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"Computers cannot create information that they weren't given in the first place.  Computers aren't magical.  They cannot improve the resolution of a grainy photo to show the face of the killer reflected in a raindrop."

With this I must strongly disagree. Computer(so well mathematics) can create data from nothing. Simplest pseudo-random number generator is doing pretty much that. Or for example camera in You smartphone is doing just that. Create colorfull image from partial data. Consoles do that in form of upscaling for example.

" They cannot improve the resolution of a grainy photo to show the face of the killer reflected in a raindrop."
Such system(algorithms) like in this vid are used in all kinds of CCTV for example(it's cheaper to run program on some ARM than buy hi res CCTV camera with good lenses).


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Armament of the PAK-FA:  

"Choke the Gripen" "Spank the Tomcat"   "Free the Viper"   "Grab your Junkers" "Ride the Fagot"


No, no, that's not the same thing at all.  What you are looking at are video smoothing algorithms that interpolate pixels based on a lower-resolution sample.


Thought experiment; if there were a small insect that was buzzing around in that image, but was smaller than the angular resolution of the camera, could the software re-create the image of that insect?


That's what you're claiming would somehow make these speculative AESA wing radars work.  

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6 hours ago, tomtom said:

With this I must strongly disagree. Computer(so well mathematics) can create data from nothing.


Yeah, this is impossible. The closest you can approximate this is through pattern recognition software (which, incidentally, is how the postpross in your brain works), but that only works if there's a pattern to be followed.

If you are looking at a patch of sky at a certain resolution, a computer can simulate a higher resolution in a way that's convincing to a human being. What it can't do is show you details that are below the native resolution level, like far away or low signature aircraft, for example.

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It is a very interesting paper!


Their methods are interesting, but somewhat limited.  What I think they are trying to do is simulate the stealth characteristics and aerodynamic characteristics of an aircraft at the same time.  This is useful because shapes that are very stealthy are not necessarily very aerodynamic and vice versa.  So being able to simulate and test both parameters at once would be very valuable.


Both of these methods are going to give inexact measurements that will give a general estimate of how the aircraft would perform in the real world.  But I don't think it would be more exact than that.


In terms of aerodynamics, they state that the computer model of the aircraft they use to simulate air flow is not structural.  I interpret this to mean that the 3D model is perfectly rigid, and does not twist or warp at all under aerodynamic forces.  But real aircraft do twist and warp as they fly; and this is why forward-swept wings are so difficult to get right.  Also, this flexibility has aerodynamic effects.  For example, forward-swept wings twist in such a way that they generate more lift while turning than would be predicted if they were rigid, but normal aft-swept wings generate less lift than they would if they were perfectly stiff.  So their aerodynamic calculations are probably only approximate.  For comparison though, here is a CL/alpha chart for the F-16 prototype:



The numbers are fairly close to what this computer simulation predicted, so it seems to be reasonably accurate at predicting the airflow around fighter jet-shaped objects.


In terms of radar cross section, again, they make some simplifying assumptions for their computer model.  Their conclusions on RCS should be considered only approximate.

In the real world, RCS can be increased a lot by very small imperfections.  There are stories of F-117 and F/A-18E/F ground crews checking the RCS of their aircraft before sending them into the air, and having the RCS be much higher than expected.  The problem would turn out to be a single panel, or even a single rivet or other fastener that was slightly out of place.  Their computer model doesn't have that level of detail.  It is clearly based on the PAK-FA, but lots of surface details like the IRST and DIRCM turrets are not modeled at all.


Furthermore, the people making these models have no idea where the designers of the PAK-FA have installed radar absorbing material (RAM).  I've seen similar studies of the F-35, and usually the computer model of the stealth aircraft is assumed to be all metal, not because this is an accurate assumption, but because people without access to sensitive information just don't know.  They also mention that their computer has a hard time doing the calculations on the engine area and on the air intakes, so they unrealistically simplify the geometry of those areas in their model to make the calculations work better.  Then they say that a lot of the radar returns from the model... come from the engines and air intakes.  So their computer modeling is least accurate at predicting radar returns from the most important part of the aircraft in terms of radar signature.


I don't really know too much about the accuracy of this sort of computer modeling vs the real thing.  But I think we can see where they have made simplifications, and I think we can see in some ways where these simplifications have caused problems.  In the places where we can compare their model's numbers to real numbers from other fighter aircraft, then their predictions are at least "in the right ballpark."  I trust their aerodynamic calculations more than their RCS calculations.  Neither is likely to be very precise.

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Armament of the PAK-FA:




While many of the technical details of the PAK-FA remain unknown and debated, a good deal of information is available about the weapons that will equip it.  Most of the information in this post is taken from Piotr Butowski's excellent new book Russia's Air Launched Weapons.





Fighter guns are weapons of tertiary importance in air to air combat, well behind medium range and short range air to air missiles.  However, guns have been used quite a lot in the air to ground role in recent conflicts in the Middle East.



The PAK-FA will be equipped with a single 9-A1-4071K 30mm cannon:




This weapon closely resembles the GSh-301 30mm cannon mounted in the SU-27 and MiG-29.  In fact, exactly what makes the new gun different is unclear.  Some very early reports credited the PAK-FA with two 30mm cannons, or with a twin-barreled GSh-30-2 as in the SU-25.  These appear to be in error.  Some more recent reports credit the new weapon with "smart" or even guided ammunition.  These reports appear to originate with a single Thai military blog, and appear to be the result of a mis-translation of a comment about new cannon shells intended to reduce bore wear.  A few other reports have noted that the new cannon has a liquid cooling system... so does the GSh-301.  The 9-A1-4071K appears to be basically the same thing as the GSh-301, no doubt with some small improvements.


