posted on Jan, 14 2007 @ 01:11 PM
I too get tired of those on this board who simply state "it is a PDE/scramjet/magic-carpet engine" with little to back them up, aside from a handful
of pictures of some contrails blowing in the breeze. However, in this case it is not totally out of the realm of possibility. The Air Force Research
Lab Propulsion Directorate (AFRL/PR) is HQ'd at WPAFB in Dayton, and they have been at the forefront of U.S. based PDE/PDC research from the
beginning. The AFRL/PR also contracts out with some local technology firms, most notably ISSI (www.innssi.com...
), which just happens to
be located in Beavercreek, OH (Dayton suburb mentioned in article). I am unaware of any planned flights of their little 'PDE-dragster' as they
call it, but I haven't been there for a year now and could easily have missed any announcements.
I highly doubt it's anything top-secret, since it was carried out during the day over a heavily populated area, instead of at night over a
lake-bed out west. In any event, PDE's are by no means top-secret. There has been an enormous amount of white-world research done on them. Most of
it is focused on replacing conventional constant-pressure combustors with pulse-detonation based pressure rise combustors. The idea being that a
constant-volume process (PD-based) is inherently more efficient than a constant-pressure process (conventional). One of the primary concerns has been
high-amplitude unsteady loads on a disk spinning at many thousands of rpm's in an environment well in excess of 2000F.
One mistake people tend to make when looking at these contrails is they immediately say the 'donuts' are too tightly or loosely spaced. Most
PDE experiments being conducted these days are multitube experiments (those outside of the basic combustion phenomenon research done within the lab).
Certainly any setup proving enough thrust (even a fraction of 'enough' thrust) would be a multi-tube setup. So if you don't know what tube setup
was flying, trying to back-calculate the firing frequency is pointless. Sometimes they fire simultaneously and sometimes in sequence. The research
community has not come to a consensus on what setup (if either) is best for whatever application.
All this being said, I too doubt it was a flying PDE test, simply on the fact that (to my knowledge) PDE's have not proven themselves all that
reliable of a propulsion system, and as a result I would think any flight test would be conducted in the safe confines of Edwards AFB, not over a
metro-area of a quarter-million people. Sadly, I do not have a counter-offer of what the apparent 'donuts' might be. The easy answer is 'some
sort of aerodynamic phenomenon', but that's not really an answer at all, without being more specific. I'll have to defer to someone else's fluid
mechanics knowledge on that.