XPost: rec.arts.sf.science   
   From: g_d_pusch_remove_underscores@xnet.com   
      
   Bruce Simpson  writes:   
      
   > On Sat, 6 Dec 2003 03:38:17 GMT, henry@spsystems.net (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   
      
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