During the recent birthday celebration in Mojave for the Rutan brothers, Burt Rutan gave a guided tour of the Scaled hangar and an up close view of the White Knight and SpaceShipOne. This was a very interesting experience, but there was also considerable interest in a "Mystery Long-EZ" sitting in a corner of the hangar. We were told not to take any photos, and there was no explanation of it's purpose. However, because of the incredible array of machinery attached to it, and the 4 very long tailpipes where the prop should be, it prompted a lot of speculation (most of it wrong) on its purpose.
At the Dayton air show (2003) a sister ship appeared (or maybe it was the same one?). Photo's were allowed and a representative sample is presented below. Viewing the display prompted Larry Anderson get some answers:
"The Air Force research laboratory is conducting research on PDE's, Pulse Detonation Engines. In these engines, the flame front is supersonic (detonation as opposed to deflagration). All the apparatus under the fuselage is to feed the proper amount of high pressure air and fuel to an automotive valve train and then into the four combustion chambers (the 4 tailpipes). Like other programs, they are using a Long-EZ airframe for the test bed. I talked to one of the engineers and he said it's quite loud. The eventual use for this system is for applications going between MACH 2 to 4! The flame front travels through the tube at about MACH 5, so you can imagine the noise level. I guess the one at Scaled will be the test bed. I can't wait to se a video of that test flight. The challenge will be to shrink the system down and lighten it up enough to get it all strapped to a flyable airframe"