Hitching a Ride on a Magnetic Bubble

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If a group of NASA-funded researchers have their way, parents in the next century can breath a little easier. Every family saucer will come equipped with a fuel-efficient magnetic bubble that speeds its occupants from planet to planet and wards off the very worst solar flares.

Most planets in the solar system already have such bubbles - they're called magnetospheres. Earth's magnetosphere is an extension into space of the familiar magnetic field that causes compass needles to point North. Our planet sits at the heart of the bubble, which occupies a volume at least 1000 times greater than Earth itself. The magnetosphere protects us from solar wind gusts and from potentially deadly solar flares. Without it, Earth might be as barren as Mars or the Moon, two worlds without magnetospheres.

"The magnetosphere not only shields us from solar radiation but it also acts something like a solar sail," says Dennis Gallagher, a space physicist at the Marshall Space Flight Center. "The solar wind pushes on the magnetosphere constantly, but fortunately Earth is just too massive to blow away."

What might happen, though, if we created a magnetic bubble around something much smaller than the Earth - like a spacecraft? Could it ride the solar wind from planet to planet? Gallagher and his colleagues think so.

"A 15 km-wide miniature magnetosphere one astronomical unit from the Sun would feel 1 to 3 Newtons of force from the solar wind," says Gallagher, "That's enough to accelerate a 200 kg spacecraft from a dead stop to 80 km/s (180,000 mph) in only 3 months.

"If we launched a space probe now equipped with such a bubble it would easily overtake Voyager and become the first spacecraft from Earth to cross the boundary into interstellar space."

The ingenious notion to use miniature magnetospheres as a form of advanced propulsion was first suggested by Robert Winglee at the University of Washington. The NASA Institute for Advanced Concepts awarded Winglee a Phase I Revolutionary Advanced Concepts grant two years ago followed by a Phase II contract, and already the idea has leapt off the drawing board and into the lab.

"We've just finished our first round of tests in a 20 by 30 foot vacuum chamber here at the Marshall Space Flight Center," says Gallagher, the experiment's principal investigator at Marshall. "We're conducting the tests as a cooperative effort between NASA and the University of Washington, with support from the University of Alabama."