Iron outside = Iron inside

Al Globus wrote:

> I would like to re-introduce a completely different approach to asteroid
> mining to this group. See
> http://www.nas.nasa.gov/~globus/papers/AsterAnts/paper.html. Basic idea:
> find very small asteroids (~1 meter diameter) and return the whole thing
> to Earth orbit. Use a large fleet of solar sail powered spacecraft to
> get large amounts of returned mass. Using a large fleet gives you
> economies of manufacturing scale and failure tolerance. Returning whole
> asteroids avoids the uncertainties of rock mining.

FWIW: I *really* like this idea, Al.

The only comment I have is have you run the numbers with a low ISP
ion drive instead of the sail? I'm think an ISP around ~1000
seconds, but I don't know of any quite that low, Hall effect
thrusters can go down to 1200 seconds; (but I'm not sure of the
efficiency at that power). The idea of using a low ISP ion drive is
that the thrust is much higher and you may even have enough power
to run several drives in parallel; they'd use more propellent but
not necessarily an impossible amount. Also, Hall effect thrusters
can run on less exotic propellents; i.e. cheaper. xenon is *very*
expensive.

It might even be a project you could run in the very near term in a
smaller way- with DS1 so successful, it would be a good time to
raise it I think.

--
- Ian Woollard (ian.woollard@...)

"Is a planetary surface the right place for an expanding
technological civilization?"
- Gerard O'Neill