Does China’s J-20 rival other stealth fighters? | Hacker News Reader

Does China’s J-20 rival other stealth fighters?

chinapower.csis.org

61 pointsprotomyth60 comments

I look forward to the day when China will supply the USA with jet fighters. We will save so much money!

That is not likely to ever happen. Defense spending in the US is mainly welfare for US defense contractors.

But you can pay them to slap a sticker on it.

For anyone interested in the rise of the Chinese military, I'd recommend you read the Department of Defense report to Congress on 'Military and Security Developments Involving the People’s Republic of China 2017':

https://www.defense.gov/Portals/1/Documents/pubs/2017_China_...

Some comments about the article and Chinese fighter development- some of these points mentioned in the article but glossed over, some are implied but not mentioned, and some completely absent:

1. Stealth for fighters isn't about keeping the enemy from seeing you entirely. That went away a long time ago. Stealth helps your survivability by making it take a little longer for you to be seen. If you can see the enemy from 50 miles away, but they can't see you until 20 miles away then you have a huge advantage in being able to launch a missile first.

2. Stealth is not just about RF, it's about visual and thermal cues too. The latest generation of missiles are going to multi-mode seekers (RF + IR is one possibility) so you need stealth in multiple domains to be effective.

3. RF stealth can only be optimized for one band. So you might design your coatings and structures to work against X-band (10GHz-ish) but be effectively 4th-gen non-stealth against early warning recievers that operate in the MHz range and against short range radar in the Ka-band (40 GHz-ish). This is why point 1 has become the way it is. The enemy will know you're there.

4. China is great at some areas, and laughably bad at others. They haven't put the WS-15 engine on the J-20 yet because they don't know how to make it right. They are currently spending tons of money on researching metallurgy so they can catch up with the rest of the developed world. It's funny that they can develop their own advanced radar and jammers but they still have to buy all their engines from Russia.

5. Good missiles are a huge component in survivability- a long range missile with lock on after launch capability can be fired in "the general direction" of a target without you having to have your own lock on them. This is good if you have an X-band radar on your jet but can get cues from a surveillance radar in another band, and your missile seeker is also in another band. This means your weak point that the enemy stealth was optimized for is covered by the strengths of your other air power. China makes great missiles.

6. Command, Control, and Communication (and Cyber, Intelligence, Surveillance, and Reconnaissance) play a huge part in a major air battle. It's not just a bunch of individuals trying to get their guy, but a coordinated strategy. China is especially dependent on control and communication, since their pilots are trained to follow orders from the ground. You need jam-resistant communications for this. China is great with RF stuff.

7. The article claims jets like the J-11 are 3rd gen equivalent and J-20 are 4th gen equivalent. This is almost surely an intentional downgrade because if this D.C. based think tank revealed what they actually thought it might hint that they know more about these jets than they want to. Calling a J-11 a 3rd gen is laughable. The latest J-11B is basically 4.5 gen. It can match or even outperform a fully upgraded F-15C in many areas. While it may not be better overall than a F-15C, it is at least 4th gen, call it 4.25 gen to a new F-15C's 4.5 gen. The same goes for the J-20, it is clearly better than 4th gen, call it 4.9 gen to the F-22's 5th gen.

8. While a J-20 might not match a F-22 one-on-one, if they can make the J-20 en masse, they will present a serious threat to the F-22. We only built 187 F-22s, haven't fully upgraded all of them (some don't need upgrading since they are only used for training), have crashed a few, and cannabalized others for parts. We'd be lucky to get 100 fully upgraded F-22s to a fight. We're hoping that we can make enough F-35s to cover that small number, but China is making the J-31 to counter.

In conclusion- Does China's J-20 rival other stealth fighters? Yes. Maybe they aren't fully competing in the stealth category, but you should be afraid of it because it has other strengths.

Edit: Danm, I almost forgot about electronic warfare (EW). Another alternative to stealth is jamming the other guy's ears off. It makes you vulnerable to anti-radiation missiles, but missile launch detection and a good on/off switch makes jamming a great self-protection scheme. Coherent distributed jamming is on the horizon, possibly to the point of fooling anti radiation missiles. China's pretty good at EW, just like they are at radar and communication stuff. The next all out war where developed countries throw all of their technology at each other is going to suck.

> China is especially dependent on control and communication, since their pilots are trained to follow orders from the ground.

Not sure where this idea comes from. Air combat cannot be commanded. Or you mean something else.

