The logical culmination of all this, of course, is weaponry in space. It’s doubtful that’ll occur or reach maturity on Obama’s watch, but space-based lasers capable of hitting missiles in their booster phase would constitute the crown jewel of any missile defense architecture that’s worth the name.  But the public is skittish about weapons sailing over their heads several times a day, so for now all the focus has been on surface- and air-based hardware. The advocates of the current generation of missile defense learned their lesson well from SDI:  don’t propose everything at once, and don’t talk about space until you have to.  That’s why they’ve made far more progress than SDI ever did. The fact that the technology has come a long way doesn’t hurt either.