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

Eugen Leitl eugen at leitl.org
Tue Sep 6 10:01:28 UTC 2005


On Mon, Sep 05, 2005 at 11:46:08PM -0700, Adrian Tymes wrote:

> Doesn't help enough.  Even if we're just talking a one-person
> spacecraft to Mars and back, the constant thrust of a nuclear rocket
> would beat out the higher ISP but lower total thrust of chemical
> rockets.

Nuclear power in space is a very hard sell politically.
The technology doesn't exist yet in the first place, and needs
to be developed and tested.

It would be probably easier to put the reactor on a long boom,
with some staggered shields for the crew module. Some water
interim would shield, too.

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.
 
> 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?

> Then calculate how much you would need for nuclear propulsion.
> 
> But you're still missing the non-physics objection: the economics and
> practicality of finding and training that one perfect (by your
> guidelines) person, not to mention the cost of specializing habitat
> manufacture (which would ordinarily be partially borne by other
> missions hoping to send their own people up, but could not because your
> habitat rules out the people they wish to send), would seem to impose
> costs that at first would grossly outweigh the savings you'd gain by
> slightly reducing the mass.  Physics is not the only determiner of
> economics, but economics is quite often the determiner of whether you
> can or can not pull off a project of this nature.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a>
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