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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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rshow55 - 06:12pm Sep 29, 2003 EST (# 14143 of 14145)
Can we do a better job of finding truth? YES. Click "rshow55" for some things Lchic and I have done and worked for on this thread.

jorian319 - 04:17pm Sep 29, 2003 EST (# 14136 http://forums.nytimes.com/webin/WebX?8@13.h1YTbtNkJG4.2637045@.f28e622/15842 asks:

"Well, Robert, if you ever come back, maybe you could respond to my post about Langley and control.

Jorian319 - look at the "dimensionless groups" in fig 3.1 of http://www.mrshowalter.net/Similitude_ForceRatios_sjk.htm - they provide "similarity groups" - Reynolds number and Mach number are two of the most famous and useful - and you can correllate an infinite set of objects - with similar geometry - if they have the same dimensionless numbers - in the ways that matter for the case. For example - a flow visualization for a set geometry and specified dimensionless ratios models, in great detail - an infinite set of different scales (with the same dimensional groups.) Modern aeronautical engineering would be unthinkable without the use of dimensionless groups -and differential equations set out in dimensionless form.

The situation in control theory is analogous - if you know what matters in enough detail to do valid, scalable modelling. That's possible.

You ask about Langley. Langley was "flying blind" in his time - and didn't know enough to do reasonable scaling. In such a case "full scale" is the way to go - because not enough is known for generalization.

If Langley had had the proper modelling - and known what mattered - he could have used scale modelling - with similararity of the relevant dimensionless groups.

In real life engineering - when people know what they are doing - a great many things are not fractal. Modelling can work very well - and with some additional work - a lot better.

In dialog where people take enough care for closure - (that takes loop-proved stability in the dimensions that matter) things aren't necessarily fractal, either. Otherwise, we'd all be dead. We cooperate pretty well within our own groups, after all. That's not an accident. Our explosive instabilities are relatively few - where communication is inadequate - and modelling wrong - as in the case of the US and N.Korea .

We can do better. And ought to. For the problems involved - it takes time and staff - and some willingness to have controlled small fights.

rshow55 - 06:20pm Sep 29, 2003 EST (# 14144 of 14145)
Can we do a better job of finding truth? YES. Click "rshow55" for some things Lchic and I have done and worked for on this thread.

In 14135 http://forums.nytimes.com/webin/WebX?8@13.h1YTbtNkJG4.2637045@.f28e622/15841 there's this - the posting didn't go up right away, and I didn't finish a thought.

I wrote:

For large perturbations of nonlinear systems that are not controlled at a higher level, divergent instability is the rule - multiple quasi-equilibrium points are not surprises, but the overwhelming expectation - and limit cycles are the best, as a practical matter, that anybody can actually hope for - or can actually get.

but I intended to finish the thought with a point that I'm pretty sure is new .

For nonlinear systems that are controlled at a higher level, with good simulation at that higher level - and with adjustments in terms of well chosen "families" of simulation models - divergent instability is much less of a problem - for any range of perturbations - multiple quasi-equilibrium points are much less of a problem, and far better control is possible. Small amplitude oscillations are usually unavoidable - so that one needs "oscillatory solutions" - but those solutions can be stable and safe - with small dissipation.

At gisterme's suggestion, I posted this - and it seems to me that there was a certain amount of interest http://talk.guardian.co.uk/WebX?14@@.ee7a163/352

. It is now technically easy to shoot down every winged aircraft the US or any other nation has, or can expect to build - to detect every submarine - and to sink every surface ship within 500 miles of land - the technology for doing this is basic - and I see neither technical nor tactical countermeasures.

That was an example of a control system with internal simulation. And a simple program for perfecting the simulation - in that case involving small scale adjustement of polynomial models - and a larger scale intercollegiate competition with model airplanes to perfect some nutsy-boltsy details.

IN NEGOTIATION PROBLEMS - THE SAME ISSUES EXIST - AND IT IS IMPORTANT TO HAVE WORKABLE SIMULATIONS OF THE ACTORS WHO WISH TO HAVE A STABLE COOPERATION - WITHIN PREDICTABLE AND STABLE LIMITS.

To get that information - generally - you need little fights - and enough controls that those little fights don't become big fights.

To get the United States government to master this material - rather than get it backwards in a way that will generate explosive instabilities - I feel I need to have face to face contact with people I'm communicating with.

Stability and explosive instability are mirror images - and it is easy to mess up the signs. In fact, with the Bush administration - sign screw-ups seem almost inevitable - without some face to face contact. For some jobs, house arrest doesn't work well enough.

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