Skylab B was a proposed second USspace station similar to Skylab that was planned to be launched by NASA for different purposes, mostly involving the Apollo–Soyuz Test Project, but was canceled due to lack of funding. Two Skylab modules were built in 1970 by McDonnell Douglas for the Skylab program, originally the Apollo Applications Program. The first was launched in 1973 and the other put in storage, while NASA considered how to use the remaining assets from Apollo. One considered option was to use Saturn VSA-515 to launch the backup Skylab station into orbit sometime between January 1975 and April 1976. That way, it could expand the Apollo-Soyuz mission by 56–90 days. Further proposals were made for an International Skylab, launched using Saturn V SA-514. This station would have been serviced by Apollo, Soyuz and later by the Space Shuttle.
Potential uses
Some uses considered for the second Skylab module included putting it into a rotation mode where it could generate artificial gravity and a plan to celebrate the 1976 United States Bicentennial with the launch of two Soviet Soyuz missions to the back-up Skylab. In preparation for the Apollo-Soyuz Test Project, McDonnell Douglas proposed a massive station by combining a Salyut station with Skylab B. This would be achieved by launching an Apollo with a multiple docking adapter with 4 docking ports to be able to dock both stations and servicing vehicles. The joint US-USSR mission would have possibly been called International Skylab. Modifications would have had to have been made to the Skylab B to support a mixed oxygen-nitrogen atmosphere to match the Salyut's atmosphere, or an airlock would have been needed to be installed to allow passage between the mixed atmosphere of the Soviet segment to the pure oxygen environment of the American segment. For future missions, the station, which would have then been called the Advanced Skylab, could have been expanded by the Space Shuttle, which was due to enter service in 1979. At the time the idea was discussed, NASA still had two Saturn V launchers, three Saturn IB boosters, the back-up Skylab space station, three Apollo CSMs and two Lunar Modules in storage. However, after the first Skylab was launched in May 1973, the plan for the Skylab B was canceled and the Apollo/Soyuz spacecraft had to use the Docking Module launched on the Apollo-Saturn IB for performing experiments in space. After Project Apollo ended and as NASA was moving to developing the Space Shuttle, the remaining Apollo hardware was donated to museums in 1976.
Possible crew
It was expected at the time by those involved that the initial crew would be the crew which served as backup for Skylab 3 and Skylab 4, and was kept in reserve for the Skylab Rescue mission :
Saturn V SA-515 was originally designated for Apollo 20, later as a backup Skylab launch vehicle.
The first stage was on display at Michoud Assembly Facility through June 2016. This was then moved to the Infinity Sciene Center in Pearlington MS.
The second stage is on display at Johnson Space Center.
The third stage is the Skylab B Orbital Workshop on display at the National Air and Space Museum. On display in the Museum's Space Hall since 1976, the orbital workshop has been slightly modified to permit viewers to walk through the living quarters.
A full-size mockup once used for astronaut training is located at the Lyndon B. Johnson Space Center visitor's center in Houston, Texas. Another full-size training mockup is at the U.S. Space & Rocket Center in Huntsville, Alabama. Originally displayed indoors, it was subsequently stored outdoors for several years to make room for other exhibits. To mark the 40th anniversary of the Skylab program, the Orbital Workshop portion of the trainer was restored and moved into the Davidson Center in 2013.
