Check out the Langstrom Field; Pournelle and Niven probably have the
equations stashed somewhere. My understanding was that it was supposed
to be a plausible force-field requiring only a few new discoveries.
--
sentience@pobox.com Eliezer S. Yudkowsky
http://tezcat.com/~eliezer/singularity.html
http://tezcat.com/~eliezer/algernon.html
Disclaimer: Unless otherwise specified, I'm not telling you
everything I think I know.