[webstersII]

Great idea, but really difficult to develop.

I worked on a program to investigate the feasibility of building one of these about 15 years ago. AFAIK all the designs are based on Scramjet technology, which is useful but has many challenges to implement for a missile.

The control system challenge is not to be taken lightly, too. Controlling a missile traveling that fast is really challenging.

[Jack Hydrazine]

How much of an efficiency gain do you get when you are running at hypersonic speeds and riding your own shock wave?

[Venturer]

Doesnt an ICBM take only about 30 minutes to go to the other side of earth. Cant they carry non-nuclear warheads?

[James C. Bennett]

Is this similar to this one that the Russians and Indians have been working on:

http://en.wikipedia.org/wiki/BrahMos

?

[buccaneer81]

Google X-37.