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Boost Phase Interception of Ballistic Missiles

Moshe Guelman

Policy Paper No. 35, From the books:

Ballistic Missiles –
The Threat and
the Response

Arieh Stav (ed.),
ACPR Publishers and
Yediot Aharonot (Hebrew), 1998
ACPR Publishers and
Brassey's (UK) Ltd. (English),

The Threat of Ballistic Missiles in the
Middle East:
Active Defense and

Arieh Stav (ed.),
Sussex Academic Press and
ACPR Publishers, 2004


In the boost phase the ballistic missile is a large, visible and vulnerable target making deception extremely difficult. Dynamically it has a very definite behavior pattern, without any random maneuvers. Destroying the ascending missile in its boost phase, before it dispenses its warheads and decoys, dramatically simplifies the lethality challenge. Destruction of the ballistic missile can be achieved by direct hits on the target booster fuel tanks, guidance system or the rocket motor avoiding the need to locate and destroy the warhead. Moreover, since destruction occurs over enemy territory, even the residual booster and reentry vehicle debris will never reach the intended target. When considering non-conventional warheads, this represents a major deterrent for anyone intending to use chemical or biological warheads. Against this impressive list of advantages there is one major difficulty to be solved. The intercepting system must be able to intercept the ballistic missile during the relatively short period of the boost phase. The faster the defensive interceptor, the farther away from the attacking missile launcher the defense can be placed. However there is a clear escalation in weight, size and cost of the interceptor depending on its velocity. The interceptor can be based on ground, air or space. The use of a ground based system located in the defender’s territory and able to reach the attacking ballistic missile during the boost phase, would require velocities as those of orbiting vehicles that would make it impractical in terms of mass and cost. For Intercontinental Ballistic Missiles (ICBM) a space based system the so-called Brilliant Pebbles concept was advanced: Thousands of autonomous miniature space vehicles orbiting Earth at low altitudes and capable of sensing, identifying and intercepting ICBMs in the boost phase. This concept would always be on-station worldwide, and could provide many opportunities to intercept all but tactical ballistic missiles. The space vehicles used for interception are unable to function below an altitude of between 100-130 km. due to aerodynamic heating that blinds the sensor in the homing vehicle.

With all the limitations associated with ground and space based defensive systems against ballistic missiles in their boost phase a third option was advanced: An air based defense system against ballistic missiles at boost phase. This system was designated MOAB (Missile Optimized Anti-Ballistic) System. This is an active defense system against tactical ballistic missiles capable of autonomously detecting and intercepting tactical ballistic missiles in the boost phase. This system is based on three basic elements:

  1. High Altitude Long Endurance (HALE) Unmanned Air Vehicles (UAV).
  2. Small, lightweight agile interceptor missiles.
  3. Passive electro-optical sensors.

Long endurance UAVs, both in energy and survivability carrying a number of interceptor missiles and passive electro-optic sensors will be able to fly at altitudes well above the maximum cloud ceiling. The passive electro-optic sensors will have the capability to detect and track ballistic missiles during their boost phase. The sensor sensitivity, field of view and search pattern are defined such that the interceptor missile interception volume is within the detector search volume. The interceptor missile kinematic and dynamic characteristics are such that it will be able to reach and destroy the ballistic missile during the boost phase. System autonomous operation for interception is achieved through processing of line of sight information provided by the passive sensors. Ballistic missile kinematic characteristics are such that estimation of its flight pattern enables discrimination and identification with almost total certainty in an extremely short period of time. Once identification is performed, and a precedence order is defined in case more than one platform detects the same ballistic missile the interceptor missile launch is enabled. The interceptor missile employs optimal guidance laws to achieve interception while its heating rate remains below a predetermined value to avoid excessive heating of the seeker dome. The MOAB system is an autonomous system capable of providing, in an effective way, early warning and active defense, within reach of present day state of the art technologies. 

For the complete text of this article in Hebrew, click here.