[sudosysgen]

The ability to "stealthily penetrate enemy airspace" is only temporary. As VHF radars improve and dual guidance missiles proliferate the F-35 will only be barely more stealthy than what came before it.

As it is right now Russian VHF radars can already guide dual-guidance missiles onto an F-35 close enough for them to detect the F-35 with their radars.

The Chinese and Russians have set up VHF radars in Syria and use them to observe Israeli F-35s every day too, so the fog of war in their favour.

The fact that stealth is only a temporary advantage has been known for a long time. It's part of the reason why the USSR decided not to pursue stealth aircraft development despite their lead on stealth design technology relative to the US - until the Soviet bureaucracy in it's classical ineptitude decided to declassify the algorithms they developed which Lockheed Martin happily adopted.

[Green_man]

Is your argument that military technology could be described as an "arms race"?

[sudosysgen]

The F-35 was developed to be used until 2070. It was done so at a time where it was clear that stealth could not be relied on past 2025 at the most.

Many compromises were made in the pursuit of an advantage known to become greatly diminished 10 years into a 50 year lifespan. I don't think this can be written off by the arms race argument.

[SubjectToChange]

I think you are greatly overestimating the effectiveness of SAMs. While also underestimating the complexity that stealth adds to those systems.

[sudosysgen]

Do not conflate SAMs and integrated air defence systems. An IADS that cue in interceptors and guide missiles from various different platforms is massively more capable than an SAM alone and massively more survivable.

But that's considering the system outside of the doctrine. The purpose of these air defence systems isn't going to mount an eternal and fully insurmountable wall against air power.

Rather, the purpose is to greatly reduce the initial effectiveness of US airstrikes for hours to weeks until American military infrastructure can be struck.

Stealth does not increase the complexity of radars. They simply operate on a different wavelength. This took some engineering to increase the precision but there is no reason for a VHF radar to be any more complex than an X-band radar.

VHF radars in many ways are more practical than X-band radars because the lower frequency allows for more mobile and more survivable radar infrastructure. For example, Israel struck Chinese VHF antennas in Syria. But because the antennas were relatively cheap and decoupled from processing, the Chinese were able to swap out the antennas and repair their radar in a day or two, thousands of kilometers away.

[Green_man]

Sorry, my previous comment was probably overly dismissive. I'd argue that developers and users of the F-35 already understand that stealth gains are not permanent. Countries and military organizations that purchased the F-35 definitely hope that the stealth advances last longer than 2025, but they will pay for improvements, new planes, and new tech long before 2070. It seems comically naïve for them to take claims of "2070" at face value without verifying, but that's just conjecture on my part.

[sudosysgen]

Is it? The B-52 has now been in service for 69 years. 50 years is certainly not impossible.

The trade-offs made for stealth are beyond the plane itself, the entirety of US military strategy (and even diplomacy to some extent) is deeply affected by a stealth-focused air-power strategy.

As for stealth advances beyond 2025, I don't see it personally. As long as your doctrine requires you to fly your planes over enemy radars, there's not much you can when the wavelength of the enemy radar is bigger than most features in your plane. It's a physical limit as solid as conservation of energy.

[Green_man]

I don't work in radar/military stealth, but my argument isn't that you're wrong about any of your technical claims. Rather, my argument is that the F-35 was designed and purchased by people who are at least as aware of those technical details as you are. This is an assumption, but I don't think it's a huge one. As a nitpick, the F-35 may still be operational in 50 years, just as the B-52 is operational today. The question is whether its stealth will still be useful, not whether it can get airborne. Nobody is using the B-52 for its stealth anymore (happy to be proven wrong), and the decision to lean on the F-35's stealth capabilities for 50 years won't simply be "The B-52 has been running for 69 years, nice!"

[sudosysgen]

The B-52 was never designed for stealth.

If stealth isn't very helpful, why would you fly the slow and expensive F-35? I don't really understand it.

I'm sure the people behind the F-35 were aware of these technical factors, maybe not the extent of Russian/Chinese investment though, but I don't think that their interests were anything beyond making as much money out of maintenance as possible.

As for the people making the purchases, many of them do think that the F-35 made the wrong tradeoffs and a lot of them are pushing for a plane that would fulfill the same role as the F-35 was designed for but with a very different set of tradeoffs.

[hajile]

They're now looking to retire the F-22 decades earlier than anticipated (announced a couple weeks ago).