The GSh-301 is a remarkable piece of weapon engineering.  It is a single-barrel weapon that manages an extremely impressive 1,500-1,800 RPM rate of fire with the potent 30x165mm round, which is nearly as powerful as the 30x173mm round fired by the A-10's GAU-8/A.  30x165mm ammunition is also used in Russian ground weapons systems such as the BMP-2, although the aircraft and ground vehicle ammunition is not exactly interchangeable.  At a mere 46 kilograms, the GSh-301 is also extremely light; less than half the mass of the GIAT 30M 791 30mm cannon in the French Rafale fighter, and capable of 60% that weapon's rate of fire.  It is absolutely mind-boggling that the GSh-301 uses an old-fashioned, recoil-operated linear breech mechanism in a day and age where all other aircraft guns use either a Gatling, Gast or revolver breech arrangement.  The GSh-301's sole vice is that, firing so quickly and being so light, it wears out quickly.


Underwing Ordnance


The PAK-FA can be fitted with up to four external weapons hardpoints under the wings and two hardpoints underneath the air intakes.  Currently, the PAK-FA is undergoing qualification trials to certify it in the use of all tactical air-launched weapons in the Russian Air Force inventory.  Apparently the Russian Air Force is completely serious when they say all weapons in inventory, as the PAK-FA has been seen carrying ancient unguided bombs on its external hard points:




Obviously, it looks a little ridiculous to attach ancient dumb bombs to a cutting-edge fighter.  Indeed, any external ordnance will slow the PAK-FA down with extra drag and will compromise the stealth characteristics of the aircraft.  However, the majority of the Russian Air Force's ordnance stockpile consists of older weapons.  Attempts to re-arm with newer, more sophisticated weapons have been hindered by budget and logistical problems (more on this later).  So, should the PAK-FA go into combat soon after it enters service, it will likely be armed with older weapons that were not designed for it.




PAK-FA with KH-31 anti-radiation missiles (AS-17 "Krypton") and R-73 (or R-74) short-range air to air missiles (AA-11 "Archer")


Internal Weapons Bays


It makes little sense to spend tens or hundreds of million of dollars on a fighter jet that was designed to have a minimal radar signature only to strap bombs, missiles, fuel tanks and other radar-reflective baggage to it.  In order to preserve its stealth characteristics, the PAK-FA is equipped with four internal weapons bays.


The two main weapons bays are mounted in tandem between the air intakes and engines.  The main weapons bays can carry medium range air to air missiles, long range air to air missiles, a variety of air to surface weapons and specially designed fuel tanks.  Two smaller weapons bays sit just outboard of the air intake.  These smaller bays carry short range air to air missiles only.



PAK-FA and F-22 internal weapons bays compared.  Main weapons bays are in red, secondary bays are in orange.


While internal weapons bays eliminate the drag and radar cross section penalties of externally carried weapons, they take up valuable space inside the fighter's fuselage.  Additionally, the bays constrain the maximum dimensions of weapons that can fit in them.  It appears that almost none of the missiles currently in the Russian Air Force inventory will fit into the PAK-FA's internal bays, since a new generation of weapons tailored to squeeze into the new fighter is currently under development.


Air to Air Weapons


Fighter aircraft are, at their hearts, fighting cocks that exist to grapple with their opposite number in thrilling, chivalrous air duels.  Or make little dots on a radar screen disappear by using long range guided missiles.  Whatever works.


Either way, a fighter will only be as good as its air to air armament.


Currently, air to air missiles are divided into short range, medium range and long range classes.


Short range air to air missiles are generally only capable of engaging targets within visual range of the pilots (a few kilometers, depending on weather), albeit at longer ranges than are possible with a gun.  Short range air to air missiles are generally infrared-guided.  The earlier models from the 1960s were only sensitive enough to detect the heat from an aircraft's exhaust when seen from behind, but by the late 1970s infrared seekers sensitive enough to detect the heat from air friction around the front of the aircraft were developed, which allowed for head-on shots.  By the late 1980s short range missiles that could be fired at targets not directly in front of their host fighter were developed.  These missiles use a gimbaled seeker head which the pilot aims using a helmet-mounted sight.  By simply pointing their head at the target, the pilot can aim the missiles at targets within a 60 degree cone.  This is known as high off boresight capability.  Newer missiles also use dual-band and imaging infrared seekers, which are much harder to fool with flares and other countermeasures.


Medium range air to air missiles are capable of engaging targets at beyond visual range.  Historically, this hasn't worked particularly well since it's been awfully hard to tell whether a radar blip twenty miles away is an enemy or not.  Also, the radar-guided missiles had various ways of avoiding their duty and missing the target completely.  But more recently the things seem to be working, and future air combat definitely feature lots of planes getting mercilessly cut down from the skies by enemies they couldn't even see.  Definitely.  The missiles will definitely work next time.  We have the assurances of the engineers.  Indeed, the likely effectiveness of medium range air to air missiles is topic of serious debate, with one side saying that they will continue to suck as they have historically and with the other side saying that all the bugs have been worked out and they'll clearly be amazing next time.  Personally, I find neither side convincing.


