[dalke]

I made a mistake. I should have said "engineering" not "physics". The physics works in that a single interceptor has taken out a dummy warhead. What doesn't work is the ability to handle the scenarios in the whitepaper, where 200 missiles are coming in, with multiple reentry vehicles and decoys.

How do you test it?

The GMD has a 50% failure rate during hit-to-kill intercept tests. That's with a single target, time to prepare, and several decades of funding.

To implement the full shield the author wants systems for boost, coast, and reentry phases. This includes "hundreds of spacecraft ... to assure a handful are within range of boosting missiles at the time of launch." There's no one word of how to test system integration.

Going back to physics, one of the scenarios in the whitepaper is to defend the US against an attack with 10 nukes, designed to take down the power grid. Won't setting off our own defensive nukes give the same result? The same magazine has a article on how woefully unprepared the US is for an EMP attack, at http://www.forbes.com/sites/peterdetwiler/2014/07/31/protect... . Frankly, it makes Forbes sound like it's still lingering in the Cold War.

And just how do you hide away enough nuclear tipped missile interceptors to be useful, for the decades until they might used, without having to ask for some pretty big permission? There's a good chance that the operators will have to practice setting off nukes over their own houses, or that of friends and family. Not good for morale.