Re: An alternative to Orion/Constellation?

On Thu, 23 Apr 2009 17:55:34 -0400, David Spain <nospam@xxxxxxxxx>
wrote:

Shuttle costs got out of control when we decided to make it big enough
to carry a significant payload other than people [1].

Because Saturn V was cancelled and NASA then needed a new way to
launch the Space Station that was the main reason it needed the
Shuttle. That made Shuttle get bigger and more expensive, and that in
turn made NASA have to sell Shuttle to Congress as "all things to all
customers".

If it were just to ferry
people it could have been made a lot smaller with a lot more launch options
which would have improved the economies of everything.

That's what Shuttle started out being... a replacement for Apollo, not
a replacement for Saturn. With no Saturn to launch the Station or deep
space missions, that left the little Shuttle vulnerable to "what are
you going to do with it?" questions. Which begot bigger Shuttle.

We should be focusing on building what I call a 'traveling space habitat'.
Something on the order of a very small space station that can be sent out
of low Earth orbit (LEO) on orbital exploration missions. First to the moon,
then maybe Venus, and eventually Mars. It would be self-sufficient and fully
reusable and capable of supporting a 6 person crew nearly indefinitely.

Well, that requires the discovery of unobtainium, otherwise the idea
is pretty good.

Such
a vehicle would get us well past the moon, but could be effectively used in
a lunar exploration program as well as giving us a pathway to the planets.

I like this idea, but I think it still needs Orion (unless SpaceX
pulls a rabbit out of its hat and actually makes Dragon work first.)
We'll need some way for the 'Transit Ship's' crew to come home that
doesn't depend on rendezvous with your new Shuttle-lite (braking into
Earth orbit from escape velocity is hugely fuel-expensive and risky
due to the van Allen belts.) I don't think flying without such a
'lifeboat' is politically acceptable in this day and age. So we need
Orion to tag along with the Transit Ship.

[1] The other reason I remember was the unique ability to 'retrieve' payload from orbit.
IIRC this was done exactly *once* with a comm sat (whose PAM module failed
to ignite?) and failed to achieve proper orbit. IIRC, the company that lost the
satellite received an insurance payout and the insurer got back the retrieved
satellite which I assume they sold to someone else to try again? It appears
that this once taunted feature of the shuttle was never really that important.

It happened twice on that one mission: Palapa and Westar. Both were
refurbished and relaunched. Shuttle also retrieved the Space Flyer
Unit launched by Japan. Shuttle also launched Long Duration Exposure
Facility on one mission and retrieved it on another. Shuttle also
rendezvoused with and repaired Solar Max, a Leasat communications
satellite, and Intelsat VI-F3, the last two of which were boosted to
higher orbit after the repairs. There were myriad small payloads
(SPAS, Spartan, Wake Shield) deployed and later retrieved on the same
mission.

Shuttle's ability to return large payloads has been very important in
the Station era, via the MPLMs, and that capability will be sorely
missed once Shuttle retires.

[2] No I'm *not* implying that a White Knight could do the job. Only something new
that was designed for a much, much smaller shuttle that launches from the carrier
craft using (expendable) rocket assist with only OMS pods and wings for return from orbit
where it would glide to a respectable runway landing.

That's a tall order. I don't think it is possible with today's
technology. You either need a hypersonic carrier plane (think XB-70,
but bigger and faster, which will be a huge project all by itself) or
a bigger Mini-Shuttle with a lot of fuel and a bigger engine (which
isn't going to be cheap, either.) Make no mistake, SpaceShipOne is a
very long way from orbital capability. It only gets to Mach 2-3, while
Mach 25 is needed. Getting that capability in a vehicle small enough
for reasonable air-launch is a long, long way down the road. SSTOs or
recoverable boosters could be much easier and cheaper to develop.
Low-cost boosters like Falcon 9 could also make air-launch a
financially high-risk concept.

As an aside, I don't for the
life of me understand this compulsion to throw everything out with each new generation
of space transport and start over.

The only time that happened was Apollo -> Shuttle, and there are a
whole host of reasons it happened then, starting with public backlash
against the perceived high cost of Apollo. Gemini was originally
Mercury Mk.II, not throwing everything before it out. Apollo predated
Gemini and was in development before Mercury flew, planned to be
America's generic manned spacecraft of the 1960s and '70s. Orion is
using the Apollo shape and I think Shuttle's OMS engine plus various
other Shuttle heritage systems. On the launch vehicle side, the EELVs
are descendants of tried-and-true systems, not clean-slate. Ares uses
Shuttle's SRB and Saturn's J-2 engine, with rumors of an imminent
return to Space Shuttle Main Engine on Ares V.

My whole engineering career in the commercial sector
has seen incremental improvements where technology is refined and refined. The one
exception being due to the break through from vacuum tubes to solid state. I suppose
a space-elevator would be the equivalent type of break through in space transport.
But I don't see one yet. But why do we go from capsule to shuttle now back to capsule?
This makes no sense.

It's all about weight. Wings are heavy and unnecessary in space. If
you're going to the moon, you don't want to be hauling any more weight
than you absolutely need. And wings probably make re-entry at lunar
return velocities harder, to boot. It's far from nonsense, although
NASA's particular execution of the concept may not have been the best.

Brian
.

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