Hammering on Larry J's point: One of the best performance thermal protection materials for heat shield and rocket nozzle throats is carbon phenolic. The Air Force developed carbon phenolic for ICBM reentry vehicle (RV) nose tips. The manufacturing process for carbon phenolic starts with a rayon thread that is weaved into a fabric. NASA almost lost a Space Shuttle before the Challenger accident due to massive spallation in the carbon phenolic throats in the solid rocket booster (SRB) nozzles. Initially they couldn't figure out why the throats were failing because the manufacturing process was more or less the same as used for the RV nose tips. Then someone discovered that NASA was using a different type of rayon thread. Someone else found a batch of the original rayon thread, performed the appropriate tests and verified that this was indeed the problem. Unfortunately the original production line for the Air Force rayon was long gone. No one knew what the formula was for that type of rayon. This became an issue with the now abandoned Mars Sample Return (MSR) project. We all knew the radical environmentalists would litigate like crazy to stop MSR due to "Andromeda Strain" concerns. We wanted to show the heat shield used for the MSR Earth return aeroshell had a traceable flight heritage. This traceablility could be used as evidence when the court challenges came. There was a frantic search for the original rayon thread used by the Air Force and fortunately some was found. That rayon has been set aside and earmarked for future use with MSR. Unfortunately this point is now moot since Genesis augered-in. All the environmentalist lawyer has to do is show the jury a video of the Genesis aeroshell tumbling down to the ground followed by a picture of it augered-in. After seeing that, the jury won't care if the MSR carbon-phenolic was made out of Air Force rayon.

Gary