January 20, 2007



[I]t's important to keep in mind that the Chinese carefully timed the launch of their kinetic kill vehicle so that it would intercept the known position and orbit of the satellite it was aiming for--intercepting a target in an arbitrary orbit is a much more difficult proposition.

The Chinese targeted a low-orbiting, obsolete, weather satellite, where the kinetic kill energy was very great. However, the really strategic satellites fly much higher--the navigation network is 20 000 km up, and the communications constellations are in a geosynchronous arc at 40 000 km. At geosynchronous altitudes, the orbital velocities are so much lower that the impact energy would be only about a tenth as high as in last week's test.

Distance introduces a second burden: terminal navigation. When a target satellite is close to the Earth, ground radars can track it and relay final course corrections, both to the rocket during its ascent and to the kill vehicle, once it has been deployed on its hoped-for collision course. Radar operates at an inverse fourth power law, which means that for the Chinese system to aim many times farther than low Earth orbit--as it would have to do to track objects geosynchronously--the demands on a ground-based radar would be simply impossible. The engineering challenges don't need much description for this audience.

The Chinese weapons system has so far demonstrated only that it can pose a threat to low-orbiting objects, of which the most important are reconnaissance satellites. But these satellites have backup. [...]

Objects can hide in space, to a greater or lesser degree, by lowering their radar reflectivity or optical brightness along the attacker's expected line of approach. This makes terminal navigation and guidance more difficult. That effect can be augmented with decoys, which can either be deployed when an attack is detected or can be sent, as a matter of routine, to fly in formation with the high-value target. A decoy doesn't have to be a throwaway subsatellite, it could be an inflatable spar a few tens of meters long with a pseudo-target at the end to attract the on-rushing kinetic kill vehicle away from the real spacecraft. Such a decoy could be deployed in a matter of minutes, and even re-stowed afterwards for future re-use.

Even the simple suspicion that a target may have such a capability would discourage a potential attacker. And the realization that a target might also be able to detect and characterize even a failed attack would be an additional deterrent. There would be no way for the attacking country to get away with attempted mayhem.

These engineering angles to China's ground-launched kinetic kill system suggest to me that the hardware's intended target isn't up in space at all.

It's media hysteria?

Posted by Orrin Judd at January 20, 2007 10:18 AM

Is it? I´m not so sure. This seems very persuasive:


Posted by: w at January 20, 2007 6:40 PM

The Chinese weapons system has so far demonstrated only that it can pose a threat to low-orbiting objects, of which the most important are reconnaissance satellites.

Indeed. Pretty much all of our imagery satellites orbit in LEO.

No important targets at that altitude, my nether regions.

Posted by: Molon Labe at January 20, 2007 8:31 PM

Persuasive only if you find jargon, opinion, and conjecture wrapped in incoherent blathering a valid substute for facts, reason, and citeable sources. At least Oberg has a trackrecord I can rely on.

Posted by: Raoul Ortega at January 20, 2007 10:45 PM

The Chinese have been quietly building their military to take on the US, trying to stay under the radar so to speak. Somebody in the PRC miscalculated this one. The response won't as dramatic as Sputnik (which directly propelled the US moon program), but there will be a response.

Posted by: Gideon at January 20, 2007 11:10 PM

All the same folks who think the Soviets had caught up to us or passed us have switched to the Chinese.

Posted by: oj at January 20, 2007 11:55 PM