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Little Flying Dragons Of China


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If they keep making more of them, it might be meant as a sort of work horse meant to get lots of anti-ship missiles in the skies. With all the tech and gizmos, it'll probably make it good enough for their intended role if in great enough numbers. They still have the H-20 bomber program which is supposed to become their so-called B-2 equivalent.

I think there is always a utility in even very basic platforms with large payload and range. The basis mechanics and engineering of large subsonic aircraft is a mature technology with very little prospect for improvement.

"If it isn't broken, why fix it?" or something like that.

 

A really good design and engineering effort using exotic materials and an expensive R&D program might for example give you a 15 % reduction in fuel consumption and 30% increase in range or something like that, and then you have virtually no more room for improvement as you are brushing up against hard limits of physics. It is a small gain in comparison to the advantages attainable by incremental improvement in other areas ; eg. radar, munitions, etc.

 

I.e. a modernised H-6 carrying some very modern hypersonic cruise missiles may be just as deadly and vastly cheaper than a B-2 using a less sophisticated munition.

 

 

Edited by KV7
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It is interesting to note that on the new Chinese stealth aircraft, at least the ones they have shown, there appears to be no thermal management at the rear, to my uneducated eye. The F-35 from the US seems to be in the same boat. The F-117, the B-2, and the F-22 all show an effort to reduce the thermal signature, why not on the F-35, and why not on these Chinese aircraft? Also now that I think of it the Pak-Fa appears to have no thermal management either.

 

FC-31 test flight

 

lLxNMLp.jpg

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It is interesting to note that on the new Chinese stealth aircraft, at least the ones they have shown, there appears to be no thermal management at the rear, to my uneducated eye. The F-35 from the US seems to be in the same boat. The F-117, the B-2, and the F-22 all show an effort to reduce the thermal signature, why not on the F-35, and why not on these Chinese aircraft? Also now that I think of it the Pak-Fa appears to have no thermal management either.

 

FC-31 test flight

 

lLxNMLp.jpg

They probably think in combat situation there is going to be after-burning, so little can be done to lower thermal signature.

Edited by KV7
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At the end of the day thermal management requires weight. All of the types you listed were attack types that could neglect performance except the F-22, and even then I think the IR reduction is limited to the 2-D thrust vectoring nozel - ie, the thermal management is somewhat integrated into the thrust vector and is possible specifically because it vectors in the vertical plane only, allowing a spread out rectangular nozzle. So a lot of compromises have to be made to spread out your IR plumb, and as noted if you're reheating all of that is for naught. Again, F-22 is an exception in that it was designed to supercruise at very high altitude (non-variable engine inlets).

Edited by Josh
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It's really hard to guess what total production will be.

 

Anyway, maybe this image is useful, probably J-10B. Can its radar quality or capabilities be speculated with this?

j-10bmaybe.jpg

https://www.facebook.com/611223845748378/photos/p.793443914193036/793443914193036/?type=3&theater

 

We can discern a few things from this picture.

 

The first thing to note is that the planar radar array appears to be fixed, with no mechanical gimbal to steer it. That definitely means it's an electronically steered array. Now, whether it's a PESA with a single wave generator and and phase-shifting elements in front or an AESA with an array of active elements on a single plane, we simply can't tell from the picture.

 

That said, there are some PESA and AESA arrays that have mechanical gimbals to allow them to pivot to the side to cover more area. SU-35's radar does this.

 

Note also that the face of the array is angled back a few degrees from the vertical. That's an old trick for reducing RCS.

 

The performance of the radar will be a function of how big it is, what wavelength it operates in, how well-made the electronic hardware is and how good the signal processing software is. We can make a pretty good guess on that first factor, and increasingly wild-assed guesses on those other factors. My personal guess is that it's nowhere near as good at a modern Western-made AESA. The Russians were showing off their best radars at trade shows and bragging about SAR resolution that was roughly equivalent to mid-1990s US stuff, so unless the Chinese have a huge leg up on the Russians in avionics (unlikely; why would they be buying SU-35s if their stuff is already better?), then their electronic hardware and signal processing are probably a decade or two behind the US. That said, this doesn't mean that these radars are directly equivalent to a 1990s US set; they have electronically steered antennas, so they most likely enjoy better scan times and ECCM.

 

Looks like an AESA, but I don't think that's particularly news.

