Hypersonic Propulsion Technology (Scramjet) And a Project I come across

[Steven Harris]

This got me started.

http://news.yahoo.com/photos/photo-of-the-day-slideshow-slideshow/artists-rendering-provided-u-defense-advanced-research-projects-photo-213706198.html

Official News of the recent tests regarding the above.

http://www.darpa.mil/NewsEvents/Releases/2012/04/20.aspx

http://en.wikipedia.org/wiki/Hypersonic_Technology_Vehicle_2

descriptions of the technology.

http://www.globalsecurity.org/military/systems/munitions/hytech.htm

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

other designs for testing.

http://en.wikipedia.org/wiki/NASA_X-43

This may be a technology that is utilized, but I have suspicions of more advanced methods of propulsion that have been and are within our ability. This technology is unsafe for manned travel without generated fields to protect it from debris, that will inevitably find the craft. This is why i believe the efforts have failed in long distances.