mir was plagued with technical problems, nor that by a series of running repairs and what amounted to damage-control operations the station remained operational far longer than was envisaged.
The Mir story began in March 1986 when Soyuz T-15 delivered two crew to the new station. After resupply and some tests, the two Cosmonauts played out the final episode in the Salyut epic. Boarding their Soyuz capsule they left Mir and changed orbits to rendezvous with Salyut 7. Transferring equipment to the venerable station they conducted a series of experiments before returning to Mir.
Salyut 7 was boosted into a higher orbit, signalling the end of its active life and after a total of 125 days in space the Cosmonauts prepared Mir for an unmanned period and returned to Earth.
The most dramatic incident in Mir’s orbital career was the collision between a Progress resupply ship and the Spektr Remote Sensing Module in June 1997. The accident caused a power loss and threatened the station with depressurisation. The international crew were able to save the station, though on Earth allegations that Mir was unsafe and should be abandoned were rife.
Mir’s active life has been plagued by equipment breakdowns and the occasional outright crisis, but has also seen endurance records smashed. Cosmonauts have remained in orbit for more than a year without serious ill effects, though two hours a day of exercise are considered necessary to avoid calcium loss in the bones and muscle wastage. Since its launch in February 1986 Mir has been almost constantly inhabited and has hosted guest Cosmonauts from several nations.
Mir has been kept in commission longer than was intended by its designers, to serve as a stepping stone for the construction of the International Space Station. US Shuttles have carried out many missions to the station, harking back to the 1975 "Handshake in Space" and ushering in a new age of co-operation in space.
But at last the story of Mir is drawing to a close. Preparations are underway for a final mission to the station, during which Cosmonauts will lower its orbit ready for ground controllers to send it into the atmosphere to burn up.
International Space Station
Taking Mir’s place on the stage of space adventure is the International Space Station. A collaborative effort by several nations, The station’s modular design is based upon technology proven aboard Mir.
Parts of the Zvezda station have been delivered by Russian Proton rockets and US space shuttles. The first such module was Zarya ("Sunrise") which arrived aboard a Proton rocket in November 1998. A second piece, the Unity node, was delivered by Shuttle a month later. The next step will be to add a service module named Zvezda ("Star"), which will provide living quarters for the crew of the station. Many more component flights and supply missions will be needed before the station becomes operational - it will take an estimated seven years to assemble, and will require continued co-operation from all nations involved in the project. Once compete, the International Space Station will be an impressive platform for scientific research and perhaps the jumping-off point for manned exploration of our solar system.
(Note: These are old articles posted to preserve them. Someday I'll update them. Really.)
An orbital station also allows the crew to conduct lengthy experiments and can be better equipped with scientific equipment than a space capsule.
Skylab
The US space station Skylab was launched on May 14, 1973. Among other missions – solar observation and early-warning of natural disasters on earth - it was intended to demonstrate that humans could live and work in space for extended periods. Three teams of astronauts spent a total of 171 days aboard the station, conducting a number of experiments while they themselves were participating in the beginnings of a greater experiment – to see if humans could survive in space long enough to make a journey to the other planets.
Skylab comprised an Orbital Workshop (OWS), which was the main living quarters for the crew and contained most of the station’s equipment, the Instrument Unit, Airlock Module, the Multiple Docking Adapter and a large telescope mount. The crew ascended to the station in an Apollo Command Service Module and returned to Earth by the same means. While aboard the station they lived and worked aboard the OWS with its larger quarters.
Skylab was beset by problems – indeed its operational life came to resemble an ongoing damage-control exercise. Launch vibration tore away part of the thermal shield and damaged one of the solar wings intended to provide power to the station. Debris jammed the other. With only a little power available from the solar panels on the Telescope Array, environmental control was almost impossible and the internal temperature of the station became dangerously high.
