[extropy-chat] Fly Me to the Moon

Mike Lorrey mlorrey at yahoo.com
Mon Jun 6 15:44:24 UTC 2005



--- Neil Halelamien <neuronexmachina at gmail.com> wrote:

> On 6/5/05, Dirk Bruere <dirk at neopax.com> wrote:
> > Charlie Stross wrote:
> > > 1. A spaceship needs wings and a retractable undercarriage like
> an
> > > automobile needs oars and sails.
> > >
> > I'd dispute that.
> > Almost all designs for a fully reusable spacecraft have wings.
> 
> And that's a good reason for why it's premature to be vouching for
> fully reusable orbital spacecraft just yet. They might be
> economically
> justifiable (and we'll see them being developed by private industry)
> once flight rates get high enough, but in the meantime a low-cost
> semi-reusable like the upcoming SpaceX Falcon rockets seems a far
> better option.
> 
> In the present day the per-unit construction cost of a spacecraft is
> definitely -not- the main driver of launch costs.

On the contrary, Space Ship One, the only private spaceship we have to
draw a baseline from, has wings. Tier two reportedly has wings as well.

Space shuttles cost a few billion to build, they cost somewhere around
$100 million to launch. If you only get 20 missions out of one, your
cost per launch is $200 million. If you can get 40 missions out of one,
your cost is $150 million. Reusability determines a large percent of
operational costs.

Space Ship One reportedly cost $20-$30 million to build (of course
there is a lot of r&d in that that will be taken up by later units).
Fuel costs are reportedly $100k-$200k per mission. If SS1 lasts 20
missions, its costs per mission would be $1.2 million. As Virgin
Galactic has priced tickets at $296,000, last I heard, and given a
minimum 50% margin, Scaled Composites must be claiming that each SS1
derivative ship can fly 80 missions, minimum. If so, then about 60% of
the cost per mission is capital investment, or else Rutan thinks he can
get is production cost per unit down significantly, to $2-5 million
each, likely.

Recall with SS1 that the larger investment is in the mothership, not
the shuttlecock, though it is likely that one mothership should be able
to service several shuttles.

Now, there really isn't any reason why a capsule program can't be
reusable. In fact, the Gemini program did reuse at least one or two of
its capsules in its Gemini B program (where they tested the viability
of building a hatch through the heatshield to access the MOL, which
would weld shut upon reentry.) With modern heat shield technologies, it
should be possible to build rather sophisticated capsules that would
have either reusable or easily replaceable heat shields.

The real contest is whether you can affordably and reliable recover the
rest of the rocket, which has been the real point of the ssto movement,
particularly saving the expensive rocket engines. Others have moved in
a different direction: making rocket engines cheap enough to throw away.

Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
"Necessity is the plea for every infringement of human freedom.
It is the argument of tyrants; it is the creed of slaves."
                                      -William Pitt (1759-1806) 
Blog: http://intlib.blogspot.com


		
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