"Star Trek" Shield May Protect Astronauts

Richard A. Lovett
for National Geographic News
November 4, 2008
A powerful magnetic shield may be able to deflect dangerous solar radiation from spacecraft traveling to the moon and other planets, a new study says.

Magnets tested in a recent laboratory experiment could divert radiation safely, a discovery that's "like Star Trek coming to life," said lead author Ruth Bamford, a plasma physicist at the Rutherford Appleton Laboratory in the U.K.

On Earth, humans are protected from radiation partly by the atmosphere. But our planet's magnetic field, called the magnetosphere, repels many of the harmful particles before they reach us.

"Life might not have been possible on Earth without a magnetic field as this first line of defense," Bamford said.

(Related: "Earth's Core, Magnetic Field Changing Fast, Study Says" [June 30, 2008].)

"With a journey to Mars, [radiation] is the most difficult problem," she said. "So the idea is, Why don't we just bring a magnetosphere with us?"

The idea of using magnetic fields as radiation shields was first proposed in the 1960s, but the concept languished until a resurgence of interest in manned expeditions to the moon and Mars.

Little Earthlings

One of the greatest dangers facing future astronauts is radiation, much of which comes from the sun via solar wind, a stream of particles from the sun's atmosphere.

Solar flares can be as deadly to life on Earth, and prolonged exposure to lower doses can cause cancer.

(Related: "Perfect Sun Storm Threatens Power, Phones" [October 29, 2003].)

Until recently, however, scientists thought shielding spacecraft would require an impractically large magnet—one capable of generating a field 60 miles (100 kilometers) or more across.

"We said, Hang on," Bamford explained. "People are small. We only need to make a little hole in the solar wind."

To test the idea, her team borrowed laboratory equipment used for work in fusion power, a process that also involves magnets. The scientists placed a small magnetized object—a simulated "spaceship"—into a flow of supersonic plasma, which consists of charged particles.

"You don't expect experiments to work first time," she said of the research, which is published today in the journal Plasma Physics and Controlled Fusion.

"But this did. It was very clear that it was doing its job."

Magnetic Bubble

Erika Harnett, a space physicist at the University of Washington in Seattle, isn't surprised that the magnetic shield worked.

A few years ago, Harnett and colleagues researched an idea for a spaceship-propulsion system called mini-magnetosphere plasma propulsion (M2P2) and saw similar results.

M2P2 creates a magnetic bubble, then fills it with plasma. In space, the bubble would be battered by the same solar radiation particles that pose a hazard to astronauts. (See sun photos.)

"The solar wind would sort of push this bubble away from the sun," she said.

Not only would this reaction protect the spacecraft from radiation, "[but] we thought it was a practical means of propulsion."

But the concept has only been tested in laboratories at a small scale, she added.

Exposure Concern

Lead author Bamford notes that her team's work is restricted to the laboratory. "We're [just] working on the physics of what would be possible," she said.

One of the problems is making sure a space crew isn't exposed to the magnetic field.

"One would have to make sure the field doesn't enter the ship itself," said Carl Frederick, a physicist and science fiction writer in Ithaca, New York.

"But the idea of having a ship, in effect, carrying its own magnetosphere with it is appealing," he added by email.

Bamford agrees that it may be necessary to protect the crew from magnetic forces.

But she believes this could be solved by careful engineering: for instance, balancing fields on the inside of a spacecraft so that the magnetic field is canceled out.

Alternatively, two spacecraft might fly in formation, with astronauts living on one and the magnetic field being generated on another.

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