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Kinetic Energy Hit-To-Kill Warhead

Kinetic kill vehicles (i.e., "smart rocks") differ from conventional missiles in that KKVs are not equipped with a warhead. Instead, the destructive capability of the vehicle is provided by the delivery to a target of a considerable load of kinetic energy. Obviously, effective operation for a given mission would require a system capable of providing accurate guidance, measured with respect to a `miss distance`, on the order of .+-.1/2 meter.

Systems that rely on collision with the incoming weapon are called "hit to kill". These systems, that use the motion and mass of a kill vehicle to strike an incoming weapon, are currently under development for upper tier (high atmosphere and space based) missile defense systems. Examples of high tier systems are the US Navy Theater Wide Missile Defense System, Theater High Altitude Area Defense (THAAD) system and the TRW and Raytheon ballistic missile defense systems.

The hit-to-kill or kinetic energy technology approach is based on the fact that when one object strikes another object at high speeds, a tremendous amount of destructive energy is released. The impact of an interceptor missile with an incoming tactical ballistic missile, aircraft, or cruise missile, can result in the total disintegration of both vehicles. Such impact can literally vaporize even metals. In contrast, blast-fragmentation warheads may only redirect or break up the target vehicle. However, even with a large hit-to-kill interceptor, the effective impact window is relatively small.

Hitting a target with a projectile is an effective, established technique of destroying the target through the transfer of KE to the internal modes or structure of the target. Usually, one considers a fast projectile hitting a slower target. For ballistic missile defense (BMD), the opposite is generally the case. Missiles and RVs travel at velocities that enable them to be killed effectively by placing something heavy in their path. The methods described in this section use KE to effect a kill and depend on the collision's KE to be higher than the cohesive energy of the solid target. The problem lies in arranging the collision at a sufficient energy to break the bonds holding the structure together.

The Kill Vehicle may be going more than 7,000 miles per hour when it hits the hostile reentry vehicle. The target reentry vehicle (warhead) is also traveling about 15,000 miles per hour. The collision between the two occurs at a relative (closing) speed in excess of 16,000 miles per hour. There is no explosion. There is a collision in space. It is very powerful and generates debris, gas and dust. The gas and dust may actually look like they burn, but only for an extremely short time. The debris and dust will reenter the atmosphere and burn up like a meteor.

Both blast fragmentation and hit-to-kill systems for use in upper and lower tier defensive applications use an (interceptor) missile to destroy an incoming (threat) missile. This requires a highly sophisticated and accurate control and guidance system. Such a control system must be capable of tracking the three-dimensional speed and direction of both the incoming threat and outbound interceptor simultaneously. This allows computers to coordinate the proper flight path and speed, in real time, to ensure that the interceptor intersects the threat with full contact to destroy the threat. Any minute deviation in the course of the interceptor can cause the interceptor to fly right past its intended target.

A kinetic kill vehicle is a lightweight vehicle weighing 40 to 300 pounds. These devices are designed for exo-atmospheric operation and have onboard propulsion and guidance systems. The propulsion system accelerates the vehicle to velocities in the range of 2 to 20 kilometers per second. Hence, kinetic kill vehicles differ from conventional missiles in that KKVs are not equipped with a warhead. Instead, the destructive capability of the vehicle is provided by the delivery to a target of a considerable load of kinetic energy. Obviously, effective operation for a given mission would require a system capable of providing accurate guidance, measured with respect to a `miss distance`, on the order of .+-.1/2 meter.

The guidance technology heretofore considered for kinetic kill vehicles involves the use of an infrared seeker with a ring laser gyroscope type inertial measurement unit. This approach envisions the use of a conventional proportional navigation scheme. While this approach appears feasible for large KKVs, it is believed to have certain limitations with respect thereto. First is the question of cost. Ring laser gyros are expensive and delicate devices. The use of ring laser gyros in inertial measurements units in KKVs (i.e., "smart rocks") would substantially drive up the cost of implementing the KKV answer to the satellite threat.

Further, and perhaps more significantly, there is an ongoing effort to demonstrate the feasibility of a further reduction in the size and weight of KKVs by at least one order of magnitude. These devices are envisioned as being on the order of 4-10 pounds in weight. A significant reduction in the weight of each KKV would significantly reduce the cost of placing these devices in orbit. To achieve mission objectives, that is, to provide guidance for the KKV to the above-noted degree of accuracy, with a ring laser gyro, would be somewhat problematic. The current state of the art in ring laser gyro fabrication is such that it does not appear to be possible presently to fabricate IMUs small enough to permit the desired reduction in size and weight.




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