DARPA orders hypersonic Nazi Doodlebug engine

'Continuous Explosion' fireball bomb/jet hybrid wanted

Rebellious Pentagon boffins, whose plans for a really cool hypersonic robot stunt plane were stymied by stick-in-the-mud Washington politicos, have managed to sneak through an alternative project. A $2m contract has been inked for initial development work on the "Vulcan" zero-to-Mach-4 hyper pulse-jet engine.

The Vulcan programme, regular readers will not be surprised to note, comes to us courtesy of DARPA - the Pentagon's intellectual game reserve where crazy applecart-bothering boffins can roam wild and hairy and free, pooping the rich fertiliser of federal greenbacks on bizarre tech-project seedlings.

Vulcan, according to a DARPA announcement last year, is to feature a normal turbine mode used to get an aircraft moving and up off the runway. Once the regular jet starts showing signs of strain, the Vulcan should start working as a Constant Volume Combustion (CVC) engine - either of "pulsed detonation" or "continuous detonation" type, using high-pressure air scooped from the front end of the fast-moving unit.

A pulse detonation design would see the interior of the Vulcan filled with an explosive fuel-air mix and this detonated - with the process rapidly repeated. In essence the engine would be setting off a devastating bunker-busting bomb inside itself, perhaps eighty times a second. This would be a much more advanced version of the "Argus" pulse jet which powered Hitler's V-1 flying bombs (aka "Doodlebugs") during World War II - some of the first cruise missiles.

The even madder continuous detonation concept would use crafty flow designs to feed fuel/air mix towards the point of explosion at the propagation speed of the detonating shockwave. The shockwave headed towards the front of the engine should then become stationary, and the explosion should keep on exploding - "continuously detonating" - out of the back of the engine as long as the fuel/air supply was sustained. In this case, the devastating bunker-busting bomb would turn into a sustained, constantly exploding fireball.

Either way, the inside of the engine would get much too hot even for jet turbine components to survive: hence DARPA specify that the turbine drive should be "cocooned" in order to preserve it.

It would seem that Alliant Techsystems (ATK), makers of mad jets and rockets to NASA and the US military, reckon they're up to the job of building Vulcan - and they've convinced DARPA they can do it. The Pentagon boffins have given ATK $2,913,613 "to perform Vulcan Program, Phase I".

This will be at least some consolation for hypersonic plane fanciers both at DARPA and elsewhere, saddened by last year's cancellation of the proposed "Blackswift" hyperplane. The Blackswift, seen by many as a successor to the extremely cool SR-71 Blackbird spyplane of cold-war fame, would have been capable of doing barrel rolls at Mach 6 from a standing runway start.

But just as Blackswift was a bit of a long shot, so too may Vulcan be. Many DARPA projects get to Phase I only to die quietly a few years further on. ®