On Mon, 23 Jul 2001, Trei, Peter wrote:

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

You're orders of magnitude away from such fluxes. You're trying to hit a moving, rapidly accelerating (possibly flying random evasion maneuvres) high-albedo vehicle -- through the Mach cone, through the 100 km of atmosphere filled with clouds, haze, random fluctuations, etc. Once it's past boost phase, it's essentially invulnerable. Chemical lasers have a limited numbers of shots, every energy leaving the vehicle must pass through it's optics aperture (which must be damn transparent). The vehicle is very complicated and delicate, and expensive. Given that you have to make many kills during few 100 s window, it doesn't appear cost-effective. If it's in LEO, I just launch a bucket of tungsten or depleted uranium birdshot in countersense orbit. Given a few iterations, I can keep surprising amounts of orbital space clean of any operable machinery.

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

If you ablate a bit of hull sufficient to change course, you've killed the vehicle, whether solid boosters, or cryogenic fuel tanks.

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.

We're not talking about a fuel pellet in the focus of a NOVA laser.