|Image credit: NASA|
The last Saturn V bore aloft the Skylab Orbital Workshop, a temporary space station. Skylab was the last vestige of NASA's ill-fated Apollo Applications Project. It comprised the 22-foot-diameter cylindrical Orbital Workshop (OWS) with two wing-like solar arrays, the cylindrical Airlock Module (AM) and Multiple Docking Adapter (MDA), and the truss-mounted Apollo Telescope Mount (ATM) with four solar arrays arranged in a "windmill" formation. The OWS, for which McDonnell Douglas was prime contractor, was a converted Apollo Saturn S-IVB stage.
Fully deployed in 435-kilometer-high orbit inclined 50° relative to Earth's equator, the 77-metric-ton OWS measured about 36 meters long. It included 347 cubic meters of living and working space pressurized to 5 pounds per square inch (psi). Skylab reached orbit unmanned and fully stocked with oxygen, nitrogen, water, food, clothing, film, spare parts, and other expendables. Apollo Command and Service Modules (CSMs) launched on two-stage Saturn IB rockets delivered to Skylab three-man crews and a small amount of cargo.
|Never mind what it says; this is the mission patch for the Skylab 2 crew. Image credit: NASA|
Skylab 1 was in fact nearly lost; it suffered damage about a minute after launch as its meteoroid shield deployed prematurely and peeled away, then lost one of its twin OWS solar array wings shortly after attaining orbit. The other wing array was stuck shut, leaving Skylab starved for power. With the reflective meteoroid shield gone, temperatures on board soared, threatening to spoil food, medicines, and film.
NASA engineers hurriedly fashioned a sun shield and specialized tools and trained Skylab 2 astronauts Pete Conrad, Joe Kerwin, and Paul Weitz in their use. They reached Skylab on 25 May 1973, and succeeded in making it habitable and functional, then spent a total of 28 days in space. The Skylab 3 crew (Alan Bean, Jack Lousma, and Owen Garriot) spent 59 days on board the repaired station. After 84 days in space, the Skylab 4 crew (Gerald Carr, Edward Gibson, and William Pogue) undocked from Skylab on 8 February 1974.
|A repaired Skylab 1 orbits the Earth. Image credit: NASA|
Only one crew - the Soyuz 11 crew of Georgy Dobrovolsky, Vladislav Volkov, and Viktor Patsayev - succeeded in docking with and entering Salyut 1; they lived on board from 7 to 30 June 1971. During return to Earth, a valve accidentally opened in their reentry capsule, venting their air supply into space. The crew wore no pressure suits, so perished.
At the time Salyut 1 flew, the U.S. and the Soviet Union were negotiating toward a U.S. spacecraft docking with a Soviet spacecraft. By the end of 1971, the sides had settled on an Apollo CSM docking with a Salyut station. The two spacecraft would each carry a new-design International Docking Mechanism (IDM). The mission was meant to be a test of the IDM ahead of its routine use on future Soviet and American spacecraft.
In April 1972, however, Soviet negotiators declared that the Salyut design could not easily be modified to include a second docking port. They suggested that a CSM dock instead with a modified Soyuz. On 24 May 1972, at a summit meeting in Moscow, U.S. President Richard Nixon and Soviet Premier Alexei Kosygin signed the Space Cooperation Agreement, an international treaty that called for a wide range of cooperative ventures, including an Apollo-Soyuz docking. On 30 June 1972, NASA named the new cooperative program the Apollo-Soyuz Test Project (ASTP). The Soviets called it Soyuz-Apollo.
A week earlier, a McDonnell Douglas Astronautics Company team had pitched to NASA a cooperative space mission much more ambitious than either Apollo-Soyuz or Apollo-Salyut. The team proposed a docking between the Skylab B, a Salyut, an Apollo CSM, and a Soyuz ferry. The resulting "cooperative space laboratory" would "address world needs" and "provide identifiable benefits from space [and] mutual technological benefits and cost savings."
The U.S.-Soviet crew would perform solar, stellar, and Earth observations, communications technology development, and biomedical studies. Perhaps most important for NASA, Skylab-Salyut would serve as "an evolutionary step between Skylab A and Space Shuttle/Station" that would permit the U.S. space agency to keep its spaceflight teams mostly intact during the projected gap in U.S. piloted flights between ASTP in 1975 and the planned first Shuttle flight in 1979.
|McDonnell-Douglas illustration of Skylab-Salyut space laboratory.|
McDonnell Douglas cited published Soviet data when it assumed that the Salyut's propulsion system could be used to match orbits with Skylab B. As the Salyut-Soyuz combination approached the U.S. station, two cosmonauts would undock from the Salyut in the Soyuz and dock with an IDM-equipped port on the side of the Skylab MDA opposite the CSM. The lone cosmonaut on board the Salyut would then pilot it to a docking with the IDM-equipped Skylab forward port.
