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Invisibleblink
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ScramJet? How about PulseJet?!
    #3376390 - 11/17/04 10:26 PM (12 years, 21 days ago)

Scramjets are just begining to make the news, but have you heard about what's been causing vapour trails above california lately?

Check out PulseJet :grin:
While they are limited in that they have to be used in conjunction with a conventional turbine engine to attain 40k feet and .7mach, these guys can hold their own once they've been activated.  Imagine sitting down in a jet in New York and arriving in New Zealand in 2 hours :shocked:
Link

PULSEJET
EXOTIC PROPULSION DESIGN

Pulsejets use the forward speed of the engine and the inlet shape to compress the incoming air, then shutters at the inlet close while fuel is ignited in the combustion chamber and the pressure of the expanding gasses force the jet forward. The shutters then open and the process starts again at a high frequency. This results in the buzzing drone for which the experimental pulsejet missile is named the "BuzzBomb". People have pointed out that pulsejets can be cooled which would solve the heating problem of the ramjets. They could also, theoretically, generate "donut-on-a-rope" contrails due to the engine's operational design.

The known advantages of the Pulsejet engine are:

    * Theoretically it has a higher fuel efficency than a normal engine that keeps constant pressure.
    * Engines can be produced in many sizes with many different thrust ouputs ranging from a few pounds to thousands of pounds.
    * They have a very high thrust-to-weight ratio, which means a lighter engine producing more pounds of thrust than it's weight.
    * They are mechanically very simple and have very little moving parts.
    * They do not depend on the oxygen in the atmosphere to provide as an oxidizer, which means it could go in or out of the atmosphere


and some more info for those interested in what comes after scramjets in the succession of technology soon to be commercialized...

http://www.pulse-jets.com/
http://www.geocities.com/erjabe007/

The world is going to be a little bit smaller in 15 years.


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InvisibletrendalM
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Re: ScramJet? How about PulseJet?! [Re: blink]
    #3378289 - 11/18/04 09:57 AM (12 years, 20 days ago)

They do not depend on the oxygen in the atmosphere to provide as an oxidizer, which means it could go in or out of the atmosphere

If they don't use oxygen from incomming air...what is the point of having shutters on the front of the engine to let air in?


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Invisibledaussaulit
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Re: ScramJet? How about PulseJet?! [Re: blink]
    #3378687 - 11/18/04 11:32 AM (12 years, 20 days ago)

its going to be a while before supersonic flight is going to be affordable and practical. The concorde didn't do well. Also it is limited by where those planes can go. They're not allowed fly over populated areas due to the sonic booms.


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OfflineSeussA
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Re: ScramJet? How about PulseJet?! [Re: daussaulit]
    #3379023 - 11/18/04 12:49 PM (12 years, 20 days ago)

> due to the sonic booms.

There is research being done on shaping the pressure waves created by super sonic flight so that the noise is directed upwards and outwards rather than the traditional cone shaped waves.


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Re: ScramJet? How about PulseJet?! [Re: trendal]
    #3379735 - 11/18/04 03:52 PM (12 years, 20 days ago)

Quote:

trendal said:
They do not depend on the oxygen in the atmosphere to provide as an oxidizer, which means it could go in or out of the atmosphere

If they don't use oxygen from incoming air...what is the point of having shutters on the front of the engine to let air in?





To start the pulsejet you use compressed air to blow across the fuel venturi which atomizes the fuel. The mixture then travels past the valves into the tailpipe. You use a sparkplug and an autocoil to create as spark. This ignites the fuel charge which burns very quickly and it self sustains the cycle. Once it is running you can remove the forced air and turn off the sparkplug.

my understanding is that for combustion to take place, you need oxygen.
I've written the author of the document and await his reply on the statement you took issue with.
I'll post the reply, but I anticipate that the error is theirs.

As soon as I get a reply, I'll let you know.
As for the feasibility of using it commercially, the reason the concorde sucked was that it was old school technology, fuel efficient and was just to expensive to keep in the air. The simplified engine design, lack of moving parts (even with an augmenter tube) and decreased fuel usage is a huge deal. As Seuss said, they are researching how to shape and direct the sonic boom away from the ground, so hopefully they make the same amount of progress on that front as on the engines.


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InvisibletrendalM
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Re: ScramJet? How about PulseJet?! [Re: blink]
    #3379996 - 11/18/04 04:55 PM (12 years, 20 days ago)

I'll post the reply, but I anticipate that the error is theirs.

That's what I was thinking. It's like someone telling me you can run a jet engine in outer space :smirk:


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Re: ScramJet? How about PulseJet?! [Re: blink]
    #3384378 - 11/19/04 03:03 PM (12 years, 19 days ago)

Alright, just so everybody knows what the responce was:

The explanation is that it operates in a normal sense while in the atmosphere, and if it was to leave the atmosphere, the craft would have to bring it's own oxidant (tetrazine?sp) with it to operate as a rocket engine. I assume the inlet would be closed for this to work as the shutters wouldn't be rotating (no air passing through) and that would permit thrust to come out both ends.


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InvisibletrendalM
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Re: ScramJet? How about PulseJet?! [Re: blink]
    #3384804 - 11/19/04 04:41 PM (12 years, 19 days ago)

In that case, I HIGHLY doubt this device would be any more efficient than the liquid-fuel rocket engines we already have...which is essentially what a pulsejet would become if you left the shutters closed and just burned the fuel in the combustion chamber.

I also suspect the thrust ratio would be lower than our best liquid fueld engines and CERTAINLY nowhere close to a solid propellant engine.


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You're here because you know something.
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You've felt it your entire life.
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You don't know what it is, but it's there....
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Re: ScramJet? How about PulseJet?! [Re: trendal]
    #3385961 - 11/19/04 08:53 PM (12 years, 19 days ago)

Quote:

trendal said:
In that case, I HIGHLY doubt this device would be any more efficient than the liquid-fuel rocket engines we already have...which is essentially what a pulsejet would become if you left the shutters closed and just burned the fuel in the combustion chamber.

I also suspect the thrust ratio would be lower than our best liquid fueld engines and CERTAINLY nowhere close to a solid propellant engine.




I don't think that the pulse jet is for outer atmosphere use by design, I think that's what it would take to back up that claim.  When in the atmosphere, it's still a much cheaper way to fly (assuming you find a way to reduce wear and tear damage so the engine will function for more than 30 minutes before failure Valveless).

Solid rocket propellant has no off switch and is  a last resort.  I sure as hell wouldn't want to be strapped into a plane with a solid booster  :blush:

The technology is proven but far from perfect.


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Edited by blinkidiot (11/19/04 09:11 PM)


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InvisibletrendalM
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Re: ScramJet? How about PulseJet?! [Re: blink]
    #3386847 - 11/20/04 12:32 AM (12 years, 19 days ago)

Oh no, I'm not saying it isn't an excellent technology, though obviously still needs development. Solid rocket fuel should/will never be used for passenger flight inside the atmosphere, it's just too dangerous and TOO damn powerful.


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You're here because you know something.
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That there's something wrong with the world.
You don't know what it is, but it's there....
Like a splinter in your mind...
Driving you mad.


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