One of the most crucial parts of a space mission is getting the crew safely back to Earth. As the Apollo spacecraft approached the Earth for re-entry, its service module (SM) activated its propulsion system to set the spacecraft on course to splash down in the Pacific Ocean. Before re-entering the atmosphere of the Earth, the astronauts, who were sitting in the command module (CM), jettisoned the SM. Thrusters turned the CM so that its broad, heat-shielded base was facing the Earth, thus slowing its descent. Although the friction from the atmosphere caused the temperature of the exterior of the CM to climb to 5,000 degrees Fahrenheit (2,760 degrees Celsius), the ablative covering of the heat shield melted and vaporized, diverting the heat away from the astronauts inside. Three large parachutes opened to slow the CM's descent before it landed in the Pacific Ocean. The crew members used a very high frequency recovery beacon and radio to signal their location to a recovery ship.
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