However, it is a good question to ask what this offers over ICBM equipped with conventional weapons. (The speed is about the same.) I'd imagine it's cost.
Both system consist of booster (which need to provide 20 Mach delta-v to its payload) and payload - upper stage which is warhead carrying vehicle. ICBM is cheaper because it follows dumb ballistic trajectory which puts no specific structural requirements on the warheads and their enclosure. The warhead vehicle traveling at 20 Mach in the upper atmosphere would cost enormously more ( and possibly would be much heavier, thus requiring bigger booster). I.e. ICBM is cheaper.
The dumb ballistic trajectory was a weak spot of the ICBM system, and thus modern ICBM warheads perform evasive maneuvers during final atmosphere re-entry.
1. Can't be shot down by any known SA missile technology (which the Russians are pretty good at)
2. Isn't a sitting duck like satellites, can't be shot down with anti-satellite weapons.
3. Can go anywhere anytime, so adversaries can't time their troop movements and other clandestine activities around your spysat flyover schedule.
4. Perfect for keeping tabs on China's opaque military buildup, since the US's sats and humint isn't as effective at that as desired.
This is actually scramjet technology, which has very general applications beyond delivering a bomb.
ICBMs can carry non-nuclear warheads but it's a VERY expensive way to get a payload on target.
yep, and when this http://www.panoramio.com/photo/13572904 sees such a highly maneuverable vehicle flying 20 Machs over Europe you don't think it would cause questions that must be answered during next few minutes? At least in case of ICBM it is clear where it flies to once it launched.