Engineers finally release their report on the August, 2011 test flight

Apr 24, 2012 06:56 GMT  ·  By

Scientists at the US Defense Advanced Research Projects Agency (DARPA) have finally released their technical report, explaining why the Hypersonic Technology Vehicle 2 (HTV-2) military drone failed to complete its test flight successfully in August, 2011.

The ultra-fast aircraft was designed to travel at speeds of up to Mach 20, which is the equivalent of 20 times the speed of sound. Its top speed was rated at around 13,000 miles (20,921 kilometers) per hour.

For comparison, the NASA space shuttles reached speeds of up to Mach 25 upon reentering Earth's atmosphere. Just like the orbiters, HTV-2 was outfitted with special, protective layers to safeguard it against the extreme heat of hypersonic flight.

However, the new report shows, this was not enough. The extreme speed HTV-2 managed to acquire subjected the drone to so much heat, that its hull was literally stripped away piece by piece. The aircraft eventually crashed into the Pacific Ocean.

One of the most interesting aspects of the August, 2011 test flight was that the HTV-2 was able to withstand massive shock waves, which forced it to roll while traveling at Mach 20, Space reports.

“A gradual wearing away of the vehicle's skin as it reached stress tolerance limits was expected. However, larger than anticipated portions of the vehicle’s skin peeled from the aerostructure,” the DARPA team says in a statement.

“The initial Shockwave disturbances experienced during second flight, from which the vehicle was able to recover and continue controlled flight, exceeded by more than 100 times what the vehicle was designed to withstand,” says Kaigham J. Gabriel, the acting director of DARPA.

“That's a major validation that we’re advancing our understanding of aerodynamic control for hypersonic flight,” the official goes on to say.

Engineers suspect that the extreme damage the drone took eventually set off the Flight Safety System, a protective mechanism that ensures the destruction of the aircraft. Once the FSS was on, it pitched HTV-2's nose into the ocean, destroying the aircraft entirely.

The HTV-2 is being developed as part of the US advanced Conventional Prompt Global Strike weapons program. One of the main goals of this program is to develop bombers capable of reaching and striking any target on the globe within an hour of deployment.