If this unique contrail is being caused by the engine, and not some other means, then of course a pulse detonation engine is one highly possible
powerplant for this aircraft. There may also be technology that is out there which we know nothing about which is creating this. It could also be a
pulse jet as you stated, however the PDE is different in a few ways.
From what I read in the links you gave and what I've read in the past, the pulse detonation engine (PDE) would probably be the most likely candidate
for such a contrail. This is from the PDE link on wikipedia you provided..
The main difference between a PDE and a traditional pulsejet is that the mixture does not undergo subsonic combustion but instead, supersonic
detonation. In the PDE, the oxygen and fuel combination process is supersonic, effectively an explosion instead of burning. The other difference is
that the shutters are replaced by more sophisticated valves. In some PDE designs from General Electric, the shutters are even removed because the
process can be controlled by timing on the periodic sudden pressure drops that occur after each shock wave when the "combustion" products have been
ejected in one shot.
The following is from an external link provided on wikipedia..
The Current State Of Development
It seems that nobody yet has the PDE developed to the point of being a practical propulsion device (or at least if they have, they're not telling
From what I've been able to gather, the main focus is currently being placed on researching and improving the detonation process. The current
generation of PDEs don't seem capable of continuous running for any length of time -- they're more or less just single-shot devices requiring
several seconds to recharge between detonations.
(comparable to the timing within this video. It seems about right)
PDE is nothing new. It was patented, originally, in 1952.
(click the following link to download the original patent in adobe PDF format)
General Electric has also been trying to improve the design on their PDE for a long time. I found this idea on patents.com and thought it was
I suppose some people call the PDE a "pulse detonation wave engine", but IMO that is just a fancy name for the same exact concept. The detonation
of the air/fuel mixture creates a shockwave, however there is no reason to put the word "wave" into the name IMO because it is understood that the
detonation of the air/fuel mixture will force air away from the blast (creating propulsion) in the form of a supersonic shockwave. What really amazes
me is how the blast is not only contained but controlled.
The loads on the components must be ungodly..Not to mention a shutter system, which probably would be dependant on hydraulic force to open and close,
would be vulnerable to constant failure. The valve system seems more likely to me and more cost effective (as is in use by the General Electric PDE
according to reference material given on wikipedia.com).
The detonation of the fuel/air mixture would expand in all directions which means the design must be honed to deal with these loads. There are ways,
however, that these detonations could be designed to take place within a giant, valved system that is conically shaped in order to minimize the blast
wave from being pushed forward (which would ultimately result in inefficiency if not accounted for). Just an idea I had.. Who knows.
[edit on 9-2-2008 by BlasteR]