Why can't space shuttles use gravity for re-entry?
Question
I was watching a documentary about space shuttle re-entry and the shuttle has to be at the right angle when they re-enter the atmosphere. Why can’t they just drop down to Earth with gravity?Andy, Hampstead
Answer
** Definitive **Name: Professor Hal
Qualification: Professor of Public Understanding at the University of Brighton and Mystery Hour legend
Answer: To answer, you have to ask why air causes friction. To do that, imagine standing in a gale with your face in the wind and you can feel the wind hitting your face. If a space shuttle hits the atmosphere at too shallow an angle, it will just bounce back – in a similar way to skimming stones on water. If it was at too steep an angle, all the force will be on the tip of the shuttle and the air tearing past it would create friction, getting too hot and breaking up. The right angle is the Goldilocks effect – not too shallow, not too steep.