Apollo (spacecraft)

After conclusion of the Apollo program, four CSMs were launched on Saturn IBs for three Skylab Earth orbital missions and the Apollo-Soyuz Test Project.

The service module was unpressurized and contained a main service propulsion engine and hypergolic propellant to enter and leave lunar orbit, a reaction control system to provide attitude control and translational capability, fuel cells with hydrogen and oxygen reactants, radiators to dump waste heat into space, and a high gain antenna.

Capable of multiple restarts, this engine placed the Apollo spacecraft into and out of lunar orbit, and was used for mid-course corrections between the Earth and the Moon.

The ascent stage contained the crew cabin, instrument panels, overhead hatch/docking port, forward hatch, optical and electronic guidance systems, reaction control system, radar and communications antennas, ascent rocket engine and propellant to return to lunar orbit and rendezvous with the Apollo Command and Service Modules.

The spacecraft–LM adapter (SLA), built by North American Aviation (Rockwell), was a conical aluminum structure that connected the service module to the Saturn S-IVB rocket stage.

[2] The exterior of the SLA was covered by a thin (0.03–0.2 in or 0.76–5.08 mm) layer of cork and painted white to minimize thermal stresses during ascent.

[3] The service module was bolted to a flange at the top of the longer panels, and power to the SLA multiply-redundant pyrotechnics was provided by an umbilical.

After the astronauts docked the CSM to the LM, they blew charges to separate those connections and a guillotine severed the LM-to-instrument-unit umbilical.

[4] Alternatively, the Commander could activate the system manually using one of two translation controller handles, which were switched to a special abort mode for launch.

When activated, the LES would fire a solid fuel escape rocket and open a canard system to direct the CM away from, and off the path of, a launch vehicle in trouble.

If the emergency happened on the launch pad, the LES would lift the CM to a sufficient height to allow the recovery parachutes to deploy safely before coming in contact with the ground.

In the absence of an emergency, the LES was routinely jettisoned about 20 or 30 seconds after the launch vehicle's second-stage ignition, using a separate solid-fuel rocket motor manufactured by the Thiokol Chemical Company.