Page 27 - Curriculum Visions Dynamic Book

Gliding back to Earth
The orbiter is not an airplane but a glider. The only engines it can use are the small ones that slow it down until it begins to sink out of orbit.
The orbiter begins reentry at an altitude about 122 km from the Earth’s surface. It then follows a glide path
8,000 km long that eventually allows the orbiter to lose enough altitude to touch down. Even then, its high landing speed means that it can only land safely on a specially built extralong runway.
As the orbiter sinks farther and farther into the atmosphere, friction with the gases of the air acts as
a natural brake, saving on the use of retrorockets. However, that same friction causes heat to build up on the leading surfaces. To prevent structural damage, these vulnerable surfaces are covered with thermal ceramic blankets and tiles, which act as HeAt sHields.
friction The force that resists two bodies that are in contact.
HeAt sHield A protective device on the outside of a space vehicle that absorbs the heat during reentry and protects it from burning up.
rAdAr Short for radio detecting and ranging. A system of bouncing radio waves from objects in order to map their surfaces and find out how far away they are.
retrorocket A rocket that fires against the direction of travel in order to slow down a space vehicle.
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