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"  Pentagon scientists have determined why an experimental vehicle, flying more than Mach 20 at the edge of space, intentionally terminated its inaugural flight. In April, the Falcon Hypersonic Technology Vehicle became unstable and, directed by its onboard computer, flew into the Pacific Ocean 9 minutes into its first test. Seven months later, the Air Force released details of the incident\u2014with news that it will launch an improved HTV late this year.  Crash Timeline: April 22, 2010 1. Launch The Hypersonic Technology Vehicle is launched from a Minotaur IV missile, which opens its clamshell fairing at the edge of the atmosphere to release the experimental aircraft.  2. Flight  The HTV glides above Earth at more than 15,000 mph\u2014roughly 20 times the speed of sound. 3. Trouble  The aircraft unexpectedly begins to roll. This phenomenon, called inertial coupling, occurs in high-speed flights when the inertia of the fuselage overwhelms the ability of flight surfaces (like the HTV&amp;#039;s flaps) to stabilize the craft.  4. Crash  The HTV, programmed to ditch if its flight becomes erratic, steers into the Pacific Ocean in a crash dive. Contact is lost 9 minutes after its release from the rocket.  Lessons: Engineers adjusted the HTV&amp;#039;s interior layout to change the vehicle&amp;#039;s center of gravity. On future flights, onboard reaction control thrusters will keep the craft stable. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/military/a6829/what-probably-went-wrong-with-darpas-mach-20-flier/>