Initially it was planned to send the first crew up to Skylab immediately, but the mission was postponed while options were explored. The first mission to Skylab attempted to repair the station by extending the jammed solar wing and attaching a solar shade to the station. Despite docking problems the mission was a success. The astronauts were able to enter the station and by heroic efforts during an extremely hazardous spacewalk, to effect some repairs to the damaged solar panels. The station became operational, though at less than anticipated efficiency. The astronauts were even able to complete most of their planned experiments and further repair Skylab. Among the sophisticated repair techniques employed was a battery repair conducted by thumping it with a hammer.
The second Skylab mission started badly but achieved a successful docking. A form of motion sickness caused by weightlessness afflicted all three crew, and in addition the Command Service Module developed a leak of manoeuvring gas. Despite these problems the mission was a success; experiments with spiders (to see of they can spin a web while weightless) and with astronaut personal manoeuvring units were conducted, among others. After further repairs to the station, the Astronauts made a safe return to Earth despite their faulty Command Service Module.
One of the goals of the third Skylab mission was the observation of the Comet Kohoutek. The crew also conducted further repairs to the station, including the repair of a damaged antenna while working outside the station.
During this mission, the Soviet Soyuz 13 began its own flight, and for the first time Astronauts and Cosmonauts were in space at the same time. When the third and final crew left Skylab, the station was depressurised. A little later it was boosted into a higher orbit to extend its time to re-entry.
Eventually the station fell into the Earth’s atmosphere and was destroyed – burned up or crashed – but Skylab remains a significant milestone in the history of humanity in Space.
Salyut
The Soviet Salyut space stations were individually less impressive than Skylab, but were deployed in a series rather than a single station. The stations were of different types, used for distinct civilian and military purposes. Operational periods of the early Salyut stations were just a few months, but their crews set a series of records for extended stays in space. Another Salyut "First" was resupply by an unmanned Soyuz vehicle. Like Skylab, the Salyut stations were launched unmanned, intended to be visited by several crews over an extended period.
Running repairs were a feature of the Salyut programme, just as with Skylab. Perhaps they will be a feature of any operation involving a device as complex as a space station. Certainly the Salyut missions were fraught with difficulties; the stuff of space adventure rather than coldly technical operations.
The Salyut stations were subject to a process of evolution, but can be said to comprise: A docked Soyuz capsule (generally considered to be a component of the station), a transfer tunnel between Salyut and Soyuz, and a main habitable area. This had three sections: a large main cylinder, a smaller cylinder and a cone connecting them. All Soyuz stations deployed a number of solar panels and various external systems such as heat regulators and manoeuvring thrusters.
Launched in April 1971, Salyut 1 was placed in a very low orbit, possibly due to the weight of the payload and the limitations of available rocket technology. The station lasted almost 6 months in orbit, but required repeated boosts to avoid re-entry. The crew of Soyuz 10 (the first mission to the station) docked with the Salyut 1 but did not enter – perhaps they were unable to do so. After about 16 hours the crew returned to Earth. Soyuz 11 succeeded in docking and the 3-man crew set a record by spending 23 days working aboard the station. All three Cosmonauts were killed by depressurisation caused by a defective valve during re-entry. Although more missions were planned and the Salyut 1 station was maintained in a ready state, Soviet planners decided that modifications to the station would be needed for future operations. No further Soyuz missions were made to Salyut 1.
Launched April 1973, Salyut 2 was, according to Soviet sources, "similar in design and purpose" to Skylab. A series of problems with the station’s orientation were reportedly overcome a week after launch and the station was boosted into a higher orbit to commence its operational life. However, Salyut 2 became unstable and broke up, the main fragments re-entering by the end of May.
Salyut 3 was launched in June 1974. Its operations included research into the effectiveness of manned reconnaissance craft. This was carried out by the crew of Soyuz 14, who photographed and reported upon a number of targets laid out in Soviet territory. The station was set up for automatic operation before the Soyuz 14 crew departed. The Soyuz 15 mission failed to dock with the station when the automatic docking system (which was being tested with a view to automatic resupply operations) twice malfunctioned and sent the Soyuz capsule out of control while close to the station. After dealing with the crisis the Soyuz crew, which included the first grandparent (aged 48) in space, made an emergency return to Earth and landed safely.
