Sukhoi Su-57 Meta Thread

originally posted by: zukli

originally posted by: Zaphod58
a reply to: zukli

And they get what they pay for. They still have big production issues on just about all their aircraft.

Correct. If I'm not mistaken, Russia spends more than 5% of GDP on defense. America only recently upped defense spending to 3% of GDP and that's because of Trump. Under Obama is was about 2% of GDP.

This is something that's often ignored in the "US spends too much on defense" debate. We spend more than any other country by far, but we also have the world's largest economy. The only sensible way to compare spending rates on anything between countries is as a percentage of GDP. When you look at it in those terms, US defense spending is perfectly reasonable. There are a number of countries that spend more than we do.

a reply to: RadioRobert

I would bet that they have the manpower and budget to reasonably design either a DSI OR an inlet that performs well under high-alpha conditions and all of the other unusual attitudes commonly seen in a supermaneuverable 5th gen fighter, but that they lack the budget/manpower/experience to build a DSI that still performs reliably under unusual/extreme maneuvering conditions.

Then again, it's arguable that the Chinese don't have that experience, either, as the J-20 looks like it's a long, long way away from being anything close to "supermaneuverable".

Hell, even we haven't really done it, as the F-35 is "only" as nimble as an F-18 and the more maneuverable YF-23 and F-22 both had/have old-school inlet diverters. I don't doubt that the US or one of our contractors has probably flown something supermaneuverable WITH a DSI at Groom or TTR, but we certainly haven't seen it in public and they certainly haven't approved something like it for production.

a reply to: Barnalby

It's all math, modeling, and trial/error.

The Chinese can't "just copy" a DSI inlet because every engine needs different things in terms of airmass, airflow, etc. Some engines are pretty tolerant and others have very particular and specific needs. Then, as you suggest, you start looking at airflow down the duct at various yaw and pitch rates, angle of attack, etc.

It's a nifty "device" and sort of ingenious. I'm not trying to thrash the idea of DSI inlets. But it's also has downsides: for example as mentioned, it is tailored to a specific mach speed. At higher and lower air flow speeds than the peak design speeds, you're throwing away efficiency compared to a traditional system of ramp and doors which can move the shockwave exactly where they want it. You need to pair that designed efficiency with the engineered efficiency of the engine itself. It's also very difficult to find a shape that will work well at transonic speed and at the higher end toward Mach 2. It gets most, but not all, of the boundary layer out of the way up and down. A diverter will often catch some, too, but not the same cross section of flow. It can help obstruct the compressor face leading to potentially a simpler duct. But there are various other methods of obstructing waves from the compressor face.

All these things are a game of compromises.

Mach limitations are sort of a big deal when you've tailored your airframe for supercruise toward that upper limit. Adverse airflow is sort of a big deal when you're tailoring your airframe for maneuverability with a true 3D TVC (not the pseudo 3D it has now) or your engine is not as forgiving (AL-31 is sort of famously tolerant -- not sure about the izdeliye 117 and -30).

The Su-57 is focused on high-performance in package that has a much reduced signature. Far more so than "reduced-signature" legacy platforms like the Rafale (which is not a knock on the Rafale). It won't be VLO, but it's not designed to be. There's also been entirely too much made of dumb details like panel gaps and alignment on the preproduction prototypes. Go check out the X-35 or YF-22 panel gaps and alignment. Even if they left it as is, those details only show at certain bands, though it may effect surface waves. Hint: the band types that aren't generally used for search-track...

There's very little in the way of "magic" in physics. There are very bright people in Russia and China working on the same problems. Given enough time and money, they can work out and do anything we can do.

There's also a giant philosophical gap with Russia where "Good enough is good enough; perfect is the enemy of good". If they can get a reduced-signature, high-performance, reliable, rugged warplane for a lot cheaper/faster production than an F-35 to go along with their other legacy Sukhois and IADS systems, they really probably aren't overly concerned that the -57 represents "2nd tier" ability to a relatively small OpFor of F-22's. It just becomes a matter of attrition. They also can't afford a massive fleet of bleeding edge aircraft across their frontiers. They need numbers. Having a large fleet of LO Su-57's is preferable to having a handful of VLO F-22's for them. It's "good enough" and the alternative isn't affordable.

Assuming the new engines pan out as advertised, they might well be better kinematically than the Raptor. Certainly better than the F-35 (which isn't a dog). And lower signature than any fighter outside them (excepting perhaps China's toys). That's nothing to sneeze at for a country with a GDP smaller than Italy's.

It is not enough to look at GDP and Military Expenditure.

We all know that R&D cost a lot of money.

In the US, a very large portion of both R&D and Production costs goes to Profit. There are many companies making these profits which is why it is so expensive.

China controls costs by largely owning the manufacturing base for its MIC.

Russia does this as well, but not to the same extent.

If you want to check out the rabbit hole here, just find out how much each country pays for a simple 50 Cal machine gum round. This will tel the story.

