PLAN Anti-ship/surface missiles

nlalyst said:

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

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Yes, I know CEC is different from multi-static radars.

But my point is that if you have CEC, you already have the datalink capability to exchange data on the radar pulses sent by each emitting platform.

Add some processing power, and then you would have a multi-static radar setup.

AndrewS said:

Yes, I know CEC is different from multi-static radars.

But my point is that if you have CEC, you already have the datalink capability to exchange data on the radar pulses sent by each emitting platform.

Add some processing power, and then you would have a multi-static radar setup.

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Multi-static radar needs to be synchronized on a pulse-to-pulse basis.

CEC does not work like that. The data exchanged are individual radar dwells, consisting of multiple pulses already processed by the one radar that emitted the pulses in the dwell.

But you are right that CEC can be used to establish a track on a VLO target: if observed by a single radar, ia VLO target might look like a spurious signal appearing and disappearing seemingly randomly and would be discarded as noise. However, if multiple radars are painting the target, each of them will get a slightly different spurious signal. Combining the dwell data with a clever algorithm may be sufficient to realize that the spurious signals were coming from one and the same target. This data may be sufficient to reconstruct a (coarse) track. Perhaps worth pointing out, CEC can combine more than just radar data. US theater ballistic missile defense systems combine radar data (for accurate ranging) with optical data (for accurate bearing).

nlalyst said:

Multi-static radar needs to be synchronized on a pulse-to-pulse basis.

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And you can do that with a datalink

nlalyst said:

CEC does not work like that. The data exchanged are individual radar dwells, consisting of multiple pulses already processed by the one radar that emitted the pulses in the dwell.

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You have to separate the datalink from the actual data transmitted.

So if you have CEC, theoretically you can also use the datalink to exchange radar pulse information or any other data you want.

What you actually want to say is that:
"the current US implementation of CEC does not include radar pulse information that could be used for bi-static or multi-static radar detection"

nlalyst said:

But you are right that CEC can be used to establish a track on a VLO target: if observed by a single radar, ia VLO target might look like a spurious signal appearing and disappearing seemingly randomly and would be discarded as noise. However, if multiple radars are painting the target, each of them will get a slightly different spurious signal. Combining the dwell data with a clever algorithm may be sufficient to realize that the spurious signals were coming from one and the same target. This data may be sufficient to reconstruct a (coarse) track. Perhaps worth pointing out, CEC can combine more than just radar data. US theater ballistic missile defense systems combine radar data (for accurate ranging) with optical data (for accurate bearing).

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nlalyst said:

@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.

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Not from a different aspect.

VLO missiles have their lowest RCS only from the front and head on. Otherwise the RCS profile resembles like a butterfly or a bird if its mapped a full 360 degrees. It greatly increases by several times the moment you begin to transfer the view of the missile to each quadrant, then to the side and top aspect.

That's also how CEC takes advantage of this. A second ship or ships would still be able to spot the missile from a quadrant or the side where the RCS is greatly increased and put that information into the unified sensor net.

The other stage is to improve seekers; adding IR or IIR, using Gallium Nitride which is several times more sensitive and powerful than Gallium Arsenide, and to use AESA.

Once again, remember that RCS is not the same as the wavelengths get longer. While the VLO missile is optimized against the X-bands, our sensor net is now on S-band, or even in L-band. Adding things like for example, the 052D's VHF radars.

@nlalyst

What is your best guess as to the distance that a missile X-Band seeker can acquire an LRASM?

My estimate is that ARH missiles would have a homing basket from anywhere from <1nm to about 3nm against a VLO missile like LRASM. Smallish missiles like AMRAAM and PL-15 would be on the lower end of the range, while large missiles like HHQ-9B may be closer to the upper range.

Now whether they manage to acquire the LRASM and maneuver into intercept before they zoom by, is an altogether different question.

Once it goes active, an ARH missile starts to scan the airspace. Getting a lock on target can take several seconds depending on the missile. If the closing speed is Mach 4+ there might be very little opportunity to detect the target, let alone maneuver to intercept.

Therefore, the launch platform will have to command guide the missile quite precisely and very close to the target, putting it on an intercept trajectory even before its ARH seeker can acquire the target.

My impression is that a SARH or TVM missile would fare far better in this kind of engagement. The illuminating beam from a ship, when engaging a target 15-20nm away, is going to be far more powerful than the ARH seeker, and the missile could start homing on target earlier, increasing its probability of intercept. It may be interesting to point out that all USN’s ARH missiles (SM-6, ESSM Blk II, SM-2 Blk IIIC) have a SARH seeker in addition to ARH.

nlalyst said:

My estimate is that ARH missiles would have a homing basket from anywhere from <1nm to about 3nm against a VLO missile like LRASM. Smallish missiles like AMRAAM and PL-15 would be on the lower end of the range, while large missiles like HHQ-9B may be closer to the upper range.

Now whether they manage to acquire the LRASM and maneuver into intercept before they zoom by, is an altogether different question.

