Page last updated at 23:57 GMT, Monday, 3 November 2008

Magnetic shield for spacefarers


Lab tests show how to produce a protective 'hole' in the plasma

Future astronauts could benefit from a magnetic "umbrella" that deflects harmful space radiation around their crew capsule, scientists say.

The super-fast charged particles that stream away from the Sun pose a significant threat to any long-duration mission, such as to the Moon or Mars.

But the research team says a spaceship equipped with a magnetic field generator could protect its occupants.

Lab tests are reported in the journal Plasma Physics and Controlled Fusion.

The approach mimics the protective field that envelops the Earth, known as the magnetosphere.

Astronauts' risk

Our star is a constant source of charged particles, and storms that arise on the Sun's surface result in huge numbers of these particles spilling into space.

As well as this plasma, or "solar wind", high velocity particles known as cosmic rays also flood through our galaxy.

The Earth's magnetosphere deflects many of these particles that rain down on the planet, and our atmosphere absorbs most of the rest.

The first time we switched it on, it worked
Ruth Bamford

International space agencies acknowledge that astronauts face a significant risk of ill health and even death if they experience major exposure to this harsh environment.

And even the spacecraft themselves are not immune to the effects. A solar flare crippled the electronics on Japan's mission to Mars, Nozomi, in 2002, for example.

But researchers from the Rutherford Appleton Laboratory (RAL), the Universities of York and Strathclyde, and IST Lisbon have shown how it might be possible to create a portable mini-magnetosphere for spaceships.

People scale

In its experimental set-up, the team simulated the solar wind in the laboratory and used magnetic fields to isolate an area inside the plasma, deflecting particles around the "hole".

It was not initially clear the idea would work, said Ruth Bamford, who led the research.

"There was a belief that you couldn't make a little hole in the solar wind small enough to do this at all," Dr Bamford, from RAL, told BBC News.

"It was believed that you had to have something very large, approaching planetary scale, to work in this way."

The team has had to take into account the physics of plasmas at the comparatively tiny human scale. To create its metre-sized trial, the team used a plasma jet and a simple $20 magnet.

"The first time we switched it on, it worked," said Dr Bamford.

What is more, the trial field seems to adjust itself automatically. "It does have the capacity to be somewhat self-regulating, just like the Earth's magnetosphere is," Dr Bamford explained.

"When it gets a strong push from the solar wind, the bubble gets smaller. The video shows us increasing the pressure of the solar wind, and the shield gets smaller but brighter."

Power issues

Many more experiments are needed, Dr Bamford admits, to understand how best to harness the effect; and a practical implementation is probably 15 to 20 years away.

Magnetosphere graphic (Ruth Bamford)
The approach mimics how the Earth's magnetic field deflects particles

To protect a spaceship and its crew, she said, the craft itself might carry the magnetic field generator. Alternatively, it was possible to envisage a constellation of accompanying ships dedicated to the purpose of providing the umbrella where it was needed most.

The approach will probably also work with a field that is not on constantly, but cycles on and off - conserving the power that is precious on long-term missions. The details of how to cycle the field and control its shape must be hammered out, however.

"There're a lot of things to work out, like control, reliability, weight to launch, and so on," said Dr Bamford.

"I don't think it'll come down to as little as sticking fridge magnets on the outside of the spacecraft."

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