The replacements will lose the tail fins giving much, much greater stealth capabilities. I suspect at that point that the F-35 will become far less desirable and will start retirement soon after.

https://www.defensenews.com/air/2021/05/13/the-f-22-is-going...

[sudosysgen]

The biggest reason the F-22 is going to be retired is mainly because parts are no longer being produced as much as they should have been.

NGAD will be stealthier at figher radar frequencies. The issue is VHF stealth, and removing the tailfins won't help for that.

[hajile]

If they were happy with the F-22, they'd pay to get the parts. I guess that when you pick a plane because of politics instead of capabilities, you get bitten (really should have gone with the YF-23 even if it didn't put jobs in as many states).

Stealth is NOT about becoming invisible. It's about reducing detection range until it's all but too late to intercept. Even worse, most of the ordinance those planes will be delivering will keep the plane many miles away when firing making interception time even shorter. The AGM-158 fires from around 230 miles away (575 miles for the ER variant). The S-400 can't even detect that far out let alone get enough resolution to react.

Physically smaller reflected cross-section means more stealth no matter the frequency. Giant flat panels radically increase the reflection from the side and marginally from the front.

VHF isn't magic. It's very imprecise to begin with. It's very vulnerable to jamming. It's super-vulnerable to weather patterns (a tropospheric ducting event could have most of the energy trapped in the wrong location). Longer wavelengths vs the X-band make it easier to absorb (E=hv). VHF installations are also very easy to target due to their size and massive power output trying to compensate for that E=hv problem.

Once you know a plane is somewhere within a few dozen miles, you have to send out fighters. They don't exactly have room for those large VHF arrays and those arrays aren't accurate enough to actually target. For that, they need to fall back on X-band, but that's the range that the stealth is optimized for. Once again, the stealth plane can see them from a long way off (maybe even passively) while they can't get their own lock until much closer which usually decides the winner.

[0] https://en.wikipedia.org/wiki/AGM-158_JASSM

[sudosysgen]

We are no longer in the 1960s. VHF radars now use AESA and have home-on-jam capabilities. Missiles have dual or even triple guidance systems.

Cross section is not a number you can compute in a vacuum. The cross section is associated to the frequency of the wave.

It's not viable to use AGM-158s for everything. When running these missions you are racing against time, you need to deliver the most munitions as fast as you can without missing faster than the enemy can strike your supply lines, bases, and carriers.

"Somewhere withing a few dozen miles" is a wildly inaccurate characterization. VHF AESA radars are accurate to 350x100m, and this number is improving every year as radar processing techniques improve.

Yes, the fighter can detect the radar from farther than the radar can detect the plane. This is true of every single radar system. The issue is that the fighter can only fire blind weapons unless it moves away.

That's the issue with the AGM-158 and other standoff weapons - the radars it's targeting can pack up and leave in a minute. It will then hit an empty field. Meanwhile you're making your attacking fighter jets a lot less stealthy carrying it.

And 350m accuracy is more than enough for a huge tactical advantage. The stealth jet has to use its radars to lock onto the other fighter jet, while the defending jet can launch munitions without turning on its radar at all or until it is way too late.

They also can't pay to get the parts that easily. It's not how these kinds of projects work. The people that designed much of it are dead or retired and the production lines are closed. Planes have to get cannibalized sometimes. Opening the lines back up after they are closed can be extremely costly and technically difficult and can involve reverse engineering.

Longer wavelengths are actually harder to absorb. I don't know where you got that they are easier to absorb? You need a lot more material to absorb a wave of longer wavelength of the same material.

E=hv is the wrong equation, because the amplitude is not fixed - the power is fixed. Larger wavelengths means thicker elements that can carry much more power without running into cooling limitations.

VHF isn't magic. Stealth isn't magic either. You can't avoid scattering and diffraction, these are physical limits. They limit VHF radar accuracy too because of the basic Rayleigh scattering equation, but you can fix this by making your aperture larger and applying some clever processing algorithms. If you're a plane, the only solution is to become bigger. Which is much more difficult.

[gumby]

Clever analogy!

[2OEH8eoCRo0]

>As it is right now Russian VHF radars can already guide dual-guidance missiles onto an F-35 close enough for them to detect the F-35 with their radars.

Citation needed

[sudosysgen]

Sure. Russian VHF radars have a detection accuracy of 100m range and 20 minutes of angle azimuth [https://www.globalsecurity.org/military/world/russia/nebo-sv...]

