[extropy-chat] FWD [forteana] Re: Are dwarfs better forlongduration spaceflight?]

Eugen Leitl eugen at leitl.org
Wed Sep 7 06:43:49 UTC 2005


On Tue, Sep 06, 2005 at 02:27:23PM -0700, Adrian Tymes wrote:
> --- Eugen Leitl <eugen at leitl.org> wrote:
> > Nuclear power in space is a very hard sell politically.
> 
> Not as hard as selling a dwarf-only mission.

Who is selling a dwarf-only mission?! Has the thread gone nuts?
 
> > The technology doesn't exist yet in the first place, and needs
> > to be developed and tested.
> 
> Development and testing are needed, but it does exist.  Then again,

Does http://www.fas.org/nuke/space/c04rover.htm strike you
as mature technology? Have you noticed that it has been never
designed for nor tested in space, officially? Few people even ever
operated nuclear reactors in space, on unmanned missions.

Do you think you can resume such tests, today?

Not in the current policitical climate. Not with current
funding.

> dev & test are needed for this mission anyway: there does not presently
> exist a rocket capable of sustaining one human life, even a dwarf's,
> while going to Mars and returning under its own power.

Rockets don't sustain life. Rockets are there to move mass.
The technology to sustain a couple of canned primates in space for more
than a year exists. It is primitive, and it will a lot of mass
for the crew module. Because larger Energiya and Ariane models
capable of lifting 100 t to LEO have been scrapped because
there's no market, you'll need a lot of missions, and docking
in orbit to assemble the craft.
 
> > Nuke-powered ion/plasma drive would be probably an optimal
> > combination even for manned flight. It would be easier to
> > assemble and fuel up the craft in orbit, and go chemical
> > all the way, with a minimum-mass crew module (with robots
> > sent ahead preparing the habitat, and the fuel still) by
> > remote control.
> 
> Easier in some respects, harder in others.  The more money and

Chemical all the way would not require any new technologies,
with the exception of maybe a large lifter, to minimize the
number of missions. But Russia and Ukraine have already
the lowest LEO lift costs, and you probably can't beat that.

> resources a project requires, the harder it inherently is: you have to
> spend effort to gain said money and resources.  I suspect this may be
> part of what you overlooked.

I personally think any funds allocated to a manned Mars mission
are completely wasted. At this stage, even a manned Moon mission
is quite premature.

If I would be sending anything, that be a teleoperated polar
factory. After the entire Luna is mapped thoroughly, and a 
24/7/365 rotating mission control distributed across time zones, 
with a wide TCP/IP pipe to LLO has been established.

> > > The scaling factor of different propulsion systems trumps the
> > > difference in crew dimensions.  For example: calculate how much
> > rocket
> > > you would need to make the trip in a few months (one way) on
> > hydrazine.
> > 
> > What is wrong with using cryogenic fuel, e.g. methane/oxygen?
> 
> *shrugs*  Nothing, for the sake of this discussion.  Just pick a fuel

I was just curious, why people were sticking to (tried and true, admittedly)
assymetric dimethylhydrazine/NOx fuel. With a large mission, cryogenic
fuels are not a problem. 

> so you can work the numbers.  Nuclear/ion propulsion beats any chemcal
> fuel by a sufficiently large margin that focusing the finite dev/test
> resources on that, rather than spending effort on minimizing the crew
> (and taking the resulting benefits), will achieve optimal payoffs.

You can't minimize the crew. But if you could build a small-footprint
closed-loop ecosystem to recycle waste and produce food, you could 
certainly minimize mass. (If it was unstable, that'd be one dangerous
mission).

> (Remember, any mission always has a finite budget.  Some potentially
> marginally beneficial ideas almost always have to tossed to the side in
> order to focus on the best paying off ideas.  The marginal and very
> mission-specific payoffs from the dwarf proposal would seem to be an
> example of this.)

I did not realize there was such a thing as a dwarf proposal.
The only way I could see it happen in an alternative universe,
where technology can't develop further, and you have to rely
on engineered people as prime factor in the expansion into deep space.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a>
______________________________________________________________
ICBM: 48.07100, 11.36820            http://www.leitl.org
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