> The article claims jets like the J-11 are 3rd gen equivalent and J-20 are 4th gen equivalent.

US has 4-gen division, Russia uses 5 gen division. China uses the same categorization as US, so J20 is 4th-gen, j-11 is gen 3.

Russian and India likes to use the 5-gen categorization, to some extent, that makes Russian fighters looks nicer.

[edit] The article actually use 5-gen categorization but list j-11 as gen 3... I have no idea how these people still have their jobs...

I can't speak for the original poster but both Chinese and Russian tactics have in the past largely depended heavily on ground based guidance. This is partly the reason for or perhaps because of their planes having inferior radar or none at all in some cases. This was the case during the Cold War. Things might have change since then. Perhaps this is where we get the notion that Chinese pilots are trained to strictly follow orders from the ground.

Lockheed advertises F-22 and F-35 as 5th generation fighters. Does the USAF have a different terminology?

> Not sure where this idea comes from. Air combat cannot be commanded. Or you mean something else.

Obviously nobody commands the entire fight since the enemy also gets a say in what happens.

What I meant is that Chinese pilots are trained to take direction from ground controllers that are looking at the integrated air picture from all of their surveillance systems. It's called ground controlled intercept (GCI). China and the former Soviet Union countries are heavily reliant on GCI. The idea is that the pilot is busy flying the plane and can't see the integrated picture in the cockpit, so a person on the ground that can see the full picture and isn't distracted by flying can make better tactical decisions about which targets to engage, when to shoot, and when to go out (turn away). A Chinese pilot hears on the radio "Callsign, turn to heading 170, Mach 0.9, target 5 miles" and doesn't know what else is going on around him. The GCI style gets severely degraded when communications go down, because the pilots lose the guidance in their ear.

The comparison is that western pilots are told what the air picture looks like and then the formation commander decides who to target. Western pilots hear "Hostiles at x position, y position, and z position" and then mutually decide who each person is going to target based on contracts (they pre-decided on the ground that #1 and #2 in formation get the northern target and #3 and #4 get the southern target, whoever is done first gets the trailing target) and then listening to the formation commander to catch any mistakes. It's complicated for the pilots but works better when communications go down.

It seems like the Chinese/Russian technique would work better over their own territory and therefore implies that it's a technique developed from a defensive strategy.

Is this a reasonable characterization?

You seem knowledgeable, so I'll ask you this: what're the prospects for bistatic radar detecting stealth aircraft?

That pretty much has to work, right? If your transmitter and receiver are set far apart, anything that interrupts the transmission will cue someone to an object being in between. But I wonder how practical that is.

Interrupting the signal isn't how multistatic radar works. You actually get two signals, the first is the transmission that traveled in a straight line to get there, the second is the one that bounced off the plane and took a little longer to get there. By measuring the time delay you know how much longer two legs of the triangle are from the third. By doing this with multiple receivers you can solve a system of equations to figure out where the plane is. Solving the system of equations to make all the triangles work out is why it's called triangulation.

Stealth works in two ways: absorption and scattering. Absorption works by soaking up some of the RF energy, but is limited. Effectively absorbing the RF is limited by physics, since you can't put a 20 cm thick coating on a plane and expect it to fly.

Scattering works by keeping the RF from being reflected back to the transmitter, which is also the receiver in a monostatic design. If you can stick a receiver into the path of scattered energy, you can theorectically detect it.

However, there are some issues to overcome to make a good multistatic system. Scattering disperses the energy, so it's not like the receivers are getting a particularly strong signal, so you need a big high gain antenna. That's easier for the home team playing defense, but kind of hard for an attacker who has to stay portable. Then you also have to overcome the communication issues. Radar requires precise timing, which is easier when the transmitter and receiver are right next to each other. You can send a precision timing signal over large distances (precision timing is one of the reasons that GPS exists, as well as Europe's, China's, and Russia's versions), but you have to actually take the theory of relativity into account when designing the system- clearly not impossible, it just makes the math a smidgen harder. You also have to control the real estate to put multiple antennas out there. You also have to get your receiver into the path of the scattered energy, so you are SOL if your receiver is on the ground and the stealth plane is scattering all the RF upwards (unless you have antennas in space...).

Multistatic systems are feasible and operational versions already exist. But there are enough tradeoffs that traditional monostatic systems aren't going anywhere. A good defense would use a bistatic system as one of the many layers of surveillance.

