Pentagon explains why hypersonic, Mach 20 drone failed
{{#rendered}} {{/rendered}}The Pentagon has finally released a report about what went wrong when its Hypersonic Technology Vehicle (HTV-2) failed just minutes into a test flight last year and barreled into the Pacific Ocean.
The unmanned, arrowhead-shaped aircraft, which one day could allow the US to strike anywhere across the globe in less than 60 minutes, was strapped to a rocket and launched from California's Vandenberg Air Force Base last August.
The drone coasted at speeds of 13,000mph (21,000kmph) -- 20 times the speed of sound -- through the Earth's atmosphere for less than three minutes before ultimately failing and switching into abort-mode just nine minutes into the flight. It splashed down short of its intended target near the Kwajalein Atoll in the Pacific.
{{#rendered}} {{/rendered}}Defense Advanced Research Projects Agency (DARPA) said an analysis of the crash showed that high speeds peeled off larger-than-expected portions of the vehicle's skin.
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Officials anticipated some of the outer shell would gradually wear away, but rapidly-forming gaps on the skin created strong shock waves around the HTV-2 and caused it to roll abruptly, the report said.
{{#rendered}} {{/rendered}}Military researchers, however, were hopeful that they could learn from the mistakes of the failed flight, especially after the first HTV-2 mission in April 2010 -- which also terminated early -- prompted successful adjustments to the craft's aerodynamic design.
"HTV-2's first flight test corrected our models regarding aerodynamic design within this flight regime," Air Force Maj. Chris Schulz, DARPA program manager, said in a statement. "We applied that data in flight test two, which ultimately led to stable aerodynamically controlled flight."
Schulz added that data collected during the second test flight "revealed new knowledge about thermal-protective material properties and uncertainties" for flights at such a high speed in our atmosphere. Going forward, that data will be used to modify how the vehicle's outer shell responds to heat stress, DARPA said.