March 25, 2004. Copyright 2004. Graphic News. All rights reserved.

WorldÕs fastest plane set to fly Saturday

LONDON, March 25, Graphic News:  NASA is making a second attempt to fly its futuristic X-43A aircraft at speeds of well over a mile per second (two kilometres per second) to become the worldÕs fastest plane. The first flight of the experimental unmanned jet in June 2001 ended in an explosion when the Pegasus booster rocket carrying it spiralled out of control after its fins came off.

NASA said it hopes to reach a speed of nearly 5,000mph (8,050km/h), or Mach 7, during its second X-43A flight, scheduled for Saturday. The 12-foot-long (3.6 metre) plane will fire its engine for 10 seconds, then coast for a few minutes before crashing into the Pacific Ocean.

If the high-risk flight is successful, it will mark the first time an exotic jet engine, called a supersonic-combustion ramjet or scramjet, has propelled a plane at so-called hypersonic speeds.

Unlike the more familiar turbojet engine -- which uses a turbine-powered fan to compress the incoming air before it is mixed with fuel -- the scramjet 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 boost 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, accelerate to Mach 7, and fly west over the ocean for 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.

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 $230 million project is purely experimental. The U.S. Department of Defence is developing a hypersonic bomber that theoretically could reach targets anywhere on Earth within two hours of takeoff from the continental United States. The first piloted prototypes may fly by 2025.

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.
/ENDS
Sources: NASA, Orbital Sciences, Reuters, Associated Press