Drag, atmospheric

The orbits of artificial satellites of the Earth or other bodies with atmospheres whose orbits come close to their surfaces are very complicated. The orbits of these satellites are influenced by atmospheric drag, which tends to bring the satellite down into the lower atmosphere, where it is either vaporized by atmospheric friction or falls to the planet s surface. In addition, the shape of Earth and many other bodies is not perfectly spherical. The bulge that forms at the equator, due to the planet s spinning motion, causes a stronger gravitational attraction. When the satellite passes by the equator, it may be slowed enough to pull it to earth. 

Residual atmospheric drag effects and chemical attack from highly energetic atoms, principally from AO and AN radicals, Leger et al. (1986), Legereta/. (1987). 

Satellites in LEO are affected by an atmospheric drag that makes the orbit deteriorating gradually and the typical lifetime of a LEO satellite is 7-10 years. 

The gravity gradient and atmospheric drag account for the micro-g rather than zero-g time-averaged acceleration environment found in a q>acecraft. A q>acecraft in a low earth orbit is typically ut 300 kUometers above the earth s surface and about 6671 kilometers from ftie earth s center. It is int esting to note that r is onty about 5% greater in low earth orbit than on the earth s surfece. So the absolute value of A is only about 9% less in this orbit than on the ground... 

After burning out, the solid rocket boosters are cut loose from the external tank by electrically fired explosive devices and are moved away by small rocket separation motors, four near the nose of each and four aft, fired by command from the orbiter. The spent boosters coast upward and then fall earthward for almost four minutes, reaching a speed of 2900 mph before being slowed by atmospheric drag. From about 3 miles each is lowered by a succession of parachutes to a splashdown of about 60 mph. 

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