An atmosphere is the gaseous envelope surrounding a planetary body such as the Earth. As a working definition for spaceflight, the upper boundary of the atmosphere is that altitude where radiation pressure replaces atmospheric pressure as the dominant perturbing influence. For the Earth, this occurs at an altitude of about 1000 km. The outer regions of the atmosphere consist of the thermosphere, which for the Earth extends from 105 to 750 km, and the exosphere, which is immediately above it (
A decisive ...