Jumping the Gun.

--- In spacesettlers@yahoogroups.com, "Karell Ste-Marie"
wrote:

> First, if we are going to conquer the stars, we need to think of
> other methods of getting there and chemical propellant is not the
> trick. I would rather create a small, portable, nuclear reactor to
> power the craft from an atmospheric side of things and then use an
> ion drive in space than use chemical propellant.

I thought long and hard about different forms of propulsion and the
supply chains that each would entail.

Nuclear has much to recommend it but I was unsure of the political
feasability of launching nuclear material into orbit. Further you'd
need raction mass so the question of where that would come from
would still remain.

Ion propulsion has a pretty impressive ISp but a very low thrust so
your ship would take a long time to get anywhere even though it was
using its fuel very efficiently. Further, where would all of the
Xenon or Argon come from?

I reluctantly settled on chemical propulsion because it had high
thrust, it would use a lot of the oxygen byproduct produced from
lunar material refining and when volitiles from NEOs were refined
into hypergolic fuels oone wouldn't have to worry about cryogenic
storage issues. Further, this allows another industry to be
established, rocket fuels, and cross subsidizes the collection from
NEOs of the volitiles like carbon and nitrogen which we would be
using in industrial quantities for agriculture and inert atmosphere.

> Water? Plenty of water on the moon (I *assume*) that the robots can
> gather (ice) and can use to power the reactor. You then have the
> basics for a facility that can grow over time.

Hydrogen has been detected at the lunar poles. Whether that hydrogen
is part of frozen water or some other compounds is an open question.
I'm not sure if there is plenty of water or not.

Also, if your base is situated at the equator, where you want it to
be if you have a mass-driver firing loads to a catcher at L-2, then
you have to deal with a secondary base at the poles whose only
purpose is to mine ice. How will you get the ice to the equator?
Launching via rocket is very energy inefficient, and in the end I
concluded that when one considers the ancillary benefit of carbon
and nitrogen, it made more sense to get the hydrogen from NEOs than
from the lunar poles.

> I'm a bit skeptic over the mass-driver idea, hell if you really
> want to go that route why not use an "elastic-powered" catapult?

Mike already addressed the energy issue, and I'm on board with his
explanation. A mass driver is very efficient at converting energy
into work. It takes a lot of energy to propell the mass to lunar
escape velocity and the mass driver has no moving parts.

I've run into people who are skeptics about the mass driver concept,
but never have I run into a mass-driver skeptic who has read
O'Neill's "The High Frontier." Have you read it? He does such a good
job in detailing the physics and rationales that I think he
addresses all of the issues skeptics have.

> If a reactor-powered subs can reach speeds of 25 knots
> underwater then you should be able to go mach 2 with a reactor-
> powered craft. A UAV would, of course, be the best choice.

I'm not quite sure what you mean by this, but I don't think a
nuclear powered UAV is going to go over well with the public.

> Now you nailed the supply part quite well, but I'm not convinced (I
> didn't check any excel documents yet on the group files) that you
> calculated the the mass driver's power requirements quite well.

I'm more than happy to be double checked. I did the work in
isolation and no one has really looked at it with a critical eye.
Feel free to do so.

TangoMan