Early medium range missiles were semi-active types, which meant that the fighter that launched the missile had to babysit the missile by continuously illuminating the target with its own radar until the moment of truth.  This was in stark contrast to infrared guided missiles, which would happily fly themselves to the target regardless of what their host fighters did.  By the 1990s, active radar guided medium range missiles were beginning to enter the inventories.  These were advertised as being "fire and forget" just like the infrared guided short range missiles, but this wasn't entirely true.  It simply is not possible to cram a radar as powerful as a fighter's into the nose of a missile, so the missiles simply could not see the target at their maximum range with their own radar.  Active radar missiles are therefore guided by semi-active homing, inertial guidance, or radio datalink if they are fired at long range, with their own radar only becoming active once they get close enough.  Their host fighter (or someone else with a big radar) must babysit the missile until it is close enough for its own radar to go active.


Long range missiles are the rarest type.  Missiles large enough to engage targets that are hundreds of kilometers away are generally too big and too heavy for fighters to comfortably tote around.  The weight and drag severely impair the fighters' agility and speed.  Such large, sophisticated missiles are also terribly expensive.  A few interceptors have been designed around giant long range missiles, but generally the concept has not been popular despite the obvious appeal of smiting your enemies from several countries away.


The maximum range of air to air missiles is extremely dependent on launch parameters.  The altitude, airspeed and orientation of the launch platform and the target must be taken into account, as well as how fast and agile the target is if it is alerted to the incoming missile.  Therefore, I am not listing missile ranges.  Without specific information about the launch parameters, the range numbers are meaningless and only useful for marketing brochures.




The K-74M2 is the latest evolution of the R-73 short range air to air missile (AA-11 "Archer").  The story of the R-73 family of missiles is rather strange.  In the late 1970s, two Soviet design bureaus, Vympel and Molniya, were tasked with developing a next-generation short range air to air missile.  The Vympel design was fairly conservative, being an evolution of their K-13 (AA-2 "Atoll"), which was a reverse-engineered Philco-Ford AIM-9B.  The Molniya design was a completely new, somewhat larger missile with fancy, cutting edge features like a gimbaled seeker head and a thrust vectoring motor.  The Molniya design was recognized as superior, but the design would end up being finalized by the Vympel design team because the Molyniya design bureau was re-assigned to design the Buran space shuttle!



An early model SU-27 carrying R-27 (AA-10 "Alamo") and R-73 missiles


When it entered service in 1984, the R-73 was the best short range air to air missile in existence without debate.  It scared the shit out of NATO pilots when they flew in exercises against ex-East German MiG-29s and found out what the thing could do.  But a variety of new missile designs like the AIM-9X and ASRAAM have eclipsed the R-73, and updating the R-73 to remain competitive has proven difficult and complicated.


The first attempt to improve the R-73 was a missile called the K-74.  This design was an R-73 intended to be launched backwards, with some extra fuel and an aerodynamic fairing to allow the missile to be mounted backwards to a pylon.  In the early 1990s there was significant effort in the USSR to develop rearward-firing missiles to defend bombers.  After the breakup of the USSR, Sukhoi promoted the rear-firing missile concept, along with any and all conceptual projects that they thought might attract customers.




As it turned out, nobody was interested in rearward-firing missiles, and the project was quietly dropped in the mid 1990s.  However, the stretched K-74 became the basis for the K-74M, which at some later point became known as the RVV-MD.  This missile featured a much better infrared seeker and some other improvements.  Production started in 2013.  However, only a few hundred of these missiles were ever produced.



A rare K-74M, or more likely just a model


The snag was that the factory which produced the infrared seeker of the missile was located in Kiev, Ukraine.  Production of the seekers was sluggish in 2013, and the military conflict between Ukraine and Russia in 2014 meant that deliveries of the seekers ceased entirely.  The Russian Radiozavod factory was tasked with replicating the Ukrainian-made seekers, but as of 2016 they have succeeded only in making the older seekers for the R-73, not the newer design for the K-74M.


Vympel has since started the development of a further improved design, the K-74M2.  Butowski believes that this new model of missile is currently in flight tests, but no pictures of it have emerged to the public yet.


The K-74M2 has slightly smaller fins so it can fit into the secondary weapons bays of the PAK-FA.  Each of the secondary bays can carry a single K-74M2.  It has a new motor with better propellant, and a new dual-band infrared seeker from the AOMZ company as well as backup radio datalink and inertial guidance modes.  These upgrades should bring it technically into parity with newer Western dogfight missiles like IRIS-T, ASRAAM and AIM-9X, although it should be noted that at 106 kg or so, K-74M2 is 20-25% more massive than those missiles.




A few years ago, Vympel was planning a new short range air to air missile that would be a completely original design, not based on the R-73 at all.  This design, the K-30, was to feature a much better seeker with double the lock-on range, computerized target identification, a dual-pulse motor and more efficient thrust vectoring.  This program has since been abandoned.  No replacement program has been announced.


Curiously, Lockheed Martin produced a mock-up of their concept for a next-generation short range missile, the CUDA:



An F-35 with oodles o' CUDAs


The CUDA is intended to be a radar-guided short range missile.  Ever since the 1960s when guided missile designers figured out what the hell they were doing, short-range missiles have mostly been infrared guided.  But Lockheed Martin seems to think that radar guidance is the way of the future for short range missiles, and it is possible that the Russian Air Force is thinking along similar lines.  If this is true, it means that there have been major technical developments in recent years, because historically infrared guidance has been more reliable and cheaper, but shorter ranged.




The K-77M is a derivative of the R-77 (AA-12 "Adder") medium range air to air missile designed for the PAK-FA.  No pictures of the missile have surfaced in the public, but according to experts the new missile is slightly longer, and has conventional fins instead of the R-77's grid fins.



