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Celera 500L (was: More Vaporware)

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bmcj

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I wasn’t comparing Celera to Pathfinder. I was only saying that props are still capable above 60,000 feet.
 

jet guy

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Aug 15, 2020
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I wasn’t comparing Celera to Pathfinder. I was only saying that props are still capable above 60,000 feet.
Yes, but they need to be quite big, just like the wing needs to be big. I'm not saying a prop can't get you that high, but how fast you get there is another matter entirely.
 

pictsidhe

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The limit for props is not going supersonic. Up high, the plane has less drag, which compensates for less thrust from a given size prop. Difficulties in flying high are getting enough air through an engine. That is doable with multiple turbos. Another 'issue' is wing loading. But, you'll find that a suitably big wing for over mach 0.5 high altitude flight, gives a pretty sane landing speed. Induced drag is harder to defeat. That needs a higher than GA aspect ratio.
One of my back burner projects is a very long range cruiser. Flying really high turned out to make it feasible at a decent speed. Claiming the opposite shows that you haven't looked into it deeply enough. The numbers do work way up there, but it needs to be done a bit differently than at 'sane' altitudes.
 

jet guy

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Claiming the opposite shows that you haven't looked into it deeply enough.
Excuse me sir, but you seem like a kind of combative fellow who really doesn't know much to be honest.

I welcome substantive debate on any technical points that I may write here, and if you have any such points to make I will appreciate hearing them. Thank you.
 

Speedboat100

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Nov 8, 2018
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Europe
Are you making that statement for all propeller driven aircraft, or just the Celera? Though unmanned, Paul Macready’s Aerovironment had the Solar Pathfinder Plus that could fly over 80,000 feet and made three hour flights that sustained over 70,000 feet, all with propellers.
Didn't Helios go beyond 120 000 ft ?
 

Tiger Tim

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Apr 26, 2013
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Thunder Bay
When you look at the promised specs of the Celera like altitude, range and cost but then not even showing concept drawings with passenger windows, do you think that saying it’s an efficient take on private transportation is just away to get around the scrutiny and limitations of designing a military UAV? Kind of like how Germany was very busy developing high speed mail planes in the 1930s...
 

trimtab

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Apr 30, 2014
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106
Location
rocky mountains, rocky, usa
Prop L/D drops markedly at sonic and supersonic speeds of course.....but they still work. The TU-95 props are ultra thin section in the outer half of the diameter (look at you tubes). The engines suck down fuel like a sailor, but are still more efficient than the jet options available to them at the time.

The Celera doesn't seem like it has the power margin to overcome the DRθ.
 

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