page_title: Skylab
section_title: Plans for re-use after the last mission
hierarchical_section_title: Skylab / Plans for re-use after the last mission
caption_attribution_description: KENNEDY SPACE CENTER, FLA. -- The command/service module for the Skylab Rescue Vehicle was removed from its Saturn IB rocket in the Vehicle Assembly Building here today. The Skylab Program ended with splashdown of the Skylab 4 crew in the Pacific Ocean Feb. 8, ending the need for the rescue vehicle on Complex 39's Pad B since early December. The SaturnIB/Apollo was returned to the VAB last week and is now being dismantled. The spacecraft is to be taken to the Manned Spacecraft Operations Building in the KSC Industrial Area Feb. 20. Both the spacecraft and rocket will be stored at KSC as backup flight hardware for the Apollo-Soyuz Test Project in 1975.
context_page_description: Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: SL-2, SL-3 and SL-4. Major operations included an orbital workshop, a solar observatory, Earth observation, and hundreds of experiments.
  Unable to be re-boosted by the Space Shuttle, which was not ready until the early 1980s, Skylab's orbit decayed and it disintegrated in the atmosphere on July 11, 1979, scattering debris across the Indian Ocean and Western Australia.
context_section_description: Calculations made during the mission, based on current values for solar activity and expected atmospheric density, gave the workshop just over nine years in orbit. Slowly at first—dropping 30 kilometers by 1980—and then faster—another 100 kilometers by the end of 1982—Skylab would come down, and some time around March 1983 it would burn up in the dense atmosphere.
  The three crewed Skylab missions used only about 16.8 of the 24-man-months of oxygen, food, water, and other supplies stored aboard Skylab. A fourth crewed mission was under consideration, which would have used the launch vehicle kept on standby for the Skylab Rescue mission. This would have been a 20-day mission to boost Skylab to a higher altitude and do more scientific experiments. Another plan was to use a Teleoperator Retrieval System (TRS) launched aboard the Space Shuttle (then under development), to robotically re-boost the orbit. When Skylab 5 was cancelled, it was expected Skylab would stay in orbit until the 1980s, which was enough time to overlap with the beginning of Shuttle launches. Other options for launching TRS included the Titan III and Atlas Agena. No option received the level of effort and funding needed for execution before Skylab's sooner-than-expected re-entry.
  The SL-4 crew left a bag filled with supplies to welcome visitors, and left the hatch unlocked. Skylab's internal systems were evaluated and tested from the ground, and effort was put into plans for re-using it, as late as 1978. NASA discouraged any discussion of additional visits due to the station's age, but in 1977 and 1978, when the agency still believed the Space Shuttle would be ready by 1979, it completed two studies on reusing the station. By September 1978, the agency believed Skylab was safe for crews, with all major systems intact and operational. It still had 180 man-days of water and 420-man-days of oxygen, and astronauts could refill both; the station could hold up to about 600 to 700-man-days of drinkable water and 420-man-days of food. Before SL-4 left they did one more boost, running the Skylab thrusters for 3 minutes which added 11 km in height to its orbit. Skylab was left in a 433 by 455 km orbit on departure. At this time, the NASA-accepted estimate for its re-entry was nine years.
  The studies cited several benefits from reusing Skylab, which one called a resource worth "hundreds of millions of dollars" with "unique habitability provisions for long duration space flight". Because no more operational Saturn V rockets were available after the Apollo program, four to five shuttle flights and extensive space architecture would have been needed to build another station as large as Skylab's 12,400 cubic feet (350 m³) volume. Its ample size—much greater than that of the shuttle alone, or even the shuttle plus Spacelab—was enough, with some modifications, for up to seven astronauts of both sexes, and experiments needing a long duration in space; even a movie projector for recreation was possible.
  Proponents of Skylab's reuse also said repairing and upgrading Skylab would provide information on the results of long-duration exposure to space for future stations. The most serious issue for reactivation was stationkeeping, as one of the station's gyroscopes had failed and the attitude control system needed refueling; these issues would need EVA to fix or replace. The station had not been designed for extensive resupply. However, although it was originally planned that Skylab crews would only perform limited maintenance they successfully made major repairs during EVA, such as the SL-2 crew's deployment of the solar panel and the SL-4 crew's repair of the primary coolant loop. The SL-2 crew fixed one item during EVA by, reportedly, "hit[ting] it with [a] hammer".
  Some studies also said, beyond the opportunity for space construction and maintenance experience, reactivating the station would free up shuttle flights for other uses, and reduce the need to modify the shuttle for long-duration missions. Even if the station were not crewed again, went one argument, it might serve 
caption: Skylab Rescue vehicle Apollo CSM being removed from its Saturn IB rocket after the last Skylab mission
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