Lockheed Martin announced Wednesday that it is getting closer to developing a viable power source based on the nuclear reaction that powers the sun. The company expects to build a prototype fusion reactor in five years and deploy ones that are small enough to fit on the back of a truck in the next 10 years. The fusion research, which has been conducted in secret at Lockheed’s Skunk Works division, suggests it’s feasible to build a 100-megawatt reactor that is 7 by 10 feet, or one-tenth the size of current reactors. Lockheed thinks that the size of its device will mean it can be used on spacecraft, ships, and city power stations. One of the more fascinating potential uses is that it may bring back the idea of large, nuclear-powered planes that virtually never need to refuel. Those ideas were left to rot decades ago because of the dangers of nuclear fision. The main problem with using fusion to produce electricity has been that the reaction takes too much energy to start and maintain, and it doesn’t produce enough energy to be useful. However, the scientists at Lockheed appear to have broken through that, mainly be developing a new method for confining the energy. Previously, a 1950's Soviet method was the best developed. Nuclear fusion, unlike fission (splitting atoms), produces virtually no radioactive waste and, even better, no greenhouse gasses. “We can make a big difference on the energy front,” said project head Tom McGuire.