but...often they don't want to enter the atmosphere completely on the first landing, so they use braking ellipses to slow the craft down, which avoids overheating of the shuttle. By entering at an andly less than 5.1 degrees, you will enter the earths atmosphere then bounce of into an ellipse. In the time you were in the earths atmosphere, some kinetic energy of the craft has been sonverted into heat energy which is dissipated while the craft is in an elliptical orbit. If this proceedure is repeated a few times, the craft slows down without using any feul and thus it prevents overheating of the shuttle and possible damage beyond the sblation layer.
In safe re-entry you also need to consider the angleof re-entry:
<5.1 degrees-go out into orbiting ellipse. If extremely shallow, you will not acheive an orbiting ellipse but will be thrush back out into space. This is a problem if there is not enough feul, food or oxygen on the craft to allow for another attemt at entering the earths atmosphere
5.1<angle of re-entry<7.1-safe re-entry proving the craft is coated with an conduction layer sandwiched between an insulating layer on the astronauts side and an ablation layer which continually dissipates heat on the outside.
7.2<angle<9-g-forces can reach up to 10g, which becomes dangerous and uncomftorable for the astronauts.
>9-craft will burn up and all will die!!!!!!!!
You also need to consider the landing, eg using parachutes bafore dropping into the ocean or airstrips etc.
