Re: Pulse detonation engine (ramblings of a mad scientist)

Message posted by lone wolf on August 15, 2003 at 22:12:02 PST:

There have been many photos of donuts on a rope contrails, allegedly made by pulse detonation engines. Using 22Hz as the lowest repetition rate mentioned in the article and an air speed of 200 MPH (probably what these planes do at low altitudes), that would put the pulse spacing about 12ft apart. That is close enough to lend some credence (sp) to the donut theory, though you can't make any hard conclusions based on such flimsy evidence.

The 22Hz to 40Hz range is audible, though few really appreciate the depth of 22Hz. [To make a long story short, the hum you hear in cheap audio gear is 120Hz, so imagine tones at 1/6th that frequency.] In any event, a plane using such an engine could be detected if it is singing in the 22hz to 40Hz range. Low frequency noise is not very directional (to people, not instruments), so even if you hear something growling at 22Hz, pinpointing the location would be pretty tough. Building instrumentation to track such a sound source is doable, which leads to something interesting. If you recall about a year ago, there was a proposal to put a wind power farm on the NTS. The DOD nixed the idea because the rotating windmills would upset their equipment. Now for those who have visited wind power farms (Tehachapi or the Altamont Pass in Calfornia), these wind mills put out lots of low frequency audio. If the DOD was doing experiments with pulse detonation engines over the Groom range and the DOD was doing their own audio tracking tests, they would not want the windmills contributing their own tunes.

I've occasionaly heard low frequency noise at night while camped out in the desert, but the possible sources for low frequency noise are plentiful. [Generators, trucks, prop airplanes, etc.]

Attached link: wind farm cancelled

In Reply to: Pulse detonation engine posted by Gary Emry on August 15, 2003 at 9:10:13 PST:


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