A wild idea I had never even thought of, X-rays are of high enough frequncy that they can penetrate the plasmasheath of high velocity vehicles. Seemingly this is for hypersonic transport, and rentry vehicles, my mind is quite boggled.
> an electromagnetic wave can penetrate the plasma if the wave frequency f is higher than the electron plasma frequency.
X-rays have a much higher frequency (i.e. much higher energy) than the radio waves we normally use for communications, so it can punch through the noise of charged particles that makes up plasma.