PLA 6th generation fighter thread
- Thread starter Blitzo
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I’m not so sure about manned fighters being turned into unmanned fighters. The latter probably needs a more extensive sensor suite and sensor integration into a computer architecture that allows for controls may not be a trivial or cheap implementation.
I agree that fighter generations are certainly not rigorous, and there are certainly exceptions and/or platforms or capabilities that sit outside of what would be commonly be understood as XYZ generation....
.... but that doesn't change the fact that fighter generations still exist, are in common use, and that trying to fit fighters into generations in a way that makes sense helps us simply and differentiate between the wide variety of fighter aircraft that have existed.
I do understand your consternation towards the malleable framework in which fighter generations are defined, and also the way in which generational descriptions emerged.
None of this changes the fact that fighter generations are still in use by military forces, companies, commentators, and the general public.
In other words, it is our job to try and look at fighter aircraft that are understood to be of XYZ generation, and to try and reverse engineer out the defining traits and capabilities of each generation.
No, because listed 6th generation traits I described are not 4th generation traits.
I both agree and disagree with this.
I agree that 6th generation aircraft will serve as decision nodes, whose capability will be greatly informed and dependent on networking and offboard capabilities (specifically via UCAVs and UAVs operating as sensor nodes, fires nodes, networking nodes, ECM nodes).
A 6th generation fighter will not be comprehensive without those offboard platforms.
However, I believe a 5th generation fighter with those same networking and offboard capabilities (e.g.: putting those 6th generation datalinks, AI/automation, and overall UAV/UCAV control into a 5th generation airframe either as an MLU/upgrade or as new production airframes), does not make the 5th generation fighter a 6th generation fighter.
Instead, it would best be considered that the 5th generation fighter is now "5.5th generation" instead.
Which is the point I was trying to raise in my last post -- i.e.: what are the physical airframe defining features of a fighter aircraft of any given generation?
Or, putting it another way -- for each generation of fighter aircraft, there are generation-defining characteristics, subsystems and technologies that can be practically drawn upon to upgrade or iterate fighter aircraft of a prior generation.
However, there are also generation-defining characteristics, subsystems and technologies that cannot be practically drawn upon to upgrade or iterate fighter aircraft of a prior generation.
I am asking -- for a 6th generation fighter, what are the generation-defining characteristics, subsystems and technologies, that cannot be practically drawn upon to upgrade or iterate fighter aircraft of a prior generation?
I was more comparing 6th generation fighters to F-22, J-20 and Su-57, that is to say they will emphasize maneuverability and likely be less maneuverable than the design priorities of air superiority oriented 5th generation fighters.
In all of those traits that I described, I took effort to write each time "compared to 5th generation aircraft".
I was not describing any of those traits (whether it is maneuverability, or stealth) in a vacuum.
The less control surfaces and the less planes of external surfaces the better.
Holding all else equal, an aircraft with less control surfaces and less planes of said surfaces is going to be more stealthy than an alternative aircraft.
If you are adding extra control surfaces to anything that isn't a high speed flying wing lacking tails, then either you lack the flight control technology to develop an airframe with those characteristics, or for some reason you value greater handling or maneuverability for XYZ reason either it be doctrinal or due to deployment basis (e.g.: an aircraft carrier).
Let's try the scientific method.
Hypothesis 1: Upgrading between generations is impossible.
Almost identical airframe:
MiG-21F - first flight 1955, introduction 1959 - 2nd generation
MiG-21bis - introduction 1972 - 3rd generation
F-4A - first flight 1958, introduction 1961 - 2nd generation
F-4C - first flight 1963, introduction 1965 - 3rd generation
Airfame being a direct development:
Mirage III - first flight 1956, introduction 1961 - 2nd generation
Mirage 2000 - first flight 1978, introduction 1984 - 4th generation
Drawings not to scale:
MiG-25 - first flight 1964, introduction 1970 - 3rd generation
MiG-31 - first flight 1975, introduction - 1981 - 3.5th generation
The conclusion is that there are at least four instances where upgrade between generations is possible. Hypothesis 1 is false.
Hypothesis 2: Upgrading between some generations is impossible
Impossibility of upgrading a 1st gen airframe for high supersonic speed of 2nd gen fighters and the impossibility of upgrading a 4th gen airframe for 5th gen VLO should be sufficient evidence.
The conclusion is that there are at least two instances where upgrade between generations is impossible. Hypothesis 2 is true.
