By the time you finish reading this sentence, the Falcon HTV-2,
the fastest plane ever built, could have flown 18 miles. It
would get from London to Sydney in less than an hour, while
withstanding temperatures of almost 2,000C, hotter than the
melting point of steel. At 3pm BST on Thursday , the US Defence
Advance Research Projects Agency will launch the Falcon
Hypersonic Technology Vehicle 2 on the back of a rocket from the
Vandenberg Air Force Base in California. If all goes to plan,
engineers will launch the Falcon HTV-2 to the edge of space,
before detaching the plane and guiding it on a hypersonic flight
that will reach speeds of 13,000mph (about 20 times the speed of
sound) on its return to Earth. The Falcon started life in 2003,
part of a US military research project to build a plane that
could reach (and potentially deliver bombs to) any part of the
world in less than an hour. The plane has been tested in
computer models and wind tunnels, but they can only simulate
speeds up to Mach 15 (11,400mph). A