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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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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.
 

Speedboat100

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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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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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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.
 

PagoBay

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Nov 16, 2013
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US Territory of Guam
Good summary here ..
This YouTube video, unless I wasn't paying enough attention, is really just a well presented repeat of the factory's claims that, like another project getting lots of "rapt" attention on HBA, do not seem attainable in the present configuration.

Peter Garrison's article in FLYING magazine is better. Garrison offers a critical but well measured review of the performance claims.

 

pictsidhe

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This YouTube video, unless I wasn't paying enough attention, is really just a well presented repeat of the factory's claims that, like another project getting lots of "rapt" attention on HBA, do not seem attainable in the present configuration.

Peter Garrison's article in FLYING magazine is better. Garrison offers a critical but well measured review of the performance claims.

Could somebody summarise it for us cheapskates with no subscription?
 

Voidhawk9

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Peter doesn't think the claims are possible either, but even if it falls short, it still looks like it has potential lower performance levels.
 

BBerson

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Garrison guessed 7000 pounds, (twice Raptors 3300-3500).
It would be interesting to see what his performance-calculation program would spit out for Raptor.
 
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