 

No way to tell if it's AESA or PESA. Rumint is that it's AESA.

 

It is interesting to note that on the new Chinese stealth aircraft, at least the ones they have shown, there appears to be no thermal management at the rear, to my uneducated eye. The F-35 from the US seems to be in the same boat. The F-117, the B-2, and the F-22 all show an effort to reduce the thermal signature, why not on the F-35, and why not on these Chinese aircraft? Also now that I think of it the Pak-Fa appears to have no thermal management either.

 

 

 

There appears to be no thermal management yet. Remember, these are still prototypes and they're still flying with the last-generation engines. That means WS-10 for the J-20, which is basically an F100/AL-31 equivalent, and RD-93 for the J-31, which is like a very poor man's F404.

 

Designing fighter jet engine nozzles isn't easy. Those things have to withstand tens of tons of thrust, massive thermal loading, and still remain very light. So it's probably easiest to just leave the old nozzles on the interim engines instead of screwing around with things right now in the interest of getting all the flight testing done quickly.

 

The definitive, mass-produced engines are likely to have some IR reduction measures. My guess is that they'll have serrated nozzle petals like the new SU-57 engine and the F135:

Pay5onw.jpg

 

For the record, the F135 does have signature reduction measures, they just work a little differently than the F119. Those sawtooth shapes reduce radar reflections and also add a bit of turbulence to the air around the nozzle eflux. This cools and disperses the exhaust and so reduces IR signature. The F-35 also has an engine bay cooling system and some sort of system of radar blockers installed in the rear of the engine to prevent radar returns from the turbine blades when view from the rear. I have no idea how that could possibly work without melting, but Pratt and Whitney have mentioned it several times in their literature.

 

Once the J-20 and J-31 get their definitive engines, I think we will see the Chinese equivalents of these technologies, whatever those might be.

 

 

 

They probably think in combat situation there is going to be after-burning, so little can be done to lower RCS.

 

 

Afterburning increases infra-red signature, not RCS, unless the aircraft is contrailing.

 

At the end of the day thermal management requires weight. All of the types you listed were attack types that could neglect performance except the F-22, and even then I think the IR reduction is limited to the 2-D thrust vectoring nozel - ie, the thermal management is somewhat integrated into the thrust vector and is possible specifically because it vectors in the vertical plane only, allowing a spread out rectangular nozzle. So a lot of compromises have to be made to spread out your IR plumb, and as noted if you're reheating all of that is for naught. Again, F-22 is an exception in that it was designed to supercruise at very high altitude (non-variable engine inlets).

 

I think you're a bit confused. IR reduction is not limited to 2D nozzles by any means, although it was the favored approach for US designers for some time. In fact, the Russians tried rectangular nozzles on a testbed SU-27:

 

 

Rectangular nozzles have a much smaller thermal signature, but they're also much heavier and produce slightly less thrust due to inefficiencies. It could well be that the IR masking approach of the F135 engine is just better, achieving similar results for fewer compromises.

 

The fixed inlets of the F-22 aren't for supercruise. Fixed inlets hurt supersonic performance. The fixed inlets are for stealth.

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I think you're a bit confused. IR reduction is not limited to 2D nozzles by any means, although it was the favored approach for US designers for some time. In fact, the Russians tried rectangular nozzles on a testbed SU-27:

 

 

Rectangular nozzles have a much smaller thermal signature, but they're also much heavier and produce slightly less thrust due to inefficiencies. It could well be that the IR masking approach of the F135 engine is just better, achieving similar results for fewer compromises.

 

The fixed inlets of the F-22 aren't for supercruise. Fixed inlets hurt supersonic performance. The fixed inlets are for stealth.

Sorry, I shouldn't have said 'only', but the 2D nozzles are the most obvious IR reduction, and I think what specifically was being discussed. I'm not aware of what other IR reduction tech was used in the F-22; if there's anything else in open source I'd like to know.

 

My comment about the lack of variable geometry inlets was that the F-22 sacrifices these* for low RCS and that it can do so because it is more of a single purpose interceptor than a fighter. Because of that, it has a very high cruise speed at high altitude and would likely not need its afterburner for engagements. But that is a unique profile for an aircraft.

 

*Its worth noting the B-1 does as well, but that aircraft optimizes its fixed inlets for low level performance. That's why the B-1B lacks the B-1A high altitude top speed.

