Is Steve Fossett flying into danger?

At 45,00ft, the dangers are invisible, unavoidable and from far away and long ago in the galaxy. The Virgin Atlantic Global Flyer pilot may be getting a buzz on his solo jaunt around the world, but he is also getting a blast from cosmic rays scudding across space. His aircraft is a platform for an experiment by the UK defence lab Qinetiq and the firm Solarmetrics to monitor the levels of stray firepower from dying stars.

Cosmic rays are a known aviation hazard: these bits of shrapnel from ancient supernova explosions slam through the galaxy at a frequency of around three a square centimetre. They can be as big as the nucleus of uranium, and can travel at 99% of the speed of light, so they pack a punch. "One of those would warm a cup of tea, if it hit one," says Clive Dyer, of Qinetiq.

Cosmic rays were first discovered in 1912 by an Austrian scientist, Victor Hess, who was measuring the conductivity of air during balloon ascents. Most of these rays slam into air molecules and decay into less dangerous debris; few hit the ground. But high-flying pilots and air crew stand a greater than normal risk and astronauts on long space missions are likely to need serious shielding.

"The Apollo astronauts lived dangerously," says Dyer. "They were unshielded." Cosmic rays with enough energy can sever DNA and ionise human cells. They can also flip transistors, scramble computer memories and shut down satellites.

Researchers have been flying radiation monitors for two decades. Having confirmed the dangers, they now want to be able to calculate the levels of cosmic radiation hazard over different aviation routes. Qinetiq's cosmic radiation and activation monitor (Cream) has flown 10 missions on board the space shuttle, six months on board the Russian space station Mir and four years on board the supersonic passenger jet Concorde. Cream has now been joined by a new compact detector called Qdos, flying for the first time.

The Fossett foray seemed the perfect opportunity: no pilot has been subjected to such consistent doses of cosmic radiation in one flight. There are radiation monitors on the two chase aircraft that follow Fossett, and a computer program to interpret the data in real time.

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