The first U.S. version of a space station, Skylab, was launched on May 14, 1973.
The astronauts on the first mission had to spend a great deal of time repairing the station, which had seriously malfunctioned from the time it took off.
They were able to fix it and complete their planned experiments within 28 days.
Two more missions used, and had to repair, Skylab successfully.
Major studies involved observations of Earth, solar flares, and the comet Kohoutek, plus research into the medical effects of long-term space travel.
Each Skylab mission set a record for the amount of time astronauts spent in space, and the crew enjoyed taking a shower once a week but found drying themselves in weightlessness difficult.