[jmcenanly]

How much gravel will they have to move to get one shuttle load of He3?

By weight, they will process 18 metric tons of regolith to obtain 33 kilograms of He3. However, during the processing, other materials will also be obtained such as oxygen,silicon, titanium, iron, aluminum, platinum,and other volatiles.

For further information see these addresses:

http://www.hq.nasa.gov/webaccess/CommSpaceTrans/SpaceCommTransSec39/CommSpacTransSec39.html

http://fti.neep.wisc.edu/presentations/jfs_hallway.pdf

[RightWhale]

Is the ratio correct?

Could it be off by a factor of a few hundred million?