RE: the polymer idea.
I was thinking of not only would the Shielding be of course Benificial, But Might be used to make hollow tubes /Lifeline to connect the Asteroids to gether. If we used a couple of hollow Asteroids, connected together Like a giant Hamster cage, we wouldn't have to worry about Starting a Nuclear Furnace, And might be able to Control The planet better.
Besides that the effect of having your propossed shield would of course help Prevent the radiation out there.
I also seem to recall, Using an Iridium based Ceramic in the use of Superconducters, I don't know if the research ever panned out, But If so, and If there is a supply of Iridium out there, then It would be the perfect melding of those robots.
just a few random thoughts,
Stephen