Published online 19 January 2007 | Nature | doi:10.1038/news070115-14


Satellite kill creates space hazard finds out how China's destruction of its own satellite could cause future damage.

What has China done?

It's not too hard to destroy a satellite - but it's very messy.It's not too hard to destroy a satellite - but it's very messy.NASA

According to US sources, China tested an anti-satellite weapon on 11 January. The weapon is said to have struck and destroyed the Feng Yun 1C, an obsolete weather satellite launched by the Chinese government in 1999.

How do anti-satellite weapons work?

There are two basic strategies according to David Wright, an expert on space weapons at the Union of Concerned Scientists in Boston, Massachusetts. The first is to build a satellite that will enter an orbit near its target and release a spray of particles to rip it apart. The second approach is to launch a small satellite with some thrusters that can, with some adjustments after launch, ram its target as it passes by. Given the debris field from the collision, Wright says, it's likely that this Chinese project used the latter strategy.

How hard is it to ram a satellite in orbit?

"In principle, it's not that difficult," says Wright. To launch your weapon, all that is needed is an intermediate-range ballistic missile, such as the Chinese DF-21. Your hunter satellite can be as light as 50 kilograms and needs little more than a digital camera-like device for guidance. This satellite may have been transmitting a signal, which would have made it even easier to spot. The trickiest part, says Wright, is making your kill vehicle manoeuvrable enough to reach its target.

So have other countries, such as the United States and Russia, tried to do it too?

“The Feng Yun 1C held some prime real estate.”

They both field-tested anti-satellite weapons in the 1970s and early 1980s. The Soviets had trouble getting their system to work, and the United States abandoned their programme in part because they realized that the debris from destroying target satellites actually endangered their own satellites. They may, however, be continuing work on strategies to jam or otherwise incapacitate satellites without destroying them.

How could it be dangerous?

The problem, says Wright, is the debris field created by the collision. Debris can easily reach speeds of 7.5 kilometres a second, about 30 times the speed of a jumbo jet, and because it's in space, it doesn't slow down. "A millimetre-sized piece of debris can very seriously damage a satellite," he says.

According to Wright's estimates, the Chinese test probably created at least 2 million such particles, along with 40,000 particles between 1 and 10 centimetres, and around 800 pieces 10 centimetres or larger.

What are the chances that the debris from this test will hit another satellite?


Unfortunately, the Feng Yun 1C held some prime real estate. Its altitude and inclination are great for weather observations, and many satellites share a similar orbit. A good portion of the debris is expected to whiz around Earth for a decade or more, and the threat, says Wright, is that it will eventually hit another satellite and create still more debris. That could result in a slow chain reaction that destroys many other orbiters.

So what, if anything, can be done about it?

For now, not much, Wright says. But he hopes that the Chinese test will spur other countries to develop an international ban on such weapons, rather than spurring a space-based arms race.

Visit our killcreatesspaceh.html">newsblog to read and post comments about this story.