The X-51a WaveRider experimental scramjet powered test-vehicle underwent another flight test yesterday, August 11th, 2010. The air-breathing, Jp-7 fueled hypersonic engine was able to achieve Mach 5 for the first time in history. Here is a press release of that event.
The X-51a WaveRider was dropped from a USAF B-52 at an altitude of 50,000 feet over the Pacific Ocean off southern California. A Lockheed Martin ATACMS rocket motor then boosted the vehicle to Mach 4.5 enabling the scramjet engine to start and accelerate to the maximum velocity of Mach 5. The ATACMS rocket had a high performance conical exhaust nozzle designed by Boeing and built by Aerojet.
The X-51 program is a joint program of the US Air Force, DARPA, NASA, Boeing and Pratt & Whitney Rocketdyne (PWR). (Here is a link to a press release from an earlier test from PWR. Here is a link to PWR Hypersonics page which has lots of videos and colorful pictures.) The X-51a is equipped with a dual mode PWR SJY61 scramjet engine that can operate as a ramjet at subsonic speeds and as a scramjet at supersonic speeds. The engine starts up on gaseous ethylene fuel and then switches to JP-7 at supersonic speeds.
The X-51 program is intended to be used by USAF for a future hypersonic cruise missile, as stated in this press release by Jane’s Defence Equipment and Technology, dated Aug. 10, 2010. It will be the only air-breathing ICBM option being considered by the USAF, one that can target any location on earth within 60 minutes. The others are all driven by rocket motors. However, the X-51 will also be considered for space launches, relying on the single-stage-to-orbit concept.
Here is a link to an article from SAE magazine date 10-June-2010 with more interesting details of a previous test.