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Instead of assuming that a VHF radar can't provide a weapons quality track for an HHQ-9, why don't you do a simple analysis of radar accuracy versus missile kinematics

Mid-course guidance of HHQ-9 to an LRASM
If a VHF radar detects an LRASM at the radar horizon (30km) and launches an HHQ-9 SAM immediately, 1st intercept is at a distance of 24km.
At that distance, with an angular accuracy of +/- 1degree, a VHF radar localises an LRASM to a line across the horizon which 838m long.
So a SAM would be directed to the centrepoint of that line.

HHQ-9 X-Band acquisition of LRASM
And let's use a conservative figure of 2nm (3.7km) for an HHQ-9 X-Band seeker to detect an LRASM.
So if we use a lower bound of a (3.7-0.4km) detection range for the HHQ-9, it still means the LRASM is definitely detected.
There is a maximum angle of about 7degrees from the HHQ-9 seeker

HHQ-9 kinematics
With a worst case distance of 3.3km, there are 2.3seconds for the HHQ-9 to manoeuvre and hit the LRASM
Now, given that fighter jets are expected to undertake 9G manoeuvres to evade missiles, we can reasonably assume that SAMs are designed with 10G+ acceleration for terminal manoeuvres.
If so, an HHQ-9 at 10G can manoeuvre to cover a line which is 581m across, which covers 72% of the possible LRASM locations.

So in summary, it is worth launching SAMs once a VHF radar first detects an LRASM at the radar horizon of 30km.

Then there is the option to launch multiple SAMs to increase the pk.
And the LRASMs become progressive easier to hit in the next engagement rounds.

On the 1st engagement round at 24km, the LRASM is anywhere along a 838m long line across the horizon.
On the 2nd engagement round at 19km, the LRASM is anywhere along a 663m long line across the horizon.
On the 3rd engagement round at 16km, the LRASM is anywhere along a 558m long line across the horizon.
On the 4th engagement round at 13km, the LRASM is anywhere along a 453m long line across the horizon.

So I think the CMO assumption of first engagement (LRASM versus Type-052D) starting at 13km is wrong.

By then, I think an LRASM should have already been subject to 4 full-length engagement cycles.

AndrewS said:

Instead of assuming that a VHF radar can't provide a weapons quality track for an HHQ-9, why don't you do a simple analysis of radar accuracy versus missile kinematics

Mid-course guidance of HHQ-9 to an LRASM
If a VHF radar detects an LRASM at the radar horizon (30km) and launches an HHQ-9 SAM immediately, 1st intercept is at a distance of 24km.
At that distance, with an angular accuracy of +/- 1degree, a VHF radar localises an LRASM to a line across the horizon which 838m long.
So a SAM would be directed to the centrepoint of that line.

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Don't forget that we are discussing the Type 517M radar here, not the Nebo-M. The former has just 4 antennas in a row, while the Nebo-M has 22 antennas. The Nebo-M is credited with an impressive 0.5 degree accuracy, although it is unclear exactly how it achieves this as its mainlobe beam is going to be around 5 degrees wide. If it uses monopulse, then its power-aperture will drop to 25% significantly impairing its detection range. But for the sake of argument, let's assume that's still sufficient to detect the LRASM at 30km range. Scaling to 517M, azimuth accuracy will be 22/4 * 0.5 = 2.75 degrees. Can you redo your calculation with this figure?

AndrewS said:

HHQ-9 X-Band acquisition of LRASM
And let's use a conservative figure of 2nm (3.7km) for an HHQ-9 X-Band seeker to detect an LRASM.
So if we use a lower bound of a (3.7-0.4km) detection range for the HHQ-9, it still means the LRASM is definitely detected.
There is a maximum angle of about 7degrees from the HHQ-9 seeker

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How did you get 7 degrees? In you example above, if the error is 838m doesn't that mean that you should draw a circle of radius 838m, as the area of uncertainty?

AndrewS said:

HHQ-9 kinematics
With a worst case distance of 3.3km, there are 2.3seconds for the HHQ-9 to manoeuvre and hit the LRASM
Now, given that fighter jets are expected to undertake 9G manoeuvres to evade missiles, we can reasonably assume that SAMs are designed with 10G+ acceleration for terminal manoeuvres.
If so, an HHQ-9 at 10G can manoeuvre to cover a line which is 581m across, which covers 72% of the possible LRASM locations.

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It would help if you specify the speed that you used for HHQ-9. Given the short range of the engagement, it will likely be close to its top speed: 2000 m/s?

AndrewS said:

So in summary, it is worth launching SAMs once a VHF radar first detects an LRASM at the radar horizon of 30km.

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No, you can't do that. First you need to figure out what it is that you detected. That's called an OODA loop.

When you redo your calculations, don't forget to take into account that the Type 517M is a rotating radar and that your signal updates are some 6s apart. In those 6s, a maneuvering LRASM can cover at least 1,5-1,8km.

@AndrewS
One more thing: Type 517 is a 2D radar. It can't tell you the altitude of the target.

nlalyst said:

@AndrewS
One more thing: Type 517 is a 2D radar. It can't tell you the altitude of the target.

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It can actually, in a rough way. Have you heard of a goniometer? A gonio illustrates how it should work.




The single signal return is being compared as it touches two different elements at two different locations and height. The difference of the return between the two points is used as a comparison. Its a principle that many metric and OTH radars use.