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

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