Last summer DARPA conducted a test of its unmanned hypersonic glider dubbed Hypersonic Technology Vehicle-2 or HTV-2. The vehicle was able to maintain stable flight for a while at 13,000 mph over the Pacific Ocean. The stable flight lasted 3 minutes before HPV-2s flight safety system plunged it into the ocean.
Since that failed mission, DARPA has been investigating possible causes for the issue, and the agency now thinks that unexpectedly large pieces of the hypersonic aircraft's skin peeled off. DARPA says that it expected some of the skin to wear down due to the extreme heat and speed of the aircraft. An independent review board has concluded that the most likely cause for the failure was “unexpected aeroshell degradation, creating multiple upsets of increasing severity that ultimately activated the Flight Safety System.”
According to DARPA officials, the shockwaves created when the skin pulled away from the aircraft were 100 times more than what the vehicle was designed to withstand. However, the vehicle was able to recover and return to controlled flight before the vehicle finally fell into the ocean.
“The result of these findings is a profound advancement in understanding the areas we need to focus on to advance aerothermal structures for future hypersonic vehicles. Only actual flight data could have revealed this to us,” Air Force Maj. Chris Schulz said.
[via The Washington Post]