Skylab was America's first manned space station. It was built from the S-IVB stage of a Saturn V Moon rocket, its hydrogen tank being converted at the factory into spacious two-storey accommondation for a three-man crew. The bottom section contained a ward room, sleep compartments and a zero-g washroom/toilet; above was the spacious workshop. The total internal volume of Skylab with Apollo Command and Service modules docked was about 368 m³ - approximately the same as a small two-bedroom house.

Water, food and clothing sufficient for all nine astronauts of the three planned Skylab missions were stowed in special containers before launch, food in compartments and freezers in the upper section and wardroom. Attached to the outside of the station were large solar "wings", retracted during launch, while covering the workshop area was a thin aluminum shield which sprang out on links for protection against micrometeoroids and excessive solar heat. Forward of the workshop was the Instrument Unit, the Airlock Module and Multiple Docking Adapter which enabled Apollo spacecraft to dock with the station and transfer their crews; and mounted at the top was a major scientific instrument for observing the Sun called the Apollo Telescope Mount (ATM).

The space station was launched, unmanned, by a two-stage Saturn V on 14-May-1973. Sixty-three seconds into the flight part of the meteoroid shield had been torn off and this had carried away one of the station's two solar wings. Although the ATM had hinged out and locked into position, deploying its own four wings, the station was seriously underpowered and was liable to overheat. On 25-May the crew of Skylab 2 lifted off in their Apollo spacecraft. After acheiving rendezvous with the station, they made a fly-around inspection and confirmed that one solar wing was missing and the other jammed by a piece of the meteoroid shield. After repairing a problem with the docking mechanism, the crew was able to enter the space station. One of their first acts was to deploy a parasol-like sunshade through an experiment airlock in the side of the workshop, which helped bring the temperature down. On 7-June two astronauts made a 3-1/2 hour EVA to free the jammed solar panel.

With the additional power available the astronauts were able to get back to the original flight plan which included solar observations, Earth photography and biomedical experiments. Skylab 2's 28-day mission ended 22-June. The crews of Skylab 3 and Skylab 4 occupied the space station on missions of 59-days and 84-days respectively. Both crews continued to conduct experiments in the fields of biology, space medicine, solar physics, astrophysics, Earth observation, and technology.

After the last astronaut team left in 1974 Skylab was expected to continue orbiting the Earth into the early 1980s. However, increased solar activity in 1978-79 caused expansion of the Earth's atmosphere causing the station's orbit to decay quicker than anticipated. Skylab made its final plunge on 11-July-1979.

SKYLAB SPECIFICATIONS

Launched: 14-May-1973
Reentered: 11-Jul-1979
Principal uses: civilian space station
Orbit: 435 km
Crew size: 3
Endurance: 600 days
Orbital storage: 730 days
Overall length: 36.1 m
Maximum diameter: 6.6 m
Habitable volume: 361 m³
Total mass: 76,295 kg
Attitude control: reaction wheels
Power: solar panels, 2 wings + 4 windmill; 11.0 kW total average
Environment: oxygen/nitrogen atmosphere at 340 mbar; nominal temperature 21.1^oC

MULTIPLE DOCKING ADAPTER
Principal uses: docking module for two CSM, one ATM
Length: 5.3 m
Diameter: 3.1 m
Total mass: 6,260 kg

APOLLO TELESCOPE MOUNT
Principal uses: solar telescope module
Length: 3.4 m
Diameter: 2.1 m
Total mass: 11,180 kg
Power: solar panels, four windmill, each 14.9 m long

AIRLOCK MODULE
Principal uses: airlock for EVA's, mounting of STS and TNL
Length: 5.4 m
Diameter: 3.1 m
Total mass: 22,225 kg

INSTRUMENT UNIT
Principal uses: guidance during orbital insertion only
Length: 0.9 m
Diameter: 6.6 m
Total mass: 2,065 kg

ORBITING WORK SHOP
Principal uses: main laboratory
Length: 14.7 m
Diameter: 6.6 m
Total mass: 35,380 kg
Attitude control: reaction wheels
Power: solar panels (in operation only one deployed)