66 THE DEVELOPMENT OF WEAPONS SYSTEM REQUIREMENTS 



earliest possible interception point. Other types of vectoring guidance — 

 for example, a tactic whereby it is attempted to guide the interceptor on a 

 tail-chase attack — introduce additional time delays, and these reduce the 

 total number of interceptions which can be made with a given early warning 

 range. 



System tactics also exercise other important influences. For example, 

 a 3-minute dead time delay was assumed between early warning detection 

 and assignment of the first interceptors to specific targets. This type of 

 operation places a high value on the time delay. Each minute of time delay 

 requires 8 additional miles of early warning detection range to maintain a 

 fixed number of interceptions. 



The effect of this time delay would be different if the system tactics 

 called for launching of interceptors to begin before evaluation was com- 

 pleted. This operation, however, incurs a risk that interceptors may be 

 launched unnecessarily. In this latter case, it would be necessary to 

 evaluate the consequences of a false alarm as a function of threat evaluation 

 time; i.e., the penalties of launching interceptors when the threat does not 

 materialize following an early warning detection in terms of fuel loss, 

 vulnerability to attacks from other directions, etc. Some of these consider- 

 ations may seem to go a little far afield, but the answers to such questions 

 are of great importance to the radar designer because they affect what his 

 equipment must do. To simplify our example, we assume that no inter- 

 ceptors are launched until evaluation of the threat is completed. 



As a second example of the effect of tactics, we might consider the target 

 assignment procedure. In our example, we assume that an optimum 

 assignment procedure could be used. That is to say, each of the 40 inter- 

 ceptors was able to make an attack during the course of the air battle — 

 except in the cases where all 20 targets were destroyed by less than 40 

 attacks. This assumption assumes a very sophisticated battle control and 

 communications system. Another method of assignment could be as 

 follows: the first 20 interceptors are assigned — one-on-one — to the first 

 20 targets. The following interceptors are assigned as back-up interceptors 

 on the same basis — i.e. interceptor 21 to target 1 , interceptor 22 to target 2, 

 etc. For 40 interceptions, this would mean each target could be attacked 

 twice. In some cases, however, the target would be killed by the first 

 interceptor thereby leaving the back-up interceptor without a target to 

 attack, resulting in a potential inefficiency. On the other hand, two attacks 

 may not suffice to kill the target since each attack has less than unity 

 success probability. 



With these alternate tactics, a substantially greater interceptor kill 

 probability would be required to meet the operational requirement for the 

 case of 40 interceptors reaching the attack zone. This value has been 

 determined to be 0.7 as compared with 0.5 when optimum target assign- 