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The F-22 also has some sort of IR-reducing paint. Ever since the 1980s, IR seeker heads on missiles have been sensitive enough to lock on to an aircraft just from the heat of friction with the air on the front of the aircraft. So, realistically, I think that the IR reduction measures on fifth-generation fighters will only serve to reduce the range at which IR-guided missiles can lock on, and quite likely not by that dramatic of an amount (at least when compared to the reductions in radar detection and lock on range).

 

The configuration of the flight control surfaces of the Raptor is also significant. Those gigantic vertical stabilizers and horizontal surfaces shroud the exhaust plume from a fair number of angles of approach.

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The F-22 also has some sort of IR-reducing paint. Ever since the 1980s, IR seeker heads on missiles have been sensitive enough to lock on to an aircraft just from the heat of friction with the air on the front of the aircraft. So, realistically, I think that the IR reduction measures on fifth-generation fighters will only serve to reduce the range at which IR-guided missiles can lock on, and quite likely not by that dramatic of an amount (at least when compared to the reductions in radar detection and lock on range).

 

The configuration of the flight control surfaces of the Raptor is also significant. Those gigantic vertical stabilizers and horizontal surfaces shroud the exhaust plume from a fair number of angles of approach.

 

FLIR on the potential plane or UAV searching for you too presumably ?

 

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FLIR on the potential plane or UAV searching for you too presumably ?

 

 

 

FLIR isn't good for picking up aircraft, but yes, IRST detection range should be significantly, if not dramatically shortened as well.

 

For whatever that's worth; IRST is vastly over-rated as a detection technique IMO, but heat-seeking missiles have a pretty undisputable track record for swatting planes.

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Would cooling aerodynamically heated parts of the fuselage even conceivably be effectual enough to warrant the trouble ?

 

I'm not sure, to be honest. I have read that a lot of the current generation RAM doesn't like exceeding mach 2.0 because of aerodynamic heating. It might be worth finding some way to wick away heat from the leading edges into the fuel to allow for a high speed dash. Pumping cooling air through the leading edge might work too, but I'm not sure how much extra power that would sap from the engine.

 

My understanding is that most anti-IR coatings work by shifting the peak emission frequencies away from the frequencies that IR sensors monitor. Air isn't uniformly transparent to IR. A lot of IR frequencies are strongly absorbed by the atmosphere, so practical IR sensors are limited to surprisingly narrow frequency windows. If the fancy paint can force most of the IR emission outside of those windows, the aircraft is much harder to pick up.

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To the point about fuel being used as a coolant and subsequently burned to offload heat, I had heard rumors of that being the case on the F-22 but I consider it a little unlikely in a small fighter type. Some of the concepts for hypersonic aircraft did use cryogenic fuel to cool the leading edge and then subsequently burned the fuel after the cool cycle in an open loop type arrangement, but as far as known these were just concepts, didn't use JP-5, and were being used in very specialized recon a/c not expected to maneuver or be mass produced. It strikes me as something that would be hard to accomplish in a small fighter turning and burning.

Edited by Josh
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To the point about fuel being used as a coolant and subsequently burned to offload heat, I had heard rumors of that being the case on the F-22 but I consider it a little unlikely in a small fighter type. Some of the concepts for hypersonic aircraft did use cryogenic fuel to cool the leading edge and then subsequently burned the fuel after the cool cycle in an open loop type arrangement, but as far as known these were just concepts, didn't use JP-5, and were being used in very specialized recon a/c not expected to maneuver or be mass produced. It strikes me as something that would be hard to accomplish in a small fighter turning and burning.

SR-71?

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Actually I looked it up and according to wiki the SR-71 did use its fuel as a coolant. The vehicle I was thinking of was actually some of the theoretical 'aurora' type aircraft suspected of using colder, more exotic fuels like liquid methane or hydrogen.

 

Not sure about the F-22, but in the case of the F-35 the leading edges of the aircraft are also the ESM system. Something I never though about was how hot that part of the plane might get during high speed and how the electronics would have to survive that environment.

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At full internal fuel load a modern fighter jet is something like one third fuel by mass (some are a little more, some are a little less). The internal fuel represents a significant heat sink. To what extent modern fighters actually cool themselves with fuel, I am not sure. I believe it's common practice to dump electronics waste heat into the fuel, but I don't know if aerodynamic heat load is routinely dumped into the fuel Blackbird-style. The SR-71 did have a lot of fuel on board though, it was somewhere north of half fuel by mass when fully loaded.

