Efforts are underway to exploit a strategy that could generate fusion with relative ease. On July 14, 2015, nine years and five billion kilometers after liftoff, NASA’s New Horizons spacecraft passed the dwarf planet Pluto and its outsized moon Charon at almost 14 kilometers per second—roughly 20 times faster than a rifle bullet. Samuel Cohen and his team hope to beat the standard timetable for fusion by about a decade using a reactor—initially for rocket propulsion—that’s a fraction of the size and cost of the huge tokamak devices. Cohen’s design takes advantage of the phenomenon of field reversed configuration (FRC), in which a dense mass of ionized plasma holds itself together. Image credit: Princeton Plasma Physics Laboratory. The images and data that New Horizons painstakingly radioed back to Earth in the weeks that followed revealed a pair of worlds that were far more varied and geologically active than anyone had thought possible. The revelations were breathtaking—and yet tinged with melancholy, because New Horizons was almost certain to be both the first and the last spacecraft to visit this fascinating world in our lifetimes. Unless, that is, Samuel Cohen succeeds with the offbeat fusion reactor that he’s developing at the Princeton Plasma Physics Laboratory in New Jersey. Cohen’s current prototype is a clear plastic cylinder that sits in the middle of his lab amidst a dense mass of cables, magnets, and power supplies, emitting a violet pulse of light every two seconds like a two-meter-long strobe light. “We’re only using hydrogen right now,” Cohen explains, referring to the ionized plasma inside the tube that’s emitting the flashes. So there are no actual fusion reactions taking place; that’s not in his research plan until the mid-2020s, when he hopes to be working with a more advanced prototype at least three times larger …