Mash them potatoes!


The R-77 was still a very new design when the Soviet Union collapsed.  It was the first Soviet air to air missile to feature an active radar seeker, giving it fire and forget capability.  Much like the R-73, the seeker was made in Ukraine, but production was transfered to Russia in the early 2000s without anything like the drama surrounding the K-74M.  The baseline R-77 was a modest export success, with a few thousand being produced, primarily for China and India.  The Russian Air Force, however, did not have the money to buy the missiles in significant numbers.  There are persistent rumors that the Chinese government bought the complete technical specifications of the missile from the Ukrainians.


In 2010 Vympel began series production of an improved version, the R-77-1, also called the RVV-AE.  This model has modest aerodynamic and electronics improvements.  This missile has been seen in small numbers on SU-35 fighters flying patrol and escort missions in Syria:




The K-77M is not yet in mass production.  In addition to the substitution of conventional fins, it will have comprehensive upgrades of its electronics and an improved motor.  These upgrades should allow an improvement in the maximum range by a factor of two, as well as high off-boresight capability.  Vympel claims that this missile will be better than the AIM-120C-7 AMRAAM and equal to successor variants thereof.  Technical specifics on the K-77M are slim, but given what is known, this claim seems plausible.  R-77-1 masses at 190kg, 25% more than the AIM-120, and K-77M probably a little heavier than that.


Izdeliye 180-PD


Mockup of a ramjet-powered R-77


This is a variant of the K-77M with ramjet propulsion, roughly equivalent to the MBDA Meteor.  The development of this missile is a private venture by Vympel, currently no government has placed orders for the design.


Izdeliye 270


This is the designation of a medium or long range air to air missile intended to replace the K-77M at some point in the future.  Nothing more is known.


Izdeliye 810


Here is where things get interesting; there is no Western missile that lends itself to comparison with this thing, except maybe for the (no longer in service) AIM-54.


Izdeliye 810, also called Grafoman or K-BD will be a development of the R-37M (AA-13 "Axehead") long range air to air missile, redesigned to fit the internal weapon bays of the PAK-FA.  R-37M is in turn a replacement for the R-33 (AA-9 "Amos") long range air to air missile used on the MiG-31.  However, R-37M is designed such that it can be used on other fighters as well.  Vympel's Izdeliye 810 proposal beat out rival NPO Novitor's K-100 proposal, which was a derivative of the 3M83 missile used in the S-300V SAM system.  



Not the Izdeliye 810, this is Novitor's losing K-100 proposal



Also not the Izdeliye 810, this is the K-37M upon which it will be based


This missile will be absolutely enormous by the standards of air to air weapons.  The existing R-37M masses at 510 kilograms, or more than two and a half times more than R-77-1, and about 9% heavier than the AIM-54.


The guidance system will be complex.  The missile will have passive radar homing, GPS/GLONASS navigation, inertial navigation, two-way radio datalink, and active radar terminal homing.  Semi-active radar is planned for the future.  The warhead will have adaptive fusing that can vary the fragmentation pattern as necessary.


In general, very large air to air missiles like this are useful against bombers, transport aircraft, tankers, AWACS, cruise missiles and other less maneuverable targets.  They are not particularly effective against fighters because these missiles tend to be less maneuverable, and not good at hitting agile targets.


Air to Surface Weapons


Unlike the F-22, the PAK-FA will enjoy a wide array for air to surface weapons when it enters service.  In this respect, it is more comparable to the F-35, being designed for both air to air and air to surface missions from the beginning.


KAB-250LG and KAB-500M




The KAB-250LG is a 265 kilogram laser-guided bomb intended to fit the internal weapons bay of the PAK-FA.  To that end it has much shorter span fins than previous Russian laser-guided bombs.  State testing began in 2015, and reportedly the bomb is accurate to within 5 meters.  The KAB-500M is essentially a wider, 500 kilogram-ish version of the same thing, again, intended for the PAK-FA.  For some reason the KAB-500M has been kept much more secret than the KAB-250LG.




The original Kh-58 (AS-11 "Kilter") was a stonking enormous anti radiation missile.  



A MiG-31 with a Kh-58 under the starboard wing and a Kh-31 under the port wing, R-77s on the outboard stations and R-33s in the conformal fuselage mounts


Continuing their penchant for ridiculously huge anti radiation missiles, the Kh-58 was fitted with improved electronics, and given a shortened fuselage and folding fins to fit inside the PAK-FA's internal weapons bay.  Overall length was reduced to 4.2 meters from 4.8 meters.  Mass is an astonishing 650 kilograms, compared to 360 kilograms for the AGM-88E.  A variant, the Kh-58UShKE(IIR) adds imaging infrared sensors to enable better precision.  As of 2013 the Chinese government was negotiating a large purchase of these weapons. 



New and improved, small enough for the PAK-FA, big enough to flatten any radar




The Kh-59MK2 is a small cruise missile ostensibly derived from the Kh-59/Kh-59M family of missiles (AS-13 "Kingbolt" and AS-18 "Kazoo").  Only the guidance is completely different, and the missile looks completely different.



Old-school Kh-59M slung under the wing of an SU-24


The old Kh-59M was round and lumpy with small delta wings and radio-link TV guidance.  The new Kh-59MK2 is boxy, with folding wings, inertial/satellite guidance and terrain contour matching terminal guidance.  It looks like it may have radar signature reduction measures, and it is clearly designed to fit inside the internal bays of the PAK-FA.  About the only thing it shares with the old Kh-59M is the engine, which is mounted in a completely different place.



