US military officials have lost contact with the fastest plane ever built during a hypersonic test flight over the Pacific on Thursday.
The Falcon HTV-2 was launched aboard a rocket from Vandenberg air force base in California, on what at first appeared to be a flawless mission.
But after separating from the rocket at the edge of space and beginning its return to Earth, the aircraft went silent during the gliding stage of the test flight, when it was due to perform a series of manoeuvres as it hurtled through the atmosphere.
Officials at the US Defence Advance Research Projects Agency (Darpa) announced they had lost communication with the speeding craft at 4.21pm BST, 36 minutes into the flight.
The unmanned “hypersonic technology flight” had been expected to reach a top speed of Mach 20, or 13,000 mph, and withstand temperatures of 2,000C caused by the ultrafast flow of air around the aircraft.
At that speed, the plane could travel from London to Sydney in less than an hour and cross the US mainland, from New York to Los Angeles, in 12 minutes.
The plane was born from a Darpa plan called Prompt Global Strike, which sought to give military commanders the ability to strike targets anywhere in the world within an hour. Had the project worked, the Falcon HTV might have replaced intercontinental ballistic missiles.
The loss of the hypersonic aircraft is a serious setback for engineers trying to perfect the art of flying at such spectacular speeds.
In April last year, the first Falcon test flight, HTV-1, ran into trouble after nine minutes when computers picked up a glitch and steered the aircraft into the sea as a safety precaution.
Darpa only built two Falcon prototypes and has no plans to manufacture any more. This test flight was their last shot at success before the project is considered for closure.
Had the latest test flight gone to plan, the Falcon HTV-2 would have separated from its rocket high above the atmosphere and entered a steep dive before levelling out and performing a series of subtle manoeuvres to test its aerodynamic performance. At the end of the flight the plane would have rolled upside down and steered a graceful arc into the ocean.
Engineers had hoped the flight would provide crucial information on the plane’s performance, including the resilience of its carbon composite body and navigation systems supposed to keep it on course as it moved at almost four miles per second.