Spacecraft

Shock waves also affect spacecraft returning to Earth. When a space­craft plunges back into Earth’s atmosphere from space, it compresses the air in front of it, and a shock wave is formed.

When air is compressed, it heats up. The shock wave created by a spacecraft reentering the atmosphere at high speed is very hot. The Mercury, Gemini, and Apollo manned space capsules, were designed to reenter the atmos­phere blunt end first.

This blunt shape helped to push the super-hot shock wave forward, away from the capsule. A heat shield protect­ed the astronauts and spacecraft from the heat that remained.

Today, the Russian Soyuz capsules use this method, and so does the Space Shuttle. The Space Shuttle reenters the atmosphere with its nose tipped up and its large underside facing the direction of flight. This deflects most of the heat­ed shock wave around the spacecraft.

As the Space Shuttle descends lower in the atmosphere, nose and tail shock

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waves form on it. They spread out and reach the ground, where people hear two sonic booms. All supersonic aircraft form two shock waves. Unlike the Space Shuttle, however, most of these aircraft are so small, and the shock waves they create are so close together that only one bang is audible.

SEE ALSO:

• Air and Atmosphere • Pressure

• Supersonic Flight