PLAN Anti-ship/surface missiles

AndrewS said:

And VHF cueing should be possible. With a VHF/UHF radar, you're looking at an angular error of <1%.
That would be good enough to send down a ARH SAM on the same bearing with mid-course guidance, until the X-Band picks up the LRASM.

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This seems reasonable. I'd be surprised if the radars on warships didn't cooperate - for instance, if a VHF picks up a stealth contact, it should cue the shorter wavelength radars to focus their energy on that fuzzy region. This beam focusing should be possible for an AESA. I wonder if that interaction is modeled in simulators like Command.

AndrewS said:

Yes, there may be other aircraft and jammers, but if we're specifically looking at a Taiwan Straits scenario, I don't see other aircraft getting closer than 200km to the defending ships in the Taiwan Straits.

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There's also the issue of the wavelengths a decoy can physically emit given the constraints on the size of its antenna. If the radars are cooperating properly, the VHF should dispel a lot of the false contacts a short wavelength radar might be fooled into believing are there.

A LRASM type missile has its strong and weak aspects.

In terms of survivability in the terminal phase, once it is detected by enemy radar it is significantly worse off than a supersonic dasher like a YJ-18. In CMO, a Type 052D hit the YJ-18 with only 1 out of 4 fired missiles (25% vs 55%). And because the missiles travel 3 times as fast as a LRASM, the total number of missiles it managed to fire before being hit was far smaller. It's been a while since I tried it, but if I remember correctly, it took just 8 YJ-18s to severely damage or sink a Type 052D.

However, the above is a contrived scenario where the missiles get detected only at radar horizon ( a bit shorter for LRASM). A non-stealth missile like the YJ-18 will be picked up well beyond a ship's radar horizon by CAP and AEW aircraft. The CAP aircraft can engage the incoming missiles and so can a DDG with over the horizon ARH missiles through CEC. In effect, the total number of engagement rounds against a YJ-18 is going to be significantly larger than against a LRASM, as the latter is far less likely to be detected before the end-game scenario in the first paragraph.

Yeah, CMO's modelling of the HQ-9B is slightly problematic here and we dont know how much of it is reality, but if the HQ-9B doesnt have CEC despite having an Active Radar Seeker, it will have severe problems engaging the LRASM even when entering radar horizon. Semi-active SAM like the HQ-16 etc are a lost cause entirely, because no FCR could actually paint the LRASM at any safe engagement ranges.

What China really needs is long range dual mode seeker SAM, equipped with active radar and ImIR, as well as onboard AI combined with CEC. Yes, that sounds super expensive, but that's likely the only way to shoot down swarms of LRASM before they sink you. Because of these complications, I have long thought about why the PLAN isnt just using a fricking Dongfeng equipped with an EMP warhead to basically nuke an entire strike package out of the skies after they have taken off. As we always know from games, AOE weapons are usually super effective against swarms lmao.

Of course in the future when railguns and lasers are deployed on PLAN ships, any subsonic missile threat becomes obsolete.

nlalyst said:

All those problems are even worse for the radar platform. What's the point of your argument? That LRASM cannot work?

If the missile is flying fully autonomously then it will have to pop-up from time to time to search its environs. If it is guided by another platform, say a F-35, than it can afford to sea skim for as long as necessary.

There is a difference between having clutter issues and having your performance degraded by clutter (which is inevitable). A VLO target (LRASM's RCS could be as low as 0.00005m2 from the front) below the clutter noise is going to be very difficult to detect. Don't forget that clutter RCS increases with range. The majority of techniques used to suppress the clutter also suppress the echo of the target. This problem is still a subject of active research. With its passive RF sensor, a VLO sea-skimmer will always have an upper hand against AEW aircraft and can plot evasive actions to stay out of their detection range (which is not going to be large to begin with).

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A missile flying autonomously is relying on inertial guidance with pre-fed coordinates and waypoints. It only needs to follow those instructions. Of course the target ship will move away, but for a supersonic missile, the ship will move away much less when the missile arrives to the target than a subsonic missile.

If the missile is flying high --- and ASMs do have high flying flight modes --- they can acquire the target from a farther distance but then the target's ESM can also pick them up.

One missile can fly high and spot for the others, relying the target coordinates to the rest of the swarm flying low, e.g. Granit, Moskit.

VLO target RCS changes with the frequency band. Something that is 0.1m2 on X-band isn't going to be 0.1m2 on the L-band. Another issue is that longer waves penetrate materials easily, hence why with longer RF, you can receive them inside a concrete building. They will not see the directional shaping of the missile. Instead, they will penetrate and reflect off the innards.

