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Missile Defense

Technology has always found its greatest consumer in a nation's war and defense efforts. Since the last attempts at a "Star Wars" defense system, has technology changed considerably enough to make the latest Missile Defense initiatives more successful? Can such an application of science be successful? Is a militarized space inevitable, necessary or impossible?

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gisterme - 09:05pm Dec 21, 2002 EST (# 6903 of 6914)

commondata 12/21/02 7:46pm

"...What in the laws of physics prevents a missile that is designed to hit another missile from also being able to hit helicopters and fixed wing aircraft?..."

There are several problems, commondata.

Velocities are a principal problem...it boils down to accumulated kinetic energy. Ordinary missiles that are designed to destroy such slow moving things as aircraft and helecopters do so while achieving relatively low velocities themselves. I can't quote exact velocities off the top of my head but I would estimate that the velocity range for AA missiles is probably around mach 4 or less. The problem that occurs if the missile is too fast is that it cannot maneuver well enough to hit a maneuvering target. If a target makes a sharp maneuver at just the right moment, the missile can't turn with it. That's how a lot of SAMs got dodged by US aircraft in Viet Nam.

Here's a website that talks about the US Nike missile program that was used to defend our airspace from the '50s into the '70s.

http://www.ed-thelen.org/

The declassified information on that site should give you some good general background about how anti-aircraft SAMs work. Air-launched AA missiles (AAMs) follow most of the same principles except they don't need the big booster to get them going...their launching aircraft takes care of that part. Although guidance technology has definately improved since the Nike days, the basic principles and limitations of more modern systems remain the same.

Notice the aerodynamic fins on the Nike missiles. These make use of passing air to allow the missile to turn.

Here's a similar site that discusses the US "Safeguard" ABM system that was briefly operational during the '70s.

http://srmsc.org/mis1000.html

This page specifically discusses the missiles themselves but there's a slide walkthrough (accesable from the home page) of a "simplified engagement" that gives some idea of time scales and distances involved with that system. There are some other interesting facts on the website as well.

That system was designed to destroy incoming re-entry vehicles (RVs) by getting close enough to the targets then detonating a nuclear warhead. The speed of the Spartan interceptor is listed as mach 10...that's about 7,400 mph...way too fast for atmospheric maneuvering.

The present NMD system has no explosive warheads on its interecptors. The NMD interceptor is designed to destroy it's target by direct impact outside the atmosphere. Here's a link that shows what the current NMD interceptor and launch vehicle look like: http://www.fas.org/spp/starwars/program/gbi.htm

If you know anything about aerodynamics you can see that the interceptor itself is not designed for operation in atmosphere. Although I didn't see a specific listing of the intercepteptor's impact velocity I'd have to assume that it is on the same order as the Spartain intercept vehicle from the '70s, mach 10. Notice that there are no aerodynamic fins on the NMD intercept vehicle. This NMD "kill vehicle" is definately not designed re-enter the atmosphere and it has no means of maneuvering in atmosphere. It maneuvers in space by use of vectored thrusters.

The references should help you realize that this NMD is not an offensive system by any stretch of the imagination. Hope that clears some things up for you, commondata. If it does, it will probably clear some things up for others too.

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