Aerojet has completed tests of a prototype of the dual-combustion ramjet engine under development for Boeing's HyFly long-range strike missile demonstrator. Windtunnel tests of the heavyweight freejet engine were conducted at speeds ranging from Mach 3.5 to 6.5.
Boeing Phantom Works was awarded a $92 million contract by the US Defense Advanced Research Projects Agency and Office of Naval Research last year to develop and flight test a hypersonic missile demonstrator able to cruise at M6, with a 1,100km (600nm) range and the ability to dispense a submunition payload over a stationary target.
Aerojet says a modified version of the heavyweight engine will be tested in November. In parallel, the company is developing the flight-weight engine for use in the HyFly tests. Boeing will fly 11 air vehicles, the last eight to be powered by the hydrocarbon-fuelled ramjet. Separation tests are scheduled for later this year, using an unpowered, controlled vehicle. Ramjet-powered M4 flights are planned for late 2004, with M6 flights planned for 2005.
The propulsion system has two sets of inlets, one for a ramjet and one for a supersonic-combustion ramjet (scramjet). Because it is difficult to burn liquid hydrocarbon fuel in supersonic flow, the ramjet acts as a gas generator for the scramjet. Kerosene is partially burned in the ramjet, which supplies a heated fuel-rich mixture to the scramjet, making it easier to start and sustain supersonic combustion.
A rocket motor will boost the missile from air or surface launch to M3.5, when the ramjet will take over and accelerate the missile to M6.5. Aerojet says windtunnel tests have demonstrated the engine's performance over the planned HyFly flight envelope.
Source: Flight International