P

originally posted by: RadioRobert
a reply to: Barnalby

It's all math, modeling, and trial/error.

The Chinese can't "just copy" a DSI inlet because every engine needs different things in terms of airmass, airflow, etc. Some engines are pretty tolerant and others have very particular and specific needs. Then, as you suggest, you start looking at airflow down the duct at various yaw and pitch rates, angle of attack, etc.

It's a nifty "device" and sort of ingenious. I'm not trying to thrash the idea of DSI inlets. But it's also has downsides: for example as mentioned, it is tailored to a specific mach speed. At higher and lower air flow speeds than the peak design speeds, you're throwing away efficiency compared to a traditional system of ramp and doors which can move the shockwave exactly where they want it. You need to pair that designed efficiency with the engineered efficiency of the engine itself. It's also very difficult to find a shape that will work well at transonic speed and at the higher end toward Mach 2. It gets most, but not all, of the boundary layer out of the way up and down. A diverter will often catch some, too, but not the same cross section of flow. It can help obstruct the compressor face leading to potentially a simpler duct. But there are various other methods of obstructing waves from the compressor face.

All these things are a game of compromises.

Mach limitations are sort of a big deal when you've tailored your airframe for supercruise toward that upper limit. Adverse airflow is sort of a big deal when you're tailoring your airframe for maneuverability with a true 3D TVC (not the pseudo 3D it has now) or your engine is not as forgiving (AL-31 is sort of famously tolerant -- not sure about the izdeliye 117 and -30).

The Su-57 is focused on high-performance in package that has a much reduced signature. Far more so than "reduced-signature" legacy platforms like the Rafale (which is not a knock on the Rafale). It won't be VLO, but it's not designed to be. There's also been entirely too much made of dumb details like panel gaps and alignment on the preproduction prototypes. Go check out the X-35 or YF-22 panel gaps and alignment. Even if they left it as is, those details only show at certain bands, though it may effect surface waves. Hint: the band types that aren't generally used for search-track...

There's very little in the way of "magic" in physics. There are very bright people in Russia and China working on the same problems. Given enough time and money, they can work out and do anything we can do.

There's also a giant philosophical gap with Russia where "Good enough is good enough; perfect is the enemy of good". If they can get a reduced-signature, high-performance, reliable, rugged warplane for a lot cheaper/faster production than an F-35 to go along with their other legacy Sukhois and IADS systems, they really probably aren't overly concerned that the -57 represents "2nd tier" ability to a relatively small OpFor of F-22's. It just becomes a matter of attrition. They also can't afford a massive fleet of bleeding edge aircraft across their frontiers. They need numbers. Having a large fleet of LO Su-57's is preferable to having a handful of VLO F-22's for them. It's "good enough" and the alternative isn't affordable.

Assuming the new engines pan out as advertised, they might well be better kinematically than the Raptor. Certainly better than the F-35 (which isn't a dog). And lower signature than any fighter outside them (excepting perhaps China's toys). That's nothing to sneeze at for a country with a GDP smaller than Italy's.

Good point. There isn't going to be war between major countries. Russia don't even need Su-57. American never went to war with Russia even when America had nukes and Russia did not have nukes. What Russia needs is more Su-35, not Su-57.

a reply to: RadioRobert

My interest was in how DSIs keep good airflow characteristics at unusual speeds and angles, and I'd imagine that it's quite difficult for anyone, USA included, to engineer a DSI+S-duct intake that can both supercruise, work well at mach 2+, AND not stall or have other major flow separation issues under high-alpha flight and similar conditions expected of a supermaneuverable air dominance fighter.

The diverters and straight intake ducts of the Su-57 seems to indicate that at least the Russian engineers have found it difficult as well. It isn't the F-35's frankly fantastic intake design, but look at what the folks at Sukhoi accomplished compared, say, to the intake design on the Eurofighter Typhoon, an aircraft with a very similar combination of speed and maneuverability, and like you said, it's a damned impressive effort, especially once you consider the shoestring budget that the Russians have to play with.

Then again, comparing the Su-57 to the Typhoon is probably as cruel as comparing the AN-94 to the G-36 in terms of what the respective parties spent on development vs the actual quality and capabilities of what they got. Perfection truly is the enemy of the good enough.

a reply to: Barnalby

The point of DSI is replace traditional intake, S duct or not. Early JF-17 prototypes had traditional intake. Later JF-17 prototypes had DSI. Production JF-17 has DSI.

"Then again, comparing the Su-57 to the Typhoon is probably as cruel as comparing the AN-94 to the G-36 in terms of what the respective parties spent on development vs the actual quality and capabilities of what they got."

You don't need to pity the Russians. They got better guns like AN-94. AK-12 comes to mind.

a reply to: tinse

For the moment, that's what they've decided. They need an immediate recap, and the new engine isn't ready for prime time. Why spend the money producing less than fully capable airframes that will have to be at minimum reengined later when it is mature? Especially if you have an immediate need and can crank out Flanker derivatives on the cheap. Wait until you mature the systems and engines before opening actual production.

