The Falcon Hypersonic Technology Vehicle 2.

The Falcon Hypersonic Technology Vehicle 2. Photo: DARPA

An experimental aircraft that could fly from Sydney to London in less than an hour at blistering speeds of 20,921km/h is due to be tested this week.

The unmanned, arrowhead-shaped aircraft, dubbed Falcon Hypersonic Technology Vehicle 2, will test new technology that would provide the US Pentagon a lightning-fast vehicle capable of delivering a military strike anywhere in the world in under an hour.

At its top speed it could travel the 17,000 kilometres between London and Sydney in about 49 minutes.

The Falcon Hypersonic Technology Vehicle 2 attached to a rocket.

The Falcon Hypersonic Technology Vehicle 2 attached to a rocket. Photo: DARPA

The Falcon is part of Lockheed Martin's "prompt global strike" concept. It is being funded by US Defence Advanced Research Projects Agency, or DARPA.

It is due to be launched aboard a Minotaur IV rocket at Vandenberg Air Force Base, north-west of Santa Barbara on Thursday, US time.

After launch, the Falcon will separate from the rocket, screech back towards earth, level out and glide above the Pacific at 20 times the speed of sound, or Mach 20.

The aircraft is expected to splash down and sink near Kwajalein Atoll, about 6400 kilometres from Vandenberg, about half an hour after launch.

The launch had been scheduled for 7am on Wednesday. But when that time rolled around, the Air Force held the countdown.

Thirty minutes later, Vandenberg officials announced on the base's Facebook page: "Today's launch of the 30W Minotaur IV rocket has been scrubbed due to poor weather downrange. The launch has been rescheduled for tomorrow, August 11, between the launch window of 7am to 1pm."

Jeremy Eggers, a spokesman at Vandenberg, later said in an email that "clouds, showers, and areas of lightning downrange have delayed our launch today. Weather conditions downrange look more favourable for a launch tomorrow."

It will be the second flight of the Falcon. The first flight, which took place in April last year, ended prematurely after only nine minutes.

DARPA said the first flight was "used to improve aerodynamic models and to optimise the vehicle design and trajectory for flight two".

The Falcon's second flight is set to be its last unless the government provides more funding. And, unlike many rocket launches these days, it is not set to be webcast.

Sustaining hypersonic flight, or speeds beyond Mach 5, has been extremely difficult for aeronautical engineers to perfect over the years.

In June, the US Air Force had to end a test flight of its experimental X-51 WaveRider plane prematurely when a lapse in airflow to the jet engine caused a shutdown.

LA Times and smh.com.au

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