Built on Facts

You’re standing around minding your own business when suddenly a mile or two away, a rocket launches into the air. It curves upward in a lazy arc and begins its descent toward you. This rocket has several pounds of high explosive in its tip and so you’d prefer to find a way to improve your outlook. The old method was to get lucky and hope you didn’t get hit. Most people in target zones don’t generally prefer this method. The new way is to install radar to give you a couple dozen seconds warning to seek cover before the rocket reaches your position. It’s a definite improvement, but it’s not going to do much to protect anything that can’t move out of the way.

Close-in weapons systems are a possibility. Shoot enough bullets at the incoming missile and you’re bound to hit the thing eventually. The problems with this idea are that it’s very difficult to hit a missile with a bullet, the thousands of bullets that don’t hit are a great danger to the surrounding area, and the systems are expensive, bulky, need constant resupply.

A laser might be an improvement. Targeting is easy since the beam travels in an extremely precise straight line. Once installed, there’s no supplies required except electricity. There’s almost no possibility for collateral damage since a miss with a laser beam will just continue up into the air. It would be an ideal system if only a laser could destroy an incoming missile. That’s the current sticking point. Practical lasers just don’t have the power necessary to heat a missile to the point of destruction in the required very short timeframe.

There is a somewhat impractical laser that can do it. Boeing has developed an airborne laser that is powerful enough, but it’s huge. It requires almost the entire volume of a 747 and is tremendously expensive. Worse, it’s chemically pumped. Instead of electricity driving the lasing process, it uses a chemical reaction. The chemicals involved are toxic, bulky, and expensive. The entire system can only make a few full-power shots before running out of chemical fuel. These are acceptable problems for defending a large area against a small number of ballistic missile launches, but generally not for defending small areas against numerous cheap tactical missiles. It has been done with ground-based systems, but it’s not ideal.

This is the current state of the art, but progress keeps moving. The lowly laser pointer produces laser light in a solid-state medium. This laser light is generally at a quite low power, but solid-state lasers can in fact generate quite high power. They do so without the fuel or cost problems of chemical lasers, just requiring electricity. Beam intensity is a bit of an issue, with the most powerful solid-state lasers being on the order of 10kW of power. A practical system needs to increase that by another 1 or 2 orders of magnitude. Heat dissipation becomes a problem as well. Raytheon is making progress, and Northrop is pushing the 100kW solid-state mark as we speak.

It will probably be a few years yet before these are ready for deployment. But when that day comes, both soldiers and civilians in areas of rocket attack will have one less danger to worry about.

My own primary research interest is laser physics, so I find this practical application doubly interesting.  Now the lasers in my group’s lab have a vastly lower average power and one of our main goals is to get the pulses as short as possible - attoseconds, ideally.  They will not do anyone’s military much good as far as I can tell, but of course that doesn’t mean the more mundane military lasers are any less remarkable.