Salyut 4 reached low orbit in December 1974, and was boosted into a higher orbit 11 days after launch. The first crew, aboard Soyuz 17, made a manual docking after an automatic approach, apparently without difficulties. Salyut 4 tested a water recycling system for use in space, and conducted observations of the Sun, the Earth and other planets of the solar system. The two cosmonauts returned safely to Earth after just under 30 days.
The next mission to Salyut 4 should have been Soyuz 18 with a planned duration of nearly 60 days. In the event, this mission lasted just a few minutes. The 3rd-satge rocket malfunctioned and the vehicle went off course. An automatic system fired the escape mechanism to detach the crew capsule and abort the mission. Despite pulling 14-15gs and expressing concern that the escape mechanism was functioning incorrectly, the Cosmonauts were safely recovered. This was the first time any manned mission was aborted between lift-off and orbital insertion, and proved both the value and workability of escape mechanisms.
The next mission to Salyut 4 was the re-named Soyuz 18. The crew boarded the station, which had been running automatically, and began a long stay of 61 days. Experiments continued, including growing onions aboard the station. After Soyuz 18, the station ran on automatic for many months, during which time the unmanned Soyuz 20 vessel automatically docked with the station and demonstrated that a station could be resupplied by automated vehicles. Salyut 4 re-entered in February 1977.
Salyut 5 was launched in June 1976, while Salyut 4 was still in orbit. Salyut 5’s mission was mainly military in purpose, though many scientific experiments were conducted. Observations were carried out of the military exercises in Siberia, to investigate the role an orbital station might have in monitoring and even participating in military operations. The crew were forced to make an early return to Earth due to environmental problems aboard the station. The second mission to Salyut 5, Soyuz 23, was unable to dock with the station and made an emergency return to Earth, landing off course in Lake Tengiz. This was the first water landing by a Soviet spacecraft. The final mission to Salyut 5, Soyuz 24, was of short duration - 17 days – and relatively routine.
Salyut 6, launched in September 1977, was a move towards a permanently manned station. Improvements in habitability and automatic station-keeping, some of which had been trialled in earlier stations, were incorporated. The first mission to Salyut 6, Soyuz 25, failed to dock and returned to Earth. Soyuz 26 achieved docking with Salyut 6’s secondary port without difficulties and the crew began a record-breaking stay of 84 days. EVA operations included inspection of the main docking port for damage caused by collision with Soyuz 25, and provided a few scares when an instrument fault incorrectly reported that Cosmonaut Grechko would not be able to return to the station due to a repressurisation valve failure. In the event there was no failure and Grechko was able to re-enter Salyut 6. In January 1978, the Cosmonauts aboard Salyut 6 were joined by the crew of Soyuz 27; scenes of their historic and emotional link-up were seen around the world on TV. After 5 days the Soyuz 27 crew returned to Earth, leaving the original inhabitants still aboard the station.
Later in January 1978, Salyut 6 was resupplied by an automated freighter named Progress 1. The refuelling operation was long and arduous, but was completed without a hitch. Progress 1’s engines were used to raise Salyut 6’s orbit, and then the freighter returned to Earth as a spacegoing dustbin filled with used air filters, containers and such like. The crew of Soyuz 26, still aboard, were joined by the Soyuz 28 mission. Various experiments were carried out, including metallurgical research, and in March 1978 the crew left the station running on automatic as they descended to a hero’s welcome on Earth.
In February 1979 Soyuz 32 carried a new crew to rendezvous with Salyut 6. Cosmonauts Lyakhov and Ryumin carried out vital maintenance work on the station, repairing or replacing components that had been designed for neither. Their workload was considerable, and continued after the first Progress resupply mission. The Progress unit was used to boost Salyut 6’s orbit after it had contributed to the hazardous and difficult repair of a fuel tank aboard the Salyut station. It was then discarded.
