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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 - 05:05pm Jul 2, 2001 EST (#6415 of 6423)
Robert Showalter showalte@macc.wisc.edu

Indented question #2:

" 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.

The controls that can actually be built in the open literature are not even close (not within an order of magnitude) to the angular and dimensional control you'd need, even with perfect input information and perfectly collinear lasars -- when you look at the combination of dynamic resonse and resolution actually needed.

One could show, at least, that controls described in the open literature fall way short. And also show that, even if controls were the only problem -- the notion of an "easy" control job with lasar weapons isn't true.

rshowalter - 05:15pm Jul 2, 2001 EST (#6416 of 6423)
Robert Showalter showalte@macc.wisc.edu

Indented question #3:

" 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.

So intensity of beam will decrease with distance -- and the decrease is significant.

Think of the geometry according to this example from Chaisson: Space telescope can just tell whether a directly facing car, 2000 miles away, has ONE headlight, or TWO. Barely -- that is, the images are barely distinguishable from the blob a single point of light would generate.

A lasar beam will be greatly diffused and spread, over 2000 miles, even if the lasar has Space Telescope optics. For a chemical lasar, it will be a hard job to get optics anywhere near that good. Partly because there are issues of mixing, and thermal distortion, that build distortion into chemical lasars.

For this reason, also, the assumption that "what you can see you can hit isn't true.

lunarchick - 05:17pm Jul 2, 2001 EST (#6417 of 6423)
lunarchick@www.com

Rail:Aussie:Three different gauges ...

New South Wales adopted the European standard gauge of 1435 mm, Victoria and South Australia built with the broad Irish gauge of 1600 mm, and Tasmania, Queensland, Western Australia and parts of South Australia used the narrow 1067 mm gauge. For many years, the different gauges handicapped the effective operation of interstate rail services.

In 1917, a person wanting to travel from Perth to Brisbane on an east-west crossing of the continent had to change trains six times.

The independent development of the State rail systems led to significant incompatibility problems, not only in relation to gauge but also equipment and operating practices.

This incompatibility of the State rail systems was brought to a head during World War II

rshowalter - 05:26pm Jul 2, 2001 EST (#6418 of 6423)
Robert Showalter showalte@macc.wisc.edu

MD6407 gisterme 7/2/01 3:25pm

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.LOzyaTPPqEw^3329621@.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 .... MD6416 rshowalter 7/2/01 5:15pm

On the basis of simple arguments, that can be much reinforced with more checking, insofar as physics and technology within DOD correspond to open literature -- the functionality claimd for lasar weapons seems to me to be incorrect. I don't think these weapons can be worth building, for the missile defense roles claimed for them.

Now, let me talk about some other issues of discrimination, where it is easy to be lulled into an over-optimistic view of what optical, radar, and lasar based weapons systems can do.

lunarchick - 05:31pm Jul 2, 2001 EST (#6419 of 6423)
lunarchick@www.com

IronHorse Rail: USA use European Standard gauge 1435mm (ready for the bridges over the Pacific & Atlantic!). Compatibility of systems can be useful for rail manufacturers / trade-wise.

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