Can you post the full article or at least the full page of this figure? How is it concluded that it is for J-20? Did the paper say so?
BTW, there is apparently an error, the recoil is no greater than 4500kg from a cannon of only 110kg.
J-20 5th Gen Fighter Thread VIII
- Thread starter Blitzo
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BTW, there is apparently an error, the recoil is no greater than 4500kg from a cannon of only 110kg.
Wow I did more reading about it and it seems everyone talks about DSI from the F-16 pov. Thanks for mentioning this.
Physically speaking there’s no reason you couldn’t design a DSI geometry that can remove (actually diffuse) a boundary layer at speeds higher than Mach 2. The bump or the boundary layer it removes also itself isn’t really the determinant of the “speed limit”. The actual physical limit is pressure recovery. If the air pressure at the inlet mouth is too low you’re not recovering enough air to feed the engine’s compression cycle, which can lead to the engine stalling. There is a “boundary layer” of laminar flow that builds up on the surface of the plane going into the inlet which gets thicker at higher speeds that can then exacerbate pressure recovery, either by disrupting the flow of air to the engines entirely or creating intermittent surged and stalled flow issues. But there are a multitude of other factors that can deal with pressure recovery and ingested boundary layer problems, including the rest of surrounding geometry around the inlet, the tunnel geometry of the inlet downstream of the inlet mouth, and the engine itself and how well it deals with intermittent flow and lower pressure recovery conditions (rule of thumb is more powerful compressor=can sustain thrust at lower pressure recovery and tougher flow conditions). The pressure recovery itself at transonic and supersonic speeds won’t only be affected by the boundary layer since there are other shocked and turbulent flow conditions around the inlet that will need to be dealt with.
The key thing to understand here is that the relationship between boundary layer and pressure recovery and “speed limit” is not universal for all inlets and all bumps and all planes and all engines. It’s a complicated composite of variables which include the plane’s own drag profile at higher speeds, how much thrust loss you see with your engine for each reduction in pressure recovery, and when the pressure recovery becomes low enough that the engine can no longer sustain the level of thrust needed to push past drag at a certain speed.
And yes, the whole Mach 2.0 speed limit thing came from the F-16’s own initial DSI test, but as I laid out that “speed limit” is only applicable to the F-16’s specific aerodynamic shape with the specific engine it was flying with and the specific geometry of its bump and inlet tunnel.
You can not think of any gun system independent of its weight, volume and recoil requirements. An aircraft like the J-20 has very little use for its gun. If they want capability against ground targets, which I presume was the primary reason as it was for the F-35, they would need a gun that can handle high RPM sustainably and 150-250 rounds. 30 mm is absolutely out of the question in this context. Would be way too heavy. 20 mm on the other hand is likely too weak against ground things.
Looks like J-20 targeted J-7 uav variant with gun.
I thought J-20 does not include a gun, does that mean that they are including a gun now? But Guns are usually the lowest technology in a plane. So, the fact that they are doing a gun test now could mean that they in the beginning Gun was not part of the J-20 design, but later they decided they needed the gun and then started development of the gun.
This badge was shown some time ago in an exhibition as one of many similar tests conducted by the test troop. The test must have been done much earlier. So the idea of having a gun is probably part of J-20 from the very beginning. The work is done, but actually mounting it on J-20 is another question.
BTW, I think people pay too much attention on this kind of things like badges, drawings, CGIs or social media posts which don't really tell much about whether or when.
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not targeting the aircraft (if it is a J-7) itself but the target pulled by the aircraft. See the red circle below. The aircraft may be piloted. This isn't strange, PLAN does that too when testing main guns according to a CCTV documentary. Any test pilot who could accidentally hit the pulling aircraft is too bad to be a pilot in the first place.