Soyuz 33 lifted off in April 1979, carrying the first civilian commander of a space mission. Despite the hazards of foul weather – the worst conditions under which a manned launch had been undertaken to date – the mission made a successful rendezvous with the station. However, during the docking approach the Soyuz engine malfunctioned and the mission had to be aborted using the emergency backup engine. The crew made an 8-g ballistic descent at night, but were found unharmed if shaken beside their overturned capsule.
While engineers tried to determine what had happened to Soyuz 33, the crew still aboard Salut 6 carried on their programme of experiments, resupplied by Progress 6 and the unmanned Soyuz 34. Soyuz 34 was sent to replace Soyuz 32 which it was thought might deteriorate to an unsafe condition during the long period in space. Normally visitors swapped ships with the crew to ensure that a relatively new vessel was available for them to leave the station at need.
In June 1979, Progress 7 brought a new radiotelescope to be fitted to the station. This was correctly fitted by the Cosmonauts, but fouled the aft docking port when the antenna was stowed. Try as they might, the crew could not free the antenna from inside the station, so in order to clear the docking port the Cosmonauts volunteered to undertake – insisted upon undertaking - an unplanned, hazardous EVA at the rear of the station where no Cosmonaut had previously worked. Despite the difficulties he encountered, Cosmonaut Ryumin was able to free the antenna and kick it away from the port. A few weeks later the two-man-crew returned to Earth after nearly 6 months in space.
In April 1980, Ryumin returned to Salyut 6 after a late personnel switch. During the period of automatic operation, a new unmanned craft, Soyuz T-1, had docked with the station. As soon as it left, Progress 8 arrived and required unloading. More experimentation was carried out using supplies delivered by Progress 9, and the first visitors arrived aboard Soyuz 36.
The first manned Soyuz T ferry arrived in June 1980. This mission was in part a proving flight for the new automatic docking systems. While the new craft was being evaluated, Soyuz 36 and 37 arrived with more visitors. The station was resupplied by Progress 11 in September, in the hope that the station could be used again even though it had exceeded its intended lifespan. The station was placed in a safe orbit and the Cosmonauts departed in October.
Soyuz T-3 docked with the venerable Salyut 6 station in November 1980, carrying the first 3-man Soyuz crew since the Soyuz 11 mission, where all 3 Cosmonauts had been killed during re-entry. This new crew carried out the most complex repair programme yet, and even managed to complete some scientific experiments.
After a resupply mission by Progress 12, yet another crew was launched aboard Soyuz T-4 in March 1981. Cosmonaut Viktor Savinykh became the 100th human in space and the 50th Cosmonaut during this mission, which included more repairs and scientific experiments. More visitors joined the crew for a short time, arriving aboard Soyuz 39. Soyuz 40, last of its kind, delivered the last visitors to the station a few weeks later, and in May 1981 the standing crew closed up shop for the last time and departed the station.
Salyut 6 demonstrated that humans could live and work in space for months at a time – or even longer - at need, and to conduct the most difficult and complex tasks within a space vehicle or during EVA. In addition to the immense amount of data gathered in many experiments, the station was the proving ground for automated capsules and systems. And it still had one final part to play.
In June 1982 Cosmos 1267, an unmanned vessel as large as the Salyut station, was launched to rendezvous with Salyut 6. Cosmos 1267 was used as a tug to propel the station through a series of manoeuvres designed to investigate its stability under power. The mission completed, both craft re-entered in July 1982 having proven that space station modules could be manoeuvred by orbital tugs and thus helped pave the way for a new generation of orbital stations.
Salyut 7 was placed in orbit in April 1982, before Salyut 6 had re-entered. Very similar to its predecessor, Salyut 7 boasted improved docking and navigation systems and solar panels.