Hypothesis 3: Generations are defined by more than one characteristic trait
Defining characteristics of 5th generation are VLO airframe, supercruise, high performance radar with phased array, networking. I deliberately excluded LPI for radar and comms as part of the proof.
The first aircraft to have both a high performance phased array radar and ad-hoc networking was the 3rd gen MiG-31. Supercruise is correctly understood as "supersonic cruise" therefore MiG-31 which can cruise at 2.3Ma fulfills the basic requirement.
The traits which MiG-31 lacks are VLO airframe along with VLO characteristics for radar and networking. The threshold trait preventing MiG-31 to be classified as 5th gen is VLO.
A similar proof could be performed for other generations but I'll omit it for brevity. The case of Mirage III and 2000 is a good example of upgrading between three generations due to the potential of the airframe.
The conclusion is that a design without "threshold trait" can't be upgraded between generations. This indicates that evolution of fighter aircraft design follows the rules of general evolutionary dynamics which is moving along lineages of multiple heritable traits with a single trait necessarily being the point of evolutionary divergence. Hypothesis 3 is false.
Hypothesis 4: The threshold trait for upgrade between 5th and 6th generation is a characteristic of the airframe
A threshold trait must cause evolutionary divergence. Divergence is a discrete quantity.
It means that if the trait is represented as a spectrum it is impossible to achieve overlap of characteristics between divergent designs and that there must be a non-singular space between the ranges.
For example if VLO defined by RCS is the threshold trait as in 5th gen then there can't be an overlap between RCS of 4th and 5th gens and there must be space between the two for a hypothetical intermediate solution. This is true as there is no such overlap and the divergence is significant enough for an airframe to be "more than 4.5gen but less than 5gen".
If airframe is the threshold trait then it should be impossible for a 5th gen and 6th gen characteristics to overlap.
We already can speculate that there will be some overlap in speed and maneuverability. The divergence between 5th and 6th gen VLO would have to be significant and consistent and F-22 and YF-23 have excellent characteristics.
The conclusion is that while not outright impossible it is very improbable that the core trait would be defined in terms of airfame because of the necessary magnitude of divergence.
At the same time necessary divergence is easily achieved by "AI pilot/optionally manned" trait.
This trait allows for a truly revolutionary leap in capabilities. Most importantly it will allow the human "pilot" to focus on controlling the swarm which eventually might result in a completely different interface where the pilot is flying the aircraft not in first-person perspective but in third-person - an approach which is much more intuitive to humans. In two-seater fighters one human operator can focus on the physical battlespace while the other can focus on spectrum/cyber/information battlespace thus turning a two-seater into an actual AWACS node.
I think hypotheses 1-4 demonstrate that my argument about 6th gen not being defined by airframe and therefore being achievable through upgrade of 5th gens is at least a strong possibility, if not the only solution.
A 5.5gen fighter will be capable of operating with unmanned systems in the same manner as 6gen but won't have an AI pilot allowing for a complete disconnect between flying the fighter and performing other tasks. I see upgraded F-35 and J-20 as such a 5.5 gen. Two-seater J-20 fulfills in my view the criteria for a "low end 6 gen" because an AI pilot will free up not one but two human operators.
In bold - steep thresholds for airframe evolution, not for distinctions between generations.
- 0th gen - traditional metal airfame (propeller)
- 1st gen - traditional metal airframe capable of sustaining forces generated by jet engine kinematics
- 2nd gen - modified for high supersonic speeds
- 3rd gen - reinforced for greater payloads and high speeds at low altitude.
- 4th gen - optimized for sustained high-g maneuvers
- 5th gen - frontal aspect VLO
- 6th gen - multi-aspect VLO optimized for low IR signature at subsonic speeds
Evolution leads to loss of traits only over sufficiently long periods of evolutionary divergence.generations for major traits. Six (practically: five) generations is a single long-lived multi-generational family. Therefore a 6th gen fighter should have all the traits of 5th gen fighter.
Since the threshold trait of 5th gen is VLO it is possible for 6th gens to be developed from 5th gens through upgrades. Such aircraft will be low-end 6th gens but they will be 6th gens just as numerous upgraded 2nd gens became low-end 3rd gens (F-104, F-4, F-5, MiG-21).
6th gen won't have a steep threshold like 2nd and 5th because these tend to occur every few generations and 5th gen just introduced one.
A side note but: everything we have seen of Su-57 so far indicates that it is not a 5th gen.
Lack of S-duct inlets exposes both engines in the frontal aspect which alone should give an RCS of approximately 1m2.
