Missile defense system

1. A method for defending against missiles that have explosive substances with piezoelectric detonators, said method comprising:

using ultrasonic radiation to excite a detonator of the missile, causing it to oscillate and thus be triggered in flight.

2. The method according to claim 1 , wherein said ultrasonic radiation has a frequency that is one of a natural resonant frequency of the piezoelectric detonator and a harmonic or subharmonic of said resonant frequency.

3. The method according to claim 1 , further comprising varying the frequency of the ultrasonic radiation to compensate for tolerances in the known resonant frequency of the detonator and uncertainties with regard to an exact value of the resonant frequency of the detonator.

4. The method according to claim 1 , wherein the frequency of the ultrasonic radiation is chosen taking account of a Doppler frequency based on one of speed of the missile and speed of the platform transmitting the ultrasonic radiation.

5. The method according to claim 4 , wherein the frequency of the ultrasonic radiation is varied to compensate for uncertainties with regard to an exact value of the Doppler frequency.

6. The method according to claim 1 , wherein emission of the ultrasonic radiation is directed.

7. The method according to claim 1 , wherein the ultrasonic radiation is emitted in the form of a high-energy beam with a small angle of aperture.

8. The method according to claim 7 , wherein the ultrasonic radiation is aligned electronically, using phased-array technology.

9. The method according to claim 1 , wherein emission of the ultrasonic radiation is undirected.

10. A system for defense against a missile having an explosive substance and a piezoelectric detonator, said system comprising:

a missile warning sensor for detecting launch of a missile;

a tracking sensor for tracking the missile;

a device for generating ultrasonic radiation suitable for exciting said detonator, causing it to oscillate, and thus to be triggered in flight; and

a positioning device for aligning the ultrasonic radiation on the incoming missile.

11. A method for defending against an incoming missile that includes an explosive material and a piezoelectric detonator, said method comprising:

detecting said incoming missile;

generating an ultrasonic radiation field; and

directing said ultrasonic radiation field to impinge on said missile;

wherein said ultrasonic radiation field has a frequency that is selected from the group consisting of a natural resonant frequency of the piezoelectric detonator, a harmonic of said resonant frequency and a subharmonic of said resonant frequency.

12. The method according to claim 11 , wherein the frequency of the ultrasonic radiation is chosen taking account of a Doppler frequency based on one of speed of the missile and speed of the platform transmitting the ultrasonic radiation.

13. The method according to claim 12 , wherein the frequency of the ultrasonic radiation is varied to compensate for uncertainties with regard to an exact value of the Doppler frequency.