The first crew arrived aboard Soyuz T-5 in May 1982. After some docking problems the crew checked over the station and got down to work. After resupply by Progress 13, the first visitors arrived in June aboard Soyuz T-6, including a Frenchman. While many of the visitor missions had been "international" in that they included personnel from allied countries, Soyuz T-6 was unique in that Jean-Loup Chretien was the first Westerner aboard a Soviet station. More docking problems ensued, but the crew – for the first time five men aboard the Salyut station – got quickly down to work, including experiments on the use of antibiotics in weightless conditions. Soyuz T-7 arrived in August 1982 with the second woman in space aboard. This week-long mission concentrated mainly on microbiological experiments.
The crew of Salyut 7 returned to Earth in December 1982, having travelled 80 million miles and spent half a year in space. They had conducted over 300 experiments and made many valuable observations of the Earth. The capsule came down in a blizzard and rolled over on a slope. Despite their traumatic landing, the Cosmonauts recovered well.
In March 1983 Cosmos 1443, an updated version of Cosmos 1267, conducted an automatic docking. This vessel carried a far greater payload than the Progress ships, and could also function as an orbital tug. It was used to lower Salyut 7’s orbit in preparation for a new manned launch.
The expected launch came in April 1983, when Soyuz T-8 attempted delivery of a 3-man crew to the station. Discovering that the docking-control radar had failed, the crew made numerous attempts to fix the fault, and then even began a manual docking operation using only a searchlight mounted on the Soyuz capsule. Despite their courage and best efforts, the mission had to be abandoned as fuel stocks ran low. The Cosmonauts made a safe if hasty re-entry.
Soyuz T-9 docked with Salyut 7 (which itself was still mated to Cosmos 1443) in June 1983, bringing aboard a new 2-man crew. While practising a station evacuation drill, the crew were alarmed by a micrometeorite impact against a station window. It was too small to cause serious damage but sharply illustrated the dangers faced by personnel working in space.
In August, the Cosmos module undocked and returned to Earth after conducting its own tests. Its place was taken by Progress 17, which marked a new innovation in resupply. Among its cargo of mission supplies, mail and spares was a consignment of fresh food loaded only hours before launch. Previously fresh food had been sent up to the orbital station but was loaded days in advance and lost some of its appeal.
After refuelling in September, things began to go badly wrong for Salyut 7. A fuel leak and other problems put most of the station’s attitude thrusters out of action and with the backup motor also out of commission the station was reported in the US as being "dead in the water".
Reports also began to emerge of a launch mishap during a hurried operation to get Soyuz T-10 to the station ahead of the expected October launch window. Two Cosmonauts had a narrow escape when a fuel leak less than two minutes before launch caused a huge fireball to engulf their craft. The automatic escape mechanism was destroyed by the fire and had to be triggered from launch control. Both Cosmonauts survived unharmed despite coming within seconds of incineration.
Suspecting that the Soyuz T-9 capsule was out of commission, some US analysts speculated that the crew were in dire straits and unable to leave their station – even if Soyuz T-10 and its 2-man crew had reached the station, there was no way to bring 4 Cosmonauts home in a 3-man ship. A rescue mission by the Space Shuttle was postulated while the press ran features on the two Cosmonauts with dire headlines such as "Marooned In Space".
In fact the station was in trouble, though things were not as bad as some thought. The fuel leak was less serious than imagined, but the corrosive fuel had caused environmental problems and reduced the station’s available power. As a result, cabin temperature was unpleasantly low and high humidity caused damp conditions on top of everything else.
The Soyuz T-10 mission (redesignated Soyuz T-10A) had been initiated in response to this situation. The crew were to have assembled the extra solar panels brought aboard by Cosmos 1443, to augment the station’s power and allow continued operations. The panels were already aboard the station, so the two men aboard were forced to attempt assembly despite never having trained for the operation. Their two difficult EVA missions were a success and, having saved the station, the crew resupplied from Progress 18, mothballed the station and returned safely to earth aboard the supposedly-defunct Soyuz T-9.
The next mission to Salyut 7, blasting off aboard Soyuz T-10 (the aborted mission had been redesignated T-10A) in February 1984, brought 3 Cosmonauts to the station for a new long-duration mission. Their number included a doctor who had been sent to study the effects of long periods in space first-hand.
