Re: Manned space flight after the moon landing

From: Jeff Findley (jeff.findley_at_ugs.nojunk.com)
Date: 09/30/04 

Date: Thu, 30 Sep 2004 14:57:40 -0400

"dave schneider" <d_schneider@emulex.com> wrote in message
news:28326d49.0409301006.3f57dbee@posting.google.com...
> "Jeff Findley" <jeff.findley@ugs.nojunk.com> wrote:
> [...]
> > Seriously though, recovering a first stage isn't really that hard. They
> > don't go all that fast compared to orbital altitudes and velocities.
It's
> > the speed of orbital vehicles that's the real challenge, not the
altitude.
>
> Makes the TPS issues easier. Was Saturn Flyback supposed to be
> autonomous and automatic post-sep? Were the control issues that well
> understood at that point?
>
> [...]
> >
> > Shuttle was "sold" to the public as a means to reduce costs. I'm sure
that
> > there were politicians who saw through that and realized the shuttle
would
> > never be as cheap as NASA claimed. They needed only to ask themselves,
> > "Just what will NASA be launching on a near weekly basis to justify the
> > "planned" high flight rate?" Honestly, if the shuttle flew once a week,
how
> > much would we be spending on payloads and missions? Sure, per flight
costs
> > for the shuttle program would drop, but NASA's overall costs would
> > skyrocket.
> >
>
> As pointed out, funding for payloads and missions was to cover
> projects from a variety of sources, of which NASA was just one. But
> there really was a belief that being reusable would make the Shuttle
> cheaper. It just moved the costs from the production line to the
> hanger, though, because what we could build for reusable and meet the
> mission goals was limited by materials (TPS) and technology (SSME) to
> some very finicky pieces. Sort of like, Michael Schumacher's F1 car
> is reusable, but not cheap to operate. A lot of people seemed to have
> missed that point at the time.

When NASA backed away from the smaller, fully reusable TSTO and moved
towards the larger, partially reusable shuttle, any hopes that operational
costs would be low evaporated. The larger shuttle was needed to gain
military backing, and the throw-away ET and SRB's were needed to keep
development costs low. Furthermore, the stage and a half design required
extremely high pressure engines (the SSME's), which are more expensive to
build and maintain compared to a lower chamber pressure design. The SRB's
proved to be more expensive to refurbish than originally though, so their
"reusability" isn't really driven by economics.

The shuttle that we got was a huge compromise, in order to gain political
support and to cut development costs. The result of this was a marginally
reusable, hard to maintain vehicle. A fully reusable TSTO shouldn't be as
expensive and difficult to operate.

> > > OTOH, there are a whole bunch of technical issues we couldn't have
> > > learned about anyway easier than the Shuttle, so it has been a great
> > > learning tool. We now have an idea of what we need to do to make a
> > > reusable winged vehicle. Perhaps the OSP winged designs have the
> > > seeds of the real thing (cue Kim Keller).
> >
> > Not true. NASA can learn volumes from smaller, cheaper programs. This
has
> > nearly always been the case with the Aerodynamics side of NASA. This
has
> > sometimes been true with the unmanned Space side of NASA. Clearly the
> > Manned Space side is the exception to this rule.
>
> It isn't clear that smaller cheaper programs could have learned some
> of the shuttle's useful lessons because of scaling factors. Something
> the size of X-43A would not have had the same lessons. Perhaps
> something the size of the OSP winged designs would have, but would we
> have saved much on the orbiter side? Would there have been a
> [political] chance to use an existing booster, or maybe the Saturn
> Flyback, to launch such an OSP?

I disagree. Much was learned about reusability by the DC-X program at a
very low cost. Before DC-X flew, there were many inside of NASA who thought
it would never fly. There was much learned about flying and quickly turning
around a rocket powered vehicle, and the cost was far lower than NASA cost
models predicted.

> > > I still favor EELV and capsules for now because I think we still have
> > > to understand the flight regimes better and followup on recent
> > > materials development before we can do reusable boosters and winged
> > > orbiters well enough to be worth it. EELV gives us better return on
> > > our dollars until the flight rate goes up significantly higher.
> >
> > This is the same old tired argument NASA always uses. "We can't reduce
> > costs because we don't have the technology". This has been proven time
and
> > again to be false. Projects done outside of NASA have been done for far
> > less than NASA cost models predict. DC-X was just one of these
examples.
> > Spaceship One is another, more recent, example.
>
> I'm not saying that at all. I'm saying that large complex solutions
> that don't leverage existing infrastructure, and that build a small
> number of very expensive vehicles don't give us as many chances to
> reduce costs as do smaller projects that extend existing
> infrastructure (OSP) or which can be done in incremental approaches
> (DC-X was, for example, a small-scale technology demonstrator; 2 more
> demonstrators were needed to get to operational designs and the
> mid-course flip on reentry is still considered unexplored territory).

The problem was that NASA thought it could combine these two demonstrators
into one large program (X-33). We all know how that went.

When I say size of a program, I don't mean the physical size of a vehicle, I
mean the cost. One could build a vehicle the size of X-33 for a fraction of
what NASA spent on the program by focusing on, at most, one new technology.

> > > I do miss the downmass capability of the Shuttle. And I will be among
> > > the people cheering if Musk, Rutan, and Carmack can prove that we can
> > > do reusable boosters for reasonable costs.
> >
> > The large downmass capability of the shuttle is overrated, to say the
least.
>
> Until there's a MOOSE for the CMGs and science racks, I'll disagree.

CMG's aren't *that* big and heavy. You don't *need* a 15'x60' payload bay
to accomidate a CMG.

> > The large upmass capability is also overrated.
>
> There are ways around that, so I agree. Short term commitments to ISS
> are the biggest issue, but that wasn't a problem in 1972.
>
> >
> > > > Space station - I don't think it is worth it.
> > >
> > > I think it is a necessary step. I don't think we could do a moon base
> > > for long duration stays without having done the ELCSS and human health
> > > work in something akin to ISS. We get to do additional science at ISS
> > > as well, with relatively quick turns.
> >
> > Again, this is B.S. Look at the state of US ECLSS on ISS. The US CO2
> > removal system isn't really being used because it breaks down too often.
>
> Ahh, but that's my point -- how can we go to Mars when we can't keep
> ECLSS (US or Russian) running more than a month at a stretch? We have
> to be able to get 6 months out of a unit even if we could do a
> continuous thrust flight to Mars.

Agreed. Unfortunately, it doesn't look like NASA will use ISS as an
opportunity to address this issue. Instead, it looks more likely that the
US will pull out of the ISS program prematurely in order to retire the
shuttle, and these lessons simply won't be learned.

Jeff 

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