I would think that as a % of vehicle weight, the heat sheilding is a very small number...

It would be better to build redundancies into the sheilding (Multiple layers, better attachment methods, even expendable sheilding, etc...) Rather than to carry an additional load of fuel (also very volitile) on each mission.

Its my understanding that just about every tile needs to be inspected and/or replaced after each mission anyway: Why not design a completely expendable tile system where the tiles could be applied in some sort of interlocking "shingle" configuration.

One thing is for certain: We've really dropped the ball on moving forward on a new generation of manned launch vehicles...

Maybe we need another joint venture with the Russians, Jappaneese, and/or Indians to get us moving in the right direction (again).

Scott