The new hotness


The 770 kilogram weapon is credited with a cruising speed of 750-1000 KPH and a maximum range of 290 kilometers.  It is intended for striking fixed targets of known location.  Currently the Russian government is not financing the development of this awesome-looking weapon.  Raduga, the company responsible for development, may be searching for a foreign partner.  In general, this new weapon seems reminiscent of the MBDA Storm Shadow / Scalp, although it is about half the weight and has considerably shorter range.



Kh-59MK2 and KH-58UShK; chicks dig it!






The KTRV Grom is a new munition loosely based on the old Kh-38 air to surface missile.  There is no explicit mention of it being intended for the PAK-FA, but it is built to exactly the same length, 4.2 meters, as the Kh-59MK2 and KH-58UShK, and it features folding wings.  I think it's reasonable to assume that it's supposed to go inside a PAK-FA.  The weapon will come in two flavors; a rocket-assisted variant (Grom-E1) and a glide variant where the rocket is replaced with more explosive (Grom-E2).  Both variants will be inertially guided with satellite correction.  Variants with more precise terminal guidance (laser, infrared or radar) are being considered for the future.  It is similar to the AGM-154 JSOW, although somewhat larger (600 vs 500 kilograms).


Executive Summary


The PAK-FA will be compatible with all legacy tactical weapons of the Russian Air Force; up to and including Khrushchev-era unguided bombs that have been rusting in depots since the 1960s, apparently.  I guess when you make huge stockpiles of bombs in preparation for World War Three, it would just be a shame not to use them on someone.  However, the majority of these older weapons are not sized correctly to fit in the PAK-FA's weapons bays, which will force the plane to carry them externally, which sacrifices performance and stealth.  In addition, a number of new munitions such as the latest version of the Kh-35U and the Russian/Indian BRAHMOS-NG will be compatible with the PAK-FA, but they are far too large to fit in the PAK-FA's internal bays and will have to be carried externally.


The majority of next-generation Russian air to air and air to ground weapons appear to be upgrades of existing designs, and part of the updates has been to re-design all the new weapons to be shorter, have smaller fins or folding fins in order to ensure compatibility with the PAK-FA's internal weapons bays.  In addition, all new designs for tactical air-launched weapons designs appear to be designed to work in the PAK-FA's weapons bays.


Comparisons With Other Fifth Generation Fighters


Assuming that the various weapons programs for the PAK-FA proceed without major delays, which is a big assumption, as shortages of funds have caused major delays so far, the PAK-FA will have an arsenal that is largely equivalent to Western counterparts.  Butowski believes that the K-74M2 and K-77M will be essentially equal to the AIM-9X and AIM-120D, respectively, but the Russian missiles are 20-25% heavier than their Western equivalents.  It is unclear when or if the PAK-FA will have a ramjet-powered R-77 derivative equivalent to the British Meteor AAM.  The Izdeliye 810 long range air to air missile is an unusual weapon with no close Western equivalent that may give the PAK-FA a unique advantage in certain missions.  It is unlikely to be a very useful weapon in fighter vs fighter combat.  Future Russian air to air missile developments remain shrouded in mystery, while the publicly displayed concepts from Western missile designers suggest that technical breakthroughs will radically change the next generation of air to air missile design.


The PAK-FA will enjoy a reasonably diverse set of air to ground weapons.  Laser-guided bombs, a family of large glide bombs, an anti radiation missile and a small cruise missile are being developed explicitly to fit inside the PAK-FA's weapons bays.  The PAK-FA does not look like it will enjoy any equivalent to the GBU-39 Small Diameter Bomb or the GBU-53 SDB-II.  Butowski mentions that SDB equivalents have been proposed, but so far little work has been done on them.  Additionally, it is not clear what the largest single weapon the PAK-FA can carry in one of its internal bays is; all weapons so far developed specifically for the PAK-FA are under 800 kilograms, which is somewhat short of the 1000 kilograms that the F-35 can carry.


All weapons designed for the PAK-FA's internal bays are 4.2 meters long.  The longest weapon which I am aware will fit into the F-35A's internal bays (F-35B's bays are smaller) is the 4.1 meter long JSOW, so the PAK-FA's weapons bays may be very slightly longer than the F-35's.  It is unclear how many of each of these weapons the PAK-FA can carry.  If, for example, it can carry four Grom-E1s, two in each main bay, and two K-74M2s for self defense, it may be able to carry a greater total tonnage of weapons than the F-35.  However, given the absence of any 1000 kilogram weapons developed for the PAK-FA, it appears likely that the F-35 can carry larger single weapons.  This remains conjectural, of course, There are no public pictures that give any indication of the exact dimensions of the PAK-FA's weapon bays.




Even less is known about the weapons bay layout of the J-20, but the fact that the Chinese were interested in buying the Kh-58UShK might mean that the J-20's weapons bays are sized to fit that missile.



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On 4/19/2017 at 1:30 PM, Collimatrix said:

It would be interesting to know what these massively higher data transfer rates would allow the aircraft to do that it would otherwise not be able to do.  Can it tolerate greater margins of instability?  Does it allow the PAK-FA to perform maneuvers like the F-35's 28 degree/sec J-turn?





PAK-FA does appear to be able to J-turn:




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6 hours ago, Ramlaen said:

Is Su-57 a confirmed name or the Internet caught in a feedback loop?


Supposedly it's from a French-language article by Piotr Butowski, and he's a subject matter expert when it comes to contemporary Russian military aviation.  But I haven't actually seen this article.


