SYDNEY, Australia (Reuters) -- The Australian test flight of a hypersonic "scramjet" engine which researchers believe will one day allow people to fly at 8,000 km (5,000 miles) per hour or more has been set back several months.

Originally due for its maiden launch in the Australian outback on August 13, the prototype engine -- built by the University of Queensland's Center for Hypersonics -- will now be fired off into the upper atmosphere on October 23, a university spokesman said.

"They say (the problem is) paperwork, but I don't know what that means," the spokesman told Reuters on Thursday.

The launch of the Australian "HyShot" engine -- developed at a cost of just A$1.0 million (US$510,000) -- has been eagerly awaited following the failed test last month of NASA's unmanned X-43A prototype, part of the U.S. space agency's US$185 million project to build a scramjet.

Researchers expect they will first be commercially applied to satellite launches because unlike conventional rockets, they do not need to carry their own oxygen supply and would therefore have more space for payload.

Eventually, scramjets may revolutionize air travel, allowing passenger aircraft to fly to London from Sydney in just two hours and making inflight movies obsolete.

Currently the fastest jet is the SR-71 Blackbird, which flies at Mach 3, or three times the speed of sound.

The Australian "HyShot" experiment will be staged at the Woomera rocket range, deep in the red centre of the continent.

Unlike the failed NASA prototype, "HyShot" is not a winged aircraft but an engine that will be launched on a booster rocket and when it falls back to earth it is expected to ignite at between 35 km to 23 km (22 miles to 14 miles) above the earth.

Developers are aiming for a speed of Mach 7.6.

NASA has launched an investigation into why its prototype veered out of control, forcing controllers to destroy it on its maiden flight.