Apollo Command/Service Module - Modifications For Saturn IB Missions

Modifications For Saturn IB Missions

The Low Earth Orbit payload capability of the Saturn IB booster used to launch the Low Earth Orbit missions (Apollo 1 (planned), Apollo 7, Skylab 2, Skylab 3, Skylab 4, and Apollo-Soyuz) could not handle the 66,900 pounds (30,300 kg) mass of the fully fueled CSM. This was not a problem, because the delta-V requirement of these missions was much smaller than that of the lunar mission; therefore they could be launched with less than half of the full SPS propellant load, by filling only the SPS sump tanks and leaving the storage tanks empty. The CSMs launched in orbit on Saturn IB ranged from 32,558 pounds (14,768 kg) (Apollo-Soyuz), to 46,000 pounds (21,000 kg) (Skylab 4).

The omnidirectional antennas sufficed for ground communications during the Earth orbital missions, so the high gain S-band antenna on the SM was omitted from Apollo 1, Apollo 7, and the three Skylab flights. It was restored for the Apollo-Soyuz mission to communicate through the ATS-6 satellite in geostationary orbit, an experimental precursor to the current TDRSS system.

On the Skylab and Apollo-Soyuz missions, some additional dry weight was saved by removing the otherwise empty fuel and oxidizer storage tanks (leaving the partially filled sump tanks), along with one of the two helium pressurant tanks. This permitted the addition of some extra RCS propellant to allow for use as a backup for the deorbit burn in case of possible SPS failure.

Since the spacecraft for the Skylab missions would not be occupied for most of the mission, there was lower demand on the power system, so one of the three fuel cells was deleted from these SMs.

The Command Module could be modified to carry extra astronauts as passengers by adding jump seat couches in the aft equipment bay. CM-119 was fitted with two jump seats as a Skylab Rescue vehicle, which was never used.