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http://defensetech.org/2007/01/22/china-sat-killer-not-yet-weapons-grade/#ixzz19SzKYlYN
Last week, I described China's satellite strike as "next-gen," and America's ability to fend off such an attack however somewhere around zero. After all, there's never been a direct ground-to-space satellite smack; and the Air Force itself says such defenses are improbable, at best.
veteran space analyst Jim Oberg says the anti-satellite test was a little easier than it looked. And there may be some defenses, after all. Because there's a big difference between a "satellite-killing demonstration and the needs of a real weapon one that would be a genuine threat to other countries' satellites," he notes.
Now it'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 forintercepting a target in an arbitrary orbit is a much more difficult proposition"¦
The missile's kill mechanism is that of a bullet: It crashes head-on into a target moving at 28 000 km/hr, adding its own speed to the total impact velocity"¦
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 [GPS] navigation network is 20 000 km up"¦ [T]he orbital velocities [there] 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 orbitas it would have to do to track objects geosynchronouslythe demands on a ground-based radar would be simply impossible"¦
Nor are space targets helpless victims to such kinetic kill attacks, especially at higher altitudes"¦ [A] target satellite can take steps to interfere with the attacker obtaining a workable targeting solution, and the farther from Earth the attack occurs, the more the odds favor the target.
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.
Read more: http://defensetech.org/2007/01/22/china-sat-killer-not-yet-weapons-grade/#ixzz19WsOQ2wV
Defense.org
Last week, I described China's satellite strike as "next-gen," and America's ability to fend off such an attack however somewhere around zero. After all, there's never been a direct ground-to-space satellite smack; and the Air Force itself says such defenses are improbable, at best.
veteran space analyst Jim Oberg says the anti-satellite test was a little easier than it looked. And there may be some defenses, after all. Because there's a big difference between a "satellite-killing demonstration and the needs of a real weapon one that would be a genuine threat to other countries' satellites," he notes.
Now it'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 forintercepting a target in an arbitrary orbit is a much more difficult proposition"¦
The missile's kill mechanism is that of a bullet: It crashes head-on into a target moving at 28 000 km/hr, adding its own speed to the total impact velocity"¦
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 [GPS] navigation network is 20 000 km up"¦ [T]he orbital velocities [there] 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 orbitas it would have to do to track objects geosynchronouslythe demands on a ground-based radar would be simply impossible"¦
Nor are space targets helpless victims to such kinetic kill attacks, especially at higher altitudes"¦ [A] target satellite can take steps to interfere with the attacker obtaining a workable targeting solution, and the farther from Earth the attack occurs, the more the odds favor the target.
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.
Read more: http://defensetech.org/2007/01/22/china-sat-killer-not-yet-weapons-grade/#ixzz19WsOQ2wV
Defense.org
