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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?

gisterme - 08:01pm Jul 5, 2001 EST (#6650 of 6661)

rshowlater wrote ( rshowalter 7/4/01 9:10am ): "...and gisterme, to her credit, did not contest the point. She said this instead - - - -"

gisterme 6/12/01 1:46pm ..."rshowlater wrote (WRT gisterme): "...She didn't. (excuse me if I have the gender wrong -- I'm only guessing.)..."

"...You do have the gender wrong, Robert. If you want to visualize gisterme, think of Santa Clause without the red suit. No...wait...that didn't come out right. :-) Think of Santa in clothing other than the red suit. :-) " "

Ho HO HO! From the referenced post you know good and well that I am not a female, Robert. I don't particularly care what personal pronown you attach to me but this does reveal that you're either VERY SLOPPY in details or you are MAKING INTENTIONAL MISSTATEMENTS. Which is it, Robert? You do seem to have been dong the "or" option a lot lately...

"... It is useful to understand how such positioning might be possible, it is complicated, but it isn't greek to me. It uses the pythagorian theorem (the square of the hypotenuse of a right triangel is equal to the sum of the squares of the other two side.) and does a lot of arithmetic -- assuming a good right angle..."

Did you just see the Wizard of Oz Robert? Learning from the Scarcrow, are we? The Pythagorean theorum isn't exactly the one you need to use to be extremely accurate (doesn't take into account the fact that a radial line from the center of the earth to the aircraft is not parallel to a radial line from the center of the earth to your radar antenna...that the earth is a sphere) but Pythagorus' theorum is okay for a pretty close approximation assuming the target isn't much farther away than the horizon...so let's approximate.

If you are at a radar antenna and you have a line-of-sight (LOS) reflection from a bogy then that gives the hypotenuse of the right triangle and the actual distance to the target. All you have to calculate for an airborne contact is the altitude (opposite side of the right triangle). Remember that we're assuming the earth is flat. Now, Robert, since you know the hypotenuse and the angle of elevation of the radar beam, how can you NOT have an accurate right angle within the error allowed by our assumption? The right angle is assumed in the calculation. If the target is more than a few miles away, you can improve the approximation by understanding that the measured angle of inclination of the radar beam is with respect to a tanget to the earth's surface at the location of the radar antenna, NOT the target. So knowing the LOS distance to the target and the radius of the earth you can adjust your apparent angle of inclination to take that radius into account. So the adjacent side of our right triangle will pass through the earth. To be really accurate you can use the general trangle formula with one vertex at the center of the earth, one at the radar antenna and the third at the target. Given two sides (one being the radius of the earth, the other the LOS distance to the target) and an angle (radar elevation WRT the center of the earth) you can very accurately solve the aircraft altitude.

"...There are limitations that come from that -- at the level of time and angle mensuration, the level of noise filtration, and the level of brute arithmetic -- that make the guidance of lasar weapons, whether from ground or orbit, far fetched."

There is no brute force arithmetic required, and it's not complicated at all, Robert. It's just simp

rshowalter - 08:02pm Jul 5, 2001 EST (#6651 of 6661)
Robert Showalter showalte@macc.wisc.edu

gisterme , I'm pleased with your posts, and will respond in the morning.

gisterme - 08:10pm Jul 5, 2001 EST (#6652 of 6661)

gisterme 7/5/01 8:01pm continued:

"...There are limitations that come from that -- at the level of time and angle mensuration, the level of noise filtration, and the level of brute arithmetic -- that make the guidance of lasar weapons, whether from ground or orbit, far fetched."

You're the only person who has suggested that lasers would be aimed by radar; however there is no brute force arithmetic required, and it's not complicated at all, Robert. It's just simple trigonometry, not even direct use of Pythagorus' theorum, really (for the right triangle approximation). Just multiply the sine of the elevation angle and the hypotenus (LOS distance) to get the height of the far side of the assumed right-angle. Noise management is always a concern in control systems but we're not trying to measure quarks here. I really DID think you knew more about radar than that, Robert. It would be very useful if your understanding were to improve. I hope it does. It's your conclusions that seem far fetched.

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