I note several grammar errors in my Nov 23 post and I think they make
it difficult to understand. I've corrected the errors (that I see) in
the text below. Sorry!

Dave W wrote:
I'm intrigued as to why there are no references to the above in any of the
'space' newsgroups.

um, I think you may be under the false impression that doing this would
somehow magically save fuel or something. If I understand you
correctly, you seem to think that if I move a large body (such as an
asteroid), and if that large body's gravity pulls a smaller body (a
towed asteroid), then I am pulling the smaller body for free (without
expending additional fuel). Sorry, but it don't work that way.

The smaller, "towed" body pulls back on the larger body, and you expend
exactly the same amount of fuel as you would expend if you connected
then up via a cable and pulled them both.

I note that this is similar to a misconception that I often hear voiced
about magnetic rail guns. Many people seem to think that there would
be no recoil in such a gun, because "the gun isn't pushing the bullet,
the magnet is pushing it." It just doesn't work that way. The gun is
pushing the bullet, and the bullet is pushing back on the gun.