New York Times on the Web Forums Science

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?

Read Debates, a new Web-only feature culled from Readers' Opinions, published every Thursday.

rshow55 - 10:26pm Feb 3, 2002 EST (#11223 of 11259)

To say "I'm doing my best" - - and mean it -- there has to be some kind of scorekeeping.

Great SuperBowl. My team won, this time. Back in the morning.

lchic - 03:34am Feb 4, 2002 EST (#11224 of 11259)

Patriots win out!

US getting a bad world press re torturing those folks in Cuba. The Aussie guy there failed his entry - couldn't make it as a 'Digger' - illiterate. Makes one wonder what they're extracting - and what he's signing!

lchic - 04:50am Feb 4, 2002 EST (#11225 of 11259)

the transactions were merely an illusion

rshow55 - 08:00am Feb 4, 2002 EST (#11226 of 11259)

The reference Mazza cited above mazza9 2/3/02 5:01pm is much appreciated, and refers to an impressive web site for the Center for Adaptive Optics http://cfao.ucolick.org/ao/index.shtml

This schematic diagram of the process involved in adaptive optics is very good, and I hope people look at it carefully. I expect to be referring to it again. http://cfao.ucolick.org/images/aos_small.gif

Below the diagram, from the same site, is this passage:

"The most basic systems use a point source of light as a reference beacon, whose light is used to probe the shape of the wavefronts. This may be a bright star, or in the case of vision research a laser spot focused on the retina. Light from this reference source is analysed by a wavefront sensor, and then commands are sent to actuators (pistons) which change the surface of a deformable mirror to provide the necessary compensations. For the system to work well, it must respond to wavefront changes while they are still small; for the earth's atmosphere, this means updating the mirror's shape several hundred times a second! (to image a STAR - a point source of exactly predictable position.)

Now, with respect to the ABL system, or any other laser weapon system designed for MD, the target isn't a star, but a moving missile or warhead (or one of many decoys).

MD11214 rshow55 2/3/02 4:02pm asks some questions, with respect to AO for missile defense:

"...-- what does the adaptive optics adapt to -- to compensate for atmospheric dispersion, and focus on a moving target (which must be tracked) in the time allotted? How well does the system "see" the target, in the first place, in order to adapt its optics to it? And how many cycles for "adaptive control" -- how many "adaptive controls" -- and how are the adaptations done in a sequence (they aren't done all at once. Somehow, these adaptations require feedback loops and the feedback has to be accurate enough to do the adapting.

"The question is "adaptive of what, with respect to what?"

There is no reference source to start from, with respect to the target.

And very little time.

Time is worth considering in another way -- for convergence to work at all, even with unlimited time, a reference source "seen" -- and feedback loops "good" to a resolution better than 1 cm in 100 miles is going to be required -- about .062 microradians -- about ten times better than the specification for space telescope .

Think of time, as a human animal can experience it. If you look at the stars - one gets a sense that they are stationary - because they are moving so slowly. Well, .062 microradians is the angle the stars sweep in the sky in .85 milliseconds.

In the Center for Adaptive Optics site, the section " What Are the Limitations to AO? " is worth reading.

rshow55 - 08:04am Feb 4, 2002 EST (#11227 of 11259)

Some of the clear language applied to Enron in Kurt Eichenwald's Talk of Crime Grows Louder, Spurred by Report . . . . seems to apply here.

Perhaps that's unfair. Perhaps we're looking at an episode, among so many, where group self deception goes very far -- and goes on a long time, without control. But analogies between the Enron case, and MD, do seem striking - - not proven, but worth careful consideration.

"To prove any case against Enron, prosecutors would have to establish that potential defendants intended to commit a crime. Under the law, a person can participate in activities that result in false information being given to investors without committing a crime, so long as he believed — even falsely — that the activities were appropriate.

Would something similar apply to 11199 gisterme 2/3/02 12:36am ? My initial response was indignant. Perhaps I was hasty about the indignation - but it does seem clear that the technical performance being claimed as plausible is not a reasonable bet -- not the sort of thing professionals should claim they can achieve.

Professionals, with pride about themselves, or care for their country, should want to do things that can work - - not participate in fraudulent disasters -- or muddles so great as to be hard to distinguish from fraudulent disasters.

If we want threats from WMD much reduced, that's achievable. Pretty directly, from where we are.

But not this way.

(32 following messages)

New York Times on the Web Forums Science Missile Defense