Apollo 12 Command and Service Module Instrument Host Overview ======================== The Apollo 12 Command and Service Module (CSM) spacecraft orbited the Moon during the Apollo 12 mission. It was piloted by Richard F. Gordon. Spacecraft and Subsystems ------------------------- As the name implies, the Command and Service Module (CSM) for the Apollo 12 mission was comprised of two distinct units: the Command Module (CM), which housed the crew, spacecraft operations systems, and re-entry equipment, and the Service Module (SM) which carried most of the consumables (oxygen, water, helium, fuel cells, and fuel) and the main propulsion system. The total length of the two modules attached was 11.0 meters with a maximum diameter of 3.9 meters. Block II CSM's were used for all the crewed Apollo missions. The launch mass, including propellants and expendables, of the Apollo 12 CSM was 28,790 kg of which the Command Module (CM-108) had a mass of 5609 kg and the Service Module (SM-108) 23,181 kg. The Apollo 12 CM was named 'Yankee Clipper'. Telecommunications included voice, television, data, and tracking and ranging subsystems for communications between astronauts, CM, LM, and Earth. Voice contact was provided by an S-band uplink and downlink system. Tracking was done through a unified S-band transponder. A high gain steerable S-band antenna consisting of four 79-cm diameter parabolic dishes was mounted on a folding boom at the aft end of the SM. Two VHF scimitar antennas were also mounted on the SM. There was also a VHF recovery beacon mounted in the CM. The CSM environmental control system regulated cabin atmosphere, pressure, temperature, carbon dioxide, odors, particles, and ventilation and controlled the temperature range of the electronic equipment. Command Module -------------- The CM was a conical pressure vessel with a maximum diameter of 3.9 m at its base and a height of 3.65 m. It was made of an aluminum honeycomb sandwich bonded between sheet aluminum alloy. The base of the CM consisted of a heat shield made of brazed stainless steel honeycomb filled with a phenolic epoxy resin as an ablative material and varied in thickness from 1.8 to 6.9 cm. At the tip of the cone was a hatch and docking assembly designed to mate with the lunar module. The CM was divided into three compartments. The forward compartment in the nose of the cone held the three 25.4 m diameter main parachutes, two 5 m drogue parachutes, and pilot mortar chutes for Earth landing. The aft compartment was situated around the base of the CM and contained propellant tanks, reaction control engines, wiring, and plumbing. The crew compartment comprised most of the volume of the CM, approximately 6.17 cubic meters of space. Three astronaut couches were lined up facing forward in the center of the compartment. A large access hatch was situated above the center couch. A short access tunnel led to the docking hatch in the CM nose. The crew compartment held the controls, displays, navigation equipment and other systems used by the astronauts. The CM had five windows: one in the access hatch, one next to each astronaut in the two outer seats, and two forward-facing rendezvous windows. Five silver/zinc-oxide batteries provided power after the CM and SM detached, three for re-entry and after landing and two for vehicle separation and parachute deployment. The CM had twelve 420 N nitrogen tetroxide/hydrazine reaction control thrusters. The CM provided the re-entry capability at the end of the mission after separation from the Service Module. Service Module -------------- The SM was a cylinder 3.9 meters in diameter and 7.6 m long which was attached to the back of the CM. The outer skin of the SM was formed of 2.5 cm thick aluminum honeycomb panels. The interior was divided by milled aluminum radial beams into six sections around a central cylinder. At the back of the SM mounted in the central cylinder was a gimbal mounted restartable hypergolic liquid propellant 91,000 N engine and cone shaped engine nozzle. Attitude control was provided by four identical banks of four 450 N reaction control thrusters each spaced 90 degrees apart around the forward part of the SM. The six sections of the SM held three 31-cell hydrogen oxygen fuel cells which provided 28 volts, two cryogenic oxygen and two cryogenic hydrogen tanks, four tanks for the main propulsion engine, two for fuel and two for oxidizer, and the subsystems the main propulsion unit. Two helium tanks were mounted in the central cylinder. Electrical power system radiators were at the top of the cylinder and environmental control radiator panels spaced around the bottom. Scientific Experiments ---------------------- The following scientific experiments were performed on board the Apollo 12 Command and Service Module: - The Photography Experiment (1) obtained photographs of the transposition, docking, lunar module ejection maneuver, and the LM rendezvous sequence from both the command and lunar modules, (2) obtained photos of the lunar ground track and of the landing site from the low point of the LM's flight path, (3) recorded the operational activities of the crew, (4) obtained long-distance earth and lunar terrain photographs with 70-mm still cameras, and (5) obtained photos of lunar surface features and of the activities of the astronauts who landed on the Moon. - The Multispectral Photography Experiment obtained photographs showing lunar surface color variations for use in geologic mapping and correlation with surface samples from spectral reflectance. - The Window Meteoroid Detector Experiment used the CM heat shield window surfaces (fused silica) to obtain information about the flux of meteoroids with masses of 1 nanogram or less. About 0.4 square meters of the window surfaces were used as meteoroid impact detectors. - The S-Band Transponder Experiment measured the lunar gravitational field by observing the dynamical motion of the spacecraft in free fall orbits to provide information about the distribution of lunar mass. For more information about the CSM and its experiments, see the Apollo 12 Preliminary Science Report (1970) and the report 'Apollo 12, A New Vista for Lunar Science' (1970) References ========== Apollo 12 Preliminary Science Report, NASA SP-235, published by NASA, Washington D.C., 1970. Apollo 12, A new vista for lunar science, NASA EP-74, published by NASA, Washington, D.C., 1970.