poormansairforce
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Deleted: it was an experiment in humor and nobody got it.
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Celera 500L (was: More Vaporware)
- Thread starter Bill-Higdon
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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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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
Well-Known Member
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.
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.
Some military aircraft are using props at high altitude.
en.wikipedia.org
Tupolev Tu-95 - Wikipedia
en.wikipedia.org
Speedboat100
Well-Known Member
Didn't Helios go beyond 120 000 ft ?
Tiger Tim
Well-Known Member
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
Well-Known Member
No. Never ascribe to conspiracy what simple history regarding investor traps built by wide eyed true believers.
Music Man v3.0.
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That's trouble, with a capital T
And that rhymes with B
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Long live the great Robert Preston
Not only that, but the prop tips go s/sonic as well.Some military aircraft are using props at high altitude.
Tupolev Tu-95 - Wikipedia
trimtab
Well-Known Member
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.
The Celera doesn't seem like it has the power margin to overcome the DRθ.
Peter Garrison reviews the Celera 500 optimistic claims this month in FLYING.
trimtab
Well-Known Member
It's a good summary using yet another approach to arrive at similar results.
Good summary here ..
PagoBay
Well-Known Member
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
Well-Known Member
Could somebody summarise it for us cheapskates with no subscription?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.
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.
Looks like the entire article is available free (3 free). Scroll down further, I guess.
Garrison guessed 7000 pounds, (twice Raptors 3300-3500).
It would be interesting to see what his performance-calculation program would spit out for Raptor.
It would be interesting to see what his performance-calculation program would spit out for Raptor.
