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ScanmanDan

What if? Break the speed of sound with a prop aircraft.

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If the prop tips going supersonic is the problem why not join them together in a circle so there is no tip?

 

Why has n't anyone designed a prop that is a thin disc at it's outside edge? There could be blades within the circle but the tips would be encompassed within a constant circle which could spin at any speed without any disturbance.

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If the prop tips going supersonic is the problem why not join them together in a circle so there is no tip?

 

Why has n't anyone designed a prop that is a thin disc at it's outside edge? There could be blades within the circle but the tips would be encompassed within a constant circle which could spin at any speed without any disturbance.

 

The tip of the prop (the junction with the ring) could still be turning at supersonic speeds, losing efficiency ... and creating tremendous acoustic and shock-wave stress on the ring. But, then you are closer and closer to a jet engine fan anyway. Saber like blades (à la A-400 M or E2- F(?) Hawkeye) allow, like swept wings on aircraft, to delay compressibility issues on blade-tips at near the speed of sound. When it becomes supersonic, the shock-wave creates havoc with whatever thrust the propeller is developing. Same problem with helicopters, which is the limiting factor why helos cannot go beyond a certain speed - that and the fact that the retreating rotor-blade loses lift as its relative speed drops to zero ... too bad for Blue Thunder !

 

Hubert

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Okay if the speed of sound is off the table for physical reasons.

 

And I have my figures right Rare Bear at 528 mph is only something like 0.7 - 0.75 Mach.  The Big Bad Russian Bear clocks in at 0.8ish which doesn't count for my purposes due to not being pure IC.  There would seem to be a little wiggle room to improve the game.  What would it take.  I continue to wonder as speed records are a funny thing.  I grew up with land speed record attempts being a big deal.  Both with geared IC engines and then rocket and jet cars.  I like them for the pure engineering exercises they are.  I just wonder what manner of beast would be needed to push the Rare Bear record.

 

Dan 

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There is a 1/33 scale paper model available here : http://www.ecardmodels.com/index.php/1-33-tu-95-bear.html

 

USD 15 to download, and then the GNP of Guatemala in paper costs to print it !

 

Hubert.

 

:rofl:

 

Hubert, you're hilarious!

 

It is a personal challenge that I have always wanted to tackle, but I have never found the right diameter of tubing to inspire me enough to start the project - imagine the foiling possiblities (probably need to buy  share in Alclad first though? :shrug:). 

 

Cheers

 

Derek

Edited by Derek B

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Great topic and thread.

So having read all of the posts I assume that propelled

Aircrafts have never attained speed of sound...super sonic level.

 

If aerodynamics of the turbo propeller jet were to be diversified

then could that speed of sound be broken.

 

And out of total curiosity what speed constitutes breaking

THAT barrier ;and would it have to be the same as a non propelled

Aircraft to be in the hall of fame?

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Thanks! Don't ever tell my boss, but I can't believe I get paid a salary to make this sort of thing!! Mind you, the following week we might be making model doggy treats, or a working post-surgical wound draining pump.....

 

Tim

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Thanks! Don't ever tell my boss, but I can't believe I get paid a salary to make this sort of thing!! Mind you, the following week we might be making model doggy treats, or a working post-surgical wound draining pump..... Tim

.....Tim,

As long as you keep us in the loop your secret is safe with ME...... :wicked:

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If the prop is the real problem on piston Aircraft, why in't it a problem on jets who also have fan blades? A jet roar are these blades exceeding the sound barrier.

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Hey Fred Jack. Jet engines actually run in subsonic airflow even if the aircraft is flying supersonic. The airflow is slowed by the intake to a speed most favorable for the engine that why you see all kinds of ramps and shock comes on fighters. Jet engines can still add thrust because they are heat engines cold in hot out and unlike a pure prop don't rely on pushing air for thrust.

 

I have been looking into props more and it seems that NACA had supersonic props working in 49-50. They just aren't way efficient and jets were. So the way is still clear for a succinctly crazy rich man.

 

Dan

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