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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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mazza9 - 03:10pm Feb 6, 2002 EST (#11308 of 11317)
Louis Mazza

RShow55:

Further elaboration. In the Terminator movie the Terminator aims a gun at his victim. The gun is equipped with a laser aiming beam. Implicit in this system is the fact that where the beam hits the target the bullet will follow, (ignoring the ballistics solutions which would include windage and gravity).

The reference beam is similar in the ABL, except the laser "bullet" will travel at the speed of light and be immune to the effects of gravity, (since the earth doesn't have the massive gravity well of a black hole of a galaxy, I'm sure you agree that gravity would not effect the beam in any discernible way)

LouMazza

rshow55 - 03:18pm Feb 6, 2002 EST (#11309 of 11317)

Mazza: The adaptive optics adapt to the atmosphere not the missile.

Adapts to the particular structure of eddies, and densities, in the light path between the target and the missile - a structure of eddies and densities that is stable for a short period of time (tens of milliseconds, at most) -- for a moving target and a moving airplane.

Mazza: The reference beam reflects off of the missile and is viewed by the ABL systems.

You have to figure angles, and brightnesses -- to see how little reflects off the missile, and back -- and how very little information that little bit of light carries.

Mazza: Any distortion is caused by the atmosphere not the target.

But that atmospheric distortion is changing -- and you need feedback to compensate for it -- and the angular resolution isn't there to get a feedback loop - - and even if there were a feedback loop, you'd get adaptive optics no better than the reference signal resolution. For a star, which is a point source, that reference is very good -- but for the missile light path, you'd do no better than 1 arc second -- and that's not nearly good enough.

Mazza: The "gun" mirror is adjusted for the atmospheric distortion so that the laser reaching the missile will arrive without distortion and at maximum power impact to "kill" the missile.

If the feedback were there, that might be thinkable -- but a feedback path with the resolution needed for that doesn't exist.

Is this clearer? I'd have to take some time with numbers -- but the "feedback path" is hopelessly inadequate for a lasar WEAPON for a target very far away from the ABL plane..

rshow55 - 03:24pm Feb 6, 2002 EST (#11310 of 11317)

mazza9 2/6/02 3:10pm

light travels in straight lines, and c is very fast. Those are conveniences. But these facts don't avoid other problems -- and light coherence versus decoherence (the difference between lasar and ordinary light) doesn't either.

The light from a real physical source diverges from its "ideal design" path because of physical imperfections in the source, and distortions in the medium. Yes, in theory, given feedback, and a reference -- AO can get optics, over a path, that approaches (doesn't reach) the optical quality of the reference.

But for the ABL case, with respect to the missile target, there's nothing remotely good enough for a reference - and with available resolutions and brightnesses, for a missile, say, 100 miles away, there IS no feedback path.

rshow55 - 03:28pm Feb 6, 2002 EST (#11311 of 11317)

In words, the ABL sounds fine. The sketches, at a commercial art level, look fine. I can see some aesthetic attractiveness of the thing -- and Boeing has done some beautiful work on some hard technical component problems.

But the key numbers needed for real tactical performance don't work.

You need words, pictures, and math together (usually, the math is simple arithmetic and geometry). Not just words and pictures.

rshow55 - 03:36pm Feb 6, 2002 EST (#11312 of 11317)

Even if you had a feedback path -- a lot of the other numbers, taken together, make tactical viability far-fetched. (VERY far fetched.)

But the feedback path that is an essential part of the logical structure of weapon function doesn't even exist. Not in any quantitatively meaningful sense. And there is no reference, analogous to the star point source, that is remotely good enough.

Are there mathematical tricks with "bootstrap focusing"? For a good feedback path, and enough time, yes -- and I've played some. They are fun -- but they can't work here, because there isn't remotely enough information in the few photons in the "loop" -- really there is no feedback loop --- and there isn't remotely enough time.

rshow55 - 03:40pm Feb 6, 2002 EST (#11313 of 11317)

Suppose, by some magic (I've no idea how you'd do it) you flashed an illumination beam on the missile, which is moving fast, 100 miles away. It would take fancy optics to do that!

How much light would make it back to your sensors? No fancy optics on that return path.

rshow55 - 03:59pm Feb 6, 2002 EST (#11314 of 11317)

Mazza: I think we have a misalignment of our communications path. Maybe some adapting is in order.(?)

Is our communication path clearer? It would be nice to know it was, before going on.

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