Traditionally, odd-numbered service numbers have been used for fighters while even numbers were used for bombers.  Obviously, this wasn't a hard and fast rule (How is the SU-25 more of a fighter than the SU-24?  SU-17 and SU-22?).  Still, SU-57 does make a bit more sense than SU-50 in that respect.

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  • 4 weeks later...

Things of note on the PAK-FA:





In red I have circled some of the apertures for various sensors and accessories.  Radar waves tend to reflect off of sudden changes in conductivity in the skin of an aircraft, and this includes any panel covers, holes, or seams.  By making these apertures faceted and planform-aligned, the designers can reduce the amount of radar energy that is scattered back to the enemy radar.


If you compare this to, say, a Eurofighter, you can see that fourth-generation fighters have much more conventional and convenient square-shaped access covers:



In green I have highlighted some interesting features of the air intakes.  These little holes are most likely a boundary layer management system.  The YF-23 had a similar system:



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  • 2 weeks later...
On 4/25/2017 at 10:04 PM, Sturgeon said:


Yeah, this is impossible. The closest you can approximate this is through pattern recognition software (which, incidentally, is how the postpross in your brain works), but that only works if there's a pattern to be followed.

If you are looking at a patch of sky at a certain resolution, a computer can simulate a higher resolution in a way that's convincing to a human being. What it can't do is show you details that are below the native resolution level, like far away or low signature aircraft, for example.



Unless you're Emeric, then it's a suppression study

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    • By LostCosmonaut
      Compared to the most well known Japanese fighter of World War 2, the A6M “Zero”, the J2M Raiden (“Jack”) was both less famous and less numerous. More than 10,000 A6Ms were built, but barely more than 600 J2Ms were built. Still, the J2M is a noteworthy aircraft. Despite being operated by the Imperial Japanese Navy (IJN), it was a strictly land-based aircraft. The Zero was designed with a lightweight structure, to give extreme range and maneuverability. While it had a comparatively large fuel tank, it was lightly armed, and had virtually no armor. While the J2M was also very lightly built, it was designed that way to meet a completely different set of requirements; those of a short-range interceptor. The J2M's design led to it being one of the fastest climbing piston-engine aircraft in World War 2, even though its four 20mm cannons made it much more heavily armed than most Japanese planes.

      Development of the J2M began in October 1938, under the direction of Jiro Hirokoshi, in response to the issuance of the 14-shi interceptor requirement (1). Hirokoshi had also designed the A6M, which first flew in April 1939. However, development was slow, and the J2M would not make its first flight until 20 March 1942, nearly 3 ½ years later (2). Initially, this was due to Mitsubishi's focus on the A6M, which was further along in development, and of vital importance to the IJN's carrier force. Additionally, the J2M was designed to use a more powerful engine than other Japanese fighters. The first aircraft, designated J2M1, was powered by an MK4C Kasei 13 radial engine, producing 1430 horsepower from 14 cylinders (3) (compare to 940 horsepower for the A6M2) and driving a three bladed propeller. The use of such a powerful engine was driven by the need for a high climb rate, in order to fulfill the requirements set forth in the 14-shi specification.
      The climb rate of an aircraft is driven by specific excess power; by climbing an aircraft is gaining potential energy, which requires power to generate. Specific Excess Power is given by the following equation;
      It is clear from this equation that weight and drag must be minimized, while thrust and airspeed are maximized. The J2M was designed using the most powerful engine then available, to maximize thrust. Moreover, the engine was fitted with a long cowling, with the propeller on an extension shaft, also to minimize drag. In a more radical departure from traditional Japanese fighter design (as exemplified by aircraft such as the A6M and Ki-43), the J2M had comparatively short, stubby wings, only 10.8 m wide on the J2M3 variant, with a relatively high wing loading of 1.59 kN/m2 (33.29 lb/ft2) (2). (It should be noted that this wing loading is still lower than contemporary American aircraft such as the F6F Hellcat. The small wings reduced drag, and also reduced weight. More weight was saved by limiting the J2M's internal fuel, the J2M3 had only 550 liters of internal fuel (2).
      Hirokoshi did add some weight back into the J2M's design. 8 millimeters of steel armor plate protected the pilot, a luxurious amount of protection compared to the Zero. And while the J2M1 was armed with the same armament as the A6M (two 7.7mm machine guns and two Type 99 Model 2 20mm cannons), later variants would be more heavily armed, with the 7.7mm machine guns deleted in favor of an additional pair of 20mm cannons. Doubtlessly, this was driven by Japanese wartime experience; 7.7mm rounds were insufficient to deal with strongly built Grumman fighters, let alone a target like the B-17.
      The first flight of the J2M Raiden was on March 20th, 1942. Immediately, several issues were identified. One design flaw pointed out quickly was that the cockpit design on the J2M1, coupled with the long cowling, severely restricted visibility. (This issue had been identified by an IJN pilot viewing a mockup of the J2M back in December 1940 (1).) The landing speed was also criticized for being too high; while the poor visibility over the nose exacerbated this issue, pilots transitioning from the Zero would be expected to criticize the handling of a stubby interceptor.

