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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 - 01:51pm Feb 8, 2002 EST (#11356 of 11364)

We're coming together on some things -- including some things said in MD10952 rshow55 1/22/02 9:15am . But if things go on as they have been lately, I may have to modify some other things I've said -- and issue some apologies. Hope they do go on that way. We're in an area where right answers are in the national interest.

mazza9 - 02:26pm Feb 8, 2002 EST (#11357 of 11364)
Louis Mazza

Gisterme:

We won the "Cold War", not by pre-emption but by pre-eminence. Our economy, ingenuity, honesty, (notwithsatnding some like Enron...I agree lchic!), is the pride of the world as measured by its results.

How do we win in a battle with Saddam? Simple, we out wait him. He's mortal, we're not!

LouMazza

rshow55 - 02:37pm Feb 8, 2002 EST (#11358 of 11364)

We may be able to do better than that. But "better", if it is really better, ought to make sense to the Russians, to the Europeans in general, and to many responsible people in the Islamic world. With some careful diplomacy, and good logic, I think the risks posed by Iraq could be neutralized, in ways massively in the humane interests of the world, inside of 24 months.

rshow55 - 02:41pm Feb 8, 2002 EST (#11359 of 11364)

I think the same could be said of the risks the world faces from N. Korea and Iran.

I'd say we could really win the war with terrorists, as well.

Maybe I'm just a bloomin' optimist.

But we could get a lot done, if we had a package of things together where Putin, the leading europeans, and some other key people enthusiastically and forcefully helped.

I think such a package could be put together if we were willing to deal with problems others have with us.

I think we'd make money, and win friends, by doing this, and believe it is entirely practical, from where we are now. George Bush has all the resources it would take to get this done, it seems to me.

gisterme - 03:06pm Feb 8, 2002 EST (#11360 of 11364)

rshow55 2/7/02 3:41pm

"...If Chaisson's 1 arc second number is the right one to use for the illumination -- there is no reference available, with respect to the missile, better than 1 arc second -- which would spread a line source to a 30" beam in 100 miles -- not nearly good enough. Nor is there light enough on the return, for long enough -- any light from the illumination onto the missile will be attenuated, on the way back, more than ten million fold..."

I haven't read Chaisson's book, Robert; but I think you may be misapplying the 1-arc second resolution figure. Your implication is that an arc second is not good enough resolution to track an ICBM through 100 miles of atmosphere. Could that be so? Let's check. Hmmm...how large an angle is an arc-second?

http://whatis.techtarget.com/definition/0,,sid9_gci524077,00.html

"The second is sometimes specified as a unit of angular measure, especially in astronomy and global positioning. In these contexts, it is also known as an arc second or a second of arc, and is equal to exactly 1/3600 of an angular degree or 1/1,296,000 of a circle. Sixty arc seconds comprise an arc minute; 60 arc minutes comprise an angular degree. One arc second of latitude at the earth's surface corresponds to a north-south distance of only about 31 m."

So an arc second is one thirty-six hundredth of one degree of arc. You knew that didn't, you Robert? Just making sure that everybody else knows what an arc second is too.

So how small of an angle is that really? Let's suppose we have a piece of plywood that's 1 meter square. Presuming that it's flat side is kept facing the observer, how far away would that piece of plywood have to be taken for the visual angle it subtends to equal 1 arc second? Let's see. Using a right trangle forumla, (because you claim to understand that, Robert), with half the diameter of the square equaling the opposite side of the right triangle(O)and the angle being half the total angle (V), the distance to the square would be the length of the adjacent side of the trangle (A). That distance is given by:

A = O / TAN(1/2 V)

So for V = 1 degree, the square would be

A = .5M/TAN(.5 degrees) = 57.3 meters away

for V = .01 degrees

A = .5M/TAN(.005 degress) = 5,730 meters away.

You can see that the relationship of distance to angle subtended is linear.

For one arc second the distance would be 36 times that or 206,280 meters. That's 206.3 kilometers. That's about 128 miles. That's roughly the distance from Los Angeles to San Diego. For a telescope with an order of magnitude better resolution, 0.1 arc seconds, as your reference indicates the HST has, the 1 M square would just be visible at about 1,280 miles. That's about the distance from Los Angeles to Seattle.

So given a flat earth, a 1-meter square piece of plywood in Seattle, viewed flat-on from Los Angeles would subtend a visual angle of 0.1 arc second. That's a really tiny angle...About 0.48 microradians.

So what can cameras on the HST really resolve?

http://www.geocities.com/CapeCanaveral/Hangar/5421/hubble.html

HST Faint Object Camera...

"...The FOC offers three different focal ratios: f/48, f/96, and f/288 on a standard television picture format. The f/48 image measures 22 X 22 arc-seconds and yields resolution (pixel size) of 0.043 arc-seconds. The f/96 mode provides an image of 11 X 11 arc-seconds on each side and a resolution of 0.022 arc-seconds. The f/288 field of view is 3.6 X 3.6 arc- seconds square, with resolution down to 0.0072 arc-seconds."

The 1M square piece of plywood would subtend an optical angle of 0.0072 arc seconds at a distance of 17,777 miles. 0.0072 arc seconds is an angle of 34.5 nanoradians.

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