He3 on asteroids?

Is there any known or guessed quantity of He3 on asteroids or dead
comets? If an object has been orbitting for 4+ billion years, it
should have collected some from the solar wind. It seems that He3
would be easier to obtain from something like Eros than the Moon, if
it existed in similar density. If there was a supply, collecting and
separating He3 could be much simpler in the micro-G environment.

I did a quick Google and found little, but am wondering what you
think?

Josh

In article ,
Josh Gigantino wrote:
Is there any known or guessed quantity of He3 on asteroids or dead
comets? If an object has been orbitting for 4+ billion years, it
should have collected some from the solar wind.

The big uncertainty is that we know essentially nothing about the depth
and age of the regolith on asteroids.

Yeah, there'd probably be some, but whether it's worth exploiting is
another question.

...If there was a supply, collecting and
separating He3 could be much simpler in the micro-G environment.

Or not, as the case may be. Handling fine powders may well be easier
in gravity.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

In article ,
says...
Is there any known or guessed quantity of He3 on asteroids or dead
comets? If an object has been orbitting for 4+ billion years, it
should have collected some from the solar wind. It seems that He3
would be easier to obtain from something like Eros than the Moon, if
it existed in similar density. If there was a supply, collecting and
separating He3 could be much simpler in the micro-G environment.

I did a quick Google and found little, but am wondering what you
think?

In principle some could build up over time. However, he3 would have an
easy time escaping the gravitational attraction of many of the very small
asteroids and comets. Intense sunlight could cook the he3 off the
surface. It's an empirical question as to whether there would be
sufficient quantities to justify extraction. After all, there's gold in
sea water...but not enough gold .

Also, actually getting fusion reactions to run with he3 on a large scale
is not a well developed technology. It's a bit premature to want to mine
he3 anywhere.

--
__________________________________________________ ___
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threat to humanity posed by the AIDS virus, 'mad cow'
disease, and many others, but I think a case can be
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eradicate." -- Richard Dawkins

Josh Gigantino wrote:
Is there any known or guessed quantity of He3 on asteroids or dead
comets? If an object has been orbitting for 4+ billion years, it
should have collected some from the solar wind. It seems that He3
would be easier to obtain from something like Eros than the Moon, if
it existed in similar density. If there was a supply, collecting and
separating He3 could be much simpler in the micro-G environment.

I did a quick Google and found little, but am wondering what you
think?

Josh

From pages 204 and 205 of _Mining The Sky_ by John S Lewis

"But the circumstances of the asteroids differ from those we have
studied on the Moon. First, the intensity of the solar wind drops off
roughly with the square of the distance from the Sun. Therefore an
asteroid near 3.2 AU from the Sun experiences a solar wind flux that is
only a tenth that felt by the Moon. Second, accumulation of solar wind
gases on the Moon is aided by 'gardening' of the lunar surface by small
impacts, which constantly expose fresh material to the solar wind and
constantly bury gas-saturated surface grains out of harm's way. On
asteroids, even small impact events can remove regolith material by
ejecting it at speeds greater than the asteroid's tiny escape velocity.
Thus, "mature" surface grains with high contents of implanted gases are
preferentially lost, not preserved. Finally, the total exposed surface
area of the asteroids is less than the surface area of the Moon. For all
these reasons, extraction of helium-3 from the surfaces of asteroids is
not likely to be competitive with that from the Moon."

An excellent book in my opinion.
http://www.amazon.com/exec/obidos/tg...92717?v=glance

Although I think the last part of the paragraph must be in error. Surely
the surface area of the asteroids is greater than the Moon's (even
though the Moon outmasses the asteroids).


--
Hop David
http://clowder.net/hop/index.html

Hop David wrote in message ...

From pages 204 and 205 of _Mining The Sky_ by John S Lewis

snip MTS quote


Although I think the last part of the paragraph must be in error. Surely
the surface area of the asteroids is greater than the Moon's (even
though the Moon outmasses the asteroids).

Thanks Hop! I sometimes forget there are these strange, rectangular
things called "books" next to my computer desk. I've got both "Rain of
Iron & Ice" and "Mining the Sky", I'll brush up on what Mr. Lewis
says.

