On Wednesday, defense giant Lockheed Martin’s claim that it would try to build a compact nuclear fusion reactor in the next decade sounded like a science fiction dream coming true.

If it works, the company’s reactor would re-create the same nuclear reaction that heats the sun and use it to power cities. Although the potential of nuclear fusion has been studied for decades, Lockheed said it is hoping to build a reactor small enough to fit on the back of a truck and ship.

But is this a realistic goal? Scientists are skeptical, mainly because of the compact size of Lockheed’s experiment.

“As far as I can tell, they haven’t paid attention to the underlying physics of nuclear fusion,” said Ian Hutchinson, a professor  of nuclear science and engineering at Massachusetts Institute of Technology.

The basis of Lockheed’s experiment, which involves building a small reactor in a space 10 meters x 7 meters wide, is not practical because it doesn’t follow the commonly-accepted techniques used to build reactors around the world, Hutchinson said.

The general design of fusion experiments on Earth involve huge doughnut-shaped structures, about as large as a gymnasium. The National Ignition Facility at California’s Lawrence Livermore National Laboratory is an example.

The single largest piece of equipment at the National Ignition Facility is its 130-ton target chamber. (Courtesy Lawrence Livermore National Laboratory)

The world’s biggest nuclear fusion reactor, called the International Thermonuclear Experimental Reactor, is under construction in France.The facility will be as big as 60 soccer fields and generate 500 megawatts of energy, while the reactor itself will be 90 meters x 130 meters.

The ITER nuclear fusion reactor under construction in France. (ITER Organization)

The compact nature of Lockheed’s reactor is what makes the company’s experiment unique and more likely to develop quickly, according to Tom McGuire, compact fusion lead for Lockheed’s California-based “Skunk Works” team.

“The smaller the size of the device, the easier it is to build up momentum and develop it faster. Instead of taking five years to design and build a concept, it takes only a few months,” the company’s Web site says.

But fusion has been a very elusive goal for close to 60 years, said Harald Griesshammer, an associate professor of nuclear physics at George Washington University.

Greisshammer said he is concerned about the risks associated with any nuclear reaction, which are complicated by Lockheed’s small design.

To understand those risks, it’s essential to learn a little more about how nuclear fusion works: When two extremely hot atoms are forced to collide with each other, their nuclei combine to form one, releasing massive amounts of energy in the process. Fusion reactions are part of what makes the sun shine.

The fusion reaction releases atomic particles called neutrons, which “bombard the walls of the reactor, weakening them” said Griesshammer.

“This is a very, very small design,” he said of Lockheed’s reactor. “I’m not sure how stable it is.”

Lockheed says the walls of its reactor will absorb neutrons and other by-products, using them to generate energy that will fuel cities or planes.

In science, breakthroughs take time and decades, even centuries of effort. It’s no different with nuclear fusion.

One of the main challenges is containing the necessary plasma within magnetic fields, scientists say. Plasma is the ungainly blob that needs to be heated so that its atoms can collide. Scientists have likened it to “trying to hold Jello with rubber bands.”

So will nuclear fusion energy be a reality, and in as little as 10 years?

“I would love it to happen in the next 10 years,” said Griesshammer. “But I am highly skeptical.”

For a more detailed look at the history of nuclear fusion efforts, check out this 2012 Washington Post story by Brian Vastag and this 2014 update by Joel Achenbach.