Jura The idiot
General
... at 9500 m elevation:
301.7*2.9*0.06 = 52.4958
(I took "301.7" m/s from where it corresponds to "9500" meters altitude)
Aerodynamics thread
- Thread starter siegecrossbow
- Start date
301.7*2.9*0.06 = 52.4958
(I took "301.7" m/s from where it corresponds to "9500" meters altitude)
SinoSoldier
Colonel
So are we assuming that this was achieved at 10+ km altitude? Did the CCTV report mention any altitude or perhaps if this was performed in any particular exercise (i.e. low-altitude penetration vs high-altitude interception, etc.)?
I don't know where it happened. It probably didn't even happen. Whatever happened, it definitely didnt happen at or near sea level.
What CCTV report are you talking about?
The very odd thing is, for all we know, the J-20 has no specialized inlets for high supersonic speeds. We have seen no evidence that the J-20 has the inlets needed to break Mach 2.
The other thing is, the J-20 is not going to attempt a shoot-and-scoot maneuver vs AEW&C because moving at high Mach means they'll be lit up on IR sensors. The only practical use of high Mach is in escape, which still implies something above 50 km as NEZ, unless the goal is to use terminal maneuvers at high speeds to evade an energy-drained missile.
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One other thing is, what's the drag estimation on the J-20? The closest thing I've seen to a drag estimation is via the VTech paper, which is of course a student-generated engineering paper. What it implies is that the J-20, even with WS-10B, should have the ability to reach Mach 1.8 supercruise due to its low drag. It just may take a while to get there, or it might require boost-supercruise by activating its afterburners to reach a speed that dry thrust can sustain.
The other thing is, the J-20 is not going to attempt a shoot-and-scoot maneuver vs AEW&C because moving at high Mach means they'll be lit up on IR sensors. The only practical use of high Mach is in escape, which still implies something above 50 km as NEZ, unless the goal is to use terminal maneuvers at high speeds to evade an energy-drained missile.
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One other thing is, what's the drag estimation on the J-20? The closest thing I've seen to a drag estimation is via the VTech paper, which is of course a student-generated engineering paper. What it implies is that the J-20, even with WS-10B, should have the ability to reach Mach 1.8 supercruise due to its low drag. It just may take a while to get there, or it might require boost-supercruise by activating its afterburners to reach a speed that dry thrust can sustain.
The 10 km altitude is assumed from the optimum supercruise altitude for the F-22. At low altitude, air pressure is so great that you can't sustain high speeds. At higher altitudes, air pressure is so low that the engines begin choking. If the J-20 is similar to the F-22, we can assume the 10 km figure applies. Besides, most jet fighters seem to show a 10 km cruise altitude anyways.
and here it seems we are all back to reality, at sea level, NOBODY is ever going to but running at Mach 2.5, NOBODY on this planet anyway, not even in the "Alien Bird" or the SR-71, or whatever,,, Jobjed is absolutely correct here!!
so in reality we can make an educated guess that the stated speed was flown at about 10,000 meters,, that's where people find the max speed hiding in most aircraft, the SR-71 likely a little higher, LOL
and, there is NO WAY the J-20 is Maching out at nearly 3 times the speed of sound, just not happening on this planet, 2.9 is bogus, and to be honest with the present engines Mach 2.5 is highly suspect, LOL.
Quickie
Colonel
It could happen at lower or higher altitude than 9500m.
At 8500m, 305.9*2.83 *0.06 = 52 km/min at Mach 2.83.
At 11000, 295.2*2.94 *0.06 = 52 km/min at Mach 2.94.
It can go a way bit up, or down, where air resistance will increasingly post a problem.
Jura The idiot
General
gosh didn't you get Today at 7:42 PM I was checking what a debater claimed Today at 5:50 PM
and what I quoted in the specific way and which was "Mach 2.9" meaning M = 2.90
Quickie
Colonel
So, who made the claim it was Mach 2.9? To cover the distance at Mach 2.5 is an impossiblity because it would have to take place at ground level.
Air Force Brat: the VTech papers seem to imply that the J-20 needs about 311.8 kN of thrust to hit Mach 2.9. That's assuming its drag estimates are accurate The scaling figures they used were 20 meters for the body, with 13 meters wingspan, which are roughly accurate, but we now know the J-20 is roughly 12.88 meters in wingspan with 20.95 meters in length. This represents an increase in fineness ratio that could allow the J-20 to go faster due to reduced drag. For reference, the current estimated afterburner thrust of the J-20 is 280 kN.