SamuraiBlue
Captain
Lower the altitude the thicker the air resulting to more drag.
Aerodynamics thread
- Thread starter siegecrossbow
- Start date
Quickie
Colonel
That's why I said depending on the drag curve. If the effect in lowering the altitude is such that the increase in drag is greater than the increase in engine thrust, then the aircraft may choose to go at a higher altitude (of course to a limit) that enable it to super-cruise at a higher mach number.
Heh!, Heh!,, thanks for tuning in to the "Disney Channel", and for what its worth? I'd like to see the same crew do a detailed analysis on Mary Poppins and that danged umbrella! hell she probably super cruises at Mach 1.8 as well??
I can't agree here; according to pilot reports as well as the information in the documentary, the J-20 is faster than you think. The J-20 apparently has enough power to reach Mach 1 without reheat, and according to the CCTV claim, the J-20 can reach 1500 km/h without reheat.
This is a Sears-Haack body, the shape that minimizes supersonic drag. Compare it to the F-22, F-35, F-2, whatever. As you can see, aircraft are not purely optimized Sears-Haack bodies. As a Japanese, you might be familiar with the Suzuki Hayabusa motorcycle, which achieves its high speeds entirely due to drag reduction. It's capable of around 420 km/h without the limiter on, and has a power to weight of .52.
The BMW S1000R, by comparison, reaches 338.2722 km/h with a power to weight of about .6.
So drag matters, it gets a lot more out of an inferior engine.
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About the performance claims, some claims come from pilots who've flown the J-20 simulators, not pilots running with the current deployed model. On the other hand, the CCTV claim seems to describe pilots actually flying the aircraft.
One other possibility is that the J-20 is not actually running stock AL-31Fs. We assume the J-20's engines are overclocked anyways, to around 140 kN, so perhaps the J-20 has better high altitude engine thrust than predicted? It only needs about 45 kN per engine to break Mach 1.
One other possibility is that the J-20 is not actually running stock AL-31Fs. We assume the J-20's engines are overclocked anyways, to around 140 kN, so perhaps the J-20 has better high altitude engine thrust than predicted? It only needs about 45 kN per engine to break Mach 1.
Actually a few early Hayabusa's did in fact break 200 MPH, NOT 260 MPH,,, LOL,,,, yes it is faster than than BMW, but the Haybusa has 1300 CC's as opposed to the BMW's 1000 CC's, hence the Busa has a lot more torque... and torque pushes you up to 200 MPH on a Busa, though it does have lots of horsepower as well.
by the way, after the Hayabusa's 200 MPH magazine tests, the Europeans slapped a speed limit on all big sport bikes, the US said make that 2 of us, and they are all electronically limited to 186 MPH,, some people may be playing with the timing and fueling to blow through that limit???
Now Kawasaki did come out with the 1400 CC, which makes more horsepower and torque than a Busa, but it still will Not break 200 MPH..
So yes the Busa is aerodynamically cleaner, tested and tweaked in a wind tunnel...
the J-20 however, is NO Busa, with the canards and ventral fins, it is making more lift than the competition, but it is also creating more drag.
so will it break Mach 1 in dry thrust?? maybe so?? in fact I would say the J-20 is solidly in F-35 country when it comes to speed and maneuverability,, it is very good, as is the F-35 in spite of the whiney windbags who tell us otherwise!
AFB: Fineness ratio. The J-20 is 1.62 vs the 1.4 of the F-22 and 1.44 of the Su-57.
As far as the F-35 goes, it has good ITR, but its STR is roughly in the range of the F-16, which as I've stated before, is 4th gen and obsolete. I would still rate the J-20 as better than the F-35 when it comes to maneuverability, STR given its lower wing loading, ITR given its lack of canards and vectored thrust. I'm still sort of surprised that the F-35 doesn't have aTVC option in the works, not because the F-35 should come with it, but just in case it needs it.
As far as the F-35 goes, it has good ITR, but its STR is roughly in the range of the F-16, which as I've stated before, is 4th gen and obsolete. I would still rate the J-20 as better than the F-35 when it comes to maneuverability, STR given its lower wing loading, ITR given its lack of canards and vectored thrust. I'm still sort of surprised that the F-35 doesn't have aTVC option in the works, not because the F-35 should come with it, but just in case it needs it.
You put those canards out there in front of that big fat wing, make lots of vortex lift, and then tell us its NOT draggy?? and those lower ventral fins are traveling in very high pressure dirty air, the more and bigger feathers you place on the back of an arrow, the more stability, but drag is what creates that stability.
and really, back to Fineness ratio, in spite of all that it takes thrust, and lots of it to push that big airplane past that massive drag build up at Mach 1.
So, you were only 60 MPH faster than real life on your Busa story, and you compared it to the admittedly more powerful, but smaller BMW 1000, when you should have used the Kawasaki 1400, which was created by Kawi, to blow past the Busa, but didn't, making your point!
I mean I have no reason to doubt that the J-20 will supercruise? and to be honest, there are in fact several 4 Gen fighters that are capable of supercruise, my only real problem is making claims for crazy numbers? even with the WS-15, while we're all rather certain it will supercruise with that bruiser? we really ought to keep our expectations realistic?
I'll let this discussion supercruise right on past now, I'm just happy to see the aerodynamics thread getting a little play, thanks to Deino....
It is more appropriate to look at canards vs tail fins, instead of only vortices produced by canards.
Canards generate lift and as such, reduce load on the wings and also drag. Down force on tail fins, increases load on the wings and also drag. It is unclear which configuration is more draggy, until actual calculations are performed on specific configurations.
So there is no particular reason, that canard-delta such as J-20, must be more draggy than tail-delta, such as F-22, or vice versa.
And higher fineness ratios exchange greater skin drag with less wave drag and hence, more optimized for supersonic speeds. The higher fineness ratio of J-20 has an advantage here.
Canards generate lift and as such, reduce load on the wings and also drag. Down force on tail fins, increases load on the wings and also drag. It is unclear which configuration is more draggy, until actual calculations are performed on specific configurations.
So there is no particular reason, that canard-delta such as J-20, must be more draggy than tail-delta, such as F-22, or vice versa.
And higher fineness ratios exchange greater skin drag with less wave drag and hence, more optimized for supersonic speeds. The higher fineness ratio of J-20 has an advantage here.