Sunday was an anxious day for the US Air Force team at Cape Canaveral. The launch of its Atlas VIn Greek mythology, Atlas was a titan who rebelled against the gods and was forced to hold the heavens on his shoulders as a punishment. rocket had already been postponed once, thanks to the violent thunderstorms which haunt the Florida coast. But, at last, there came a break in the weather - the spacecraft's boosters roared into life and sent it hurtling skywards. Written on its noseconeThe cone-shaped nose at the front of a rocket, guided missile, or aircraft. The cone is shaped to minimise aerodynamic drag. were two words: "America Strong".

The slogan was the only clue to the rocket's purpose. On board was a X-37B space plane - an unmanned craft capable of spending more than two years in orbit before gliding back to Earth and landing on a runway so that it can be used again. But how long its flight would last, and what it was supposed to discover, was a closely guarded secret.

The X-37B has been in operation for 10 years. One theory is that is spying on China's orbiting space laboratory. Whatever the truth, the PentagonThe headquarters of the US Defence Department, so-called because it has five sides. In 1967, peace protestors attempted unsuccessfully to levitate it (making it rise into the air) until all evil emissions had fled, in the hope of ending the Vietnam War.'s announcement 18 months ago that it was creating a Space Command has added to alarm over extra-terrestrialBeyond the Earth. One of the most successful sci-fi films ever was ET the Extraterrestrial, about an alien who makes friends with a group of children. rivalry between the global superpowers.n

Space warfare could take many different forms, but the satellites on which every country depends for communications are an obvious target. Disabling them could leave a conventional army unable to function properly, and a nation's infrastructure in chaos.

The Chinese, Russians, and Americans already have missiles which can shoot down objects in space. But rather than risk open warfare, attackers are likely to choose weapons which cannot easily be traced.

"The immediate form would be cyber-attacks, either against the satellites or the ground stations that control them," says Michael Schmitt, an expert on space law at Exeter University.

Attacking a satellite, with an intense beam of microwave radiation sent from another, is one possibility being explored. So is using a laser beam to disable the solar panels which provide a satellite's power.

A cruderMore simple, more basic, or more rough and ready. method would be to send a satellite into an enemy's path to cause a collision, or to deliberately destroy your own satellite so that the enemy is hit by the resulting debrisThe remains of something that has been destroyed. It comes from the French word "debriser" (to break up). When the Chinese destroyed one of their own weather satellites, it produced an estimated 150,000 pieces of debris..

Nuclear weapons could also be employed. Although the use of these in space is banned under an international treaty, some countries have refused to ratify it - the USA is among them.

Some argue that the key element in warfare is cutting-edge technology. An army is useless without reliable communications and, since those are controlled by satellites, a country which has the upper hand in space will always come out on top. It might also be possible to create lasers in space which are powerful enough to knock out missiles fired on Earth.

Others say that war in space is a sci-fi fantasy. Trying to develop super-weapons made sense when wars were decided by conventional armies fighting pitched battles, but today's conflicts involve more rough-and-ready methods. However sophisticated satellites become, the future of war is more likely to be an individual carrying a backpack on to an aeroplane or into a concert hall - or a plane plunging into a building.