Unmanned X-51 Air Force Jet Sets Speed Record

Using a supersonic combustion ramjet motor, Boeing and the U.S. Air Force successfully tested an unmanned X-51A WaveRider, setting a speed record. It is the world's first hypersonic scramjet flight using hydrocarbon fuel, Boeing said.

In its first flight attempt, the Boeing X-51A WaveRider successfully completed the longest supersonic combustion ramjet-powered flight in history -- nearly three and a half minutes at a top speed of Mach 5, the aerospace giant announced. The Air Force described the X-51 is an unmanned scramjet demonstration aircraft for hypersonic (Mach 6, or approximately. 4,000 mph at altitude) flight testing.

It flew autonomously for more than 200 seconds, powered by its Pratt & Whitney Rocketdyne supersonic combustion ramjet (scramjet) motor, as it transmitted telemetry data to ground stations. Something then occurred that caused the vehicle to lose acceleration. At that point, the X-51A was terminated as planned. Even before analyzing the terabytes of telemetry data transmitted by the X-51A during flight, Air Force officials called the test an unqualified success.
"The technology proven today is something The Boeing Company has worked on for the past seven years," said Alex Lopez, vice president of advanced network and space systems, a division of Boeing Phantom Works. "It is thrilling to be a part of history and advance hypersonic science to the next level. Boeing is looking forward to transitioning the technology to operation in the near term, but for now, we are exhilarated."
The X-51A was carried aloft under the left wing of an Air Force Flight Test Center B-52H Stratofortress that took off from Edwards Air Force Base, Boeing reported. It was released while flying at approximately 50,000 feet over the Point Mugu Naval Air Warfare Center Sea Range; four seconds later, a solid rocket booster from a U.S. Army tactical missile accelerated the X-51A to about Mach 4.5. The X-51A's engine ignited on a mix of ethylene and JP-7 jet fuel. After a short period, the X-51A ran exclusively on JP-7 jet fuel.
"We are ecstatic to have accomplished many of the X-51A test points during its first hypersonic mission," said Charlie Brink, X-51A program manager with the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio. "This gives us huge confidence. We built four test vehicles to get a successful flight, and we hit many of our goals right out of the gate, the first time around."
In April, the Air Force successfully launched a top secret Orbital Test Vehicle (OTV), also known as the X-37B and commonly described as an unmanned space plane that can re-enter the earth's atmosphere. Although an artist's rendering of the spacecraft in the OTV mission overview provided by ULA resembles a pint-size space shuttle, the Air Force has released few details about the classified project, or when it will return, other than to term the robotic vehicle a "flexible space test platform" that would conduct various experiments to allow "satellite sensors, subsystems, components and associated technology to be efficiently transported to and from the space environment."