Re: Foam and rescue possibilities

Henry Spencer wrote:
In article <1151241756.918806.205200@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Alex Terrell <alexterrell@xxxxxxxxx> wrote:
Anyone who understands a bit about structural engineering or materials
science knows that the strength of a metal (or metal alloy) generally
decreases with increasing temperature.

Though its brittleness decreases with falling temperature, and this
effectively reduces its performance.

I think you mean "increases with falling temperature". But whether that's
an issue depends on the metal. This problem has an exaggerated reputation
because our commonest structural material, carbon steel, is affected...
but in fact, a wide variety of structural metals *don't* get brittle when
they get cold.

Now you remind me, I do recall this is less of a problem with aluminuim
alloys.

snip

Maybe, and maybe not. Doing that *reliably* is not simple; for example,
you need helium purges to keep moisture from freezing in the gap. And
there is still a need for some protection against heating on the way up,
especially on the nose (air friction) and the base (radiant heat from
the SRB plumes).

Centaur used to jettison its insulation before ignition. Complexity went
down and payload went up when they switched to permanently-bonded foam.
--
I guess this is more complex than I thought. Given the number of
remaining shuttle flights should be as low as possible, the answer
should be to do as little as possible.

With an inline SDHLV, the impact issue largely goes away. However, it
does seem they're now going for a complete redesign. In which case it
might make sense to jettison most of the insulation. Won't happen
though.

.

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