"Jorge R. Frank" wrote in message ...
Bill Bonde wrote in
:

I wasn't suggesting not having
insulation while the tank was on the ground, just having some means to
remove it immediately before lift-off. I don't think this is *that*
wild of an idea. A two piece foam form that is well supported and
mechanically moved from a position insulating the tanks away to allow
lift-off would eliminate ice build up problems and too much boil off
while Shuttle is on the ground.

It sounds extremely wild to me. The forms would necessarily be complex
shapes due to the need to accommodate the SRBs and orbiter, so the removal
would not be a straightforward translation-motion. The removal would also
be a time-critical process that must work perfectly every time, else
catastrophic results could ensue.

How about a cold dry helium balloon covering, the balloon is over
pressurized and shatters as shuttle clears launch tower. The balloon
fits over ET and it can made reflective of solar energy. The balloon
strength would mainly have to be strong enough to withstand a windy
day and it's helium pressure would be low. The total weight of balloon
could be a few pounds.

It seems much easier to me to simply
reformulate the foam so it doesn't fall off in the first place, or failing
that, to prevent the big pieces from coming off and recertify the orbiter
(hardening the TPS as necessary) to handle impacts from smaller pieces.

I don't have any idea whether heat
generated during the flight would cause problems by too rapidly
heating the liquid fuels or heating them in the wrong places too much.

It would. In fact, protection from ascent heating was the original reason
for having the foam on the outside of the tank - the ice formation problem
was not appreciated until the mid-to-late 1970s.