"Shields up!" barks Captain James T Kirk as the Starship Enterprise braces itself for another blast from the Klingon cruiser, referring to that essential accessory without which the crew could never have ventured beyond the final frontier.

And while real astronauts are not thought to face quite the same risk from alien species, engineers are developing a similar shield to protect them from the solar wind, a stream of high-energy charged particles from the sun travelling faster than the speed of sound.

They say protecting crew members on long-term missions to Mars or the moon will be essential because the stream of particles causes mutations to DNA which can lead to cancer.

UK researchers have created a scaled-down version of the solar wind in a lab in Oxfordshire to study how to use magnetic shielding to protect astronauts. "We now have actual measurements that show a 'hole' in the solar wind could be created in which a spacecraft could sit, affording some protection from 'ion storms', as they would call them on Star Trek," said Dr Ruth Bamford, a physicist at the Rutherford Appleton Laboratory in Chilton.

The question of how to fend off the solar wind has been given some urgency by an international plan - the Global Exploration Strategy, signed by 14 space agencies including those of Britain, China, France and the US - to return to the moon and send astronauts further into space. George Bush has committed the US to a return trip to the moon by 2020 and the ultimate aim is to send people on the eight-month voyage to the red planet.

Bamford and her colleagues took a tip from our own planet when designing their "ion shield". Earth's magnetic field produces a magnetic shell called the magnetosphere which deflects charged particles in the solar wind. "We wouldn't have life on Earth if we were fully exposed to the radiation coming from the sun," she said. "It's our first layer of defence."

The team simulated the solar wind in the lab using an intense beam of charged high-energy particles. They placed a powerful magnet in this beam to investigate how effective it was at deflecting the particles. Bamford said it worked perfectly. The pinky glow of the plasma beam curved around the magnet just as the team had predicted. "It seems like quite a simple thing to do and it is, but what we are trying to do is put numbers on how effective this is," said Bamford. "I think a lot of people in space science didn't necessarily believe it could work as well as it did - and it worked superbly well."

Now that the team have demonstrated the principle, their next challenge is to make a device energy-efficient enough to be powered by a spacecraft, Bamford said.