Monday, April 30, 2012

Nuclear fusion; better news than flying cars

In Where's my retro future?, I commented on something better than flying cars.
Flying cars aren't alone among examples of things Americans thought we'd have by now; Popular Science has an entire slideshow of technologies people expected would exist by now, including personal jetpacks, nuclear fusion, and robot armies, along with reasons why they haven't appeared. Too bad, as nuclear fusion would come in very handy right now.
As for when humans might achieve sustained controlled nuclear fusion, the Popular Science article isn't optimistic.
Don't hold your breath for this one. “It's been 35 years away for half a century, and it's still 35 years away. And I suspect 35 years from now it will still be 35 years away,” said Seife, “If you look at civilizations in 2500, then I wouldn't be surprised if they used fusion.”
Maybe that time frame will be a bit shorter now, as the following article I included in Overnight News Digest: Science Saturday (White House Correspondents Dinner edition) on Daily Kos indicates.

Princeton University via Physicists see solution to critical barrier to fusion
By John Greenwald
April 23, 2012
Physicists have discovered a possible solution to a mystery that has long baffled researchers working to harness fusion. If confirmed by experiment, the finding could help scientists eliminate a major impediment to the development of fusion as a clean and abundant source of energy for producing electric power.

An in-depth analysis by scientists from the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) zeroed in on tiny, bubble-like islands that appear in the hot, charged gases—or plasmas—during experiments. These minute islands collect impurities that cool the plasma. And it is these islands, the scientists report in the April 20 issue of Physical Review Letters, that are at the root of a long-standing problem known as the "density limit" that can prevent fusion reactors from operating at maximum efficiency.

Fusion occurs when plasmas become hot and dense enough for the atomic nuclei contained within the hot gas to combine and release energy. But when the plasmas in experimental reactors called tokamaks reach the mysterious density limit, they can spiral apart into a flash of light. "The big mystery is why adding more heating power to the plasma doesn't get you to higher density," said David A. Gates, a principal research physicist at PPPL and co-author of the proposed solution with Luis Delgado-Aparicio, a post-doctoral fellow at PPPL and a visiting scientist at MIT's Plasma Science Fusion Center. "This is critical because density is the key parameter in reaching fusion and people have been puzzling about this for 30 or 40 years."

The scientists hit upon their theory in what Gates called "a 10-minute 'Aha!' moment." Working out equations on a whiteboard in Gates' office, the physicists focused on the islands and the impurities that drive away energy. The impurities stem from particles that the plasma kicks up from the tokamak wall. "When you hit this magical density limit, the islands grow and coalesce and the plasma ends up in a disruption," says Delgado-Aparacio.

These islands actually inflict double damage, the scientists said. Besides cooling the plasma, the islands act as shields that block out added power. The balance tips when more power escapes from the islands than researchers can pump into the plasma through a process called ohmic heating—the same process that heats a toaster when electricity passes through it. When the islands grow large enough, the electric current that helps to heat and confine the plasma collapses, allowing the plasma to fly apart
This discovery may solve a scientific problem with fusion that will cut off five years from the 35 mentioned above. As for the engineering, financial, and political problems, I those are still worth ten years each. Still, thirty years is better than thirty-five, so it's reason to hope.

For today's song, I present Thomas Dolby singing "Wind Power" (lyrics here), a choice I find both ironic and fitting--ironic given the subject of today's post, fitting given that I started the month with one of his songs and then featured him performing two days later, so I may as well close out the month with him.


  1. Replies
    1. Thorium reactors would be a lot more achievable than fusion ones, that's for sure.

  2. Lapsing into atypical seriousness, Narb wonders why there is no national fusion program akin to what was done for the space program. A few billion thrown around for research and little press attention doesn't cut it: we need to put some serious wood behind the fusion arrowhead and solve the open problems.

    Just think, we could spend tons of cash creating a system that would effectively put Countries Made Of Sand out business instead of using that money to invade them. Talk about managing both foreign and domestic policy...

    1. Narb, you may just get your wish: "Lockheed says makes breakthrough on fusion energy project"--it's the most read article on Reuters as of midnight last night.