RE: Air Force Turns 747 Into Holster for Giant Laser (washingtonp ost.com)
With high-powered lasers, one of the important destructive mechanisms is blast - the outer layer of the illuminated object vaporizes, and flies away from the rest of the target. The reactive force of this gives the target a hell of a kick. Kicking off strict alignment with it's flight path, or putting a big dent (or even better a hole) in the side of a missile under several G's of stress traveling at a high Mach number is not healthy for the missile. Laser's have problems though - as they heat the air the refractive index changes, leading to 'blooming' or beam expansion. At too high a power density they can also ionize the air, which makes it effectively opaque. Dust, haze, and clouds are also problems. Using *very* short pulses eliminates many of these problems. Peter Trei -- From: Steve Schear[SMTP:[EMAIL PROTECTED]] Sent: Monday, July 23, 2001 1:34 AM To: [EMAIL PROTECTED] Subject: Re: Air Force Turns 747 Into Holster for Giant Laser (washingtonpost.com) At 09:14 AM 7/22/2001 -0500, you wrote: Point this baby at the ground... http://washingtonpost.com/wp-dyn/articles/A27248-2001Jul20.html I wonder what the destructive mechanism is for this system? Heat by radiant absorption seems an obvious but impractical method. If it is, then as the article mentions there may be some inexpensive and practical countermeasures to such a system, such as making the exterior of the missile body into a multi-faceted mirror able to reflect both IR and radar energy (although doing the same for the nose cone might prove more difficult due to aerodynamics). steve
RE: Air Force Turns 747 Into Holster for Giant Laser (washingtonp ost.com)
On Mon, 23 Jul 2001, Steve Schear wrote: I have a hard time imagining that a mirrored and faceted vehicle exterior would provide enough absorption to enable this mechanism, otherwise the laser's own mirrors would like destruct from the same exposure. Not necessarily, if the beam is focused on the target but its intensity is lower at the source. If I'm not mistaken, the 747 stuff does precisely this, even incorporating adaptive optics to combat atmospheric distortion. But on the whole you're probably still probably -- this does sound more like starwars than efficient anti-missile technology. But I also think the question Choate posed is a valid one: what happens when the target is *not* a ballistic missile, but people, equipment and vehicles on the ground, normal aircraft, or air-to-air missiles? One would think that the lower velocity differentials and expected distance-to-target make aiming much easier, and that effective counter-measures would be significantly more difficult to erect, considering that such conventional targets have properties very different from those of ballistic missiles (e.g. aircraft raise questions of aerodynamics and payload efficiency, wearable materials with albedos high enough are difficult to come up with, rotation and aerodynamic engineering cannot be used to dissipate the heat generated by a hit, people/cars/tanks/whathaveyou often need to be difficult to spot using aerial and satellite imaging, and so on). Such weapons capability could be *quite* useful, especially if the 747 can be effectively defended against anti-aircraft missiles, and the laser has a range and targeting capability on par with anti-ballistic missile applications. Hits on critical infrastructure, control over a nation's airspace, death-from-above FUD, that sort of thing. Sampo Syreeni, aka decoy, mailto:[EMAIL PROTECTED], gsm: +358-50-5756111 student/math+cs/helsinki university, http://www.iki.fi/~decoy/front
RE: Air Force Turns 747 Into Holster for Giant Laser (washingtonp ost.com)
At 1:43 AM +0300 7/24/01, Sampo Syreeni wrote: But I also think the question Choate posed is a valid one: what happens when the target is *not* a ballistic missile, but people, equipment and vehicles on the ground, normal aircraft, or air-to-air missiles? One would think that the lower velocity differentials and expected distance-to-target make aiming much easier, and that effective counter-measures would be significantly more difficult to erect, considering that such conventional targets have properties very different from those of ballistic missiles (e.g. aircraft raise questions of aerodynamics and payload efficiency, wearable materials with albedos high enough are difficult to come up with, rotation and aerodynamic engineering cannot be used to dissipate the heat generated by a hit, people/cars/tanks/whathaveyou often need to be difficult to spot using aerial and satellite imaging, and so on). Such weapons capability could be *quite* useful, especially if the 747 can be effectively defended against anti-aircraft missiles, and the laser has a range and targeting capability on par with anti-ballistic missile applications. Hits on critical infrastructure, control over a nation's airspace, death-from-above FUD, that sort of thing. IANALS (laser specialist), but I am given to understand that with the high energy demands of these types of lasers, and the problems with getting good energy levels through airborne dust, clouds, etc (and especially in combat areas where dust and other airborne particles are rather common) make lasers less than ideal against ground or low flying targets. Against high flying aircraft, you may be right.
