November 16, 2004. Copyright 2004. Graphic News. All rights reserved.

WorldÕs fastest plane makes final test flight

LONDON, November 16, Graphic News:  NASAÕs third and final test flight of its futuristic $230m X-43A aircraft, travelling at speeds of almost 3.5 kilometres per second (over two miles per second), aims to confirm its position as the worldÕs fastest plane. 
NASA said it hopes the X-43A will reach a speed of nearly 12,190km/h (7,600mph), or Mach 10, during its flight. The 3.6 metre (12-foot) plane will fire its engine for 10 seconds, then coast for a few minutes before crashing into the Pacific Ocean.
The first flight of the experimental unmanned jet, in June 2001, ended in an explosion when the Pegasus booster rocket spiralled out of control after its fins came off, but the second flight, in March 2004, was a success when it flew at Mach 6.83 (8,150km/h / 5,060mph), becoming the first air-breathing aircraft to go hypersonic, or faster than Mach 5. Mach 1 is the speed of sound, which varies by temperature and pressure and is about 1,194km/h (742mph) at sea level. 
Unlike the more familiar turbojet engine -- which uses a turbine-powered fan to compress the incoming air before it is mixed with fuel -- the supersonic-combustion ramjet, or ÒscramjetÓ, 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 1,640 metres per second (5,400 feet 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 12,200 metres (40,000 feet) before releasing it. An Orbital Sciences Pegasus booster rocket will ignite to boost the X-43A to an altitude of about 30,500 metres (100,000 feet) and its test speed of around Mach 5. The X-43A will then separate from the Pegasus, accelerate to Mach 10, and fly westwards over the ocean for about 27 kilometres (17 miles) before ditching into the ocean.
Despite the success of the X-43A, the future of U.S. hypersonics research appears bleak. Following President BushÕs announcement in January that America would revive manned missions to the Moon and attempt an expedition to Mars, plans to develop a larger hypersonic vehicle -- the X-43C -- were scrapped and funding for the project has been channelled into conventional rocket development. 
/ENDS

Sources: NASA, Orbital Sciences, Reuters, Associated Press