Missile Defense

Here are gisterme's words, with some emphasis added, and labeled comments, from me.

"Joking aside, your point is right, radars can't begin to approach that kind of angular resolution."

(Comment: can't begin to approach microradian accuracy -- with .1 microradian accuracy insufficient for lasar weapon aiming, along the lines the administration describes for public consumption.)

(Radars's) " best accuracy is for ranging "

(Comment: That's common ground between us, and for very low noise environments, the ranging data is as good as the ability to resolve time, which can be superb...

To make these proposals practical, there have to be a long list of "miracles." And it is getting clearer exactly how miraculous these magical breakthoughs have to be...

The missile defense proposal supported so recently by Congressman Weldon , has been put "on the back burner" in favor of lasar schemes. Here are references to the kinetic kill programs publicised by Weldon:

MD3647 rshowalter 5/10/01 7:59am

MD3650 rshowalter 5/10/01 10:55am MD3651rshowalter 5/10/01 11:58am MD3652 rshowalter 5/10/01 12:06pm

...

Do you really think that collinearity has improved THAT MUCH?..

Back in ancient days, when the speed of light was the same, and radar wavelengths also the same for many systems, people knew that a differently shaped object would have a different echo pulse -- and though you might not know where the object came from, within a milliradian -- you might know details of geometry of the object itself that would, for the range, correspond to nanoradians or less.

That tells you that radar can have wonderful geometrical and angular resolution in a sense - for a "frame of reference about a particular target" but not even remotely that resolution for telling you where the target is...

"using a line-of-sight speed-of-light weapon like a powerful laser one doesn't need to know the exact range to the target."

That's right.

But you need angular controls to be exact, at every stage, or you need to be able to tolerate the angular spread that builds up.

For the proposed systems I'm aware of, at the level I understand them, assuming basic technical performance similar to open-literature performance, that build up is far too much for practical operation of the weapon...

sets out some technical arguments clearly, but it seems to me, when I check, and you can check too, that it makes the implicit assumption that, for a lasar weapon system, "what you can see you can hit."

MD6410 http://forums.nytimes.com/webin/WebX?14@184.6HDeaurHrNN^5107088@.f0ce57b/6897.... MD6411 rshowalter 7/2/01 4:42pm
MD6413 rshowalter 7/2/01 4:53pm .... MD6414 rshowalter 7/2/01 4:56pm
MD6415 rshowalter 7/2/01 5:05pm ....

" What are the characteristics of the thing you're shooting -- how do properties of the bullet (or lasar beam) change with distance?

Lasar light is better than ordinary light because it is in phase -- and phase interactions don't cause it to spread as it travels -- so lasar beams can be very intense, and they can be as tight as the optics that generated them.

That optics generates a spreading angle -- and the spreading angle will be greater (for a real military lasar - which is a chemical lasar -- much greater) than the angular resolution of Space Telescope...

" How do the controls work?

The controls have to work somehow - and the nuts and bolts detail of how they are physically constructed limit what you can hit, even if you had "perfect" input information -- and even if you had a "perfect" set of properties in the projectile or lasar. And generally, the faster controls have to track something - up to a point -- the more prone they are to oscillate about the target -- until, if you turn the gain up too much, they diverge from the target -- with the kind of servo control instability shown by the con trails of a MD test last year, that was shown atop Dao's essay "Please Don't Disturb Us With Bombs" in a Week in Review piece...

"what do you mean exactly by "see"? --see what? -- see how well?..

IF that were true, the idea might be a beautiful and brilliant one.

But with the real limitations associated with those indented questions -- the idea of missile defense using lasars looks ugly to me...

Really good people are working their hearts out, on jobs that they can't do -- and forced to lie about it (or, at the least, to deflect attention from fundamentals.)

Whether money is being stolen or not -- it sure is being wasted.

For example, the "space based lasar" program -- for missile defense - is VERY far fetched when you look at Space Telescope resolution, and consider the much higher levels of resolution the program has to ask for technically -- for control systems, optics, and radar resolution and a stack up of related reasons ...