Re: An old idea I recall - Building a Spacestation from Shuttle ETs


Greg D. Moore (Strider) wrote:
<neil.fraser@xxxxxxxxx> wrote in message
news:1147755323.008560.277330@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
One of the proposals put fourth was to allow the
shuttle ETs to be jettisoned later in the flight plan such that
they would not immediately fall back to earth and burn up on reentry.
[...]
Does anyone remember the proposal, who was backing it,
and why it was abandoned?

Definitive link:
http://www.orbit6.com/et/

There were three major problems which I recall:
1. One potential objection was access to the tank, but NASA actually
performed a test in the neutral buoyancy tank to verify that a
space-suited astronaut could safely fit through the existing H2 port.
Still, it's pretty small to be your only docking point.
2. Another potential objection was that the foam covering the tank
would slowly boil off, meaning the space around the tank would be
highly cluttered for a long time.
3. Another objection was the fumes from unburned propellant left in the
tank. These could be a health problem. One solution was to open the
tank to space and let it sit for a few weeks.

Yes, those fumes from Oxygen and Hydrogen are deadly.

Seriously, I don't think this was a serious consideration.

The others you mention, especially the "pop-corning" of the foam was a big
one.

Yeah, it is a big deal with all that debris from the SOFI breaking up
and creating a big hazzard to shuttles attempt to dock to the station,
or over time a potentially serious hazard to other spacecraft as the
debris spreads out. All of this is making me have flashbacks to Tom
Abbott and his wacky ET space station concepts that kept getting shot
down just about every other week...


My concern would be the lack of shielding. ISS modules have
sophisticated multi-layer hulls designed to withstand impacts from
orbital debris. Shuttle's ET would be a single *** of aluminum
alloy. The next Apollo-era washer you meet results in a really bad
day.

Yes and no. There are ways around this, including post-flight addition of
shielding.

If you can carry sufficent shielding in the orbiter, but with the
payload penalties, I don't see more than a small amount of that being
done on the first flight, and then there's issues of guidence and
navigation control that had to be addressed immediately. So you could
take up a small propulsion unit to dock with the ET once it was in
orbit for attitude and altitude adjustments, but then you might not
have enough room left over for that all important debris shielding...
Effectively it would require shuttles launching within weeks of each
other, without any serious delays to get the tank in a stable,
long-term orbit, and get the basics installed.

Also note that given the volume of the tank, a small enough leak would take
a pretty long time to really become a problem. Long enough that you could
probably find it and repair it or at least evacuate the station. (note that
the much smaller station Mir had enough air to give them time to close the
hatch w/o any injuries.

s

Personally I think the only way to adequately address all the problems
would be to use a one-off custom-built and highly modified ET. One
shuttle flight could take it to orbit (empty cargo bay and only two
crew to offset the loss of performance). Subsequent flights could fit
it out (docking hub, solar panels, radiators, etc). Not the freebie
that the idea originally entailed, but a nice big space none-the-less.


Yeah, but ET providing nice big volumes has long since become obsolete
in the face of the more efficent Transhab-derived inflatable module
station concept, which can provide nearly the same volume, but can be
launched on a much smaller vehicle for far less cost, and already has
ample amounts debris shielding, and some support equipment already
installed and ready to go. Like the ET station, a propulsion module of
some sort would have to be either prelaunched or sent up on the same
mission. The other advantage is that you don't have to in any way alter
a critical piece of launch vehicle hardware to serve a duel function as
a space station module as well as act as a fuel tank. I think the final
death-blow to the ET station concept came with the Columbia accident.
Any changes made to the ET are going to be strictly for safety from
here until the end of the program.
-Mike

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