I agree on the surface area issue. Thousands of roughly spherical
objects all rotating slowly should have a vast collective surface. For
the NEOs that are "rubble piles", there would be that much more
surface area, and a method for trapping He3.

Josh

Would Mercury, being much, much closer to the Sun, have a much higher
quantity of He3 than the Moon (not that getting there would be a picnic ?

How about huge He3 collectors at either a solar orbit closer to the sun, or
at one of the LaGrange points, with a surface area of, say, one of the
theorized Solar Power Sattelites envisioned in the 70's - would they work,
or would the amounts of He3 over a reasonable period of time be too
negligable to even consider them?


"Josh Gigantino" wrote in message
om...
Hop David wrote in message
...

From pages 204 and 205 of _Mining The Sky_ by John S Lewis

snip MTS quote


Although I think the last part of the paragraph must be in error. Surely
the surface area of the asteroids is greater than the Moon's (even
though the Moon outmasses the asteroids).

Thanks Hop! I sometimes forget there are these strange, rectangular
things called "books" next to my computer desk. I've got both "Rain of
Iron & Ice" and "Mining the Sky", I'll brush up on what Mr. Lewis
says.

I agree on the surface area issue. Thousands of roughly spherical
objects all rotating slowly should have a vast collective surface. For
the NEOs that are "rubble piles", there would be that much more
surface area, and a method for trapping He3.

Josh

"Joseph S. Powell, III" writes:

How about huge He3 collectors at either a solar orbit closer to the sun, or
at one of the LaGrange points, with a surface area of, say, one of the
theorized Solar Power Sattelites envisioned in the 70's -

_WAY_ too small, given the miniscule flux of He3 involved.


would they work,
or would the amounts of He3 over a reasonable period of time be too
negligable to even consider them?

The latter.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Gordon D. Pusch) wrote in message ...
"Joseph S. Powell, III" writes:

How about huge He3 collectors at either a solar orbit closer to the sun, or
at one of the LaGrange points, with a surface area of, say, one of the
theorized Solar Power Sattelites envisioned in the 70's -

_WAY_ too small, given the miniscule flux of He3 involved.

Well, what happens if you get really close? That is, you graze the
photosphere? Assuming that you have a collector that handles 5000 K
temperatures. Hmmm, still bet the He3 concentrations are extremely
small. Probably makes more sense to use solar cells instead.


Karl Hallowell

(Karl Hallowell) writes:

(Gordon D. Pusch) wrote in message ...
"Joseph S. Powell, III" writes:

How about huge He3 collectors at either a solar orbit closer to the sun, or
at one of the LaGrange points, with a surface area of, say, one of the
theorized Solar Power Sattelites envisioned in the 70's -

_WAY_ too small, given the miniscule flux of He3 involved.

Well, what happens if you get really close? That is, you graze the
photosphere? Assuming that you have a collector that handles 5000 K
temperatures. Hmmm, still bet the He3 concentrations are extremely
small.

Youbetcha. He3 is a rare isotope, cosmically speaking --- only 1.37 ppm of
all helium is He3.


Probably makes more sense to use solar cells instead.

Especially since we haven't a =CLUE= how to burn He3 in a fusion reactor,
and if Todd Rider's Ph.D. Dissertation is correct, there may be be fundamental
thermodynamic reasons why =ANY= He3-burning "reactor" smaller than a brown dwarf
will consume more energy than it generates...


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

In article ,
Roger Stokes wrote:
Even at .7 ppb of the Earth's atmosphere, I assume it must still be cheaper
right now to refine it on Earth...

You don't get it from the atmosphere. Rather, it's a product of tritium
decay. Most modern nuclear weapons contain small amounts of tritium for
"boosting" fission yield (either of the whole bomb, or of the fission
trigger for a fusion bomb), and it must be repurified regularly because
He3 poisons the reaction. So the US nuclear arsenal, in particular,
generates a steady trickle of He3 as a byproduct of bomb maintenance.

and try some fusion experiments, rather than
go to the moon to get it - what's the reason it hasn't been done?

We don't have a fusion reactor that works even for the D-T reaction, never
mind for one involving He3. The basic physics of the He3 reactions have
been understood for a long time; it's the engineering details of the
fusion reactor that might, or might not, be able to overcome the problems.
We can't run meaningful experiments on that until we can build one.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |