At mach 5 I think you can presume a couple of things.
1. It’s not going to be making right turns. The turns will be gradual.
2. It will expend enormous amounts of fuel. Which will make it short range. Nothing like a cruise missile (1500 miles+).
I had a friend that worked for thee FAA he use to watch SR71s turn. He said it took about two states for that maneuver. That was at about Mach 2.5.
Honestly, I didn’t see anything in the article to tell me why it is ‘uninterceptable’. It’s just fast. Short range. smaller warhead. Won’t be in production for four years. Which means we will have perfected our short range lasers by then.
Also check out Phalanx (CIWS) Block 1B LPWS Testing and Firing
http://www.youtube.com/watch?v=cgpQBZF2sZQ
At that speed you only need a small dent or blemish to make it all come apart.
During the Star Wars days the solution the Russians had for our ICBMS was to blow up a thousand pounds of sand in an orbit going east to west. You don’t need to be sophisticated. It’s just more impressive.
For 18,000 mph
http://en.wikipedia.org/wiki/Terminal_High_Altitude_Area_Defense
And what exactly is a cruise missile??Is it something that’s defined by range alone?
http://www.fas.org/nuke/intro/cm/index.html