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Boost Phase Interceptor
Range Requirement

Dan Rosen

Policy Paper No. 34, From the books:

Ballistic Missiles Ė
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


The main parameter influencing the Boost Phase Intercept concept of operation is the interceptorís kinematic range. Clearly, larger interceptor range capability, defines a larger ground coverage, and that is generally observed as a significant advantage, if not an absolute necessity, especially where possible locations of TBM launchers cannot be delimited into compact area cells.

The operational situation requires the interceptor to destroy the TBM while it is still in its boost phase (once the TBM thrust is cut off, the interceptor faces most of the difficulties associated with a terminal phase intercept!). This requirement translates into the need of the interceptor to traverse the range to the TBM during a given time span, and thus associates the range requirement directly with an interceptor velocity requirement.

The effort to reach large kinematic ranges, has driven various American concept designers to interceptor velocities of over 3 km./sec. This, in turn, places a heavy technological burden on the interceptor design, resulting from the aerodynamic heating. Another outcome is a significant increase in the interceptorís weight.

This weight increase, as well as the complications resulting from the need to "blind" the interceptorís seekerhead with a thermal shield, and to guide it via a data link from a remotely stationed sensor, etc., were hitherto considered as an unavoidable penalty resulting from the operational requirement.

This paper examines the question of the required interceptor range from an overall system operation view, considering not only the ground area coverage of a single interceptor, but the need to cover a given ground area simultaneously with N interceptor missiles defending against a coordinated launch of numerous TBMs.

The aerial platforms considered, are UAVs. It is assumed that the interceptors payload weight of the UAV is given, being an outcome of a design optimization taking all other operational requirements as endurance, patrolling altitude, radar cross section, etc., as existing constraints. From here, the number of UAVs required for covering a given area cell with N interceptors is calculated, and is clearly proportional to the interceptorís weight.

It is shown that the interceptorís weight may be approximated as proportional to R3, R being the interceptorís kimematic range.

Next, the number of patrolling cells required to cover an area of S km.2 is calculated, assuming each area cell to be a circle of radius R, and from here the total numbers of interceptors and of UAVs are calculated, all in terms of the interceptor range R as parameter.

The outcome of this analysis, which may come as a surprise to the advocates of the increased range interceptor, is that both the number of the required interceptors, as well as the number of the required UAVs to carry them, are directly proportional to the interceptorís kinematic range. Attributing any price tag to a UAV and to an interceptor shows that increasing the interceptorís range will be heavily penalized not only by the increased number of UAVs to be simultaneously operated, but also directly by the life cycle cost of an operational weapon system.

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