The first visitors to Salyut 7 on this mission arrived in April aboard Soyuz T-11, including an Indian guest Cosmonaut who practised Yoga instead of the standard exercises. The station was a little crowded with six personnel aboard, and shortly after the guests’ arrival, space was more populated than ever before as five Shuttle Astronauts were in orbit at the same time.
After the guests’ departure, Salyut 7 received a shipment of spares for the repair of the main propulsion unit. This ambitious task was aided by a folding work platform and framework developed specially for the mission. The repairs were difficult in the extreme – on their second EVA the crew spent a whole hour trying to unjam a single nut. This pushed their EVA to five hours. Their first, at four hours, had set a new Soviet record.
The repairs were a complete success, and by comparison the EVA operation the Cosmonauts had trained for, adding more solar panels to the station, proved straightforward. This evolution was completed in a single 3-hour EVA.
More visitors arrived in July, a stay which set another record – the first EVA by a woman, who was also the first woman to twice reach space. EVA experiments with a hand-held electron-beam cutter/welder proved to be a success.
The crew continued their work after the guests had left, setting a new endurance record, and returned to Earth in October 1984.
Salyut 7 continued to orbit under the control of its automatic systems for some time. At some point, ground control lost contact with the station and it became clear that the station was unstable and in a decaying orbit, headed for an inglorious end after 3 years off stalwart service.
Nine months after the departure of the previous crew, a 2-man mission to Salyut 7 blasted off. The Cosmonauts had been training for a routine occupation of the station. Now they were to undertake a risky salvage operation under unknown circumstances. Making a seat-of-the-pants manual approach to the station, which was tumbling out of control, the crew achieved docking and boarded Salyut 7.
The station was in a sorry state. With the temperature so low that the drinking water had frozen and frost had formed on the walls, no power in the batteries and the air still and lifeless, there seemed little hope. But for the determination of the Cosmonauts and the ingenuity displayed at every turn by space explorers of all nations, the mission would have failed utterly.
With advice from their ground controllers the Cosmonauts began working to restore some power to the station, which was so cold that they had to frequently retire to their Soyuz capsule where they had jury-rigged a stove to heat food and drinks. The capsule was not designed nor equipped for this role but with nothing better the Cosmonauts made do or adapted what they had.
Amazingly, they succeeded in bringing Salyut 7 painfully back to life, and late in June a resupply ship arrived, bringing vital spares to restore the station to operational life. The Cosmonauts performed much work outside the station, benefiting from recent improvements in EVA suits, incorporating lessons learned in earlier Salyut missions.
By September, Salyut 7 was ready to receive visitors and a crew changeover. Normal operations continued, including an ambitious experimental programme. However, by November it was apparent that something was wrong aboard the station and shortly afterward it was announced that the Cosmonauts had returned early to Earth due to the illness of one of their number. Western analysts have interpreted the "illness" as psychological rather than physical.
Despite this downbeat ending to the last Salyut mission, the stations had proved beyond doubt that not only could humans live and work in space for extended periods of time but could conduct repairs and alterations to a space station or vessel far beyond what the designers had expected. The wealth of scientific data and experience with space operations gathered in the course of the Salyut missions prepared humans to take another step down the road to the stars.
And when the time came to take that step, Salyut 7 had a final part to play.
Spacelab
The International Spacelab project, an orbital laboratory, was a rather different concept to Skylab or Salyut. Rather than a semi-permanent station to which crews ascended, Spacelab was conceived as a payload unit to be carried into orbit and returned to Earth in the payload bay of the US Space Shuttle.
In November 1983 a crew of six Astronauts under the veteran John Young made a perfect takeoff aboard the shuttle Columbia and reached orbit before the inevitable space-station troubles began. The door connecting the crew compartment of Columbia to the pressurised Spacelab bay jammed and required the efforts of the entire crew to free.
