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While Science Fiction and not directly related, one of the Tom Clancy novels went into the Science of missile intercept pretty extensively(was a very important

While Science Fiction and not directly related, one of the Tom Clancy novels went into the Science of missile intercept pretty extensively(was a very important part of the book. This book brought to my attention the mathematics and for lack of a better term difficulty of having a missile intercept system. Not only the mathematics but the but the raw limitations of physics that must be dealt with. In the case of the book it was ICBM's which travel much faster, 7 km/s (15,700 mph)[1], compared to the 3749.11 mph of the skud missile. For anyone interested the book is Tom Clancy - The Bear and the Dragon. [1] http://en.wikipedia.org/wiki/Missile_defense http://en.wikipedia.org/wiki/Missile_defense

arethuza 13y ago
This clip of a Sprint ABM test gives some idea of how incredibly fast ICBM RVs are - it makes the 0-Mach 10 in 5 seconds Sprint look like it is hardly moving: https://www.youtube.com/watch?v=msXtgTVMcuA https://www.youtube.com/watch?v=msXtgTVMcuA
- hga 13y ago
  As I remember, source would be Jerry Pournelle, I think, from the time ICBM RVs hit enough atmosphere that mass separates warheads from decoys (if your decoy weights as much as a warhead, it's pointless), to the time it hits, is about 10 seconds. Not a lot of time for a discrete point defense (as opposed to e.g. throwing a curtain of stuff up between you and the RVs).
  - fosterku 13y ago
    I think that is why systems try to hit the missile on the way up before RV separation. The navy has Missile Systems, such as the TBMD section of the Aegis weapons system, that uses US/ship based SM-3 missiles to hit a Ballistic missile on it's ascent. However, this means you have to detect the BM early and launch your missiles from somewhere in the ocean so that you could hit the target around it's apex. They do this by sharing radar data between land and ship based radars, getting the SM-3 close to target, and then using a kinetic warhead to make contact with the BM. I would think that the patriot missile system uses a similar theory. It probably use a radar to detect the scud launch and then calculate the correct time to deploy a missile for intercept. The patriot would either be flown close to the scud using telemetry based systems on the patriot, or by using mid course/terminal guidance from the patriot launcher. Terminal guidance would fly the missile in front of the scud and "patriot go boom". If the terminal guidance is slightly off, you don't go boom in front of the scud and the scud hits it target. In some fire control radars, the terminal guidance is constructed of data the radar receives from a missile downlink, where the missile reports it's position to the launcher in order to use a more precise radar on the ground to direct the missiles path towards a target. I think it's more popular to use a combination of missile communications uplink/downlink and combine it with Ground based radar data, to determine where the missile is, where the target is, and where the expected point of missile intercept should be.
  - cameldrv 13y ago
    Sprint was a last ditch system. It was supposed to intercept the warheads that leaked through the Spartan system, and at only about 100k ft. At that point, the Decora would have burned up. Of course both types of interceptor had nuclear warheads. 100 sprints going off over Grand Forks wouldn't be very pretty... The real point was to defend the missile silos though, and they might have worked for that.
    - hga 13y ago
      Enhanced radiation ("neutron bomb!!!") warheads for Sprint, emphasize the neutron flux, lessen the explosive yield. Better way up there than the RV warheads detonating on the surface, although the successor proposed LOADS planed for a 75K foot intercept to among other things decrease EMP effects. And, hey, wouldn't all those bright lights in the sky look pretty ^_^?
checker 13y ago
My favorite project in school was writing a function that would calculate the angle and speed to shoot an interceptor given the location of the battery, the speed of the interceptor, and the location and speed of the incoming missile. If we didn't use the right mathematical methods, the calculation would take too long and the missile would cruise right by the small window.
- TeMPOraL 13y ago
  Math and physics seem to be much more fun when discussed in military context. I suppose it's because, unlike pretty much anything else in life, military problems have at the same time both importance (if you fail, people die / equipment gets destroyed) and a time limit (you need to make your decision fast, otherwise you fail).
VLM 13y ago
"3749.11 mph" Six sig figs... impressive. I was under the impression the scuds were not quite built up to that level of precision. This is to some extent meta-humor as the whole point of the story is the programmers involved needed an engineer helping them who understands sig figs and the effect of built up error tolerances.
- jug6ernaut 13y ago
  The article listed the speed of a scud at "1,676 meters/second", "3749.11 mph" was simply a conversion from that unit to MPH. I can only hope that for the sake of my post that my lack of attention to the increase of perversion of the velocity of the skud missile does not in some way invalidate my claim :P. https://www.google.com/search?q=1%2C676+meters+per+second+to+miles+per+hour https://www.google.com/search?q=1%2C676+meters+per+second+to...
  - bct 13y ago
    > The article listed the speed of a scud at "1,676 meters/second" Which looks suspiciously like a rounded "3750 mph to meters per second" conversion. Indeed, "scud 3750 mph" turns up a lot of hits.
sten 13y ago
I hated that book. But couldn't put it down. Looking back it's amazing what he got right, like the darkstar drone system for example. But even more amazing is how much he got wrong, that western government media of the war would be sufficient to overcome local propaganda and cause an over through of the Chinese government in a matter of days.

