NEAs ( TGD)

Moderate sized NEAs seemed to be covered with a layer of dust and gravel.
Should be reasonably easy to scoop up (this needs to be tested). If this is
true, a small facility on a convenient NEA could supply materials to other
small vehicles for return to earth. Perhaps use a shuttle between the NEA
and NEA low orbit so the return vehicles don't need to land.

I like small because it's relatively easy to do, you use lots of them so you
get economies of scale and have built-in redundancy. See
http://www.nas.nasa.gov/~globus/papers/AsterAnts/paper.html for my thinking
before I realized you could probably scoop up the dust.

John Frazer wrote:

> I must be sounding schitzophrenic -first one thing, then another.
> Playing devil's advocate, trying to bolster _and_ pick apart
> proposals. All part of developing ideas.
>
> However, NEAs are starting to look better all the time.
>
> >-go to the Moon
> >
> >Yes, in that it is a nearby source of raw materials
> >outside of the steepest part of the Earth's gravity well.
>
> Nearby, yes, but NEAs are more accessible (distance doesn't matter
> nearly as much as relative velocity), as well as richer sources.
> Now we have some choices: If you pick a light CC (like Diemos),
> you've got volatiles aplenty, but very little metals (probably about
> like Lunar ores). An extinct short period comet core may be nothing
> but crumbly ices, with a covering of dark dust. Halley's comet core
> has a density of .2gm/cc (20% of water). Even though it's mostly
> hollow, most of what's left is ices.
> Go to an Iron asteroid, and you've got 80% iron/nickle/cobalt, with
> attendant rich Pt & precious/strategic metals, but very little
> process chemicals to work them with.
> Get some of each? Certainly, in the long run, we'll do this.
>
> The best bet is to find a little chunk of a stony-iron. As close to
> 1AU/1year orbit as possible.
> Such a stony-iron would probably have about 30% metals, and the
> remainder would be about 20% volatiles. Still, if we're catching a
> 300 meter asteroid, we're rich!
> A stony-Iron NEA seems to be the best bet. Far better than Luna,
> infinitely better than Mars surface. The retrieval mission would be
> the second thing built; first, the LEO ET station. It receives the
> first small samples from the NEA, and as the shipments build up, it
> builds the shielded HEEO base, with rotating habitat section. The NEA
> chunk is brought to HEEO, to pace near the HEEO station.
>
> When somebody uses the O'Leary idea of a mass driver bringing an
> asteroid chunk back, the idea of a Lunar mine may be in trouble.
> This may also happen with a mass driver or high strength tether
> facility at the NEA, and another (couple) in Earth orbit. (The rock
> doesn't need to be _in_ HEEO, if it can get loads to there
> frequently.)
> I'm not sure how often a reasonable tether/mass driver can throw
> payloads back to HEO, but the needed delta-V is tiny at the best
> times. If you can throw (SWAG) 100kg loads with 3km/sec, then you can
> probably have loads coming into HEO to be caught, through most of the
> year. At the best times, less than 1km/sec.
>
> It's also interesting in that this very exact type of NEA (stony
> iron, 1AU/1year) is the greatest threat to Earth! It approaches
> slowly, so when it hits the atmosphere, it doesn't build up a
> ferocious pressure wave of superheated air, to crush it high above
> the ground. It's more solid than a light CC, so it's crush strength
> is higher. Even worse, since we rarely have it in our night skies
> while it's near enough, we have trouble seeing it.
>
> A question: Could rock dust be vaporised and used as propellant in
> an arc jet of some kind? Solar thermal? Is this any better than a
> mass driver rocket? It seems simpler, but the idea of electrically
> propelling rock vapor is rather technically horrendous.
>

Al Globus
aglobus@..., (650) 604-4404
http://www.nas.nasa.gov/~globus/home.html

The dinosaurs weren't spacefaring. We are. I don't think that's an accident.
Maybe we are life's taxi to the stars.

I think we should:

1. Devote half of NASA's budget ($7 billion) to reaching NASA's 2020 goal of
reducing launch costs to Low-Earth-Orbit to $220/kg with a 0.01% failure
rate.
This should enable space tourism. The resulting orbital hotels will need to
develop efficient orbital life support and other necessary technologies.

2. Build orbital space colonies. The materials in the largest asteroid are
sufficient for orbital colonies with a combined surface area about 500 times
greater than Earth's. Eros alone could make over ten thousand space colonies,

each with about about 10 square kilometers of 1g living area.

3. After a few generations of orbital living, people won't need their colony
to be near Sol. Then small groups of colonies with populations in the
tens-of-thousands can set out on multi-decade journeys to nearby stars.

Except the launch goals, none of this is even a little bit official.