The old joke about nuclear fusion is that it's the "energy source of the future, and always will be" – but budgetary realities have raised new questions about just how much of a future fusion power has.

A campaign to get to the long-sought break-even point in a fusion reactor fell short last year at the Lawrence Livermore National Laboratory's $3.5 billion National Ignition Facility. Now it looks as if NIF will be turning its focus more toward nuclear weapons applications.

Meanwhile, the U.S. contribution to the international $13 billion ITER fusion research project is coming under increased congressional scrutiny. There's a chance that federal funding will be held up just as the decade-long effort is due to hit its stride.

Is fusion worth the cost?

It's enough to make some wonder whether civilian fusion research is worth the tens of billions of dollars that have been put into it over the past half-century - particularly when you consider how much progress is being made on other energy technologies ranging from natural gas to biofuel to solar and wind to next-generation nuclear fission.



"Nobody said it was going to be easy," said Daniel Clery, the author of a new book about the fusion quest. "But just because it's hard doesn't mean it's not worth doing. The potential rewards are so great, how can we not try?"

Clery's book, "A Piece of the Sun," builds upon his reporting for Physics World, New Scientist and the journal Science to tell the story of fusion research from its beginnings in the 19th century, when it dawned on physicists that the sun couldn't possibly be powered by coal. Eventually, they figured out that the sun's energy came from a reaction that fused hydrogen atoms into helium atoms under intense heat and gravitational pressure. In the process, a tiny smidgeon of matter is converted directly into a tremendous amount of energy, in accordance with Albert Einstein's famous equation, E=mc^2.

The same reaction was applied to the development of thermonuclear bombs, beginning in the 1950s, and researchers wondered whether it could be harnessed in the same way that nuclear fission was harnessed for commercial reactors. If it could, fusion fuel could be extracted from common materials and turned into energy, at far less cost and with far less radioactive waste than is the case with fission.

Roller-coaster ride

The quest has been a decades-long roller-coaster ride of hope and disappointment, as traced in Clery's book. Not that long ago, experts hoped that the laser-powered National Ignition Facility would reach the break-even point by 2010, with more energy coming out of the reaction than was put into it. Last year, though, NIF's managers had to acknowledge that the reactor was "refusing to play ball," Clery said. In February, a report from the National Research Council said the results being seen at NIF were "not yet fully understood."



That report said it was still worth pursuing the scientific quest, but in its latest budget proposal, the Obama administration seeks to end support for academic experiments at NIF. Physics Today quoted an official at the National Nuclear Security Administration as saying that the facility will "have to focus on its principal missions, which are in support of stockpile stewardship." And Sen. Dianne Feinstein, D-Calif., said it was "hard to justify" NIF's $486.6 million budget request in light of its failure to achieve the fusion energy break-even point, also known as ignition.

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"We totally respect that we spend taxpayers' money, and we have to answer to Congress and the executive branch, and make sure we keep them accurately informed of our progress," Ed Moses, principal associate director for Livermore Lab's NIF and Photon Science Directorate, told NBC News. "It's never a smooth ride, especially in times like this, when budgets are so tight for federal projects."

Moses pointed out that the National Research Council's report praised NIF's performance, and voiced confidence that the facility would eventually achieve its ignition goal. "This is one of the most challenging scientific and technical problems that big science has ever taken on," he said. "We can only provide capabilities on schedule. We can't make Mother Nature bend to our needs on schedule."

The U.S. contribution to ITER, an experimental magnetic confinement reactor that's to be built in France with support from 34 nations, is coming under scrutiny as well. On Tuesday, Feinstein said federal funding for ITER should be cut off unless the Department of Energy provides Congress with a "baseline cost, schedule and scope."

A spokesman for the U.S. ITER effort, Mark Uhran, told NBC News that the Energy Department's standard management procedures don't "really have provisions for dealing with ... what happens when the United States gets into an international project to build an asset." Nevertheless, the department was working out a way to respond to Feinstein's "valid concerns," Uhran said.

The current plan calls for the ITER reactor to begin operation by 2020, with experiments continuing through 2040. The first reactor materials were delivered to the construction site just this month, and the first U.S.-made components are due to be shipped later this year. "We're on the cusp of moving out of the design phase and into the development phase," Uhran said.

How long away?

Is commercial fusion power fated to remain an energy mirage, always looming seductively on the horizon? Will researchers and funding agencies give up on the dream? Or will there actually be a breakthrough? Those questions can't be answered at this point, but Clery says the answers will come in the next decade.

"The next 10 years will be crucial, because first of all, we'll know whether NIF works or not," Clery said. "The other factor is ITER. We'll see in the next decade how well ITER works, and then we'll have a good idea quite quickly whether it will be able to get to break-even."

And then there are the dark horses in the fusion quest, ranging from Sandia National Labs' Z Machine ... to a new generation of fusion devices known as stellarators ... to the low-cost "Wiffleball" plasma experiments being conducted for the Navy ... to academic experiments at the University of Missouri, the University of Washington and elsewhere ... to privately funded fusion ventures such as Tri Alpha Energy, General Fusion and Lawrenceville Plasma Physics.

Even if there is a technological breakthrough, it could take years longer to commercialize the technology. "The big question is, can you make an economic reactor? Just because it works doesn't mean you can make it work in practice," Clery said.

In the current era of cheap fossil fuels and increasingly affordable renewable energy, there's just not enough incentive to move forward more quickly with fusion research. But that could change if there's a breakthrough, of if there's a desperate need for the "always-on" baseline power that fusion could provide.

At the end of his book, Clery quotes the late Soviet pioneer Lev Artsimovich's assessment of when fusion energy would be available: "Fusion will be ready when society needs it," Artsimovich said. Considering the alternatives, will society ever need fusion? Feel free to weigh in with your comments below.

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Alan Boyle is NBC News Digital's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with NBCNews' stories about science and space,sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.