The following is information relating to the highly secretive Aurora Project, whose existence has been denied 'officially' by the US Government. Hence, all the information below is based on speculation and unidentified information sources involved in such a project.
The Aurora Project as a secret coming into existence is not known to anyone yet. It is believed that the project is a follow-on of the XB-70 Valkyrie. The developers are probably the Lockheed-Martin, who have had a lot of experience in the field of high speed stealth planes (e.g. SR-71 Blackbird). The Aurora Project, I believe is the development for a future generation reconnaisance plane.
The Project, according to sources, is to create a plane that sustains speeds of upto Mach 6-8 (Mach 1 is the speed of sound), and incorporate stealth features.
The Aurora aircraft has an airframe like a flattened American football, about 110 feet long and 60 feet wide, smoothly contoured, and covered in ceramic tiles similar to those used on the Space Shuttle which seem to be coated with "a crystalline patina indicative of sustained exposure to high temperature. . . a burnt carbon odor exudes from the surface."(See graphics)
Not much is known about the propulsion system, but the following speculations are likely.
At subsonic speeds, probably the power comes from conventional jet engines in the lower fuselage, fed by inlet ducts which open in the tiled surface.
Once at supersonic speed, there are three possibilities for the propulsion that carries the plane up to its Mach 6+ speed: