Hi Lee

To focus across 36,000 km will require BIG optics and to sense the missiles will require BIG optics. Nice fat targets for anti-ABM weapons. Energy weapons are also power-hungry and require BIG space-reactors - solar arrays are even better targets - which has been under-invested in for +20 years.

Small, fast kinetic-kill weapons are cheaper, but as JimO said the whole concept is fundamentally a non-starter and has been since Reagan began the whole shadow-game to destabilise the Soviets. But the enemy didn't know it then and it worked.

They know it now, so it's pointless waste. High-speed quasi-orbital strike capabilities still have rapid-response merit which is why the USAF is working on an unmanned space-plane, but orbital ABM systems are stupid.

Adam