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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?

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

rshow55 - 05:37pm Feb 4, 2002 EST (#11239 of 11259)

MD11238 mazza9 2/4/02 4:55pm

So adaptive optics has been under development since 1953, it works as well as it does in astronomy, and computers are much faster than they used to be.

Angular resolution on radar is lousy, as you say, but radar can measure distance very well, too -- by measuring time.

Radar distance measurements are not as good as light wave (laser) distance measurements, but both hinge on time resolution of the systems involved.

Lasers bounced off the moon can measure the distance to the moon to inches (and are better than radar distance measurements, because of a cleaner reflector signal, but not by so very much.) Radar signitures can do time resolutions that give information about "cm scale" shape issues, also.

The lasers, and optics, have nothing remotely resembling the angular resolution that would be needed "to count the rivet holes on a missile at 100 miles." Not by many orders of magnitude.

(Back later -- we' ve dealt with these issues before.)

gisterme - 06:12pm Feb 4, 2002 EST (#11240 of 11259)

mazza9 2/4/02 4:55pm

"...This return signal would be sensed and used to measure the turbulence between the missile body and the ABL station. The feedback loop would send the trubulence correction signals to the deformable mirror, continuously, and when the "SHOT" is fired ...ZAP YOUR DEAD" "

The other thing that would be derived from that reference laser would be exact range to the target so that the MEMS mirror could focus the reflected, corrected beam to converge at that distance, thereby concentrating the transmitted energy into a small point on the target ...just like frying ants.

Didn't you put up an earlier post, Lou, that talked about the multiple-laser system associated with aiming the ABL? Still got that link?

mazza9 - 06:54pm Feb 4, 2002 EST (#11241 of 11259)
Louis Mazza

Gisterme:

The ABL website can be reached:

HERE

Peruse this site and you can glean as much unclassified material as the law allows.

You know I had a Top Secret access with SIOP access as well. I can appreciate RShow55's naivite!

LouMazza

rshow55 - 07:47pm Feb 4, 2002 EST (#11242 of 11259)

You put numbers in the fantasy -- and ABL is just that -- a fantasy. The "reference lasar" has to refer to the target. How does that "reference lasar" focus on the target with enough resolution to aim the lasar -- again, what does the adaptive optics adapt to?

For the astronomy case, you've got an essentially perfect reference -- a star as a point source -- and AO doesn't permit exact focusing to the point -- but approximates it . That is, the adaptation is less precise than the reference it refers to.

In the ABL case -- what is the reference with respect to the target?

The reference that the adaptive optics can do no better than approximate.

Where does the "precision" that the adaptive optics refers to come from ?

There's a quote gisterme cited from Mazza

" This return signal would be sensed and used to measure the turbulence between the missile body and the ABL station. The feedback loop would send the trubulence correction signals to the deformable mirror"

How does this happen? This "feedback loop" is exactly what doesn't exist.

There IS no feedback loop between missile body and ABL -- at least, none worthy of the name, with even remotely enough angular resolution to be useful -- for enough time.

Your dialog indicates that you think "pulling yourself up by your own bootstraps" works - - -

keep talking . . .

rshow55 - 08:35pm Feb 4, 2002 EST (#11243 of 11259)

Claims of enormously tight angular resolution for lasers, keyed to a measurement of earth-moon distances, were made in MD6424 gisterme 7/2/01 5:03pm and are being repeated now. In MD6424 they referred to

. Measuring the Moon's Distance Apollo Laser Ranging Experiments Yield Results (from LPI Bulletin, No. 72, August, 1994) http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html

a fine experiment. Because gisterme mistook distance resolution by means of time resolution for distance resolution by means of angular resolution, gisterme inferred a resolution of 1.58e-9 radians.

In MD6427-6428 I referred back to Measuring the Moon's Distance Apollo Laser Ranging Experiments Yield Results (from LPI Bulletin, No. 72, August, 1994) and found this:

"The reflectors are too small to be seen from Earth, so even when the beam is precisely aligned in the telescope, actually hitting a lunar retroreflector array is technically challenging. At the Moon's surface the beam is roughly four miles wide. Scientists liken the task of aiming the beam to using a rifle to hit a moving dime two miles away.

That correspond to a spreading angle of about 8x 10e-6 radians. -- an angle about 5000 times greater than gisterme had inferred.

The idea that lasers, of themselves, yeild "magically tight" optical resolution is simply wrong.

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