Designing a new orbiter

"Pete Lynn" :

If I were picking an out there shuttle replacement, (not optimal
design), it might go something like this:

- Say five ton payload.

I would settle for 2+ tons and crew - the more flights the better.

- Modify the NASA 747 to enable air launch from beneath, this adds
launch site flexibility among other things.

Scaled Composites probably could build an entire new craft with a better
design for drop launching for what NASA would probably spend modifying thier
own plane.

- Use side/top mounted Vectran inflatable ETs, (perhaps only ~3% of dry
mass). Fuelled at altitude to avoid insulation and deflated prior to
reentry.

Would not dumping them be easyier? Retracting the tanks while working in a
vacuum does not sound easy to me.

- Use propane/LOX and perhaps 4-5 Merlin engines with extended nozzles
for Vacuum, (335 ISP?), perhaps upgrade them a little, rob the rest of
the Falcon V for parts.

Henry Spencer has mentioned related (cheap) hydrocarbons that have strained
bonds that would boost your ISP a bit.

- Change the orbiter wing for a metallic single skin Rogallo type wing,
with the leading edge and lower surface well insulated. The wing shape
has enough arch, (lateral area), to not need a tail fin. Operate at a
much lower wing loading - fluffy design. My guess is wing and TPS might
get down to as low as 10-15% of drymass.

Okay.

- The wing shape would likely enable a water landing, or one could just
use standard type landing gear.

In terms of water landings: Please think of thermal shock and steam
explosions. Unless you can get rid of all of the heat before landing this
sounds like a bad idea to me.

Vectran inflatable tanks as per Bigelow inflatable habitats is the high
risk part. This is not necessary but this is NASA and it would be
really cool, it has very significant drymass advantages. They could be
replaced with more conventional ETs that could remain in LEO.

Or the ETs could be dumped to burnup during re-entry. If ETs are needed,
inflatable do not seem a good idea to me.

Development cost might be around $200 mil, hopefully less than $500/kg
to LEO, depending on flight rate.

Nope, not if done by NASA and the carrier plane is going to cost too. $500
million seen a lot closer. To get it done for $200 million you will have to
drop the cargo size down to 2 tons at best and find an off the shelf aircraft
to air lift you orbiter.

Question! Since you clearly stated a design with lots of wing area, is it
possible to glide this craft when fully loaded? If yes, then air launch from
above the carrier would be possible without firing the engines. You only
fire the engines after separation. If possible, then the modification to a
standard 747 would probably be a lot cheaper for carrying on top and you
might just meet your $200 million goal.

All the private RLV building faliures suggest $200 million is too little -
you have no margin for error or if an investor pulls out or otherwise can't
meet thier planned commitment. On the other hand $1 billion and over seems
to be too much money - people get careless in spending and the large amount
attacts the very type of wasteful people you don't want.

Earl Colby Pottinger

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