Pat Flannery wrote:


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.

I'm not really concerned about it at this point, because obviously I'm
going to be flying a Delta IV upper stage to rendezvous, so the hydrogen
tank is what I've got there. As far as a SSTO booster, since I intend to
reuse the engines, I'll soon have more tanks than I know what to do
with. I was interested in the discussion on mass charge ratio of
propellants, so I am interested ultimately in some novel hydrogen
acceleration strategies. Certainly I can store water in the hydrogen
tank, anyways, and maybe I can get in through the intertank segment.
Remember, I'm also removing the engine, but retaining pressurization.

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).

I'm flying hundreds of high fidelity simulated SSTO flights a day.

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.

For a really big tank, for instance, a 7 engine SSTO, that would work.

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.

Of course, that's the whole point, buff out the intertank and thrust
structure with small residual fuel tanks, and run sustainer engines to
get the fuel where you want it while they're circularizing the orbit.

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.

I'll shade it then, and use it up as fast as possible. So basically I'll
be rendezvousing with a large oxygen tank, on a large tank farm, and
spending a couple of weeks retrofitting a habitat while the engines are
being swapped out. The habitats are converted into solar powered growing
rooms, and the entire structure is migrated up to geosynchronous using
some exotic solar powered atomic mass driving thingum. Or whatever.

The astronauts will have to fly direct. That's why we need an RL-60.

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