Cause of hypersonic plane crash revealed-Flying at 20 times the speed of sound proved too much for the top-secret aircraft. 'Impulsive shock wave

It turns out that tearing through the atmosphere at 20 times the speed of sound is bad for the skin, even if you're a super high-tech aircraft developed by the government's best engineers at its far-out research agency.

DARPA, the Defense Advanced Research Project Agency, has made public its best guess about what might have caused its unmanned arrowhead-shaped Hypersonic Technology Vehicle (HTV-2) to suddenly lose contact and crash in the Pacific just a few minutes after slicing through the sky at Mach 20 last August: it was going so fast its skin peeled off.

After an eight-month investigation, DARPA concluded that even though the HTV-2 was expected to lose some of its skin mid-flight, "larger than anticipated portions of the vehicle's skin peeled from the aerostructure," the agency said in a statement Friday.

The agency said it expected the HTV-2, which goes so fast it can make the commute from New York to Los Angeles in 12 minutes, to experience "impulsive shock waves" at such speeds, but
[link to news.yahoo.com]