Evil Geometery

In the military, a common problem concerns finding the optimal placement of a bomb such that it hits all targets( given the bomb's explosive power as a constraint). Think of the targets a set of points on a map, and imagine drawing the smallest possible circle that encompasses all the points. The center of this circle would be a good spot to place this bomb. Given these set of targets , find the blast radius of a hypothetical bomb that is dropped at the optimal point.