The first of four X-51 Waverider scramjet test flights was an "unqualified success" Wednesday, shattering the previous endurance record for scramjet engine operations, the U.S. Air Force said in a statement.

The X-51A Waverider launched on a tactical missile from a B-52H bomber. Credit: U.S. Air Force/Mike Cassidy

After dropping from the wing of a B-52H bomber, a tactical missile accelerated the small experimental vehicle to Mach 4.5 over the Pacific Ocean off the coast of California at around 10 a.m. PDT Wednesday. The expendable solid rocket motor cleanly separated from the X-51, which successfully fired its scramjet air-breathing engine moments later.

The revolutionary engine, which consumes conventional JP-7 jet fuel, burned for more than 200 seconds to push the X-51 Waverider to five times the speed of sound, or approximately 4,000 mph. The vehicle reached an altitude of about 70,000 feet.

The Air Force test broke a previous scramjet duration mark set by NASA's X-43 test vehicle in 2004.

Scramjets work by capitalizing on meager oxygen at high altitudes. The air-breathing engine allows aircraft to reach hypersonic speeds without carrying heavy oxidizers to support engine combustion.

Read our preview story for more details on scramjet technology.

"We are ecstatic to have accomplished most of our test points on the X-51A's very first hypersonic mission," said Charlie Brink, the X-51A program manager with the Air Force Research Laboratory at Wright-Patterson Air Force Base, Ohio. "We equate this leap in engine technology as equivalent to the post-World War II jump from propeller-driven aircraft to jet engines."

Boeing Co.'s Phantom Works division built the X-51, and Pratt & Whitney Rocketdyne designed and provided the vehicle's scramjet engine for the Air Force and the Defense Advanced Research Projects Agency, or DARPA.

The X-51 transmitted live data to a P-3 Orion chase plane and ground stations throughout the flight, but something occurred before the scheduled end of the scramjet burn causing the vehicle to lose acceleration, Boeing said in a statement.

Before the flight, officials cautioned the X-51 was an experimental program. Engineers hope to learn and make improvements to three other vehicles scheduled to fly later this year.

Artist's concept of the X-51A Waverider in flight. Credit: U.S. Air Force

In an Air Force press release, Brink said he would give Wednesday's test a solid B.

The military is developing scramjet technology for applications in high-speed offensive weapons, space launch vehicles and transportation.

"This is a new world record and sets the foundation for several hypersonic applications, including access to space, reconnaissance, strike, global reach and commercial transportation," said Joe Vogel, Boeing's director of hypersonics and X-51A program manager.

Scramjets could power a "Prompt Global Strike" missile being considered by top governmental officials for surprise attacks anywhere in the world within an hour of launch from the United States.

Soaring off the ground on a conventional rocket, the scramjet would take over at high altitudes hugging the edge of space and guide the weapon to targets around the world. The missile would use the crushing kinetic energy of impact to destroy targets.

Scaled-up scramjet-powered aircraft could revolutionize commercial transportation and make 90-minute flights possible to any point on Earth.