High Energy Laser:
High energy lasers destroy missiles by focusing an extremely intense beam of light on the incoming threat, overwhelming it with heat so intense that the missile is destroyed in flight.
Performance: Kill probability - By sending the beam to the target continuously while tracking it, this technology provides for high kill probabilities. High energy laser weapon testing has demonstrated superb performance against katyushas and related threats, with 100% successful intercepts of dozens of rockets.
Cost: All the high technology hardware is built into the laser itself – only the beam is sent to the target. This means the initial procurement cost for the laser (the beam "launcher") is fairly high, but the cost per kill is quite low, limited to the cost of operating the laser. With current technology, chemical lasers operate by burning rocket fuel, at a cost of around one thousand dollars per shot. New technology may someday replace the chemical laser with an electric laser, with cost per kill dropping still further.
Anti-missile Missile (interceptor):
Anti-missile systems destroy threats by monitoring the incoming threat’s trajectory, then launching a defending missile to intercept it. Advanced, accurate radars are used to determine the threat’s trajectory and to launch the anti-missile on the appropriate path for interception. When the interceptor gets close to its target, onboard sensors take over the guidance, fine-tuning the defending missile’s trajectory so that it will precisely meet the threat.
When the defending missile reaches the incoming missile, there are two different methods to destroy the threat:
Proximity Fuzed Warhead – Interceptors using proximity fuzed warheads need not physically impact the threat to destroy it. Once they come close enough to the threat, an on-board warhead is detonated and the resultant explosion destroys the threat.
Hit-to-Kill Technology – Hit-to-kill interceptors do not carry a warhead, but rather are designed with the accuracy to physically impact the threat. At typical collision velocities (many times the speed of sound), the threat missile is completely destroyed.
Performance: Kill probability with modern missile interceptors is excellent, and can be improved even more by providing the missile defense commander with enough interceptors to allow use of more than one interceptor per target. Alternatively, for long range threat interceptions, the intercept can generally be planned to allow for a “second shot” if the “first shot” was unsuccessful. Several different missile interceptors have now been tested successfully against medium and long range missiles, demonstrating good kill probabilities against these threat classes.
Cost: Since most of the technology is built into the missiles, the cost of the launchers is low, but the cost of the missiles -- cost per kill -- is fairly high. Cost of an intercept with a defending missile depends on the range required, and the size and complexity of the missile. Typical costs can range from several tens of thousands of dollars for a very short range interceptor, to a few million dollars for a long range, multi-stage interceptor.