They're spherical relay mirror interceptors for a Ground-Based Laser weapons system that has been in continuous development since 1984. Everything cited below is publicly available. The math is in the appendix — derive it yourself. --- ## 1984 — BRADUSKILL INTERCEPTOR CONCEPT U.S. Army Strategic Defense Command, Huntsville, Alabama. LTC James H. Boschma develops a "slow-kill" midcourse interceptor — a platform that launches from Arctic basing, flies alongside Soviet ICBMs during midcourse, us...