Apollo command and service module

The crewed Apollo spacecraft paired a detachable command module for the astronauts and Earth reentry with a service module carrying propulsion, power, oxygen, and water systems.

Apollo command module: The cone-shaped Apollo spacecraft section that housed the crew and returned them to Earth. It separated from the service module before atmospheric reentry.
Apollo program: The United States human spaceflight program that landed astronauts on the Moon from 1969 to 1972. The command and service module was the crewed spacecraft for Apollo lunar missions.
Apollo 7: The 1968 crewed Earth-orbit mission that tested the Apollo command and service module. It was the first crewed flight of the spacecraft.
Gemini spacecraft: The two-astronaut spacecraft used in NASA's Gemini program before Apollo. Gemini was smaller and lacked Apollo's separate service module.
Apollo service module: The uncrewed cylindrical Apollo spacecraft section that supplied propulsion, electrical power, oxygen, and water. It carried the systems and engine the command module lacked.
Apollo Lunar Module: The Apollo spacecraft designed to carry astronauts from lunar orbit to the Moon's surface and back. It docked with the command and service module for the lunar missions.
Apollo 8: The 1968 mission that carried astronauts around the Moon without landing. Its crew tested the command and service module in lunar orbit.
Mercury spacecraft: The one-astronaut spacecraft used in NASA's first human spaceflight program. Mercury returned its capsule without Apollo's modular lunar-flight architecture.
Service Propulsion System: The Apollo spacecraft's restartable hypergolic engine used for major trajectory changes. Its engine performed translunar injection, lunar-orbit maneuvers, and the return burn.
Saturn V: The multistage American launch vehicle that sent Apollo crews and spacecraft toward the Moon. It launched the spacecraft on crewed lunar missions.

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