 

That said, I think that cooling the aircraft down is of limited importance to IR stealth in modern fighters.

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No reason that wouldn't work to cool the wing, but I assume it creates drag and reduces lift. Any cooling mechanism is going to add weight and complexity. The mechanism of using coatings to emit the heat in unexpected frequencies is probably the most light weight option that could be imagined. I assume the coating must absorb the heat across the most key frequency ranges based on resonance and probably has to be composed of at least two different materials covering different IR bands, and that molecular vibration then re-emits that energy across a different band. Basically IR spectroscopy only as a functional way of changing frequency instead of an analysis of the material. I can't think of any other way it could work. Florescence requires the energy be of higher frequency so it would have to be an IR to longer IR conversion; you can only go down in energy.

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Another new H-6 variant in the works, the H-6N, seems to focus on cruise missiles or seems to also be designed for launching a single DF-21D air launch version. Easily identifiable by its aerial refueling probe at the front.

H-6No1.jpg

 

H-6No2.jpg

 

A Chinese web page and its text below:

 

近日,美国媒体“国家战略”发表文章称,中国曝光轰6系列最新改进型轰6N轰炸机。该机型较轰6K而言,无论机载电子系统、雷达系统还是发动机都有较大改进,最突出的是这是一款可空中加油的远程战略轰炸机,挂载我国最先进的巡航导弹,将极大提高我国的战略核威慑力和台海拒止能力。

轰6N作为轰6系列的最新改进型,相对于轰6K,最明显的改进便是机头前部的那根巨大的加油管,意味着轰6系列轰炸架首次具备空中加油能力,结合我们早已改装成熟的轰油六或伊尔76改装的加油机,将大幅增加轰六N的作战半径,如果配备以运20改装的大型空中加油机,将使得其作战能力成倍提升。

以轰6K具备4000公里的作战半径,完成一次空中加油的轰6N作战半径可达5000公里以上,如果挂载我国最新长剑20巡航导弹,其作战半径可达到惊人的6500公里以上,这意味着即使在本土,轰6N也具备对关岛战略核打击能力,东南亚大部分国家也都将在其打击范围内。

长剑巡航导弹是我国于上世纪90年代自主研发的新型远程巡航导弹,可挂载常规弹头,也可挂载核弹头。2006年陆基版的开始装备部队,并在2009年国庆阅兵上首次公开亮相。该巡航导弹长8.3米,弹重2.5吨,直径68厘米,最大巡航速度0.75马赫,射程1500-2500公里,可在核常弹头间灵活切换,打击2000公里外目标的末端精度CEP小于3米,其作战能力远胜于美国战斧巡航导弹。

目前,该弹已发展至第二代东风-10A巡航导弹,并在此基础上衍生出陆基、舰载、空射和潜射等多个版本,而空中的轰-6K轰炸机挂载导弹型号则为K/AKD-20,对应型号为长剑-20。其采用不同的制导方式,灵活的发射平台,令敌军防不胜防,是世界上少有的性能先进的巡航导弹。

更难能可贵的是,中国还以长剑-20巡航导弹为基础研发出了空射版远程反舰导弹鹰击-100。该导弹射程550-800公里,重点加强了复杂航路规划能力,通过自动航路规划,鹰击-100导弹可以规避飞行路线上的敌方防空威胁,极大的增强飞行和攻击的灵活性。介于长剑20是一款可以携带核弹头的远程巡航导弹,其空射版的鹰击-100也未尝不可以,这就意味着空射版“东风21D”、“东风26”很有可能已经列装部队。如此以来,轰6N就如同火箭军的空基发射平台一般,可同时具备对陆地、海上目标进行远程精确核打击能力,极大提高我国的战略、战术核威慑力。

 

http://mil.news.sina.com.cn/china/2017-08-23/doc-ifykcypq4611991.shtml

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The most notable change from the K is the refueling probe. That pretty blantanly points to them building some kind of strategic tanker fleet. I had always assumed they would build such but it isn't clear which airframe they will adopt. To the extent they have a tanker fleet I think it was ~20 old H-6's with modifications - perhaps the surviving H-6 fleet will be converted as they are replaced with H-6K/N. Though a conversion of the Y-8 would probably be more capable.

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