There is actually a way to defeat clutter against a low flying object with a radar source above it on long frequency. Its called MTI or Moving Target Indicator.

The problem of passive sensor is that you don't exactly know what your target's RF is going to be before hand, which means you have to rely on pre-conflict intelligence gathering methods, ranging from spying to ELINT. But if you don't happen to have this information then it doesn't work. Of if your opponent decided to change his frequency bands. Or if the target radar happens to be multimodal which means it can produce a wide variety of waveforms. Or if the target radar has LPI or Low Probability of Intercept. Or if the target radar is immersed in a forest of non hostile commercial radars. Or if the target radar can mimic a civilian radar. Or if the target radar uses pseudo random jitters and chirps. Or if the background has so much backscatter and ambient sources that they interfere with waveforms from friendly and hostile radars alike, making them unrecognizable.

The advantage of an active radar is that it keeps a sample of its own signal to begin with, and use that sample as a reference to find its proper echo even in the face of heavy interference.

nlalyst said:

You missed the context: the discussion was about a missile with a passive RF seeker.

All the propagation and multipath scatter problems apply just as well to the radar, but doubly so because the emitted RF signal has to travel a two-way path instead of one-way in a passive system.

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You also missed the point that an active radar seeker only works in high bands, X-band, sometimes Ku, K, or even mmwave. The higher the frequency, the better the directional gain and angular accuracy and resolution. This counters clutter. On the other hand, passive RF requires you to work at longer frequencies, anything ranging from VHF to Ku band. Against longer frequencies, an aperture the size of a missile seeker has poor directional gain, angular accuracy and resolution, not to mention it has to deal with what's bouncing off the water surface and the atmospheric layers.

If the missile is flying below the radar horizon, it has nothing but to rely on the backscatter caused by the target's S or L-band search radars, which is already inaccurate given the size of the seeker's aperture. Furthermore, backscatter is horrible in determining range, because range is determined from a direct line of sight return, since you are computing range off a straight line. With scatter, the wave is traveling back and forth bouncing between the water surface and the atmospheric layers, which takes much longer and with no constant, and the receiver can receive the waves from different directions.

Insignius said:

Yeah, CMO's modelling of the HQ-9B is slightly problematic here and we dont know how much of it is reality, but if the HQ-9B doesnt have CEC despite having an Active Radar Seeker, it will have severe problems engaging the LRASM even when entering radar horizon. Semi-active SAM like the HQ-16 etc are a lost cause entirely, because no FCR could actually paint the LRASM at any safe engagement ranges.

What China really needs is long range dual mode seeker SAM, equipped with active radar and ImIR, as well as onboard AI combined with CEC. Yes, that sounds super expensive, but that's likely the only way to shoot down swarms of LRASM before they sink you. Because of these complications, I have long thought about why the PLAN isnt just using a fricking Dongfeng equipped with an EMP warhead to basically nuke an entire strike package out of the skies after they have taken off. As we always know from games, AOE weapons are usually super effective against swarms lmao.

Of course in the future when railguns and lasers are deployed on PLAN ships, any subsonic missile threat becomes obsolete.

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If you have active seeker, you can engage the target from above while the target is beyond the radar horizon. The lowest RCS is only at the frontal aspect, but not if the target is being attacked from the top or the side in an interception route.

The missile will have to be continuously updated from the surface source, but because the target has low RCS, the missile has to be guided from the surface until it is much closer to the target than the usual. For this you will need a powerful surface radar strong enough to track the low RCS target and guide the missile until it is much closer to the target before the seeker is released. Just so happens this should be how the HHQ-9 works with the Type 346x radars.

Having a bigger missile seeker with more powerful batteries and emitters, use of AESA and Gallium Nitride would also help.

In terms of CEC, it would have to be done from a ship with a much higher vantage point than a 052D or 055. Guess what, the mast of an aircraft carrier. I have mentioned time again and again, the Shandong is fitted with CEC, the panels of these is right underneath the Type 382 radar. For the Liaoning, it was retrofitted back in 2019. 003 will also have it outright.

With semi-active, its even better. Stealth works against a monostatic radar application. Monostatic means the transmitter and the receiver is at the same location. Stealth works by denying the reflection towards the same direction as the transmission. That's what all those angles are for.

But SARH happens to be a bistatic application. Bistatic or multistatic means that the transmitter and the receiver are in different locations. Stealth shaping will deny the echo being returned to the transmitter, but it deflects the echo elsewhere. This means that if the receiver is at a different location, it will receive it. So yes, a SARH missile flying higher or at the sides on an interception course will pick it up. The main problem is to make sure the transmitter is aimed at the target, and you need a bigger and more powerful radar that will keep the target illuminator in sight. It so happens this is how SPY-1 with SPG-62 works.