      Wrecked J2M in the Philippines in 1945. The cooling fan is highly visible.
      However, the biggest flaw the J2M1 had was poor reliability. The MK4C engine was not delivering the expected performance, and the propeller pitch control was unreliable, failing multiple times. (1) As a result, the J2M1 failed to meet the performance set forth in the 14-shi specification, achieving a top speed of only 577 kph, well short of the 600 kph required. Naturally, the climb rate suffered as well. Only a few J2M1s were built.
      The next version, the J2M2, had several improvements. The engine was updated to the MK4R-A (3); this engine featured a methanol injection system, enabling it to produce up to 1,800 horsepower for short periods. The propeller was switched for a four blade unit. The extension shaft in the J2M1 had proved unreliable, in the J2M2 the cowling was shortened slightly, and a cooling fan was fitted at the the front. These modifications made the MK4R-A more reliable than the previous engine, despite the increase in power.
      However, there were still problems; significant vibrations occurred at certain altitudes and speeds; stiffening the engine mounts and propeller blades reduced these issues, but they were never fully solved (1). Another significant design flaw was identified in the summer of 1943; the shock absorber on the tail wheel could jam the elevator controls when the tailwheel retracted, making the aircraft virtually uncontrollable. This design flaw led to the death of one IJN pilot, and nearly killed two more (1). Ultimately, the IJN would not put the J2M2 into service until December 1943, 21 months after the first flight of the J2M1. 155 J2M2s would be built by Mitsubishi (3).
      By the time the J2M2 was entering service, the J2M3 was well into testing. The J2M3 was the most common variant of the Raiden, 260 were produced at Mitsubishi's factories (3). It was also the first variant to feature an armament of four 20mm cannons (oddly, of two different types of cannon with significantly different ballistics (2); the 7.7mm machine guns were replace with two Type 99 Model 1 cannons). Naturally, the performance of the J2M3 suffered slightly with the heavier armament, but it still retained its excellent rate of climb. The Raiden's excellent rate of climb was what kept it from being cancelled as higher performance aircraft like the N1K1-J Shiden came into service.

      The J2M's was designed to achieve a high climb rate, necessary for its intended role as an interceptor. The designers were successful; the J2M3, even with four 20mm cannons, was capable of climbing at 4650 feet per minute (1420 feet per minute) (2). Many fighters of World War 2, such as the CW-21, were claimed to be capable of climbing 'a mile a minute', but the Raiden was one of the few piston-engine aircraft that came close to achieving that mark. In fact, the Raiden climbed nearly as fast as the F8F Bearcat, despite being nearly three years older. Additionally, the J2M could continue to climb at high speeds for long periods; the J2M2 needed roughly 10 minutes to reach 30000 feet (9100 meters) (4), and on emergency power (using the methanol injection system), could maintain a climb rate in excess of 3000 feet per minute up to about 20000 feet (about 6000 meters).


      Analysis in Source (2) shows that the J2M3 was superior in several ways to one of its most common opponents, the F6F Hellcat. Though the Hellcat was faster at lower altitudes, the Raiden was equal at 6000 meters (about 20000 feet), and above that rapidly gained superiority. Additionally, the Raiden, despite not being designed for maneuverability, still had a lower stall speed than the Hellcat, and could turn tighter. The J2M3 actually had a lower wing loading than the American plane, and had flaps that could be used in combat to expand the wing area at will. As shown in the (poorly scanned) graphs on page 39 of (2), the J2M possessed a superior instantaneous turn capability to the F6F at all speeds. However, at high speeds the sustained turn capability of the American plane was superior (page 41 of (2)).
      The main area the American plane had the advantage was at high speeds and low altitudes; with the more powerful R-2800, the F6F could more easily overcome drag than the J2M. The F6F, as well as most other American planes, were also more solidly built than the J2M. The J2M also remained plagued by reliability issues throughout its service life.
      In addition to the J2M2 and J2M3 which made up the majority of Raidens built, there were a few other variants. The J2M4 was fitted with a turbo-supercharger, allowing its engine to produce significantly more power at high altitudes (1). However, this arrangement was highly unreliable, and let to only two J2M4s being built. Some sources also report that the J2M4 had two obliquely firing 20mm Type 99 Model 2 cannons in the fuselage behind the pilot (3). The J2M5 used a three stage mechanical supercharger, which proved more reliable than the turbo-supercharger, and still gave significant performance increases at altitude. Production of the J2M5 began at Koza 21st Naval Air Depot in late 1944 (6), but ultimately only about 34 would be built (3). The J2M6 was developed before the J2M4 and J2M6, it had minor updates such as an improved bubble canopy, only one was built (3). Finally, there was the J2M7, which was planned to use the same engine as the J2M5, with the improvements of the J2M6 incorporated. Few, if any, of this variant were built (3).
      A total of 621 J2Ms were built, mostly by Mitsubishi, which produced 473 airframes (5). However, 128 aircraft (about 1/5th of total production), were built at the Koza 21st Naval Air Depot (6). In addition to the reliability issues which delayed the introduction of the J2M, production was also hindered by American bombing, especially in 1945. For example, Appendix G of (5) shows that 270 J2Ms were ordered in 1945, but only 116 were produced in reality. (Unfortunately, sources (5) and (6) do not distinguish between different variants in their production figures.)
      Though the J2M2 variant first flew in October 1942, initial production of the Raiden was very slow. In the whole of 1942, only 13 airframes were produced (5). This included the three J2M1 prototypes. 90 airframes were produced in 1943, a significant increase over the year before, but still far less than had been ordered (5), and negligible compared to the production of American types. Production was highest in the spring and summer of 1944 (5), before falling off in late 1944 and 1945.
      The initial J2M1 and J2M2 variants were armed with a pair of Type 97 7.7mm machine guns, and two Type 99 Model 2 20mm cannons. The Type 97 used a 7.7x56mm rimmed cartridge; a clone of the .303 British round (7). This was the same machine gun used on other IJN fighters such as the A5M and A6M. The Type 99 Model 2 20mm cannon was a clone of the Swiss Oerlikon FF L (7), and used a 20x101mm cartridge.
      The J2M3 and further variants replaced the Type 97 machine guns with a pair of Type 99 Model 1 20mm cannons. These cannons, derived from the Oerlikon FF, used a 20x72mm cartridge (7), firing a round with roughly the same weight as the one used in the Model 2 at much lower velocity (2000 feet per second vs. 2500 feet per second (3), some sources (7) report an even lower velocity for the Type 99). The advantage the Model 1 had was lightness; it weighed only 26 kilograms vs. 34 kilograms for the model 2. Personally, I am doubtful that saving 16 kilograms was worth the difficulty of trying to use two weapons with different ballistics at the same time. Some variants (J2M3a, J2M5a) had four Model 2 20mm cannons (3), but they seem to be in the minority.