At a range of 60km that means 350m inaccuracy in azimuth and 100m inaccuracy in range.

350m is within IR and optical range, so any IR-capable missile can be cued in. The 9M96 missiles are rumored to have IR/optical capability but this is just a rumor, while the 9M100 missiles do have that capability.

As for radar missiles, the F-35 has a minumum RCS of 0.0015 sqm. Being generous to the F-35 and saying it must be detected by 1km, it means that any radar capable of detecting a 1sqm target at a distance of 25km can detect and F-35 at a distance of 1km.

This does require estimation but 25km range against 1sqm target is realistic.

[rich_sasha]

I think it's a bit more complex than that. This is the accuracy of a point detection. For a SAM system, you need to shoot the missile roughly where the plane is going - it's moving pretty fast. So your estimate of velocity will be vastly lower quality than the point estimate of position.

You also need to update the missile's course using updates on the plane's velocity changes - so again, you need even greater accuracy on the radar.

Finally, because it's all a lot more nebulous, it is easier for the plane to take evasive action. It's generally a lot easier to detect a radar / missile launch than it is to detect the airplane. With radar countermeasures in place, the SAM radar really has an uphill struggle to overcome.

I'm not saying it's not doable (though not too long ago I remember reading that these radars are just not accurate enough to guide a missile), merely that these dry numbers don't necessarily convey the full picture.

[sudosysgen]

Not really. New AESA radars are able to home on countermeasures, so if the F-35 decides to use ECM or jamming, then all the better, the missile will be able to discriminate when it gets close.

The F-35 is going to be going at around 300m/s, and the time for the missile to get there from 60km away is going to be around 100s. You should be able to integrate position to get a +- 10% estimate of velocity with our 300m error, then. In reality a lot of the error isn't stochastic either so you can get a lower velocity error.

Again you don't need the radar to guide a missile. You just need to get the missile close enough for it to pick up the F-35.

If you read an article that said that the VHF radars can't guide the missiles, they are definitely right. But the Russians and Chinese don't plan on that. Their missiles now have on-board guidance, they just need to get close enough for their own guidance systems to pick up the target. That means that instead of needing 10m of accuracy, which I agree with those articles the VHF radars cannot do, you only need to get within a kilometer.

[rich_sasha]

I don’t want to labour the point as I’m no expert, but is it enough to be close enough to the target and lock on? The rocket has some amount of kinetic energy for manoeuvering, and presumably less at the terminal stage. If the initial radar fix puts it in the wrong position/velocity relative to the target, can it make up for it with its own late lock-on?

I understood this is why you need that precise radar fix: you need a pretty good idea of the target trajectory so the chasing missile is not only in the right place, but also flying at an advantageous angle relative to its target.

As for on-missile guidance, I thought that was a thing since a long time ago? The radar guides initially, then the final stage is done by the rocket. Is there something newer/different now?

[sudosysgen]

Until pretty recently, missile used semi-active guidance. Basically, they would have a receptor that would detect the radiation scattered back from radar. The issue in this case is that the signal would not be much more precise or even usable due to the low frequency. So active guidance fully from the missile is needed.

Ground based missiles are quite different from A2A missiles in that they are much larger and have much more kinetic energy to spare.

Maneuvering always kills kinetic energy though. So what these missiles do is that they gain altitude before maneuvering, reducing speed and drag, and once the maneuver is done (lock acquired), they maneuver and gain a lot of kinetic energy by coming back down.

There is basically zero chance a ground based missile fired from 50-60 km will lack energy even if it has to maneuver a few hundred meters to correct for inaccuracy.

[2OEH8eoCRo0]

Could you explain how a radar system is able to determine the direction/velocity of a track?

[sudosysgen]

If you have multiple radars, you can use the doppler effect. You can also differentiate position numerically. Or you can do both!

[mikewarot]

>Citation needed

This is close, and it's from 2014

https://news.usni.org/2014/07/29/chinese-russian-radars-trac...

VHF and lower frequency radars see right through any stealth coatings and bounce off the airframe, engines, etc.

[SubjectToChange]

Then why are Russia and China developing stealth aircraft of their own?

[sudosysgen]

Because neither Russia nor China are planning to use their stealth aircraft over the airspace of another superpower. Good luck fitting a meter-wave AESA on an aircraft.

Beyond that, neither Russia nor China are trading-off anywhere near as much as the US for stealth. Both of their designs are less stealthy but carry better weapons over a longer range with better kinematics at a lower cost.

