"Steve Maudsley" wrote in message

Why do you want to use missiles to hollow it out?

Bearing in mind that most asteroids are quite dense, often with some
metallic composition, then some heavy blasting will be necessary to
get fairly rapid results.

I just realised there is a problem with this idea, missile impacts
would leave the hole radioactive. But if post detonation radioactivity
only affects the asteroid's inner walls down to a few inches in depth,
then small scale robotic diggers which excavate a few inches of rock
all the way around the interior of the hole and then blowing them out
of the hole with perhaps compressed air, could eliminate the
radioactiveness. RATs (rock abrasion tools) on the Mars rovers do
something similar today.

I suspect that smaller scale engineering would be better in order to
preserve the structure since an asteroid isn't usually large enough for
gravity to glue it together. And then I would be inclined to glue the debris
onto the outside or stuff it into string bags so that I could use it later
if I wanted to move the asteroid.

Good idea, but this calls for another level of robotic articulation.
Perhaps a fly around robot with a vacuum cleaner style of suction
mechanism, pulling stuff into heavy duty plastic bags could do the
trick.

So there is a way round the ring problem...

AAI