In December a classified meeting will be held for the US department of defense's dual-mode engine programme Vulcan at which the supersonic powerplant's configuration will be presented to senior military officials.

Vulcan is a Defense Advanced Research Projects Agency (DARPA) project and will demonstrate an engine that could accelerate a vehicle from rest to over Mach 4. This acceleration from the subsonic to supersonic is why Vulcan is called dual-mode. The engine would be the basis for a vehicle, missile or otherwise.

The Vulcan's configuration will be selected from a number of different options, some of which were presented at the American Institute of Aeronautics and Astronautics' 45th Joint Propulsion Conference held in Denver, Colorado. What is decided is that the engine will use a turbojet and a constant volume combustion engine (CVC) in combination. Examples of CVC are Continuous Detonation Engines (CDE) and Pulse Detonation Engines (PDE). The basic operation for a CDE or PDE is a propellant injected into a tube, open at one end and the fuel is ignited. The detonation wave travelling down the tube generates the thrust. DARPA has also stated that it wants to see a shared inlet for the CVC and turbojet.

DARPA Vulcan programme manager Thomas Bussing speaking at the AIAA conference described two possible configurations, the CVC and jet side by side and the jet surrounded by the CVC. He also explained that above M4 the turbojet would have to be "cocooned" from the airflow but studies so far suggested that that "is quite reasonable".

Vulcan has four phases, with the next, second, phase from fiscal year 2010 to FY2011. This could see a CVC concept demonstration and then in early FY2011 there will be engine simulations, component demonstrations, further design studies and a preliminary design review for Vulcan. Phase three is from FY2011 to FY2013 and with the fourth phase, from FY2013 to FY2014, a CVC system will be combined with a gas turbine.

Source: Flight International