Apollo spacecraft

The Apollo spacecraft was designed as part of the Apollo Program, by the United States in the early 1960s to land people on the moon before 1970 and return them safely to earth. It was made up of multiple units or modules that worked together to perform the mission of landing on the moon and returning to earth. The main parts of the Apollo spacecraft were (going from top to bottom) the launch escape system, the Command Module, the Service Module, the Lunar Module and the lunar module adapter.

Service Module (SM)

The Service Module was a portion of the spacecraft that is unpressurized and contains fuel cells, batteries, high gain antenna, radiators, water, oxygen, hydrogen, reaction control system, propellant to enter and leave lunar orbit, and service propulsion system. On Apollo 15, 16 and 17 it also carried a scientific instrument package, mapping camera and a small sub-satellite to study the moon.

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A major portion of the service module is taken up by propellant and the main rocket engine that placed the Apollo spacecraft into and out of lunar orbit. The main rocket engine was also used for mid-course corrections between the earth and the moon. It was capable of multiple restarts.

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It remained attached to the Command Module throughout the mission. It is jettisoned just prior to reentry into the earth's atmosphere.

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• Specifications:
• Length: 7.56 m
• Diameter: 3.90 m
• Mass: 24,523 kg
• Structure Mass: 1,910 kg
• Electrical Equipment Mass: 1,200 kg
• RCS Thrust: 16 × 440 N
• Propellants: N₂O₄/UDMH
• RCS Specific Impulse I_sp: 290 lbf·s/lb (2.84 kN·s/kg)
• RCS Impulse: 3,517 kN·s
• Service Propulsion Engine (SPS) Engine Mass: 3,000 kg
• SPS Engine Thrust: 98 kN
• SPS Engine Propellants: N₂O₄/Aerozine_50 (UDMH/N2H4)
• SPS Engine Propellants: 18,413 kg
• SPS Engine Specific Impulse I_sp: 314 lbf·s/lb (3.08 kN·s/kg)
• Spacecraft delta v: 2.804 km/s
• Electrical System: Fuel Cells
• Electric System: 6.30 average kW, 670 kW·h