Can some knowledgeable person(s) answer this question for me, as it is something that I've thought about whenever I've seen a space mission.
Upon re-entry, spacecraft such as the Shuttle, rely on heat shields or tiles, to protect the craft from burning up.
Now, I understand that the vast speed of re-entry causes the friction of the atmosphere on the craft to reach high temperatures.
So my question is this. Why do spacecraft have to re-enter at such high speed?
Why can't the craft be slowed down in space prior to re-entry, 'nudged' downwards gently with it's thrusters until it reaches the point where gravity takes over, and then drop naturally? As it's my understanding that any object that is just falling, such as a parachutist, prior to opening his chute, will travel downwards at approximately 125MPH. Or is that wrong?