After this setback, Spacelab was deployed successfully and operations began on a three crew on/three off basis to maximise returns from the station. After a few days, however, the strain of the awesome workload placed on the crew began to tell. After a sharp exchange with Mission Control, the schedule was adjusted to a more humanly-possible one.
Later in the mission three of the six astronauts held a press conference while the others staged a memorable – but silent – protest at the staged and scripted nature of the supposedly open conference.
At the very end of the longest Shuttle mission to date, Columbia, which had performed perfectly so far, developed a number of faults caused by a vibration – itself caused by a fault with the manoeuvring thrusters. After a fraught 4-orbit period spent trying to find the fault, Columbia made a clean re-entry and touchdown at Edwards Airforce Base. More drama ensued just after landing as smoke was observed coming from one of the Orbital Manoeuvring System pods. A fuel leak had caused a fire which destroyed nearby equipment which included power-generating units. Valuable lessons were learned from the incident, which almost ended in tragedy.
Spacelab 3 flew ahead of Spacelab 2, in April 1985. As with Spacelab 1, the orbital laboratory was pressurised and habitable "in shirtsleeves" while the Astronauts conducted their research. Two dozen rats and two squirrel monkeys accompanied the human personnel on the mission, which was to include research in four major fields including life sciences.
Shuttle Challenger blasted off after a slight delay caused by a problem at Mission Control, to make a perfect orbital insertion. The shuttle performed flawlessly for a week, with only a minor problem with a water dispenser. The scientific equipment was less co-operative, however. The usual orbital-operation problems began when a satellite antenna jammed the launch unit and could not be freed. Two of the five atmospheric experiments failed, and monkey faeces drifted into the shuttle’s flight deck, causing some aggravation among the flight crew. Several repairs were improvised by the crew or directed by Mission Control, allowing most of the experiments to be conducted.
Despite a problem with the payload bay door latches, Challenger made a safe landing to conclude a mission judged to be an overall success despite the problems with various equipment.
Spacelab 2 blasted off in July 1985 aboard the shuttle Challenger, carrying a variety of experiments in several fields. The configuration of the lab was different this time, an open load carried in a shuttle pallet rather than a self-contained laboratory unit. Indeed, the Shuttle itself was to be an integral part of the experimental sequence, using its OMS engines to create a temporary "hole" in the ionosphere for ground instruments to use.
An earlier launch attempt had been aborted on the pad due to technical problems but this time the launch went flawlessly until booster separation, when the temperature of a high-pressure fuel pump began to climb. An abort at this stage would require a most hazardous manoeuvre, but Challenger managed to clear the danger zone before the pump exceeded safety limits and automatically shut down. After several anxious moments it became clear that the shuttle would be able to limp into a safe abort orbit on her two remaining engines and make a textbook return to base.
Then a second gauge began to show excess temperature, which quickly reached dangerous levels. Losing a second engine at this point would probably mean a crash-landing in the Atlantic. Suspicious that two engines would suffer identical failures, Mission Control cross-checked with other systems and deduced an instrument failure. The decision to override the sensor was a weighty one, but as Challenger lit her OMS engines to augment the thrust of her remaining two main motors and struggled into orbit it became clear that the courageous decision to continue the mission was the right one.
With much of her OMS fuel used up in reaching orbit and an engine gone, Challenger was not able to reach the planned orbital height, yet the Astronauts succeeded in completing a reduced experimental package which included important experiments to detect cosmic "background noise" and ionospheric disruptions. The lower orbit proved to be an ideal height for the plasma physics experiments.
After completing 90% of the intended experiments, Challenger and Spacelab 2 returned to Earth for a perfect landing.
The fourth and final Spacelab mission was flown with a pressurised laboratory module similar to Spacelab 1 and 3, designated Spacelab D-1. Experiments from several nations were carried, of which many came from Germany (D stood for Deutsche). The mission comprised a record-breaking eight personnel aboard the shuttle Challenger. Liftoff and orbital insertion took place in late October 1985, and proceeded without flaw. The workload was as usual intense, with the lab manned in two shifts by teams of three. Despite the fact that the mission was jointly controlled from the US and Germany, excellent teamwork resulted in a smooth mission which conducted many experiments including extensive research into weightlessness adaptation.
