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Apply shuttle ET foam in a vacuum.



 
 
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  #41  
Old August 2nd 05, 06:50 PM
Jeff Findley
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"Derek Lyons" wrote in message
...
"Jeff Findley" wrote:
Exactly. And the ET, as designed and built, needs its aluminum-lithium
structure to remain cold since it's quite a bit stronger at LH2/LOX
temperatures than even at room temperature. Add to that the effects of
aerodynamic heating, and you'll find that you really do need the foam on

the
outside.


In other words, George (incorrectly) stated as a general principle
something that appears to be Shuttle specific.


Other vehicles have the same issue to deal with if they use cryogenic
propellants and metallic tanks that are integral structural components.
They may not have to deal with the aerodynamic heating issue as much because
their nose is a payload shroud, not a LOX tank. But in general, you can
make your metallic cryogenic tanks lighter by insulating the outside rather
than the inside. You also don't have to worry about the insulation coming
loose and being ingested by the LH2/LOX intakes.

Jeff
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  #42  
Old August 3rd 05, 04:41 AM
George William Herbert
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Alex Terrell wrote:
The pre-launch reason to have foam there is to prevent ice buildup
on the outside of the tank. Because, if you think foam shedding is
bad for Shuttle Tiles and RCC leading edge sections, you should
see what ten pounds of nice solid liquid-hydrogen subchilled
water ice will do to any surface of the shuttle...


If this is the major reason, why not ditch the foam 30 seconds before
launch. Ice build up after that would be negligible.


This was tried on an Ariane stage, which ended up heavier
and less reliable with the detachable foam than it was with
the replacement, glued on permanently fixed foam, according
to Henry.


-george william herbert



  #43  
Old August 3rd 05, 04:44 AM
George William Herbert
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Carsten A. Arnholm wrote:
George William Herbert wrote:
The pre-launch reason to have foam there is to prevent ice buildup
on the outside of the tank. Because, if you think foam shedding is
bad for Shuttle Tiles and RCC leading edge sections, you should
see what ten pounds of nice solid liquid-hydrogen subchilled
water ice will do to any surface of the shuttle...

Foam on the outside does both jobs. Foam on the inside of the tanks
would help prevent water ice buildup on the outside, but not help
with ascent heating. External ablative shielding plus internal
foam would do both better than we get right now, but would be
heavier.


Even better would be to put the actual space vehicle in a position where
falling objects will not hit it. That means on the top and not on the side,
under or whatever.


It was clear shortly after Columbia burned up that
nobody was ever going to build a new vehicle that
way ever again. That's not the question.

The issue at hand is whether people properly understand
the factors that led to the external foam on the ET
or not.

If you don't understand them, you're going to get something
else wrong somewhere else, eventually...



-george william herbert
/

 




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