User blog comment:Mr.Robbo/Darned FTL!/@comment-5135903-20130705105907/@comment-5135903-20130706113919

I mentioned that there would have to be some sort of system of "mass production" of negative mass/energy for large-scale wormholes, rather than more 'discrete' methods for micro-wormholes, though you pointed it out a lot more clearly.

You might be interested in this paper by Serguei Krasnikov (who invented the Krasnikov tube), in which he proposes that wormholes could be constructed that are held open by only the quantum fluctuations of the vacuum, thereby eliminating the requirement for negative mass/energy.