[SubjectToChange]

Why does it matter whether you are over another superpower's land? As you said, these systems are deployed in Syria and anywhere else. Besides, China is certainly designing their planes to be able to fight to US navy. The fact of the matter is that if a country can afford it, they design stealth aircraft.

[labcomputer]

> Why does it matter whether you are over another superpower's land?

One of the fairly easy ways to defeat stealth is by operating your radar at a low frequency. As the wavelength becomes "much longer" than any characteristic dimension of the airplane, the shape of the airplane matters less and less and the wave will penetrate deeper and deeper layers of radar absorption material.

But there's no such thing as a free lunch.

The problem is that the resolution of your radar depends on the physical size of your antenna relative to the wavelength (either the diameter of the dish, or the spacing of the antenna elements in a multi-static or phased array). So low frequency = long wavelength = bad resolution. You know a plane is in your airspace, but not where in your airspace.

You can solve the resolution problem by installing a physically large antenna. The size of the antenna should be several times longer than the wavelength. That might mean having a single very large dish or it might mean coherent transmitters located hundreds or thousands of meters apart. Great, now we have defeated stealth and have high resolution.

But remember how we were talking about wavelengths much longer than the airplane? How do you carry an antenna that is several times longer than the wavelength for a wavelength that is several times longer than your airplane? I can think of one way: trail wires behind you--but that turns you into a flying bullseye. You might as well file a flight plan.

That creates an asymmetry: It's much easier for the side on the ground to get a good picture of what is going on in the air.

[sudosysgen]

The systems are not fully deployed in Syria. Israel routinely flies F-16s in Syria without much of an issue.

They are in Syria in a pure intelligence capacity.

Beyond Russia and China (and possibly Venezuela), there are no fully operational VHF capable air defence systems

It's also incorrect to consider stealth as a yes/no. It's not a yes/no. It's a sliding scale with tradeoffs. Clearly China and Russia judged stealth to be much less important than the US did.

The USSR could definitely afford stealth aircraft and had all the necessary technology to make it before the US, yet they didn't, and for a reason.

As far as fighting the US Navy, the Chinese doctrine against the USN doesn't involve Chinese airplanes getting within VHF radar range of American large surface vessels before a crippling blow is already delivered.

[SubjectToChange]

The point about Syria is that if Russia and China want to fly over _any_ other country then they must assume that they will encounter VHF radar. And if VHF radar does render stealth technology useless then any include it at all in their designs? Why not slide that scale to zero? Well, probably because there are benefits to stealth and VHF radar is not as easy or cheap as you believe it to be.

You can say that the F35 trades off too much and that a "less stealth" would be better. But that's fundamentally baseless speculation.

[sudosysgen]

Russian and Chinese stealth fighter-interceptors are fundamentally based on air defense and area denial missions. You're exactly right, their main use case is not to fly over enemy countries as much as flying over friendly countries, the ocean, and their own soil.

[hajile]

Stealth is necessary for attacking, but not defending. Further, stealth is only necessary for attacking sophisticated enemies.

Russia and China have no plans to attack the US within the next few decades, so they continue to research, but not to implement. It also doesn't help that US radar is a couple generations ahead as well.

Their current interests involve countries where a fast, hard-hitting plane is just as good as a stealth plane, so they save money at every stage from design to building to cost per hour flown.

[sudosysgen]

Stealth is just as useful for defending and for attacking, and arguably I'd say even more useful for defence because the attacker will never be able to field counter-stealth radars. Stealth when combined with counter-stealth radar on your home turf gives you a huge advantage as you now know a lot more about your enemy than your enemy knows about you. Non stealth aircraft plus counter stealth radar is a lot less of an advantage.

US VHF radar is likely not ahead at all. The US has never fielded a VHF radar, while the USSR and by extension Russia and China have done so since the 70s. The US has UHF radar and is definitely ahead in conventional radar though.

The interests of China and Russia do involve attacking sophisticated opponents such as Japan or Western Europe in order to destroy American infrastructure in a defensive war. It's just that instead of using stealth fighters to do so, they intend on using overwhelming numbers of missiles including hypersonic cruise missiles, of which the US doesn't even have a prototype yet.

These decisions weren't made in the last few years. They are tactical decisions as a matter of doctrine that were made in the late Soviet era. It's not a coincidence that these countries are ahead in counter stealth and ahead in hypersonics but behind in other things, they invested in what was most useful to fit their doctrine.