After a near-perfect mission, Challenger and Spacelab D-1 made a textbook touchdown and conducted some manoeuvres during roll-out to test modifications to the landing gear.
Spacelab D-1 was a total success.
Mir
Launched in February 1986, the Russian station Mir ("World") was a direct descendant of the Salyut stations, and benefited from experience gained in Salyut operations. Constructed on a modular basis, Mir has five docking ports at the "front" end and an aft port used by Progress resupply vessels in much the same manner as the Salyut stations.
The first module added to Mir was Kvant (Quantum) I, in March 1987. Kvant II joined the station in 1989. The station was fully operational long before this, being designed to take additional modules at any time.
The interior of the station was designed with Salyut experience in mind. Crew comfort and habitability were greatly improved, as would be expected with a station intended to be permanently manned. By moving much of the experimental equipment into modules and thus creating a main habitation area, it was possible to create small individual cabins for each crewmember and a gymnasium area. In addition, much of the station’s running was automated, increasing the amount of time available for Cosmonauts to spend on experimentation rather than housekeeping.
It should be no surprise to anyone familiar with space station operations that Mir was plagued with technical problems, nor that by a series of running repairs and what amounted to damage-control operations the station remained operational far longer than was envisaged.
The Mir story began in March 1986 when Soyuz T-15 delivered two crew to the new station. After resupply and some tests, the two Cosmonauts played out the final episode in the Salyut epic. Boarding their Soyuz capsule they left Mir and changed orbits to rendezvous with Salyut 7. Transferring equipment to the venerable station they conducted a series of experiments before returning to Mir.
Salyut 7 was boosted into a higher orbit, signalling the end of its active life and after a total of 125 days in space the Cosmonauts prepared Mir for an unmanned period and returned to Earth.
The most dramatic incident in Mir’s orbital career was the collision between a Progress resupply ship and the Spektr Remote Sensing Module in June 1997. The accident caused a power loss and threatened the station with depressurisation. The international crew were able to save the station, though on Earth allegations that Mir was unsafe and should be abandoned were rife.
Mir’s active life has been plagued by equipment breakdowns and the occasional outright crisis, but has also seen endurance records smashed. Cosmonauts have remained in orbit for more than a year without serious ill effects, though two hours a day of exercise are considered necessary to avoid calcium loss in the bones and muscle wastage. Since its launch in February 1986 Mir has been almost constantly inhabited and has hosted guest Cosmonauts from several nations.
Mir has been kept in commission longer than was intended by its designers, to serve as a stepping stone for the construction of the International Space Station. US Shuttles have carried out many missions to the station, harking back to the 1975 "Handshake in Space" and ushering in a new age of co-operation in space.
But at last the story of Mir is drawing to a close. Preparations are underway for a final mission to the station, during which Cosmonauts will lower its orbit ready for ground controllers to send it into the atmosphere to burn up.
International Space Station
Taking Mir’s place on the stage of space adventure is the International Space Station. A collaborative effort by several nations, The station’s modular design is based upon technology proven aboard Mir.
Parts of the Zvezda station have been delivered by Russian Proton rockets and US space shuttles. The first such module was Zarya ("Sunrise") which arrived aboard a Proton rocket in November 1998. A second piece, the Unity node, was delivered by Shuttle a month later. The next step will be to add a service module named Zvezda ("Star"), which will provide living quarters for the crew of the station. Many more component flights and supply missions will be needed before the station becomes operational - it will take an estimated seven years to assemble, and will require continued co-operation from all nations involved in the project. Once compete, the International Space Station will be an impressive platform for scientific research and perhaps the jumping-off point for manned exploration of our solar system.
(Note: These are old articles posted to preserve them. Someday I'll update them. Really.)