The United States Air Force has committed significant resources to developing the Airborne Laser (ABL) for theater missile defense. It plans on using the ABL to attack missiles during the short period the missile is under power
– the so-called boost phase. There are several advantages to attacking missiles during this period. First, ballistic missiles are most vulnerable during the initial seconds of their flight. During this time they are relatively slow, subjected to large dynamic forces, and extremely short missile burn times coupled with the relatively slow speeds of interceptor missiles have, until now, produced safe havens for launch sites far behind enemy lines.
Lasers deliver their blows to the target at the speed of light, effectively removing speed considerations from determining safe havens. Distance, however, still plays a role in protecting the missile from attack. Lasers are limited to lines of sight above clouds and the more turbulent portions of the atmosphere. This requirement has the effect of hiding the missile below the horizon for larger fractions of its powered flight at longer distances from the ABL. Furthermore, the laser beam broadens as it travels away from the ABL, lowering the concentration of energy. This implies that even while the ABL has less time to shoot at the missile it requires more time to accomplish the same damage. Such considerations limit the ABL's areas of operation. Different internal structures in the missile also affect the ABL's range. The author's calculations indicate that the ABL would be effective against missiles launched from North Korea or Iraq. On the other hand, missiles launched from the western border of Iran against Israel would be completely out of the ABL's range if it remained in friendly airspace.
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