Su-57 News and Discussion -version_we_lost_count!-

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https://forum.keypublishing.com/attachment.php?attachmentid=261761&d=1532801194&thumb=1

In this picture we can see one of the reasons why designers did not choose s-duct, it would sacrifice the big weapons bay.

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In this picture we can see one of the reasons why designers did not choose s-duct, it would sacrifice the big weapons bay.

New to this forum ...

Assuming you forgot that there is a third dimension, which is not visible in this diagram...

One would would assume the Russians are not so naive in engineering, remember my university lecturer in Australia who was Russian and very impressed with his ability...

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New to this forum ...

Assuming you forgot that there is a third dimension, which is not visible in this diagram...

One would would assume the Russians are not so naive in engineering, remember my university lecturer in Australia who was Russian and very impressed with his ability


Hi, KGB

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New to this forum ...

Assuming you forgot that there is a third dimension, which is not visible in this diagram...

One would would assume the Russians are not so naive in engineering, remember my university lecturer in Australia who was Russian and very impressed with his ability...

I do not know if it is new or not. But you know there is some russian patent about the use of blockers on entrance of intakes before the engine. It must to go just in front of the elephant.

https://forum.keypublishing.com/attachment.php?attachmentid=261418&d=1531229929&thumb=1

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Have we any news on the current state/status of the PAKFA program?

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Just a question. Using a linear drag equation (as opposed to detailed non-linear, i.e, Cd drops as speed increases), the Su-57 seems to be able to hit a max speed of around Mach 2.7 or 2.8.

Is this the real secret of the Su-57? I.e, it's "stealthy", in terms of being LO, but it's willing to sacrifice stealth for speed?

We know with the F-22, it's supposed to be able to reach Mach 2.45, presumably at altitude, but it avoids hitting high speeds due to damage to composites and stealth coatings. With the J-20, we recently received a report that it's capable of a Mach 2.9 max speed. With regard to the Su-57, the report of Mach 2.1 supercruise implies that it should be able to hit Mach 2.76 (as a minimum).

Is that the actual secret of the Su-57; it's less a replacement for the Su-27, and more a replacement for the MiG-31?

That's to say, let's say the Su-57 is engaging F-35s. Since the F-35 is relatively slow and unagile, it has a relatively low NEZ factor. The Su-57, once the F-35 has been detected, scoots rapidly at the F-35, reaching its maximum speed of Mach 2.7, then loosing R-74 IR missiles at the F-35, hopefully from outside its targeting, but not detection range. It then zoom climbs, attempting to shed off as much speed as possible, then dives to resume its maximum speed, outrunning retaliating AIM-120s.

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@Inst:

where to start with the questions?

1) Do you have the Cd of the PAK-FA?
2) When you state max speed for that plane, what engine and thrust are you considering?
3) Where does this report about the J-20 doing Mach 2.9 come from? It has DSI intakes in the end, how are they supposed to operate at that speed?
4) Who says the PAK-FA can supercruise at 2.1 M?

Apart from the questions regarding the remarkable data you are submitting, advantage in speed is indeed an important issue that I suspect Russians have not put aside. Therefore the intakes equipped with adjustable ramps despite being heavier and more complex, for instance. I think also their oversized capture area have to do with a max speed probably above 2.5 M that would make it a very capable interceptor, even when MiG-31 is superior in that regard from what we know. Of course a F-35 would be in a dire situation when confronted with such a plane, not being capable of engaging and disengaging due to inferior kinematics and ceiling and having a relatively low A2A payload of MRAAM with only Mach 4 speed. In comparison, Su-57 would count on up to 4 x LRAAM with modern and powerful seekers and Mach 6 capable. Unless their VLO is magic, all aspect and wide band to incredible levels they will be toasted.

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Of course a F-35 would be in a dire situation when confronted with such a plane, not being capable of engaging and disengaging due to inferior kinematics and ceiling and having a relatively low A2A payload of MRAAM with only Mach 4 speed. In comparison, Su-57 would count on up to 4 x LRAAM with modern and powerful seekers and Mach 6 capable.

IMHO, RVV-BD is faster but Meteor can sustain high speed all the way, JNAAM based on Meteor airframe but with an AESA seeker
http://www.airrecognition.com/index.php/archive-world-worldwide-news-air-force-aviation-aerospace-air-military-defence-industry/global-defense-security-news/global-news-2017/august/3704-japan-plans-to-invest-66mn-in-jnaam-missile-development-project.html

Just a question. Using a linear drag equation (as opposed to detailed non-linear, i.e, Cd drops as speed increases), the Su-57 seems to be able to hit a max speed of around Mach 2.7 or 2.8.

