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Solar Storm! Shields Up!
4 November 2008 (All day)
Any fan of Star Trek knows the drill: An enemy ship attacks, the red alert blares, and the shields go up. Back in the real world, a team of physicists has now shown that such deflector shields are possible and could help protect astronauts from potentially lethal radiation as they travel to the moon, Mars, or beyond.
Humans have worked in low Earth orbit for years now and have briefly forayed to the moon. But so far they have not ventured for more than about a week into outer space, where they risk periodic exposure to high-energy particles from the sun and cosmic rays. Those particles are powerful enough to damage or destroy any DNA molecules they encounter. The danger is practically nonexistent closer to home, because Earth's magnetic field acts as a giant shield, deflecting much of the harmful radiation away. If humans colonize the moon or travel to other planets, they'll need a portable version of the geomagnetic field.
Such a device might come from nuclear-fusion research. Fusion reactors must generate powerful magnetic fields to confine particles undergoing high-temperature, high-density thermonuclear reactions. The difference in a spaceship is that the reactor would work inside out--repelling charged particles away from the ship instead of confining them inside.
That setup just might work, according to a paper published today in Plasma Physics and Controlled Fusion. Using computer simulations of plasma--the state of matter created in fusion reactors and encountered in space as solar storms and cosmic rays--the researchers calculated that a magnetic force field only a few hundred meters wide could provide astronauts substantial protection against harmful radiation. The team says the power requirements for a protective force field would actually be thousands of times smaller than those for a nuclear fusion reactor--on the order of kilowatts--and the magnets required would be far smaller.
"I'm delighted to say that the [simulation] worked the first time we tried it," says plasma physicist and lead author Ruth Bamford of the Rutherford Appleton Laboratory near Didcot, U.K. The simulated force field blocked incoming radiation completely, though Bamford cautions that the device probably wouldn't provide complete protection in real space conditions. For one thing, it couldn't block out x-rays or gamma rays. In any event, she says, "our aim isn't perfect protection but to bring down the radiation to acceptable levels."
That goal might remain elusive. Physicist Geoffrey Reeves of Los Alamos National Laboratory in New Mexico says it's "notoriously difficult" to replicate the space environment in the laboratory. Although the experiment screens out the bulk of the solar wind, it does not necessarily eliminate the most energetic solar particles, which make up a small part of the radiation but are "where the main hazard lies." Physicist Yue Chen, also of Los Alamos, agrees. The paper presents "exciting work," he says, but the researchers still need to prove that creating a magnetic bubble to protect a spacecraft is viable, he says.