arethuza 13y ago

This clip of a Sprint ABM test gives some idea of how incredibly fast ICBM RVs are - it makes the 0-Mach 10 in 5 seconds Sprint look like it is hardly moving: https://www.youtube.com/watch?v=msXtgTVMcuA https://www.youtube.com/watch?v=msXtgTVMcuA

hga 13y ago
As I remember, source would be Jerry Pournelle, I think, from the time ICBM RVs hit enough atmosphere that mass separates warheads from decoys (if your decoy weights as much as a warhead, it's pointless), to the time it hits, is about 10 seconds. Not a lot of time for a discrete point defense (as opposed to e.g. throwing a curtain of stuff up between you and the RVs).
- fosterku 13y ago
  I think that is why systems try to hit the missile on the way up before RV separation. The navy has Missile Systems, such as the TBMD section of the Aegis weapons system, that uses US/ship based SM-3 missiles to hit a Ballistic missile on it's ascent. However, this means you have to detect the BM early and launch your missiles from somewhere in the ocean so that you could hit the target around it's apex. They do this by sharing radar data between land and ship based radars, getting the SM-3 close to target, and then using a kinetic warhead to make contact with the BM. I would think that the patriot missile system uses a similar theory. It probably use a radar to detect the scud launch and then calculate the correct time to deploy a missile for intercept. The patriot would either be flown close to the scud using telemetry based systems on the patriot, or by using mid course/terminal guidance from the patriot launcher. Terminal guidance would fly the missile in front of the scud and "patriot go boom". If the terminal guidance is slightly off, you don't go boom in front of the scud and the scud hits it target. In some fire control radars, the terminal guidance is constructed of data the radar receives from a missile downlink, where the missile reports it's position to the launcher in order to use a more precise radar on the ground to direct the missiles path towards a target. I think it's more popular to use a combination of missile communications uplink/downlink and combine it with Ground based radar data, to determine where the missile is, where the target is, and where the expected point of missile intercept should be.
- cameldrv 13y ago
  Sprint was a last ditch system. It was supposed to intercept the warheads that leaked through the Spartan system, and at only about 100k ft. At that point, the Decora would have burned up. Of course both types of interceptor had nuclear warheads. 100 sprints going off over Grand Forks wouldn't be very pretty... The real point was to defend the missile silos though, and they might have worked for that.
  - hga 13y ago
    Enhanced radiation ("neutron bomb!!!") warheads for Sprint, emphasize the neutron flux, lessen the explosive yield. Better way up there than the RV warheads detonating on the surface, although the successor proposed LOADS planed for a 75K foot intercept to among other things decrease EMP effects. And, hey, wouldn't all those bright lights in the sky look pretty ^_^?

checker 13y ago

My favorite project in school was writing a function that would calculate the angle and speed to shoot an interceptor given the location of the battery, the speed of the interceptor, and the location and speed of the incoming missile. If we didn't use the right mathematical methods, the calculation would take too long and the missile would cruise right by the small window.

TeMPOraL 13y ago
Math and physics seem to be much more fun when discussed in military context. I suppose it's because, unlike pretty much anything else in life, military problems have at the same time both importance (if you fail, people die / equipment gets destroyed) and a time limit (you need to make your decision fast, otherwise you fail).

VLM 13y ago

"3749.11 mph" Six sig figs... impressive. I was under the impression the scuds were not quite built up to that level of precision. This is to some extent meta-humor as the whole point of the story is the programmers involved needed an engineer helping them who understands sig figs and the effect of built up error tolerances.

jug6ernaut 13y ago
The article listed the speed of a scud at "1,676 meters/second", "3749.11 mph" was simply a conversion from that unit to MPH. I can only hope that for the sake of my post that my lack of attention to the increase of perversion of the velocity of the skud missile does not in some way invalidate my claim :P. https://www.google.com/search?q=1%2C676+meters+per+second+to+miles+per+hour https://www.google.com/search?q=1%2C676+meters+per+second+to...
- bct 13y ago
  > The article listed the speed of a scud at "1,676 meters/second" Which looks suspiciously like a rounded "3750 mph to meters per second" conversion. Indeed, "scud 3750 mph" turns up a lot of hits.

sten 13y ago

I hated that book. But couldn't put it down. Looking back it's amazing what he got right, like the darkstar drone system for example. But even more amazing is how much he got wrong, that western government media of the war would be sufficient to overcome local propaganda and cause an over through of the Chinese government in a matter of days.