April 25, 2001. Copyright 2001. Graphic News. All rights reserved.

WorldÕs fastest plane will ÒscramÓ

LONDON, April 25, Graphic News: The Wright brothers made aeronautical history by flying the worldÕs first heavier-than-air plane 118 feet (36 metres) in 12 seconds in 1903. Now NASA plans to fly its futuristic X-43A aircraft at speeds up to two miles (3.2 kilometres) a second to become the worldÕs fastest plane.

The first unpiloted X-43A will make its maiden flight in on May 19, flying under its own power for just 10 seconds before crashing into the Pacific Ocean.

Unlike the more familiar turbojet engine -- which uses a turbine-powered fan to compress the incoming air before it is mixed with fuel -- the X-43A uses ÒscramjetÓ technology. The scramjet (supersonic-combustion ramjet) compresses air using the forward speed of the aircraft itself. Air is forced at hypersonic speed down an ever-narrowing funnel before the fuel is ignited. The scramjet has no rotating parts but the air must be travelling at more than 5,400 feet per second (1,640 metres per second) before the fuel, in this case hydrogen, can be burnt.

To make sure the airflow reaches this hypersonic speed, the X-43A will be given a boost. A NASA B-52B converted bomber will take off from Edwards Air Force Base in California and haul the X-43A to about 24,000 feet (7,315 metres) before releasing it. An Orbital Sciences Pegasus booster rocket will ignite to accelerate the X-43A to its test speed of around Mach 5 and an altitude of about 100,000 feet (30,480 metres). The X-43A will then separate from the Pegasus and fly west over the ocean for 10 seconds -- slightly shorter than the Wright brothersÕ historic flight -- and travel about 17 miles (27 kilometres) before ditching into the ocean.

NASA said the plane would be designed to fly at up to Mach 10 -- more than three times faster than a speeding bullet and 10 times the speed of sound. Mach 1 is the speed of sound, which varies by temperature and pressure and is about 742 mph (1,194 km/h) at sea level.

Two other X-43As will fly after the initial test at six-month intervals. If successful, the 12-foot-long (3.6-metre-long), surfboard-shaped planes will smash the speed record of Mach 6.7, set by a rocket-powered X-15 in October 1967. Currently, the worldÕs fastest air-breathing aircraft, the SR-71 ÒBlackbird,Ó cruises slightly faster than Mach 3. The X-43A would be the first air-breathing plane to go hypersonic, or faster than Mach 5.

The X-43A, or Hyper-X, will probably never carry commercial passengers because of the high acceleration, heat generated by friction with the atmosphere and the difficulty of turning a plane at such high speeds.

The U.S. government has pursued the idea of routine hypersonic flight for four decades, including an abortive $2.4 billion effort begun under President Reagan to build a ÒNational Aero-Space PlaneÓ capable of zipping halfway around the globe in a few hours.

ÒThe concept is pretty simple, itÕs just that no one can seem to make it work,Ó said Howard McCurdy, a professor of public affairs at Washington D.C.Õs American University.

The $185 million project is purely experimental. Engineers will collect flight data needed to build future planes perhaps 200 feet (60 metres) in length. The first piloted prototypes may fly by 2025.
/ENDS
Sources: NASA, Orbital Sciences, Reuters, Associated Press