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The information below provides a basic foundation for understanding the types of missile threats and defenses.  Send us an email with your questions (michael@imda.org.il).  We would be glad to respond and post additional questions and answers on the site.

Missiles and Rockets
1. What is the difference between a missile and a rocket?
2. What is the difference between short-range, medium-range, and long-range missiles or rockets?
3. What is a “ballistic” missile?
4. What is a “cruise” missile?
Missile Defense
1. What is “comprehensive missile defense?”
2. Is “comprehensive missile defense” realistic?
3. Are modern missile defense systems effective?
4. What is a typical measure for cost effectiveness of missile defenses?
5. What technologies can be used to destroy a missile?
Missiles and Rockets
Q: 1. What is the difference between a missile and a rocket?
A: Missiles have on-board guidance systems, providing for course correction in flight to assure impact close to the designated target point. Rockets are unguided after launch. Their impact point is determined – to some extent – by their launch geometry. They are intrinsically far less accurate than missiles, due to the inability to provide perfect launch geometries, as well as changes in trajectory due to flight instabilities and weather effects. (Note: These terms are frequently misused or used interchangeably).
Q: 2. What is the difference between short-range, medium-range, and long-range missiles or rockets?
A: These are not, unfortunately, precise and unambiguous terms. Terminology tends to vary depending on local geopolitics, battle space and the threat environment. In general, however, short range rockets or missiles fly less than 75 km, medium-range from 75 to 500 km, and long-range more than 500 km.
Q: 3. What is a “ballistic” missile?
A: "Ballistic” describes the curved flight path of any object that is not self-propelled. A rock thrown into the air takes a ballistic trajectory after it leaves your hand. When applied to missiles, “ballistic” refers to the trajectory the missile takes after its rocket engines finish “boosting it,” or firing – analogous to a rock, after your hand stops “boosting it” into the air.
Thus, the first stage of a ballistic missile’s trajectory is the “boost” phase, when the missile’s rocket engines accelerate it up into the air. After the rocket engines stop firing its trajectory becomes “unboosted” or ballistic, starting the “mid-flight” phase as its momentum continues to carry it up in a curved trajectory, heading toward the target. The final part of the trajectory is usually referred to as the “terminal” phase, as it falls toward its final ground impact.
Q: 4. What is a “cruise” missile?
A: “Cruise” missiles are basically remotely-controlled or self-controlled airplanes. They are guided by on-board guidance systems or sensors, and may fly close to the ground (as close as 10 meters). There are cruise missiles that can fly thousands of kilometers, capable of rapid, pre-programmed or sensor-driven change in direction. For example, cruise missiles can be programmed to fly through a mountainous region, hugging the ground as they fly through valleys and over passes, changing course as required by the geography.
Missile Defense
Q: 1. What is “comprehensive missile defense?”
A: Comprehensive missile defense refers to a combination of passive defense (shelters), attack operations and deployment of a combination of different missile defense systems with different, complementary capabilities. This is sometimes also called a “system of systems.” This “comprehensive” missile defense system then uses different approaches or weapons to effectively destroy incoming enemy missiles of all types and ranges.
Q: 2. Is “comprehensive missile defense” realistic?
A: Yes. With the aggressive missile defense development efforts that have matured in the last several years, there is now a range of defensive weapon choices and technologies with proven performance in testing, capable of engaging everything from short range to medium and long range threats.
Q: 3. Are modern missile defense systems effective?
A: Yes. Like all other weapon systems, the goal is highly effective performance, not perfection. And with overlapping defense systems, modern missile defenses can provide excellent protection.
Q: 4. What is a typical measure for cost effectiveness of missile defenses?
A: Missile defense cost effectiveness is analogous to a very common calculation in the business world. Cost effectiveness of “risk avoidance” plans for a business are measured by comparing the cost of the plan to the potential cost of failing to implement the plan. Thus, the cost of a missile defense system must be compared to the potential cost to the nation of a missile war taking place without the defense.
Q: 5. What technologies can be used to destroy a missile?

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.




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