Is this the real secret of the Su-57? I.e, it's "stealthy", in terms of being LO, but it's willing to sacrifice stealth for speed?

We know with the F-22, it's supposed to be able to reach Mach 2.45, presumably at altitude, but it avoids hitting high speeds due to damage to composites and stealth coatings. With the J-20, we recently received a report that it's capable of a Mach 2.9 max speed. With regard to the Su-57, the report of Mach 2.1 supercruise implies that it should be able to hit Mach 2.76 (as a minimum).

Is that the actual secret of the Su-57; it's less a replacement for the Su-27, and more a replacement for the MiG-31?

That's to say, let's say the Su-57 is engaging F-35s. Since the F-35 is relatively slow and unagile, it has a relatively low NEZ factor. The Su-57, once the F-35 has been detected, scoots rapidly at the F-35, reaching its maximum speed of Mach 2.7, then loosing R-74 IR missiles at the F-35, hopefully from outside its targeting, but not detection range. It then zoom climbs, attempting to shed off as much speed as possible, then dives to resume its maximum speed, outrunning retaliating AIM-120s.


The alleged leak of J-20 top speed was confirmed to be a mistake https://forums.spacebattles.com/threads/chengdu-j-20-top-speed-leaked.667711/
Moreover, the distance when stealth aircraft can detect each other 30-45 km , they won't have enough time to accelerate to stop speed.

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1: no, I don't have the Cd of the Su-57, and when it comes to complex aircraft Cd is insufficient, you need to know what the Cd is at various speeds.
2: one thing I've noticed is that drag matters more than engine; Cd affects drag linearly, while thrust needs to increase by the square to increase effective speed.
3: As moon_light shows, it's possibly a mistake, but there's evidence for the J-20 being that fast. The VTech paper on the J-20 shows that the J-20 is a low drag aircraft and that it'd be able to sustain Mach 2 via supercruise, and extending the graph, somewhere between Mach 2.8 and Mach 2.9 on full afterburner.
4: http://theduran.com/russias-su-57-fifth-generation-fighter-entering-production-next-year/

@Moon_light: I'm really not sure about whether the J-20's top speed is a mistake. Remember, the J-20 has a higher fineness ratio than the F-22 (1.62 vs 1.4), and it has a higher angle of wing sweep.

About the combat uses of high speed; the trick is that stealth fighters aren't going to be detecting each other at 30-45km. In actuality, AEW&C and ground-tracking counter-stealth radars will be giving detection, but not weapons-quality tracks, far in advance of 30-45km.

These get passed onto stealth fighter IRST and EODAS, which are better at tracking than detection (IRST have a very small field of view).

The goal of using high speed is to throw missiles with greater starting kinematics; instead of having the missile need to accelerate to its maximum speed, it can use its fuel to sustain speed for longer. This extends the missile's range and improves its terminal kinematics.

If we assume, say, a Su-57 moving at 20k meters and Mach 2.8, and launching a R-74M2 at a F-35 moving at Mach .9 at 10 km altitude, the R-74M2 will go further than any AIM-9X BLK2s. The F-35 can try to target the Su-57 with AIM-120s, outranging it, but the AIM-120 needs tracking data from the F-35 because even against a less-stealthy opponent, the X-band radar on the AIM-120 is not going to be able to achieve a lock except at very close ranges.

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Now we have:
J-20 with a Vmax of Mach 2.9...with AL-31F engines (or WS-10B). Or throw in the WS-15 that isn’t ready yet. Sure Mach 2.9.
And a Su-57 with a supercruise speed of Mach 2.1...

Glad to see this thread is firmly rooted in reality as usual. Just a dead thread without TR-1 or Berkut.

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Think drag, not thrust. Even in the Su-57's case, it has a slightly higher fineness ratio than the F-22, as well as a higher wing sweep than the F-22. The F-22 is generally believed to have a Mach 1.8 supercruise, but it's also rumored that it's achieved Mach 2 supercruise. Remember, the Concorde was supercruise capable with only a .4 T/W ratio. The MiG-25, likewise, was a 20k ton empty-weight fighter that could achieve Mach 3 with engines producing only 100 kN of thrust each.

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I'm really not sure about whether the J-20's top speed is a mistake. Remember, the J-20 has a higher fineness ratio than the F-22 (1.62 vs 1.4), and it has a higher angle of wing sweep.

Mirage IV have higher fineness ratio and higher wing sweep than Mig-25, doesn't mean it is faster. A fixed inlet are not meant to provide good pressure recovery at very high speed like > Mach2.


