Too Fast to Follow

The US military lost contact with an unmanned hypersonic test aircraft shortly after its launch, defence officials have said.

The Falcon Hypersonic Test Vehicle 2 (HTV-2) - capable of reaching any target in the world in less than an hour - began a test flight from atop a rocket on Thursday.

Contact was also lost with a similar craft during the first mission.

The HTV-2 is designed to travel at 13,000mph (21,000km/h).

The Defense Advanced Research Projects Agency (Darpa), which is funding the HTV-2 programme and overseeing the tests, said the small craft was capable of reaching speeds of Mach 20.

The aircraft took off using a Minotaur IV rocket from Vanderberg Air Force Base in California early on Thursday.

Engineers programmed the HTV-2 to launch from the edge of space, separate from its rocket and crash into the ocean.

No information was available on whether the goals of the mission were achieved.