ONE INNOVATION AFTER ANOTHER:

"The only answer to the 'always 30 years in the future' argument is that we simply demonstrate it," Slough said. And that's what he and his colleagues intend to do this summer, at their lab inside a converted warehouse in Redmond, Wash.

It's obvious that nuclear fusion works: A prime example of the phenomenon can be seen every day, just 93 million miles away. Like other stars, our sun generates its power by combining lighter elements (like hydrogen) into heavier elements (like helium) under tremendous gravitational pressure. A tiny bit of mass from each nucleus is converted directly into energy, demonstrating the power of the equation E=mc2.

Thermonuclear bombs operate on a similar principle. But it's not practical to set off bombs to produce peaceful energy, so how can the fusion reaction be controlled on a workable scale?

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 blows up."

That's where the magnetic field plays another role: In addition to compressing the metal rings around the deuterium target, the field would channel the spray of plasma out the back of the chamber, at a speed of up to 67,000 mph (30,000 meters per second). If a rocket ship could do that often enough -- say, at least once a minute -- Slough says you could send a human mission to Mars in one to three months, rather than the eight months it took to send NASA's Curiosity rover.

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