# In what atmospheric densities or pressures have aerobrakings been performed?

How deep have spacecrafts gone into an atmosphere for doing aerobraking for orbital insertion (or as tech demos)? I suppose it is the braking force of the atmosphere that counts, is that closely correlated with atmospheric density or pressure and does elemental composition matter much?

Typical densities are around ${10}^{-8}\,\mathrm{kg/m^3}$. A desired dynamic pressure, $q={1\over 2}\rho v^2$ is targeted, with the periapsis raised and lowered as needed to get to that $q$, where too low of a $q$ makes the process take too long, and too high of a $q$ can damage the spacecraft due to forces from the drag.
• Yes. The density at the surface is about $7\times 10^{-5}\,\mathrm{kg/m^3}$. Assuming it stays that way. Pluto's atmosphere varies quite a bit over time. It was once thought it could freeze out completely. – Mark Adler Oct 16 '16 at 21:21