Space Travel

[djtaz11398]

Why cant space craft coming back to earth just slow down when they are entering the atmosphere and just drop back to earth. why do they have to enter at speed, thus causing friction and heat? I know its somthing to do with the atmosphere but cannot understand it, is it solid in some way?

[Mortartube]

Because the space craft would have to carry a huge amount of extra fuel to power any retro rockets for braking purposes. Using the atmosphere to slow the craft is the most efficient way to do the job.

[andy hughes]

If the craft were to freefall into the atmosphere, there is a danger it would simply 'bouce' off and go whirling into outer space. The trajectory and angle have to be potted with incredible precision to ensure that the craft travels through the correct amount of atmosphere to slow its decent to a level where it can then float to earth.

[seb brown]

The resistance is a lot stronger when endering the earth's atmosphere compared to in space. The atmosphere isn't solid, but just massively more dense. It's a bit like moving from air into water. The spacecraft has to approach at speed, at a very accurate angle to be able to penetrate the atmosphere at all, otherwise as the last person said, it would just bounce off or more likely disintegrate. The friction on entering the atmosphere which causes all the heat, is a result of the movement from almost none to very high resistence, as the space craft breaks the atmosphere and pushes through it, slowing down rapidly as a result.