For most purposes, I prefer text to video. But one has to be flexible. Since the late John Walker sometimes linked to Scott Manley’s videos, let’s continue the tradition.
In this relatively short video, Mr. Manley reviews the technology of heat shields for re-entering spacecraft. Who among us knew that the porosity of heat shield tiles was greater than 90%?
Most interesting point is Mr. Manley’s speculation that the limitations, fragility, and sensitivities of heat shields will turn out to be a major limitation on the rapid reuse of spacecraft.
That was certainly the case for the Space Shuttle. Of course, SpaceX has since demonstrated very convincingly the ability to do reasonably fast turn-arounds on booster rockets. But those sub-orbital first-stage boosters do not reach the very high re-entry speeds of orbiting spacecraft, and thus can dispense with the need for most heat shielding.
