Missile Defense

Suppose there is an angular vibration angle of theta --- -- the physical motion of the beam (perpendicular to the beam) at a distance d due to this angular vibration is

sine theta d

or, for theta in radians, for the small angles here,

theta d

Now, for a d of a few hundred or thousand kilometers, plug in your sweep angle due to vibration.

That vibration caused beam sweep will disipate energy that needs to be concentrated if the lasar is to do any damage...

And show him the destruction...

But I'd bet that, right now, DOD couldn't impress a Congressman with a full scale destruction demonstration, using a lasar, at a range between lasar and target of 10 meters or less.

If it can't do a lot of damage from a short distance, it surely can't do so from a much longer distance.

Whatever you do, and whatever you imagine, beam spreading is going to be greater than 0...

And for reasons of physics and geometry, the energy delivered is likely to be much less.

gisterme, you may recall your phrase, slightly modified:

" N times brigher and M times bigger."

Well, for a lasar weapon, the reasons you can't necessarily hit what you can see are basically independent of brightness (how big N is) if the signal is bright enough.

And for burning a hole in something with a lasar, the target you hit has to have a small area, so that the lasar energy can be concentrated enough to do some damage...

"...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...

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...

[quoting gisterme] ..."A large-antenna radar could probably give position data about as accurate as GPS

(Comment: that's a few meters resolution..."

I smell kipper snacks. Once again, NOBODY BUT ROBERT SHOWALTER has ever suggested that a radar could be used to aim a laser weapon.

"...-- for aiming a lasar weapon, with real controls, you'd need resolution to a few millimeters, real time.)..."

Wrong...

Good stuff!

Safire and I don't agree about everything -- but we agree on what's in that essay...

MD6523 lunarchick 7/3/01 7:57pm ... cites http://www.fas.org/spp/starwars/program/us_starwars_laser_02.jpg as "one big blur" -- look at how far out in time things are "scheduled" . Many years out, for really basic tests of hardware that has to be shaken out well, for a long time, before anything tactical on lasar weapons can make sense...

" . ...

MD6433 smartalix 7/2/01 7:37pm

I think MD6432 is also strongly reinforced by gisterme's posting, but that the first line of MD6434 almarst-2001 7/2/01 8:04pm . ...