The Apollo spacecraft was designed as part of the Apollo Program, by the United States
in the early 1960s to land men on the moon before 1970 and return them safely to earth.
Spacecraft and Subsystems
As the name implies, the Command and Service Module (CSM) 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.
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.
For the long-duration Skylab missions the spacecraft was almost identical to the
command and service module used for Apollo missions. Modification was made to accomodate
long-duration Skylab missions and to allow the spacecraft to remain semi-dormant while
docked to the Skylab cluster. A crew of three men and their
provisions were carried. The mission of this spacecraft was to ferry a crew of three to
the Skylab complex and return them to earth.
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 sandwhich 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 re-startable 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.
For the J-Series, the configuration was changed: The six sections of the SM held three
31-cell hydrogen oxygen fuel cells which provided 28 volts, an auxiliary battery, three
cryogenic oxygen and three cryogenic hydrogen tanks, four tanks for the main propulsion
engine, two for fuel and two for oxidizer, the subsystems the main propulsion unit, and a
Scientific Instrument Module (SIM) bay which held a package of science instruments and
cameras to be operated from lunar orbit and on Apollo 15 and 16 a small Particles and Fields Subsatellite to be put into lunar orbit.
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.
Crews
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