August 14, 2011
Flight 1 engineering changes believed effective
On Thursday, 11 August, the HTV-2 experienced a flight anomaly post perigee and into the vehicle’s climb. The anomaly prompted the vehicle’s autonomous flight safety system to use the craft’s aerodynamic systems to make a controlled descent and splash down into the ocean. Controlled descent is a term typically associated with a human-in-the-loop directing or guiding the unscheduled landing of an aircraft. For DARPA’s Hypersonic Technology Vehicle 2 (HTV-2) controlled descent takes on new meaning thanks to the vehicle’s safety system.
“We’ve confirmed that the HTV-2 made impact with the Pacific Ocean along its flight trajectory as planned in the event of an anomaly,” explained Air Force Maj Chris Schulz, USAF, Ph.D., DARPA HTV-2 program manager and PhD in aerospace engineering. “This flight safety system is a significant engineering advance in that the system prompts a vehicle to monitor the parameters under which it is operating and exercise safety protocols completely autonomously should those parameters be breached.”
“According to a preliminary review of the data collected prior to the anomaly encountered by the HTV-2 during its second test flight,” said DARPA Director Regina Dugan, “HTV-2 demonstrated stable aerodynamically controlled Mach 20 hypersonic flight for approximately three minutes. It appears that the engineering changes put into place following the vehicle’s first flight test in April 2010 were effective. We do not yet know the cause of the anomaly for Flight 2.”
A detailed analysis conducted by an independent Engineering Review Board following the first flight test, prompted engineers to adjust the vehicle’s center of gravity, decrease the angle of attack flown and use the onboard reaction control systems to augment vehicle flaps during the vehicle’s second flight test. Those changes appear to have been effective. “An initial assessment indicates,” said Schulz, “that the Flight 2 anomaly is unrelated to the Flight 1 anomaly.”
During the reentry phase of the flight plan, the craft is traveling at Mach 20, under extreme conditions as it attempts to enter the glide phase of flight. In the coming weeks an independent ERB will investigate the most probable causes of the new anomaly encountered during the second test flight of HTV-2.
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