If the transmitter requires the target echoes to be able to track the target and keep the antenna focused on it, then you might have a problem. This is a more common SAM fire control radar arrangement. Do note that for some missile systems they accompany the guidance radar with some EO; Croatale and by extension, HQ-7, are examples. They can spot and track the target on EO and guide the missile, either by command guidance or SARH illumination.

AndrewS said:

The reason being that if LRASMs were be so effective, that would be to the advantage of the China, because the US is way more dependent on maritime access than China.

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Build more carriers and new bombers - it'll become more correspondingly more useful.
Every weapon belongs to its system.

Insignius said:

I have long thought about why the PLAN isnt just using a fricking Dongfeng equipped with an EMP warhead to basically nuke an entire strike package out of the skies after they have taken off. As we always know from games, AOE weapons are usually super effective against swarms lmao.

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(1)LRASMs doesn't start from ships - only from planes.
(2)To do that you'll need an actual nuke.

Tam said:

If you have active seeker, you can engage the target from above while the target is beyond the radar horizon. The lowest RCS is only at the frontal aspect, but not if the target is being attacked from the top or the side in an interception route.

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Top-down intercept against sea-skimming targets is the most difficult one, to begin with - and is affected by lower RCS/interference the most. Furthermore, the proximity of the surface tremendously improves the efficiency of onboard EW jammer.
It is doable of course(for many decades), but it's still relatively complicated.

Insignius said:

Yeah, CMO's modelling of the HQ-9B is slightly problematic here and we dont know how much of it is reality, but if the HQ-9B doesnt have CEC despite having an Active Radar Seeker, it will have severe problems engaging the LRASM even when entering radar horizon. Semi-active SAM like the HQ-16 etc are a lost cause entirely, because no FCR could actually paint the LRASM at any safe engagement ranges.

What China really needs is long range dual mode seeker SAM, equipped with active radar and ImIR, as well as onboard AI combined with CEC. Yes, that sounds super expensive, but that's likely the only way to shoot down swarms of LRASM before they sink you. Because of these complications, I have long thought about why the PLAN isnt just using a fricking Dongfeng equipped with an EMP warhead to basically nuke an entire strike package out of the skies after they have taken off. As we always know from games, AOE weapons are usually super effective against swarms lmao.

Of course in the future when railguns and lasers are deployed on PLAN ships, any subsonic missile threat becomes obsolete.

Click to expand...

If the HQ-9B has an Active Radar Seeker, logically it has to be able to receive mid-course guidance.

It's interesting to note that swarms of LRASMs don't currently exist.
LRASM has only recently been introduced, so only about 100 exist today.
And the plan is to only buy 48 LRASMs per year, until hypersonic missiles are ready.

Tam said:

But SARH happens to be a bistatic application. Bistatic or multistatic means that the transmitter and the receiver are in different locations. Stealth shaping will deny the echo being returned to the transmitter, but it deflects the echo elsewhere. This means that if the receiver is at a different location, it will receive it. So yes, a SARH missile flying higher or at the sides on an interception course will pick it up. The main problem is to make sure the transmitter is aimed at the target, and you need a bigger and more powerful radar that will keep the target illuminator in sight. It so happens this is how SPY-1 with SPG-62 works.

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Thinking about it, if you have CEC, it should be a straightforward to setup a bistatic or multistatic radar.

You can exchange details of each AESA pulse - the exact time, frequency and unique waveform.

Then it should be a straightforward processing and pattern recognition problem for an airborne AWACs or Destroyer

@AndrewS
CEC is a completely different concept from multistatic radar. You have it mixed up.

@Tam
A VLO sea-skimming missile radar return is more likely to be below the clutter signal return (depending on range anf angle) compared to a normal missile. Filtering out the clutter, in this scenario , without filtering out the missile signal is a major challenge and still a subject of active research.

ARH missiles will be seriously challenged to attack a VLO missile. Because their seekers typically work in X-band or higher bands, the RCS of the VLO ASCM will be relatively smaller compared to a search&track S-band radar (10-100 times lower) Furthermore, their transmitter power and their antenna aperture size are vastly smaller. Compared to an AEW radar, they could be anywhere from 1,000 to 100,000 times weaker, reducing detection range from 5,6 times to 17.8 times. If an AEW aircraft can detect and track the LRASM from 17.5nm, then an ARH seeker will achieve the same from 3.1nm in the optimistic scenario, or 1nm in the most pessimistic scenario. Add to that the fact that the ARH seeker is scanning its homing basket which takes non-trivial time to complete and the intercept becomes even more difficult.