Left Flank

Here's a simple concept for turning space into a wasteland unfit for satellites running civilian and military technology essential to modern life: just blow up a few satellites in orbit.

One shot China has been practising became clear a year ago, on January 11th 2007. In a nuclear-proof air force command centre, built on giant shock-absorbing springs within Cheyenne Mountain, outside Colorado Springs, officers tracked a missile fired from a mobile launcher deep inside China. It followed what one American official said was a «strange» trajectory, designed neither to land a warhead nor to put a payload into orbit. Instead it intercepted one of China's ageing weather satellites. The impact about 850km (530 miles) above Earth created a huge field of space debris, contributing about 28% of the junk now floating around in space.

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The core fear is that any conflict in space would cause the most injury to America since America has the most to lose. Damaged planes crash to the ground and destroyed ships sink to the bottom of the sea. But the weightlessness of space means that debris keeps spinning around the Earth for years, if not centuries. Each destruction of a satellite creates, in effect, thousands of missiles zipping round randomly; each subsequent impact provides yet more high-speed debris. At some point, given enough litter, there would be a chain reaction of impacts that would render parts of low-Earth orbit—the location of about half the active satellites—unusable.

As matters stand, ground controllers periodically have to shift the position of satellites to avoid other objects. This month, NASA was tracking about 3,100 active and inactive satellites, and some 9,300 bits of junk larger than 5cm, about 2,600 of them from the Chinese ASAT test. Given their speed, even particles as small as 1cm (of which there may be hundreds of thousands) are enough to cripple a satellite.

For America, then, avoiding a space war may be a matter of self-preservation. The air force has adopted a doctrine of «counterspace operations» that envisages either destroying enemy satellites in a future war or temporarily disabling them. But for the most part, America's space security relies on passive measures: sidestepping an attacker by moving out of the way of possible strikes; protecting the vital organs of satellites by «hardening» them against laser or electromagnetic attack; replacing any damaged satellites; or finding alternative means to do the job, for example with blips or unmanned aircraft.

More esoteric space research has ideas such as sending small satellites to act as «guardian angels», detecting possible attacks against the big birds. It also includes plans for breaking up satellites into smaller components that communicate wirelessly, or deploying «space tugs» that would repair and refuel existing satellites.

I dare any Republican to suggest a big wall in space. This is yet another reason why NASA needs a strong dose of privatization, so that it can assume its proper role of defense, not exploration.