The U.S. Air Force and Defense Advanced Research Projects Agency are setting up an engineering review board to investigate the loss of the second, and final, Hypersonic Test Vehicle (HTV-2) shortly after launch from Vandenberg AFB, Calif., on Aug 11.

Contact with the vehicle was lost around nine minutes into the flight. In accordance with loss-of-signal precautions the HTV-2 destroyed itself before completing a third of its planned 30-min., Mach 20 gliding flight towards a target area near the Kwajalein Atoll in the Pacific Ocean.

In its first statement on the failed test, Darpa says “the Minotaur IV vehicle successfully inserted the aircraft into the desired trajectory. Separation of the vehicle was confirmed by rocket cam and the aircraft transitioned to Mach 20 aerodynamic flight. This transition represents a critical knowledge and control point in maneuvering atmospheric hypersonic flight. More than nine minutes of data was collected before an anomaly caused loss of signal. Initial indications are that the aircraft impacted the Pacific Ocean along the planned flight path.”

Darpa HTV-2 program manager Air Force Maj. Chris Schulz says “we know how to boost the aircraft to near space. We know how to insert the aircraft into atmospheric hypersonic flight. We do not yet know how to achieve the desired control during the aerodynamic phase of flight. It’s vexing; I’m confident there is a solution. We have to find it.”

HTV-2 was designed to demonstrate the high lift-to-drag aerodynamics and high-temperature materials needed for sustained hypersonic flight, with the goal of validating technology for a vehicle able to reach anywhere in the world in 60 min. The Aug. 11 test was a repeat of the first HTV-2 flight last April which ended when a control anomaly developed at around the same point in the flight. The second vehicle was modified with a sturdier flight control system as a result of investigations into the loss of the first HTV-2, though it is not yet known if these changes had any impact on controllability or if the second loss was due to unrelated causes.

Data from the review board will “inform policy, acquisition and operational decisions for future Conventional Prompt Global Strike programs — the goal of which, ultimately, is to have the capability to reach anywhere in the world in less than one hour,” says Darpa in the statement.