|MadSci Network: Engineering|
Space Shuttles do not experience the same kind of temperatures on launch that they do on re-entry. When a Space Shuttle is in orbit it travels at about 17,500 mph relative to Earth. As a shuttle returns to Earth it only slows by about 200 mph before encountering the atmosphere at a shallow angle. When a shuttle encounters the atmosphere moving so fast the air ahead of it is compressed greatly and heats up. The air is heated so much that it glows and ionizes to become a plasma (a gas with electrically charged particles). The same thing happens when a meteor enters Earth's atmosphere, and the heat from the superheated gas ahead of it usually burns up the meteor completely. Space Shuttles have protective tiles covering the spacecraft that dissipate this heat so that the orbiter does not burn up like a meteor.
On launch, a Space Shuttle starts out with zero speed and accelerates quickly nearly straight up. Launching straight up allows a Shuttle to get through the densest part of the atmosphere quickly before it has a very high velocity. Once the denser parts of the atmosphere are cleared the shuttle turns to accelerate to orbital speeds. The orbiter still encounters some heating from compressed air ahead of it, but it is minimal compared that encountered during re-entry.
I hope that helps to answer some of your questions. For more information about the Space Shuttle, check out How Space Shuttles Work at HowStuffWorks.com which also has many links at the end of the article.
Education and Public Outreach Scientist, UC Berkeley
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