      In addition to autocannons and machine guns, the J2M was also fitted with two hardpoints which small bombs or rockets could be attached to (3) (4). Given the Raiden's role as an interceptor, and the small capacity of the hardpoints (roughly 60 kilograms) (3), it is highly unlikely that the J2M was ever substantially used as a bomber. Instead, it is more likely that the hardpoints on the J2M were used as mounting points for large air to air rockets, to be used to break up bomber formations, or ensure the destruction of a large aircraft like the B-29 in one hit. The most likely candidate for the J2M's rocket armament was the Type 3 No. 6 Mark 27 Bomb (Rocket) Model 1. Weighing 145 pounds (65.8 kilograms) (8), the Mark 27 was filled with payload of 5.5 pounds of incendiary fragments; upon launch it would accelerate to high subsonic speeds, before detonating after a set time (8). It is also possible that the similar Type 3 No. 1 Mark 28 could have been used; this was similar to the Mark 27, but much smaller, with a total weight of only 19.8 pounds (9 kilograms).
      The first unit to use the J2M in combat was the 381st Kokutai (1). Forming in October 1943, the unit at first operated Zeros, though gradually it filled with J2M2s through 1944. Even at this point, there were still problems with the Raiden's reliability. On January 30th, a Japanese pilot died when his J2M simply disintegrated during a training flight. By March 1944, the unit had been dispatched to Balikpapan, in Borneo, to defend the vital oil fields and refineries there. But due to the issues with the J2M, it used only Zeros. The first Raidens did not arrive until September 1944 (1). Reportedly, it made its debut on September 30th, when a mixed group of J2Ms and A6Ms intercepted a formation of B-24s attacking the Balikpapan refineries. The J2Ms did well for a few days, until escorting P-47s and P-38s arrived. Some 381st Raidens were also used in defense of Manila, in the Phillipines, as the Americans retook the islands. (9) By 1945, all units were ordered to return to Japan to defend against B-29s and the coming invasion. The 381st's J2Ms never made it to Japan; some ended up in Singapore, where they were found by the British (1).

      least three units operated the J2M in defense of the home islands of Japan; the 302nd, 332nd, and 352nd Kokutai. The 302nd's attempted combat debut came on November 1st, 1944, when a lone F-13 (reconaissance B-29) overflew Tokyo (1). The J2Ms, along with some Zeros and other fighters, did not manage to intercept the high flying bomber. The first successful attack against the B-29s came on December 3rd, when the 302nd shot down three B-29s. Later that month the 332nd first engaged B-29s attacking the Mitsubishi plant on December 22nd, shooting down one. (1)
      The 352nd operated in Western Japan, against B-29s flying out of China in late 1944 and early 1945. At first, despite severe maintenace issues, they achieved some successes, such as on November 21st, when a formation of B-29s flying at 25,000 feet was intercepted. Three B-29s were shot down, and more damaged.

      In general, when the Raidens were able to get to high altitude and attack the B-29s from above, they were relatively successful. This was particularly true when the J2Ms were assigned to intercept B-29 raids over Kyushu, which were flown at altitudes as low as 16,000 feet (1). The J2M also had virtually no capability to intercept aircraft at night, which made them essentially useless against LeMay's incendiary raids on Japanese cities. Finally the arrival of P-51s in April 1945 put the Raidens at a severe disadvantage; the P-51 was equal to or superior to the J2M in almost all respects, and by 1945 the Americans had much better trained pilots and better maintained machines. The last combat usage of the Raiden was on the morning of August 15th. The 302nd's Raidens and several Zeros engaged several Hellcats from VF-88 engaged in strafing runs. Reportedly four Hellcats were shot down, for the loss of two Raidens and at least one Zero(1). Japan surrendered only hours later.

      At least five J2Ms survived the war, though only one intact Raiden exists today. Two of the J2Ms were captured near Manila on February 20th, 1945 (9) (10). One of them was used for testing; but only briefly. On its second flight in American hands, an oil line in the engine failed, forcing it to land. The aircraft was later destroyed in a ground collision with a B-25 (9). Two more were found by the British in Singapore (1), and were flown in early 1946 but ex-IJN personnel (under close British supervision). The last Raiden was captured in Japan in 1945, and transported to the US. At some point, it ended up in a park in Los Angeles, before being restored to static display at the Planes of Fame museum in California.

      F6F-5 vs. J2M3 Comparison
      Further reading:
      An additional two dozen Raiden photos: https://www.worldwarphotos.info/gallery/japan/aircrafts/j2m-raiden/
    • By Belesarius
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    • By Belesarius
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