Randall Clague wrote:
That's unclear, it depends on what form the reentry architecture takes.One thing that deserves mention, in light of the shock with which NASA's calm comments about being unable to inspect the TPS or repair it if they did find a problem with it have been received, is that an SSTO will have even less margin than Columbia did.
There's lots of potential problems inherent with the shuttle reentry design:
a) tiles tend to fall off; the black tiles are particularly dangerous to lose
b) tiles modify the aerodynamics by their absence
c) control of the shuttle during reentry is computer controlled- computers are traditionally spectacularly bad at handling modifications to aerodynamics (software bugs spoil your whole day.)
d) only certain attitudes allow for survival (if nothing else because the black tiles are on the base only), so loss of attitude control is fatal
e) the tiles are below the hydrogen tank, so catch falling debris (Buran didn't have this problem; this Shuttle problem may be partly/mostly a result of using hydrogen)
f) the body of the shuttle is aluminum, this loses 50% of its strength at 300C, if they had used titanium, a lot of the upper thermal insulation goes away entirely, and the vehicle is somewhat less susceptible to small heat leaks
It really isn't clear to me that an SSTO would have these problems. For example the Roton wasn't to have tiles in anything like the same way; and attitude control was rather more passive.
-R
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