by the relationship 1 as pictured in fig1 the windmill should be aft of the center of gravity for longitudinal stability i e the windmill should pull the interceptor backwards a simple mathematical model of the interceptor after deployment involves two forms of newton 39 s second law one for the linear motion and the other for the angular motion where d is drag due to transferal of linear momentum to torque which is a quadratic function of the velocities and will decelerate the interceptor and u03b1 is a drag parameter this drag will then provide a positive torque with efficiency u03b5 and radial length r 0 that will spin up the interceptor a detonation for a planar blast is preferably triggered when an air blade contacts the incoming projectile a significantly more effective method is to sense the location of the propeller that strikes the target to trigger a directional charge in the most u201c passive u201d design the propellers would be spring loaded and deploy at a preset time following launch there are a number of scenarios of intercept that we shall examine such scenarios result due to for example variations in the initial distance the distance of the target from the location to be protected as the interceptor is fired distance of intercept speed of incoming projectile and the charge necessary to deflect or destroy the target the problem is therefore a multi objective design problem some design parameters are the initial spin rate of the.