Independent assessment of Airborne Laser (Score 1)

The American Physical Society produced a report on the feasibility of various boost-phase ballistic missile interception capabilities, back in 2003. There's a brief summary here [www.physicstoday.org], and the full report is available here [www.aps.org]. From the section of the summary talking about airborne laser (ABL) defenses:

In assessing the usefulness of the ABL, the study group adopted its publicly reported design goals: 3 MW of power focused into a 1.2-m-diameter beam (close to the diffraction limit) that could illuminate the target missile for up to 20 s. We also considered the utility of systems with greater and lesser capabilities. We found that if the ABL achieves its design goals, it would have a range of about 600 km against liquid-propellant ICBMs. That would be useful against liquid-propellant ICBMs launched from North Korea, but not from Iran. Against solid-propellant ICBMs, its range would be only about 300 km, too short to be useful in any of the scenarios we examined. The ABL's range is relatively insensitive to its power.

Note that they assumed that all the publically stated goals could be reached -- i.e., they ignored any possible engineering difficulties. Also note that the laser needs to stay focused on the target for several seconds, not just a few milliseconds as some posters have claimed: given the proposed beam power, it takes that long to heat up the . Solid-propellant rockets are harder to destroy because they're structurally much stronger (most of a liquid-propellant rocket is a thin-skinned metal fuel tank).