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  #21  
Old December 6th 03, 05:57 AM
Henry Spencer
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Default Pulse Jets

In article ,
MattWriter wrote:
I'm curious why the pulse-jet keeps cropping up in discussions of possible or
alleged advanced high-speed aircraft. Isn't the thing inefficient as heck?


Pulsejets and Pulse Detonation Engines are completely different devices,
despite the similarity in name and the vague similarity in operating
principle.

(One important difference is that pulsejets went from concept to flying
hardware very quickly, while PDEs have been The Engine Of The Future for
nearly half a century now.)
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #22  
Old December 6th 03, 11:46 AM
Conrad Hodson
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Default Pulse Jets

On Fri, 5 Dec 2003, pervect wrote:

A week or so ago I saw a rather neat Junkyard Wars episode on
pulse-jets. I'm also rather intrigued that it was felt to be a safe
enough gadget to build for the TV show.


Safe enough if you wear earplugs, and don't stand in line with it, but
that applies to other jet engines too.

It was an amazingly simple contraption, a jet with no moving parts.


Actually, most of them have moving parts in the intake end; reed valves or
spring-loaded flaps. Without those you wouldn't have much of an engine,
it'd just sit there and fart flame out both ends.
I
was wondering where I could find out more about the history of these
devices, and perhaps some information as to why they are apparently
outdated and no longer in use. I believe they were used in the V2
rockets in WWII (?).

No, V2 was a true rocket carrying its own liquid oxygen supply. You're
thinking of V1, the buzz-bomb, which was the world's first cruise missle.
Strictly a low-altitude airbreather, but cheap and rugged.

Pulse-jets are a ton of fun for amateurs, but never caught on for large
craft. They tend to shake their airframes brutally, and they go through a
lot of fuel compared to turbojets. Incidentally, if you ever check out a
British movie called Operation Crossbow, it features Sophia Loren as Hanna
Reitsch, test-flying a piloted prototype of the V1.

I don't have the URL's right now, but I did a search a few years ago that
turned up everything from blueprints to references to a model engine that
was sold back in the Fifties. Ear-shattering noise, and it turns red hot
if it's bench-fired without a slipstream to cool it, but it's got a hell
of a power-weight ratio and is very thought-provoking device if you want
to write an alternative history story. The Tredegar Iron Works could have
built the damn things, or even the more advanced shops of Napoleon's day.

Conrad Hodson
  #23  
Old December 6th 03, 11:46 AM
Conrad Hodson
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Default Pulse Jets

On Fri, 5 Dec 2003, pervect wrote:

A week or so ago I saw a rather neat Junkyard Wars episode on
pulse-jets. I'm also rather intrigued that it was felt to be a safe
enough gadget to build for the TV show.


Safe enough if you wear earplugs, and don't stand in line with it, but
that applies to other jet engines too.

It was an amazingly simple contraption, a jet with no moving parts.


Actually, most of them have moving parts in the intake end; reed valves or
spring-loaded flaps. Without those you wouldn't have much of an engine,
it'd just sit there and fart flame out both ends.
I
was wondering where I could find out more about the history of these
devices, and perhaps some information as to why they are apparently
outdated and no longer in use. I believe they were used in the V2
rockets in WWII (?).

No, V2 was a true rocket carrying its own liquid oxygen supply. You're
thinking of V1, the buzz-bomb, which was the world's first cruise missle.
Strictly a low-altitude airbreather, but cheap and rugged.

Pulse-jets are a ton of fun for amateurs, but never caught on for large
craft. They tend to shake their airframes brutally, and they go through a
lot of fuel compared to turbojets. Incidentally, if you ever check out a
British movie called Operation Crossbow, it features Sophia Loren as Hanna
Reitsch, test-flying a piloted prototype of the V1.

I don't have the URL's right now, but I did a search a few years ago that
turned up everything from blueprints to references to a model engine that
was sold back in the Fifties. Ear-shattering noise, and it turns red hot
if it's bench-fired without a slipstream to cool it, but it's got a hell
of a power-weight ratio and is very thought-provoking device if you want
to write an alternative history story. The Tredegar Iron Works could have
built the damn things, or even the more advanced shops of Napoleon's day.

