Space: December 3, 1999


: NASA has received the first of three X-43A unmanned aircraft designed to fly with Supersonic Combustion Ramjet (SCRAMJET) engines. These aircraft will be boosted into the atmosphere by a rocket until they are going fast enough to ignite their hydrogen fuel. The aircraft will be tested at Mach-7 in May 2000, working up to Mach-10 by Sept 2001. While the tests will, it is hoped, prove that Scramjet actually works, there are many technological hurdles before reaching an operational manned tactical or strategic aircraft. For one, the engineers must find a way to use hydrocarbons (e.g., jet fuel) to power it, as this does not require pressurized sub-zero-temperature tanks. This leads to the problem of building a hydrocarbon engine able to function at the speed of Scramjet. Another problem is that Scramjet won't work below Mach-6, so the aircraft would have to carry some other type of engine to handle the original take-off and then land the plane at the end of the mission. The Air Force has visions of Scramjet aircraft carrying satellites to the edge of space or bombing Iran from US bases in two hours.--Stephen V Cole