Furthermore the corner reflector created by protruding engines on the ventral side compromises LO entirely in any aspect other than frontal which his already compromised by exposed turbines.
There are other minor details like lack of serrations on edges and joints, lack of proper shaping of IRST dome etc.
It seems to me that the Russians weren't even trying to built a 5 gen. They were trying to build an aircraft that wasn't completely outdated due to lack of material technology at the time - PAK-FA is almost 20 years old and the prototype flew 10 years ago when Russian industry was trying to resuscitate itself after a period of coma.
I think you're overthinking this. Generations are not official designations. They're just for identifying and naming. We have no idea what sixth gen fighters will bring specifically so trying to identify a set definition for sixth gen fighters is a bit silly.
.... I never said that generations are "defined" by airframes.
What I said was that generations are defined by a number of characteristics, subsystems and technologies.
This is the part of my last post which best describes my position:
"Or, putting it another way -- for each generation of fighter aircraft, there are generation-defining characteristics, subsystems and technologies that can be practically drawn upon to upgrade or iterate fighter aircraft of a prior generation.
However, there are also generation-defining characteristics, subsystems and technologies that cannot be practically drawn upon to upgrade or iterate fighter aircraft of a prior generation.
I am asking -- for a 6th generation fighter, what are the generation-defining characteristics, subsystems and technologies, that cannot be practically drawn upon to upgrade or iterate fighter aircraft of a prior generation?"
This is a dicey topic and frankly wasn't a debate I wanted to start.
For the purposes of general discussion I include Su-57 as a 5th generation fighter.
In practice, the exact extent of that will likely depend on what Su-57's actual RCS is, which is something that we don't want to get into a contentious discussion everytime Su-57 is mentioned.
The Su-57 does have S-ducts. Also just because the turbine fan blades are partially exposed doesn't mean it isn't stealth. The YF-23 also had partially exposed turbine fan blades.
Sukhoi has a patent available online for mesh screens to reduce frontal aspect RCS of the engines. The mesh screens are retractable so you can tradeoff between stealth and acceleration in flight.
Izd. 30 engine is also supposed to use some amount of radar absorption materials in the fan blades themselves further improving engine stealth. Composite materials are used in the fan blades in certain commercial aircraft engines already like the CFM LEAP. Russia also has access to this technology and is going to use it in their PD-35 civil engine.
Using S-ducts similar to the F-22 reduces aircraft performance because of constriction of the airflow. The way this is countered in the F-22 is with increased engine power to achieve same acceleration but this reduces range. S-ducts also waste internal space. This further reduces range since aircraft can carry less fuel internally as a result. The F-22 weights more than the Su-57, it is way taller because of the S-ducts, and yet it carries 20% less fuel internally. The Su-57 designers simply made different optimizations.
The F-22 is way taller than the Su-57 and has way larger vertical tail surfaces than the Su-57. Yet no one seems to think this is a problem in terms of stealth for whatever reason. People claim Su-57 is only good for "frontal stealth" yet F-22 has way larger side area.
The F-35 was optimized for stealth and low cost so it uses a DSI which means its performance is optimized to a given Mach range. In that particular case it means it can neither do Mach 2 nor supercruise despite having an engine which is twice the power of the one in the Super Hornet.
The IRST dome in the Su-57 is made of radar transparent material. The IRST sensor itself is not radar transparent but it can rotate to hide its frontal aspect and the back of it is coated with radar absorbing materials. People talking about spherical surfaces being problematic for stealth are misinformed in this case since that formula assumes a solid object. Which is not the case for an IRST sensor dome.
The Russians and the US are not measuring RCS values in the same way. In fact no one seems to know how exactly the US is getting the numbers they claim to be getting in the first place from what I have seen. Russia also supposedly has two Su-57 stealth configurations. One which is for austere conditions and another where they apply extra RAM coatings in case of need for full war against peer adversaries. They simply don't apply these in most cases. This reduces airframe maintenance costs tremendously.
If anything I think Su-57 will be 5.5th gen or 6th gen once the improved engines come out. Its avionics are already way more advanced than the ones in the F-22. They have more processing power than either the F-22 or original F-35 avionics being based on a more modern Elbrus 2K VLIW processor. Original F-35 used several decrepit PowerPC based processors.
It is hard to discuss 6th generation matters since this is still a work in progress. A lot of the designs lack vertical tails, sure, and there is talk of optionally manned capabilities. But much of the rest is still open for discussion. Even the engine technology to be used is still not really decided.
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I wonder how mature some of the combined-cycle turbine/ramjet projects are.
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