Conrad Hodson
  #24  
Old December 6th 03, 07:47 PM
Bruce Simpson
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Default Pulse Jets

On Sat, 6 Dec 2003 02:46:55 -0800, Conrad Hodson
wrote:

It was an amazingly simple contraption, a jet with no moving parts.


Actually, most of them have moving parts in the intake end; reed valves or
spring-loaded flaps. Without those you wouldn't have much of an engine,
it'd just sit there and fart flame out both ends.


Which is why most valveless pulsejets ( the ones with no moving
parts) are designed to have the intake and exhaust tubes both facing
in the same direction -- towards the rear.

The one I used on Scrapheap/JunkyardWars was based on the engine that
Lockwood developed for Hiller in the 1960s. This in turn was based on
much earlier designs developed in Europe a few decades earlier. In
essence, Lockwood simply optimized the European designs for use as a
"lift" engine which produces maximum thrust at comparitively low
airspeeds.

--
you can contact me via http://aardvark.co.nz/contact/
  #25  
Old December 6th 03, 07:47 PM
Bruce Simpson
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Default Pulse Jets

On Sat, 6 Dec 2003 02:46:55 -0800, Conrad Hodson
wrote:

It was an amazingly simple contraption, a jet with no moving parts.


Actually, most of them have moving parts in the intake end; reed valves or
spring-loaded flaps. Without those you wouldn't have much of an engine,
it'd just sit there and fart flame out both ends.


Which is why most valveless pulsejets ( the ones with no moving
parts) are designed to have the intake and exhaust tubes both facing
in the same direction -- towards the rear.

The one I used on Scrapheap/JunkyardWars was based on the engine that
Lockwood developed for Hiller in the 1960s. This in turn was based on
much earlier designs developed in Europe a few decades earlier. In
essence, Lockwood simply optimized the European designs for use as a
"lift" engine which produces maximum thrust at comparitively low
airspeeds.

--
you can contact me via http://aardvark.co.nz/contact/
  #26  
Old December 6th 03, 10:59 PM
Jim Davis
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Default Pulse Jets

Conrad Hodson wrote:

Incidentally, if you ever check out a
British movie called Operation Crossbow, it features Sophia
Loren as Hanna Reitsch, test-flying a piloted prototype of the
V1.


Although Sophia Loren was in "Operation Crossbow", Hanna Reitsch was
played by Barbara Rueting.

Jim Davis
  #27  
Old December 6th 03, 10:59 PM
Jim Davis
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Posts: n/a
Default Pulse Jets

Conrad Hodson wrote:

Incidentally, if you ever check out a
British movie called Operation Crossbow, it features Sophia
Loren as Hanna Reitsch, test-flying a piloted prototype of the
V1.


Although Sophia Loren was in "Operation Crossbow", Hanna Reitsch was
played by Barbara Rueting.

Jim Davis
  #28  
Old December 7th 03, 04:54 AM
Allen Meece
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Default Pulse Jets

Are the pulse jet principles adaptable to pulse detonation rocket engines?
Can PDE's break the price/performance barrier of constant pressure rockets? I
sincerely hope so because we're up a blind alley as far as ever achieveing CATS
with the engines we've got.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~
  #29  
Old December 7th 03, 04:54 AM
Allen Meece
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Default Pulse Jets

Are the pulse jet principles adaptable to pulse detonation rocket engines?
Can PDE's break the price/performance barrier of constant pressure rockets? I
sincerely hope so because we're up a blind alley as far as ever achieveing CATS
with the engines we've got.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~
  #30  
Old December 7th 03, 09:53 PM
Oren Tirosh
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Default Pulse Jets

Bruce Simpson wrote in message . ..
...
If anyone has any specific questions then fire away and I'll do my
best to answer them.


Are you familiar with the work of Macrosonix? Would such nonlinear
resonance techniques be applicable to improving pulsejet compression
ratios?
 




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