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Missile Defense

Russian military leaders have expressed concern about US plans for a national missile defense system. Will defense technology be limited by possibilities for a strategic imbalance? Is this just SDI all over again?

rshowalter - 04:35pm Jul 2, 2001 EST (#6410 of 6418)
Robert Showalter showalte@macc.wisc.edu

MD6407 gisterme 7/2/01 3:25pm is a great, constructive posting. The logic in it makes an implicit but basic assumption -- and an easy assumption to make about lasars. But the assumption as to be checked.

The assumption is that

"What you can see you can hit . "

Everybody who has done any shooting with a pisol or a rifle, or looked at radar controlled artillery, knows it isn't true with a rifle or a kinetic projectile - and wouldn't be in a vaccum. Is it true with a lasar ?

Big questions are

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

also

"How do the controls work?

and also,

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

People seem to be implicitly assuming that there are no technical problems, for lasar weapons, connected with these questions.

In the context of missle defense, there are problems, and system limitations, associated with each of the indented sets of questions above.

rshowalter - 04:42pm Jul 2, 2001 EST (#6411 of 6418)
Robert Showalter showalte@macc.wisc.edu

It may be that the idea of missile defense using lasars is a beautiful idea, if there are no problems with these questions.

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.

Let me go through the indented sets of questions, referring to what launch sensors, and Space Telescopes, can see and not see, and how it matters.

lunarchick - 04:46pm Jul 2, 2001 EST (#6412 of 6418)
lunarchick@www.com

Seems as if technical 'experts' are locked out of process.

On reducing bureauocracy .. that's simple .. reduce budgets and tell organisers to introduce effective process.

The trend now is to forget the '3' in services, and fuse them into a service. Lops off two heads of bureauocracy!

rshowalter - 04:53pm Jul 2, 2001 EST (#6413 of 6418)
Robert Showalter showalte@macc.wisc.edu

Indented question set #1:

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

The space telescope has an angular resolution of about 5 x 10e-7 radians (that means that, working hard, it could just resolve points of light that far apart.) Optics uses the notion of a point a lot -- a point has an angular extent of 0 radians -- it has no angular area at all. But it can be resolved. For space telescope, all but the very nearest stars are points for all practical purposes -- with an angular extent far too small to resolve - so that the light from the star blurs out to a blob at the angular resolution of the telescope.

The optics can "see" a blob of light, below its resolution - and spreads that light out with some blurring due to the fact that the optics isn't, and physically can't be, of perfect resolution.

So for some purposes, angular resolution isn't so important -- brightness is -- for seeing.

But not for hitting.

Question: Suppose you had a "perfect" lasar beam, and just now, could think of light moving infinitesly fast -- how much angular resolution would you need to HIT a star with 10e-10 radians angular extent in reality?

You'd need 10e-10 radians resolution on the controls, and a spreading angle of less than 10e-10 radians.

But with just a milliradian resolution on detection optics, you'd "see" a blob corresponding to the star just fine -- if it was bright enough. Well enough to see it, but not nearly well enough to hit it.

So resolution for detection of the existence of an object, within a range of angles, is not the same as resolution of detection sufficient to hit the object, even if everything else was perfect.

rshowalter - 04:56pm Jul 2, 2001 EST (#6414 of 6418)
Robert Showalter showalte@macc.wisc.edu

The arguments for lasars in missile defense implicitly ignore this crucial distinction. There are other difficulties, also important, associated with the other indented questions in MD6410.

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