Re: How big would an SSTO be?
- From: Len <len@xxxxxxxxxxxxxx>
- Date: Mon, 09 Jul 2007 07:18:29 -0700
On Jul 8, 10:33 pm, David Cornell <djc...@xxxxxxxxxxxxx> wrote:
Len wrote:
We haven't done a study of the "likely operational costs
of recovering and reassembling the stages of a TSTO versus
the savings in developmental (and perhaps operational costs)
that a TSTO would have over an SSTO of similar capacity."
Rather we start with no preconceived notions of this sort.
Our TSTO takes of from a 3000 m (or longer) runway with the
ability to either reject takeoff or continue on one derated engine
immediately after liftoff from the runway. We can also abort and
make a powered landing at the launch site anytime prior to
staging at mach 2 at 40 km--providing orbiter propellants
are jettisoned. After staging, the orbiter can jettison
propellants and glide 26 km back to the launch site, if
necessary. We view none of this as an "operational
disadvantage" of staging.
As for reassembly, a simpler version of the 747/shuttle
overhead crane can lift the empty 12,500 kg orbiter onto
our carrier--which does not seem to be particularly
challenging.
Staging eliminates propulsion altitude-compensation
problems. It also allows some operational luxuries
like engine-out abort at takeoff, with a powered
landing with the empty orbiter on board. Finally,
for our "kite plane" design approach, staging is
not only straightforward and relatively easy, but
it also permits the designer to address certain structural
and thermal requirements separately. Many of
the purported "operational advantages" of an
SSTO are actually loaded questions.
A lot depends upon the basic design concept.
It is always possible to design a monstrosity
like the Space Shuttle. No amount of testing,
experience, of funding can turn a bad concept
into a good concept.
Len,
Thanks again for the informative response. I did not mean for my
question to imply that an SSTO was necessarily "better" than a TSTO. I
was only wondering how the
"cost" (there must be some cost) to reassembling the pieces fit into the
overall
cost/benefit analysis. There are many obvious benefits to the design
you describe
and those benefits seem to much more than compensate for the need to
send out a 747 to bring back the orbiter.
I have a lot of questions about space craft design and how one decides
which approach looks most promising, but I won't bother you with them
now. You have already been more than generous with your time and your
replies at least give me a glimmer of the thought process that goes into
trying to design something that will work in the real world.
David Cornell
David,
My response wasn't so much in answer to your
comment, as it was to to the general assumption
that SSTO is self-evidently better than TSTO from
the operational point of view.
If one could get every feature one wants with an
SSTO, then, sure, it would be highly desirable.
And I have chased this dream to the extent that
--in limited circles in the mid-sixties and again in
the early seventies--I was know as Mr. single-
stage-to-orbit.
The point is that with current technology--and the
technology that is likely to be available in the
next decade or two, tradeoffs are necessary.
Within this reasonable trade space, I have come
to the conclusion that TSTO can actually be
more desirable from the operational--as well as
performance--point of view, than a realistic SSTO.
Len
.
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