text: because there is very little resistance in space. objects in motion will stay in motion unless a force acts on them. since they are in space, there's not really much of a foce acting on them with one exception: gravity.\n\ngravity of course pulls the satellites down towards the earth. but the satellite is moving at a fairly constant velocity in a direction which is tangent to the earth. so the direction of travel is always perpendicular to the force of gravity, which means that the satellite stays in perfect orbit.\n\nif it used its fuel to speed up, it would overcome the earth's gravity and fly off into space. if it used its fuel to slow down, the earth's gravity would overcome the satellites speed and pull it in. orbit is the perfect middle ground between these two.\n\nnow if there were a bunch of air in space, then the air molecules would cause friction that would slow the satellite down. the earth's gravity would then pull it in and cause it to crash. so to overcome the air molecules, the satellite would need a constant thrust to keep it in orbit. but since there is little or no resistance in space, it doesn't need to hit its boosters at all. it just needs to get up to the perfect speed and physics will take care of the rest.\n\nsorry if this was unclear. it's late ;p