To your point '4':

"China is great at some areas, and laughably bad at others. They haven't put the WS-15 engine on the J-20 yet because they don't know how to make it right. They are currently spending tons of money on researching metallurgy so they can catch up with the rest of the developed world. It's funny that they can develop their own advanced radar and jammers but they still have to buy all their engines from Russia."

It wasn't all that long ago that Russia had the drop on just about everybody in the world including the USA when it came to Titanium processing. They quite possibly still do. It's not rare at all to see a country be 'great in some areas, laughably bad in others', this is simply a reflection of their investment into that particular tech to date. And if China has so far proven one thing it is that they are pretty good at catching up.

You're right about the history and every country will have their own strengths and weaknesses, but there's a difference between Russia being one step ahead of several countries and China being several steps behind several countries. Russia is singularly good at something, while China is singularly bad. The top student in a class typically doesn't laugh when everyone is worse than them, but the entire class often laughs at the one student that still can't grasp what everyone else understands, and has for a while. In this case the class is the countries with a permanent seat on the UN security council.

China didn't realize how far behind they were at metallurgy until they tried making jet engines. Jet engines are complex, so we weren't surprised the first time a domestic Chinese engine sucked. Not surprised about the second engine sucking either. But it's kind of funny now seeing as they still haven't gotten the hang of it.

There also was a time when Russia (and Germany) were well ahead of the United States in terms of access to space.

I would expect China to take as long or shorter than it took the rest of the countries that mastered that particular skillset. Incidentally, I had a tour of the company that makes the machines that mill the final contours of those turbine blades and I'm not at all surprised that this is extremely complex knowledge, I know quite a bit about CNC machining and they managed to surprise me more than I had expected possible.

> It's funny that they can develop their own advanced radar and jammers but they still have to buy all their engines from Russia.

How is that 'funny'? There are five nations on Earth that can design modern aircraft high-powered jet engines from scratch:

USA, UK, France, China, Russia.

Six if we include India which does so with French and US assistance. The fact that China is able to play in that league is impressive in itself, even if they are the weakest player.

Everyone else is nowadays confined to licensed production or a lower tier of performance.

Splitting UK/France off from other parts of western Europe doesn't make that much sense, though, considering how in the past decades R&D has been distributed over the continent, as has manufacturing.

Am I missing something here about point 7?

>It is worth noting, however, that China’s criteria for defining aircraft generations differs from accepted international standards. China defines aircraft generations based upon when an aircraft was integrated into the air force. Per China’s criteria, the J-20 is considered a fourth-generation aircraft.

You're right, I misread the table. I thought they were claiming that aircraft in the same row had similar capabilities. I can't seem to edit my original comment since it's been too long.

Fun little note: The afterburning turbofan engines used in this aircraft are supposedly similar in performance to the P&W F119 engines used in the Raptor. The company behind the engine is/was working on a high bypass version which aims to power the Y-20 [1]

[1] https://en.wikipedia.org/wiki/Xi%27an_Y-20

There is speculation that those are still in the prototype stage and the current ones are running on Russian Saturns. China is still catching up in turbofans that have sufficient power and reliability (they can get one or the other, but not both ATM).

They should team up with Renault.

High performance turbofans and modern semiconductors are the most closely kept technologies in the west and Russia. You can’t easily reverse engineer them from end products, they are all about process. It’s reasonable that these are the last technologies left for China to master.

Partnerships are out of the question.

Speaking of modern jet fighters, here us a scary Fly-by of Su35 beside Su30 in Syria (couple of days ago), at full speed meters apart:

https://m.youtube.com/watch?v=SlNyL9jxRP0

Is the POV from the pilot of the 30 or the 35?

The real gold is the article linked halfway through

http://www.ausairpower.net/APA-2011-03.html

> This study has therefore established through Physical Optics simulation across nine radio-frequency bands, that no fundamental obstacles exist in the shaping design of the J-20 prototype precluding its development into a genuine Very Low Observable design.

Well I read that 3 or 4 times and still don't understand it, but the pictures sure are pretty!

They turned all the pictures we have of the prototypes into a 3D model and ran radar simulations on it. They concluded that China has developed an actual stealth plane and not just one that looks pretty.

As opposed to the "stealth" plane that Iran unveiled a few years back that doesn't fly and isn't shaped right. They were just imitating shapes they had seen before and didn't put it together right.

This mirrors the impression I got when I first saw the pictures of it. The round nozzles can't be good for its radar profile (as from a wide range of angles, there's a significant surface area facing the observer).

