US intercepts ballistic missile in Hawaii test

[Kathianne]

This is good news.

http://news.yahoo.com/s/ap/20090318/ap_on_re_us/missile_defense_test


US intercepts ballistic missile in Hawaii test

Tue Mar 17, 10:53 pm ET
HONOLULU – The military says its ground-based mobile missile defense system has successfully shot down a medium-range ballistic missile during a test in Hawaii.

The military says the target missile was shot down Tuesday over the Pacific Ocean.

...
The Missile Defense Agency said in a statement that the Terminal High Altitude Area Defense system had "completed a successful intercept."
The technology is specifically designed to shoot down ballistic missiles during their last stage of flight.

[emmett]

Having things work the way they are suppose to is good.

[DannyR]

I've been kind of surprised that the program has had such a high failure rate over the the years and isn't 99% effective by now.

Intercept technology isn't all that hard, assuming you have a computer onboard fast enough to do the calculations, even in a 3d environment against a fast moving target. Its just simple math.

I'm guessing the hard part of the technology must be the mechanics of the sensing devices used to locate the inbound missile.

I think I'd still like to see some sort of laser technology that can kill the birds as they liftoff rather than the inbound track. Keep all that pesky potential nuclear debris on foreign soil.

[Nukeman]

I've been kind of surprised that the program has had such a high failure rate over the the years and isn't 99% effective by now.

Intercept technology isn't all that hard, assuming you have a computer onboard fast enough to do the calculations, even in a 3d environment against a fast moving target. Its just simple math.

I'm guessing the hard part of the technology must be the mechanics of the sensing devices used to locate the inbound missile.

I think I'd still like to see some sort of laser technology that can kill the birds as they liftoff rather than the inbound track. Keep all that pesky potential nuclear debris on foreign soil.OK I am going to put on my conspiracy hat here and say that I think the success rate is MUCH higher than they report. You know all that "disinformation" thingy.... I thin they only report the few errors to give our "enemies" a false since of security, could you even imagine what the world would be like if they thought that the US was COMPLETELY UNTOUCHABLE by ANY type of missle or rocket!!!! We would have every rogue country out there trying to take us down BEFORE we could make it work perfectly all the time.......

[moderate democrat]

another factor that might contribute to the THAAD early failure rates is the inherent need for absolute accuracy. I believe that the missile does not contain any explosive warhead or any sort of fuse and must, therefore, achieve a direct hit. that's tough.

[Little-Acorn]

I've been kind of surprised that the program has had such a high failure rate over the the years

The concept is referred to as "hitting a bullet with a bullet".

Try it sometime.

Only difference is, a bullet from a GOOD rifle is going around 2,300 mph. A ballistic missile in its terminal stage is going around 18,000 mph.

Shooting an explosive warhead at a missile is of only limited use. The missile is going so fast that, even with modern very-high explosives, if the warhead explodes one inch behind it, the explosion will never catch up to the missile - the missile outruns the fragments and blast wave every time.

The incoming missile (actually just a warhead, the rest of the missile has been cut loose long ago) is so fast that the only way you'll ever even get it to notice you, is to hit it head-on with something. But again it is coming so fast, that the only way a guided weapon has any chance, is to make its last course corrections at least a hundred miles before it hits - steering and guidance rockets and control systems cannot operate any faster. That means that the last correction you can give before impact, must put it EXACTLY on course from a hundred miles away. Basically you're aiming a rifle at a target maybe a yard or two across, from a hundred miles away.

And most radar sensors small enough to fit in the nose of a missile, cannot determine the missile's exact course precisely enough, from that far away, to get the knockdown missile close enough every time. Even heat sensors have an inaccuracy factor - there's no such thing as a perfect one. If you set off an explosive warhead that throws out fragments, far AHEAD of the missile, one of the fragments might get lucky. But the fragments spread out, of course, and the sky is a roomy place.

The fact that they can EVER hit an oncoming missile with the first shot, is nothing short of astounding. I'm not at all surprised at the initial high failure rates. Rather, I'm astonished at the recent successes.

[DannyR]

OK I am going to put on my conspiracy hat here and say that I think the success rate is MUCH higher than they report. You know all that "disinformation" thingy.... You are probably right. Better to keep nations like N. Korea working on just extending missile technology rather than developing advanced stealth systems, MIRVs and other counter measures

[DannyR]

The concept is referred to as "hitting a bullet with a bullet". Try it sometime. Only difference is, a bullet from a GOOD rifle is going around 2,300 mph. A ballistic missile in its terminal stage is going around 18,000 mph.

Those sound like fast speeds, but they aren't. Its very difficult for a person to do of course... our brains don't work that fast. The speeds however are very slow compared to modern computer computational time. Know an incoming trajectory, its child's play to compute an intercept course. Its basic physics and very simple math. I've programmed similar such things for my astronomy classes and the speeds are far far greater.


And most radar sensors small enough to fit in the nose of a missile, cannot determine the missile's exact course precisely enough, from that far away, to get the knockdown missile close enough every time.As I said, I thought this was the hard part and limiting factor. Obviously a simple math formula grows much more complex if you can't give a solid position on the target.

[theHawk]

Not to mention wind and possible rain would really screw things up.

[DannyR]

Not to mention wind and possible rain would really screw things up.I wouldn't think wind would be much of a factor. We're only talking a couple hundred miles an hour at upper levels of the atmosphere. That would push the incoming warhead slightly, but not much compared to its own speed.

Rain and clouds though I bet are a big factor. Water vapor in the air would certainly screw up laser sighting from the ground. I've no idea how it would impact radar though. Rain is obviously visible on radar, but I've also been told it depends on the frequencies used. I had a discussion with a cop about how rain interferes with police radar guns and he said it doesn't. He may have just been screwing with me though. ;)

Oh, did the math. A missile travelling at 18,000 mph could have its course calculated 8-10 times over for each foot it travels by an over the counter floating point chip (some ATI Radeon GPU's can do 2.4 teraflops). I certainly hope the military is using something as powerful as what someone could buy at the local Best Buy.