Note that the Falcon 9 first stage is not travelling at orbital velocity, or even that near it really. At separation time -- when it starts to slow down to re-e

Note that the Falcon 9 first stage is not travelling at orbital velocity, or even that near it really. At separation time -- when it starts to slow down to re-enter -- "[f]or a reusable Falcon 9, [speed] is around Mach 6, depending on the mission." (Quoting Elon Musk, the SpaceX CEO, on Twitter.)