I expect any radar engineer is aware of this, so I wonder why such a trade-off was made.

There are a lot of words but not much hard content. Less stealthy (especially from the rear), more internal volume compared to the F-22.

Only about 11 produced so far.

I appreciate your post.

For those wondering, China is the place where companies across the world are going to hide slave labor and incredible environmental devastation.

That is why their prices are so cheap and 6 million manufacturing jobs have been lost. Slave labor and the greatest destruction of environment the world has ever seen.

Sure, but I'm not convinced that the crazy price of programs like the F-35 is due to being environmentally responsible and respectful of labor rights. If the US want to compete they also need to improve.

And right now F35 does not even fly

The F35s have been flying for 3 years now. Just not many of them, for very long, or very cheap.

How many carrier strike groups can china deploy? How much power can they project 3,000 miles from home? Is the answer none? why yes it most likely is...

China doesn't need to. It only needs to threaten Taiwan, Korea, Japan and other US allies in the region. Then they will switch alliances.

It's more likely they'll further militarize.

This crosses out of intellectual curiosity, which we want here, and into nationalistic agendas, which we don't, so please don't take HN threads in such directions.

We detached this subthread from https://news.ycombinator.com/item?id=15919819 and marked it off-topic.

A) Are we sure it even flies?

B) Do they have the very nuanced tech to handle the complexities of stealth?

C) Most important: it's a team, not a pilot. What makes US Air Power so effective is the coordination, and multi-role availability etc. AWACS, communications, meshed fighter groups, all sorts of strike packages from cruise missiles to drones etc.. So when you need to go in stealth and do the AA + Comms network, you can do that. When you need low-air with some jamming support etc. you can do that. When you need to hit something way past the horizon you can do that. When you want to linger forever you can re-fuel and do that.

Hopefully it will never matter, but the ability to project power makes a difference, even if it's not used.

Time to get some good gear into India ...

They'll figure it out.

Of course it flies: https://www.youtube.com/watch?v=VyCagF0RUQQ

a) yes

https://www.youtube.com/watch?v=k_CK3N8mOXs

b ) you can probably assume, considering the vast tech industry in China, that if they haven't yet they will soon.

c) Why would you assume their operational and strategic capabilities are lacking in these areas? The Chinese have a very capable armed forces

https://www.globalfirepower.com/country-military-strength-de...

https://www.lowyinstitute.org/issues/chinese-military

a) Just because you show a video of an airframe in the air, does not remotely mean that the Jet specified, with all it's gear, is flying and operable.

b) No - stealth for jets is a very, very specific thing with lots of nuance that has no civilian counterpart. What 'tech' does China make that surpasses most of the world? Almost none. The article today about their car factories: all Swedish and Swiss robots. So they're not even at that stage. Same thing with Engines - a very key component that most nations do not seem to be able to do on their own. Apparently the new US F series have surfaces tweaked down to the mm, bigger than that, it's not stealthy. And it requires a lot of specialized maintenance.

c) The Chinese have no experience whatsoever operating in the kinds of systems that the US has. Those things take experience and time to develop. Can the Chinese AF effectively deploy drones 1/2 way around the world now? That's not 'one tech' - that's a whole pile of tech and operational abilities rolled into one. And that's just drones. How many re-fuellers do they have ready? How many Aircraft carriers (really, 0). How many forward stations can they deploy to in an instant?

No, as far as they have come along the last 20 years, this is one area they are going to be quite far behind in, for still some time yet. I roughly say they are about where they are with their aircraft carrier.

> a) Just because you show a video of an airframe in the air, does not remotely mean that the Jet specified, with all it's gear, is flying and operable.

So it acutally cannot fly, that's what you are saying.

> What 'tech' does China make that surpasses most of the world? Almost none.

China tech is among the world's most advanced. Let's not confuse being the absolute #1 with just being advanced.

> c) The Chinese have no experience whatsoever operating in the kinds of systems that the US has.

"had" They used to have a despicable internet economy, look at what they are doing now.

a) I'm not saying one way or the other, I'm saying we don't really have lot of info on what it actually is and does.

b) China is not among the world's most advanced in the series of technical bits necessary for this: stealth, jet aircraft engine, weapons systems, underlying operational capabilities.

c) China hasn't dropped live munitions on an actual target in what, decades? Do they have a single AFB out of their borders? Do they have an operable aircraft carrier? Do they interoperate with dozens of other nations? Have they flown actual stealth missions?

You have to do all of that to get good at it.

