#61
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Pulse Jets
What's the difference between a pulsejet and a PDE? A pulsejet is just the
old V-1 Buzzbomb engine; a pipe with a kerosene burner and a one way flapper on the front. Simplicity itself. Which is why it's still interesting while inefficient. short-lived flappers are the hangup. The PDE is a potential thing of beauty; a rocket engine which uses discrete supersonic explosions rather than continuous combustion whith subsonic exhaust. ^ //^\\ ~~~ near space elevator ~~~~ ~~~members.aol.com/beanstalkr/~~~ |
#62
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Pulse Jets
Bruce Simpson writes:
On Sat, 6 Dec 2003 03:38:17 GMT, (Henry Spencer) wrote: They're no longer used for a couple of reasons. They are not actually very good jet engines, compared to more sophisticated designs (which can be made in quite small sizes at relatively low cost, if you try hard). And the noise and vibration are tremendous -- the Germans looked into pulsejet fighters but the idea never went anywhere, partly because it was very difficult to provide a livable environment for the pilot. Indeed. My most recent engine (200lbs-thrust) has been measured at 145dB and no amount of hearing protection can stop the pressure waves from rattling your skull -- thereby rattling the bones of the inner ear. However, if you think pulsejets are bad news -- wait until you've experienced being within close proximity of a PDE. I did build a simple yet intermittently capable pulsed detonation chamber using acetylene and oxygen as fuel. It was very small, just 50mm diameter and 2.5 metres long. However, the shock waves that it generated felt like someone beating on your skull with a ball peen hammer. By comparison,a pulsejet, even a very large one, is more like someone beating you rapidly about the head and body with a pillow. This is one of the many reasons I find the claims that the alleged "Aurora" spyplane is powered by a PDE to be rather implausible: Unless the thing is an unmanned drone, the pilot is going to be in _very_ bad shape after the flight is over, and his middle and inner ears and vestibular system are highly unlikely to ever function again. I can't imagine that many pilots would volunteer (or even accept orders!) to fly a plane that would result in them losing their hearing, sense of balance, and flight-certification for the rest of their lives after a single flight !!! There is no way that a PDE will ever be used on a manned craft that doesn't have excellent acoustic insulation. between the occupants and the engine when travelling at sub-sonic velocities. It's also an engine that will most definitely not be used anywhere near a populated area. If the bitched about the Concorde and its single shockwave, imagine what they'd say about a reasonably sized PDE spitting out anywhere from 60-300 shockwaves a second! That's another reason why I don't believe in the alleged PDE-powered "Aurora:" Spy-planes are supposed to be _stealthy_ --- not announce themselves, LOUDLY ! -- Gordon D. Pusch perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;' |
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