Last year, Pentagon mad science arm Darpa was working on one of its wildest projects yet: a microchip-sized nuclear reactor. The program is now officially done, the agency says. But these sorts of far-out projects have a habit of being reemerging under new managers and new names.

The project, known as the "Chip-Scale High Energy Atomic Beams" program, is an effort aimed at working on the core technologies behind a tiny particle accelerator, capable of firing subatomic particles at incredible speeds. It's part of a larger Darpa plan to reduce all sorts of devices to microchip-scale – including cryogenic coolers , video cameras and multi-purpose sensors. All of the projects are ambitious (this is Darpa, after all). But this had to be the most ambitious of the lot. Here's how Darpa's plans for fiscal year 2009described it:

Chip-scale integration offers precise, micro actuators and high electric field generation at modest power levels that will enable several order of magnitude decreases in the volume needed to accelerate the ions. Furthermore, thermal isolation techniques will enable high efficiency beam to power converters, perhaps making chipscale self-sustained fusion possible.

Achieving controlled nuclear fusion - the reaction that powers the sun - has been a dream for more than sixty years. Currently hopes are focused on the $13 billion International Thermonuclear Experimental Reactor (ITER). This is a giant "Tokamak" device, containing high-temperature plasmas inside donut-shaped magnetic fields. Construction started last year at Caradache in France; the plan is for ITER to produce its first plasma in 2018, and generate significant amounts of power (the target is five hundred megawatts) by 2026.

In contrast, the Chip-Scale High Energy Atomic Beams project had a budget of just $3 million, and rather shorter timescales; the plans for fiscal year 2009 include: "Develop 0.5 MeV [mega electron-volt] proton beams and collide onto microscale B-11 target with a fusion Q (energy ratio) > 20, possibly leading to self-sustained fusion." The energy ratio is the amount of power you get out compared to how much you put in. ITER has a design Q of 10, producing its output with a fifty megawatt input. The Darpa scheme would be twice as efficient.

And much smaller. The electromagnet for ITER alone weighs 925 tons, so it's not likely to be made small enough for a vehicle or any other mobile application, Darpa, on the other hand, cheerily indicates that its project will go on to produce "handheld power sources."

No further information is available. A few months ago, a Darpa media contact told Danger Room: "At the point we're way too early in programmatics to have anything to talk about" – and promised to get in touch as soon as there was anything to discuss. Later, the budget for fiscal year 2010 came out; Chip-Scale High Energy Atomic Beams are gone. Where did the project go? No one at the agency seems to know. "I'm afraid that if the program's not in the budget request then we're not pursuing it anymore and are therefore not tracking that activity any longer – we also don't keep any information on things we're not doing," a Darpa rep told me.

Darpa cancels research programs all the time for failing to meet strict performance goals. The agency is also sensitive to the perception that its veering from the world of hard-to-reach science... and into the realm of science fiction. Take that Danger Room favorite, nuclear isomer triggering. It's a process so controversialthat it has been labeled pseudoscience. Darpa dropped their funding of research in this area after it was revealed by New Scientist magazine in 2003.

But the military research into isomers still continues. Both the Defense Threat Reduction Agency and the U.S. Army continue to fund isomer studies. So perhaps the military has dropped its handheld nuclear reactor completely. Or maybe we'll find out soon that the studies continue quietly elsewhere, in another corner of the vast military research complex.

Photo: NASA

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