Air Force Turns 747 Into Holster for Giant Laser (washingtonpost.com)

[Jim Choate]

On Sun, 22 Jul 2001, Steve Schear wrote:

> I wonder what the destructive mechanism is for this system?

There was an article in IEEE Spectrum last year (I think) on one of the
systems. The main failure mechanism is weakening of the aeroshell and due
to increased loading the missile comes apart. The same sort of thing
happened in Desert Storm with some of the Scuds that used plywood sheeting
instead of aluminum. It's one of the primary factors of their high failure
rate.

> Heat by radiant absorption seems an obvious but impractical method.

It's the one they use primarily.

> 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).

While reflecting the thermal energy is a good idea, doing the same for
radar isn't since it allows more conventional systems to be used to track
the missile, contrary to the goal of delivering large quantities time on
target. Of course reflecting the IR allows one to use a 'dual component'
system whereby another missile homes in on the reflected laser (standard
IR designator sort of stuff).

Another aspect is to beam the exhaust. By creating hydrodynamic shockwaves
in the exhaust cone it should become possible to cause the engine to come
apart due to back-pressure or simply creating ancillary thrust vectors
and causing the guidance system to mis-calculate. Thrust attack like this
must take place very early in the launch or at each stage seperation.
You've probably got no more than 30-60 seconds out of a 30 minute flight
(for a ICBM that isn't sub launched, then you've got single/double stage
and about 15 minutes max).

While the current systems won't do it, it should even be possible with
high power short pulse width systems to heat the air in front of the
rocket to cause turbulence.


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