Slough and his colleagues are working on a system that shoots ringlets of metal into a specially designed magnetic field. The ringlets collapse around a tiny droplet of deuterium, a hydrogen isotope, compressing it so tightly that it produces a fusion reaction for a few millionths of a second. The reaction should result in a significant energy gain. "It has gain, that's why we're doing it," Slough said. "It's just that the form the energy takes at the end is hot, magnetized metal plasma. ... The problem in the past was, what would you use it for? Because it kinda...