I will be a long while.

The stance you're taking is one that is dangerous. China has a billion people and a lot of really smart ones.

a) The J-20 does fly, but it isn't fully operational. But functioning prototypes do exist and have fired missiles. If you aren't satisfied with pictures and videos I guess you'll just have to join the PLAAF and become a pilot yourself.

b) China may bad at engine construction and lag in stealth, but they are world class at designing weapons and their operational ability. The PL-12 and upcoming PL-15 are extremely advanced and their integrated air defense is seriously good.

c) China has drops live munitions on regular occasion. They do it during training and during weapons development. Just because the US and Russia are dropping bombs in Syria doesn't mean they are getting good practice out of it. China's aerospace development is far beyond their aircraft carrier development. Don't think that just because they can't project power across the globe that they are impotent. The ability to operate carriers and resupply underway is exclusive to the USA. Literally every other country has to stop at a friendly port to resupply. China threatens plenty of countries within its range.

The thing about war with China is that it's asymmetric, so they don't have to be as good as the USA to cause problems. If China attacks Taiwan (a commonly hypothesized scenario) they have a huge home team advantage while the USA has to drag everything halfway across the world. The USA can't rest because as soon as they are close enough to defend Taiwan they are under 24/7 threat from Chinese subs, ships, cruise missiles, and planes. China gets to use 100% of it's military for that fight, and the USA cannot use 100% because of the long logistical tail.

"China has a billion people and a lot of really smart ones."

So does India. So does Africa.

1) "But functioning prototypes do exist and have fired missiles." I agree, but what do those prototypes actually do? Is the real question.

2) " they are world class at designing weapons and their operational ability." - how many real targets have they hit i the last decade? I'm sure they are smart. But not even the Chinese know how their gear will work in the field.

3) "China has drops live munitions on regular occasion. They do it during training and during weapons development. Just because the US and Russia are dropping bombs in Syria doesn't mean they are getting good practice out of it. "

Uhh, yes - it does. And when I'm referring to 'dropping munitions' - I'm referring to the massive machine of operations support and tech that underlie 'the dropping of those bombs'.

Do they have the forward air controllers? Are they good? If not - Air Force is severely hampered. Do they have the AWACS capabilities - or will their entire AF be rendered useless in the blink of an eye by e-warfare. The list goes on and on.

> Just because you show a video of an airframe in the air, does not remotely mean that the Jet specified, with all it's gear, is flying and operable.

This was not your question.

> Are we sure it even flies?

This was.

I feel you're holding a very anti-china-pro-team-america opinion here, you should provide some resources to back up your speculative claims that China does not have the technological capability to operate the third largest armed force in the world.

"Are we sure it even flies?"

'It' refers to some great J-series jet with crazy specs.

Not an empty prototype airframe.

china has famously hacked many of the major manufacturers and supply chain partners of american military aviation over the last decade. i don't think it's a stretch that they may have learned some advanced information about stealth.

and NATO, in particular the USAF, can deploy in volume. The Russians field some interesting planes but then you find out they have six of them, only three flyable.

The usual joke/factoid is the US Navy is the #1 air force in the entire world, with the US Army and the US Air Force running a close second and third with orders changing depending upon how one counts.

The USAF (air force) is the biggest air force in the world, the USN (navy) is second, the Army is in the top ten but number three is Russia.

It's more of an assessment of capability rather than raw size.

For example the air component of the USMC is larger than the UK RAF but the latter is more experienced and capable in long-range power projection.

The IDF/AF is smaller than the Russian air forces but many times more capable.

> A) Are we sure it even flies? Yes, you can just google it, and found video of public flight in air show.

> B) Do they have the very nuanced tech to handle the complexities of stealth?

According to many sources, China stolen the F117 debris, and apparently that's why US bombed Chinese embassy because of a "outdated map".

C) Most important: it's a team, not a pilot.

Y-20 the heavy weight transport aircraft. J-16 the F-15E equivalent J-10 the F-16 equivalent Kj-2000 Kj-200 Kj-500 AWSACS air craft Aircraft carriers J-15 carrier jet

> What makes US Air Power so effective is the coordination Beidou: equivalent to GPS

> meshed fighter groups China is one of the leaders in swarm drones

> According to many sources, China stolen the F117 debris, and apparently that's why US bombed Chinese embassy because of a "outdated map".

Would you mind linking to a few of the many sources?

It's a rumor, circulating on Chinese and English forums, and I have not kept reference.

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