About the combat uses of high speed; the trick is that stealth fighters aren't going to be detecting each other at 30-45km. In actuality, AEW&C and ground-tracking counter-stealth radars will be giving detection, but not weapons-quality tracks, far in advance of 30-45km.
If we assume, say, a Su-57 moving at 20k meters and Mach 2.8, and launching a R-74M2 at a F-35 moving at Mach .9 at 10 km altitude, the R-74M2 will go further than any AIM-9X BLK2s

Your assumption doesn't make any sense, since when can Su-57 fly at Mach 2.8?. Why only Su-57 accelerate to high speed and high altitude while F-35 is still at its cruising speed and altitude?. Fly fast (especially Mach 2.8 fast) make you very easy to detect by Infrared sensor and radar.
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Inst- think reality. The F-22’s supercruise speed isn’t secret... and it isn’t Mach 2.

Fineness ratio and wing sweep do not determine Vmax: inlets, materials, and engine design does. I can assure you that neither the J-20 or Su-57 will operate much above Mach 2.

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The MiG-25, likewise, was a 20k ton empty-weight fighter that could achieve Mach 3 with engines producing only 100 kN of thrust each

Engine thrust isn't a fixed value, it changes with speed and altitude, mig-25 has very high V-max because it's engine and inlet provide high thrust even at high speed and altitude. Similarly the Bell X-1A with straight wingcan reach Mach 2.44 because rocket engine doesn't lose thrust with speed.
https://www.thoughtco.com/thmb/ONfCjkcVpJCgq6N4z8KyYYxzhvw=/768x0/filters:no_upscale():max_bytes(150000):strip_icc()/bell-x-1-large-56a61c545f9b58b7d0dff7a2.jpg

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Actually, the F-22 has an official supercruise speed of Mach 1.5. It has a reported supercruise speed of Mach 1.7. It has an estimated supercruise speed of Mach 1.83. It has a rumored supercruise speed of Mach 2.

And as to whether fineness ratio / wing sweep determining VMax, it's a complex of all these things. How much drag is imposed on the aircraft? How much engine power is being outputted at a given speed and altitude? What is the ability of the airframe to withstand aerodynamic heating, and at what altitude?

Two things need to be factored in. First, the J-20 does not have a pure DSI intake; it has bleed valves on the side of its inlets, so that it does have control over engine bleed at high speed.

Second, aerodynamic heating actually lessens at high altitudes as air pressure drops by 75% from 10k meters to 20k meters. The problem with supersonic inlets is that turbulent boundary layer air starts to choke the engine above a certain speed. But how do reduced pressures factor into DSI choke? Does it become easier to manage high-speed turbulence as altitude increases?

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Actually, no. The F-22 has a demostrated supercruise of Mach 1.72 official from SAR reports. Any “rumors” are just that rumors. As for the rest:

Boundary layer air bleed systems are present in the F-22, F-35, and Su-57. They have zero to do with Vmax (other than regulating airflow), an inlet optimized for Mach 1.8 won’t reach Mach 2.9 no matter how many BLC vents. DSI have been tested to roughly Mach 2, where recovery falls off. The rest I am just not going to spend the time to discuss. Primarily because no LO aircraft based on current materials is going to have a top speed much above Mach 2. Period. And none of the engines or inlets of the above mentioned would be capable of speeds like Mach 2.9.

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I'll also point out that the F-22 has fixed, not variable inlets, meaning that DSI is not necessarily a barrier to performance, and the F-22's designer reported that the F-22 is capable of Mach 2.42+.

The Su-57, in contrast, has variable inlets, which probably compromise its stealth more than the F-22's fixed and the J-20's DSI, but suggest greater high-speed engine power.

This is, of course, a standing hypothesis, but it seems to fit the data well. The F-22, J-20, and Su-57 are designed as high-speed stealth fighters. In the J-20 and Su-57's case, the need for speed has compromised their stealthiness to an extent (and for that matter, if you're going to repeatedly superheat your aircraft, the stealth coatings are almost a waste of time). The F-35, in contrast, is going in a different direction, where it wants to stay subsonic, and thus IR stealthy, and exploit excellent sensors, both radar and IR.

Mach 3 isn't such a big challenge, ultimately. The technical specifications on the F-15 show that Boeing has an air superiority aircraft, albeit of the fourth generation, that can achieve Mach 3 speeds.

And as I've explained, there are real tactical advantages to having a very-fast stealth fighter, namely in the ability to plonk IR missiles or interceptor missiles further.

