Project Skylab - Post SL-4 Plans

Post SL-4 Plans

Skylab was abandoned after the end of the SL-4 mission in February 1974, but to welcome visitors the crew left a bag filled with supplies and left the hatch unlocked. 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.

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." Since 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, while plans had originally called for Skylab crews to perform only limited maintenance they successfully made major repairs during EVA, such as the SL-2 crew's deploying 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 it with 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 manned again, went one argument, it would serve as a useful experimental platform.