If the US could produce new F-15X's for a third or less the price of an F-35, that'd be the way to go here, too.

a reply to: RadioRobert

Super Hornet entered service with APG-73 mechanical radar. F-15E entered service with F-15C'S weaker engine. Most planes I would say enter service with earlier systems, only get later systems at a later stage. This is not surprising Su-57 enter service with Su-35's engines, only get more powerful engines in later batches.

a reply to: RadioRobert

The Russians also have a habit of rolling out incremental, but substantial upgrades to existing aircraft designs, such as the Mig-25 becoming the Mig-31, or all the canards, cockpits, and new engines that they've slapped onto the Su-27 airframe. I honestly can't wait to see what the "tranche 2" Su-57s will look like once they get the real engines (and whatever else the engineers decide to graft onto them).

a reply to: Barnalby

Same can be said of Americans and French. Hornet developed into Super Hornet. Mirage III developed into Mirage 2000. Hell, F-15X is being proposed as the future of America air force.

a reply to: rutman

You only replace with a DSI if the tradeoffs make sense. There's a reason Lockheed hasn't pumped out DSI F-16's despite having produced one, for example. Why haven't customers demanded DSI on new Falcons or refits to old fleets if it is the new one-size fits all solution? The answer is, it isn't.

Again, this isn't to say DSI inlets don't work, or don't have advantages in weight and production. But overall, a traditional system with doors and ramps will work better over a wider range of the flight envelope if you're willing to pay the penalties.

a reply to: RadioRobert

US air force don't buy F-16 anymore. The new planes like F-35 used by the US has DSI. China J-10B/C has DSI. There are many advantages of DSI over traditional intake.

originally posted by: rutman
a reply to: RadioRobert

US air force don't buy F-16 anymore. The new planes like F-35 used by the US has DSI. China J-10B/C has DSI. There are many advantages of DSI over traditional intake.

F-16 with DSI work started in the 90's. Flight testing finsihed in 96. The USAF took delivery of their last Viper in 2005. Literally hundreds of Vipers have been built since 96.

Noone has ordered a single DSI Viper despite the development work being done and paid for. Why not?

originally posted by: RadioRobert

originally posted by: rutman
a reply to: RadioRobert

US air force don't buy F-16 anymore. The new planes like F-35 used by the US has DSI. China J-10B/C has DSI. There are many advantages of DSI over traditional intake.

F-16 with DSI work started in the 90's. Flight testing finsihed in 96. The USAF took delivery of their last Viper in 2005. Literally hundreds of Vipers have been built since 96.

Noone has ordered a single DSI Viper despite the development work being done and paid for. Why not?

Because it wouldn't be advantageous given the F-16's role? Is that what you're getting at?

a reply to: face23785

It's just because it isn't a perfect solution to everything. A variable ramp isn't perfect either. It gets you better pressure recovery and less shock losses across the envelope, but at the cost of higher complexity, cost and weight.

It's like the decision of swing-wing or fixed wing. Some planes experience a lot of variation in airspeed in a typical mission profile. Variable-sweep let's you have an optimum angle of sweep across the entire envelope. Lower stall speeds are possible, higher dash speeds are possible, better efficiency is possible because you are tailoring the wing across the entire envelope. There's a cost to pay for that in weight, cost, and complexity. So not every plane is going to have variable -sweep.

Most mission requirements can be met without paying that price. But requirements needing longer ranges, higher speeds, high loads, etc may find swing wings give enable high-end performance through wing-loading and still have manageable low-speed handling and take-off characteristics.

The F-22 didn't get into production until 97. No effort was made to introduce a DSI inlet -- it was never proposed. Not because the technology didn't exist, but because at supersonic speeds, the variable -ramp lets you put the shockwave right where you want it lessening shock losses and increasing recovery. The F-22 spends a lot of its mission profile at supersonic speed (super cruise). It is already short-legged and needs as much efficiency as possible. It uses variable ramps to get it. Sukhoi probably made this choice for similar reasons.
DSI will continue to get used because most aircraft don't spend a lot of their mission-profile at extremely high speed. It definitely has its perks. It just isn't magic.

A single-gear bike does just fine for many purposes. Some riders are going to take rides that require th extra weight and complexity of gear assemblies that allow them to go uphill easier, allow a higher top speed, etc. In practice, the DSI is probably more akin to the difference between a 10-speed and a 21-speed with alpine gearing. Unless you're doing a lot of uphill and high-speed biking, the 10-speed is just fine for your purpose. If you can be "pretty good" across most if the spectrum you probably don't need to introduce the drawbacks of variable ramps. If you're spending a lot of time in the higher-end of the envelope or want to squeeze out efficiency across the board, you'll pay the price.

The primary benefits of a DSI are weight and cost savings.

Afaik it has marginal effect on performance. The F-16 DSI for example has only shown slightly better power at subsonic speeds.

It is probably more stealthy, requires less RAM I guess.