I think that's the entire point of Sino-Russian reduced stealth in LO or VLO. The point isn't to completely evade detection, or to end up being stealthy enough to get into a dogfight where you die to HOBS-missiles anyways, but the point is to be stealthy enough to defeat the smaller radar seekers on medium-range air-to-air missiles. Your opponent may see you, he (and it's usually a he) may even be able to track you, but he won't be able to hit you.

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Primarily because no LO aircraft based on current materials is going to have a top speed much above Mach 2.

https://forum.keypublishing.com/showthread.php?95072-What-is-to-believe-in-Super-Hornet-propaganda&p=1479095#post1479095

"Above 1,600 mph" or Mach 2.43 / 2.44.

As I've said before, LO aircraft based on current materials don't want to go above Mach 2 because it wrecks their stealth coating. But the funny thing is? The Su-57 and J-20 aren't as stealthy as US aircraft, so that losing the stealth coating isn't that big a deal compared to wrecking it on the F-22.

And in an emergency case, where the choice is whether to hit Vmax to get past a missile, or to hit the ejector button, both the pilot and airforce are better off if the stealth coating and engines are ruined, with the airframe surviving for repair and overhaul, than if the pilot hits the button and hopes the opposing pilots don't decide to open up with guns.

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Super Inst. now look up issues with F-22 inlet coatings. We are not talking an aerodynamic limit for the F-22 et. al. It is a materials limit. If you want to believe the Su-57 or J-20 can reach speeds above Mach 2-2.3 go ahead. And yes, theoretically the F-22 can reach roughly similar speeds 2.3-2.4. Operationally, it has been limited to speeds just above Mach 2.

And the J-20 reaching anywhere much above Mach 2 is fantasy. Simply put neither the inlet or current engine has that capability. And no one piece canopy or RAM could survive that thermal environment.

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First, a small correction. The J-20 does not have a one-piece canopy, the prototypes featured such a canopy, but the production version has a two-piece canopy.

Second, I think we have a huge misunderstanding here. Your point is that stealth coatings can't survive past Mach 2. I absolutely agree on that.

But my point is that I think the Chinese or Russians DON'T CARE if their stealth coatings survive. The J-20 and Su-57 aren't pure stealth aircraft; you've seen all the videos of people complaining about poor edge alignment on the Su-57, or the canards on the J-20. They're all stealth-compromised.

What I'm suggesting is that while US stealth fighters may be operationally limited to 2.05 Mach or 2.1 Mach, Chinese and Russian stealth fighters will not have the same operational limits because stealth is less important to them. At the discretion of the wing commander, they will employ tactics that will burn off the stealth coating on their aircraft and ruin their stealth properties. If the aircraft gets back home to base in repairable status, it will need a substantial rehaul to reapply the stealth coating. But the Chinese and Russians don't care.

Let me put up an analogous example.

The Dutch and Chinese pirates under Koxinga were fighting over Taiwan. Koxinga managed to capture a Dutch man-o-war, a ship superior to any Chinese ship under his command. The Dutch vessels in the area made an attempt to recapture it, only to discover that Koxinga had repurposed it as a fire ship, and used it to destroy the other major Dutch warship in the area, leaving Koxinga with naval superiority.

The Dutch were utterly flabbergasted at Koxinga's decision. The man-o-war was expensive, powerful, and thus valuable. Koxinga sacrificing it was unthinkable. But think about it from Koxinga's point of view. He just captured a ship that was light-years ahead of his military capabilities. He didn't have the trained technicians needed to run the ship, or to maintain the cannons, and so on. In his hands, it was less valuable than it was in Dutch hands, and using it as a fire ship was the best move.

The Dutch really did not expect Koxinga to wreck his man-o-war like that, and that was the only way the fire ship managed to destroy its target. The Dutch expected Koxinga to think the same way they did, to employ the same operational doctrines they did, and so they did not expect the fire ship tactic and lost their Taiwan fleet.

So that's what I mean by Mach 2.8 J-20s and Su-57s. The Chinese and Russians don't emphasize stealth as greatly as the United States and its allies do. For them, if the stealth is enough to ruin an AIM-120 lock at range, it's good enough for them. If it allows them to get the aircraft back to base in one piece, or to launch a hit-and-run attack on slower F-35s with kinematically-advantaged WVR missiles, it's good enough for them. Remember, the Russians traditionally viewed their airpower as a neutralizing factor to disrupt enemy air superiority; they're not a great air power. The Chinese tend to fight wars of deterrence or wars of attrition, and having their force come back in one piece is less important than achieving the desired political or strategic effects.