The cosmonauts and astronauts would work together on board Skylab-Salyut for at least 24 days (the longest period a Soyuz had operated in Earth orbit as of June 1972). The three cosmonauts would then undock in the Soyuz and return to Earth. The Soviets could then launch at least one more crew to the station. After up to 70 days in orbit, the first U.S. crew would return to Earth in its CSM. A second CSM would then deliver a second crew. If they docked immediately after the first crew departed, the second crew could remain on board Skylab-Salyut for up to 70 days.
|Image credit: Junior Miranda|
If the international station adopted Skylab's oxygen-rich 5 psi atmosphere, the Salyut and Soyuz would require improved fireproofing and beefed-up thermal control systems to keep its electronics cool in the thin air. If, on the other hand, the Soviet 15 psi pressure were adopted, Skylab B would need substantial structural changes to withstand the increased pressure and extra tanks of oxygen and nitrogen to make up for air lost through accelerated leakage. The CSM could not withstand 15 psi without suffering damage, so would need to remain isolated from the Skylab/Salyut/Soyuz cluster. McDonnell Douglas suggested that a small airlock for pre-breathing be placed in the MDA for CSM access.
|Image credit: Junior Miranda|
Some modifications would be required no matter which atmosphere was adopted. McDonnell Douglas assumed that Skylab B would provide all attitude control for the international station. To meet this requirement, NASA would need to equip it with control moment gyros 30% more capable than those planned for Skylab A. The Skylab B MDA structure would have to be beefed up to handle greater docking loads, as would its ATM trusses. In addition, a new thermal radiator would be needed to dissipate the heat produced by the three Soviet cosmonauts when they worked on board Skylab B. McDonnell Douglas proposed that this be added to the Fixed Airlock Shroud at the front of the OWS, close to the MDA.
Possible Salyut changes would include enlarged solar arrays; these might be needed because the four arrays on the Skylab B ATM would shade the Salyut's forward pair of arrays, reducing the Soviet station's electricity supply by up to a quarter. McDonnell Douglas assumed that Skylab B and the Salyut would not share electricity, so the U.S. would be unable to make up the difference. The company added, however, that, by relieving the Salyut of attitude control responsibilities, Skylab B might save it as much electricity as it took away.
|Apollo-Soyuz crews pose with a model of their docked spacecraft. At left in brown are Deke Slayton, Thomas Stafford (standing), and Vance Brand; at right in green are Alexei Leonov (standing) and Valeri Kubasov. Image credit: NASA|
After reaching an unusually low 188-by-228-kilometer orbit – required because the Soyuz could not climb higher – the ASTP Apollo CSM detached from the Saturn IB S-IVB stage that had injected it into orbit and turned 180°. It then docked with an Apollo-type port on the Docking Module (DM). The DM, which had reached orbit within a streamlined shroud between the CSM's large engine bell and the top of the S-IVB stage, included an international docking system and an airlock to enable the ASTP crews to move between the U.S. and Soviet spacecraft atmospheres without harm. After they extracted the DM from the spent S-IVB, the American ASTP crew maneuvered their spacecraft toward a rendezvous with Soyuz 19.
The ASTP CSM docked with Soyuz 19 on 17 July 1975. Following two days of ceremonies and mutual experiments, the two spacecraft undocked, redocked with Soyuz 19 playing the active role, and then went their separate ways. Soyuz 19 landed in Soviet Kazakhstan on 21 July and the ASTP CSM splashed down in the Pacific Ocean on 24 July, six years to the day after Apollo 11 returned from the moon. It was the last time American astronauts flew in space until the first Space Shuttle flight in April 1981.
In 1974, NASA studied a 1977 ASTP mission. At about the same time, work began toward a Shuttle-Salyut docking in the early 1980s. New cooperation was hampered by U.S. domestic politics: the Administration of Gerald Ford felt unable to commit to a new international piloted flight ahead of the November 1976 presidential election.
|Shuttle-Salyut concept. Image credit: Junior Miranda|
U.S.-Soviet relations gradually soured, however. A Shuttle-Salyut technical meeting planned for April 1978 was indefinitely postponed. In September 1978, NASA ceased Shuttle-Salyut planning pending the outcome of an U.S. government interagency review of U.S.-Soviet space cooperation in which the Department of State played the central role. The Soviet invasion of Afghanistan in December 1979 subsequently halted for a decade almost all discussion of dockings between U.S. and Soviet piloted spacecraft, though superpower space cooperation with a lower profile - for example, the Cosmos biosatellite program - continued.
Skylab B never reached orbit; it became an exhibit in the National Air and Space Museum in Washington, DC. NASA studied reboosting Skylab 1 into a higher orbit and reusing it in the Space Shuttle era, but Shuttle delays and a faster-than-expected rate of orbital decay meant that it reentered Earth's atmosphere on 11 July 1979.
Basic Data of the Scientific Orbital Station “Salyut,” USSR, no date (1971?)
US/USSR Cooperative Space Laboratory (Skylab/Salyut), McDonnell Douglas Astronautics Company Eastern Division, 23 June 1972
Skylab News Reference, NASA Office of Public Affairs, March 1973
Apollo-Soyuz Test Project Information for Press, USSR/NASA, 1975
Thirty Years Together: A Chronology of U.S.-Soviet Space Cooperation, NASA CR 185707, David S. F. Portree, February 1993, pp. 9-26 (http://ntrs.nasa.gov/search.jsp?R=19930010786 - accessed 15 July 2015)
Mir Hardware Heritage, NASA RP 1357, David S. F. Portree, March 1995, pp. 33-35, 65-72 (http://history.nasa.gov/SP-4225/documentation/mhh/mhh.htm - accessed 21 July 2015)
NASA's 1992 Plan to Land Soyuz Space Station Lifeboats in Australia
A Forgotten Rocket: The Saturn IB