kT wrote:

I mean really, haven't you guys simulated any of this at all?



In the case of the LOX/LH2 combo, the differences in weight per volume
of the two propellants is so great that the LOX is almost certainly
going to end up forward for stability reasons, even on SSTO designs.
If you are going to use a LOX/LH2 propellant combo, then you want to
move into the LH2 tank, as that's going to be around four times the size
of the LOX tank.
This was how Skylab, the closest thing to the Krafft Ehricke Atlas
station, was built (it would have been even closer in the original
"wetlab" concept).
Using any other propellant combination than LOX/LH2 (barring exotics
like fluorine or ozone) will give you an inferior Isp, and make the
whole SSTO concept probably unworkable with any useful payload at all.
So assuming the capsule is on top, you are going to want to have a
insulated tunnel through the LOX tank down to the LH2 tank.
The alternative is to jettison any remaining propellants on-orbit, and
after everything has warmed up head down through the LOX tank into the
LH2 tank, but I thought you might want to keep some of the LOX for
breathing.
Even then though you are going to have to do something to store it, as
it will boil off fairly quickly once the sun starts warming the exterior
of the LOX tank.

Pat