http://www.newscientist.com/hottopics/tech/article.jsp?id=99994408&sub=Security%20and%20Defence
The US military has begun development of an ultra-high speed weapons system that would enable targets virtually anywhere on Earth to be hit within two hours of launch from the continental US.
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The Pentagon has split the project into two tasks. The nearer-term task, aiming for 2010, is the development of a weapons delivery system and rocket to launch it. The Common Aero Vehicle would be an unpowered but manoeuvrable hypersonic craft capable of carrying about 500 kilograms of munitions over a range of 5500 km.
The CAV would be launched into space by the new rocket, before being guided down by GPS to its target. DARPA hopes the rocket could also be used for satellite launches and such a launcher will be unveiled on 4 December by California-based company Spacex, one of the grant recipients.