An independent review board concluded that a U.S. Defense Advanced Research Projects Agency (DARPA) hypersonic aircraft launched in April was automatically destroyed when its flight profile exceeded the limitations set for the test, according to a Nov. 16 agency press release.

There will be very slight modifications made to DARPA’s second Hypersonic Technology Vehicle-2 (HTV-2) carbon fiber aircraft before its planned late 2011 test flight, the press release said.

The HTV-2 program is intended to demonstrate technologies for a next-generation U.S. long-range conventional strike missile. For its maiden flight, the delta wing-shaped, Lockheed Martin-built HTV-2 aircraft was launched to the edge of space aboard a Minotaur 4 rocket. The craft separated properly from the rocket’s faring and began a high-speed glide over the Pacific Ocean intended to cover some 5,700 kilometers in less than half an hour. Nine minutes into the flight, contact with the vehicle was lost.

A six-month investigation found the most likely culprit for the anomaly was higher-than-predicted yaw, or horizontal rotation, of the aircraft, though the analysis was based on limited knowledge of several key parameters, the release said. For the next flight, engineers will adjust the aircraft’s center of gravity and decrease the angle of attack during re-entry. There are two HTV-2 aircraft that have yet to fly.