Naval missile guidance thread - SAM systems

[nlalyst]

I know how TVM works. It won't be called TVM if its command guidance. It means Track Via Missile and that means radar data from the missile takes priority. You're talking about range? Its about rate of closure, not range. Rate of closure is best calculated from data from the missile related to the target, than a ground station observing the missile from afar along with the target from afar. You do not 'refine' weak data with strong data, you disregard the weak data and rely only on the strong data. In this case this is not about the range resolution towards both the missile and the target, but the rate of closure between the missile and the target. Pulse compression is also an issue with earlier seekers due to the complexity of the circuit involved; CW is preferred because of its simplicity and reliability. The overall size of the circuits are much smaller and this matters especially to the bulkier Soviet era circuitry.

You're the one who said range was important. Now it's rate of closure ... And yet, we don't even know what guidance law is being used?

Your whole argument that these systems are CW is based on the made up claim that SARH/TVM cannot work in PD mode. Yet the AIM-7 is perfectly able to home in PD SARH mode. As are a multitude of ICWI homing missiles. All the while the illuminating radar keeps tracking the target. Just a while ago, you yourself called ICWI a form of PD. But at the same time you keep saying that PD SARH homing cannot work. Talk about consistency.

AIM-7M has a monopulse seeker. Its still a CWI. People toss around the word PD because it sounds cool but they don't really know what it means, and they don't want to bother knowing the difference between CW and PD. That's one reason when they see a Slotted Array antenna they call it PD, even if slotted arrays can be used for both.

I suggest you visit the DCS forum boards. This has been discussed ad nauseam there. PD STT mode on AWG-9 is certainly not CW.

Official data confirms this (

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)

General Characteristics AIM-7
Primary Function: Air-to-air guided missile
Contractor: Raytheon Co.
Power Plant: Hercules MK-58 solid-propellant rocket motor
Thrust: Classified
Speed: Classified
Range: Classified
Length: 12 feet (3.64 meters)
Diameter: 8 inches (0.20 meters)
Wingspan: 3 feet, 4 inches (1 meter)
Warhead: Annular blast fragmentation warhead
Launch Weight: Approximately 500 pounds (225 kilograms)
Guidance System: Raytheon semiactive on either continuous wave or pulsed Doppler radar energy
Date Deployed: AIM-7F, 1976; AIM-7M, 1982
Unit Cost: Approximately $125,000
Inventory: Classified

Same guidance modes are available on the Seasparrow:

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[Gloire_bb]

YJ-83 (and NSM) is viewed as a much more precise tool for dealing with cluttered areas with more sea traffic, as well as clutter from littoral environments. For now, it makes a better complement to the Type 054A's mission. It doesn't mean its not capable of handling supersonic missiles --- Type 054A/P will equip CM302 which is the export version of the YJ-12 --- should the customer demands it. The ship is obviously built and over engineered with such options in the mind early in its beginnings. We have also seen the Shenzhen replace its 16 YJ-83s with an equal number of YJ-12s, and the same may happen to the Type 052B refits.

Yep, purpose matters I believe.
PLAN frigates are a multi-purpose green water force - 054A/(B?), backed by YJ-12 equipped "strike" destroyers.
For Pakistan - something similar apparently is intended, but I am just guessing - I don't know all that much about the Pakistan navy.

 

[Tam]

Yep, purpose matters I believe.
PLAN frigates are a multi-purpose green water force - 054A/(B?), backed by YJ-12 equipped "strike" destroyers.
For Pakistan - something similar apparently is intended, but I am just guessing - I don't know all that much about the Pakistan navy.

Pakistan is simple. As with navies that only have frigates as their main front line force, the intention is to arm these frigates to the hilt. So they want the best features as possible, including CM302 (YJ-12) for the Type 054A/P.

They probably complaining why their ships didn't get the new target emitters but that can be saved for the next batch of 054A/P.

The reason why frigates have become the front line forces of so many navies is one reason for their rapid power and mission creep, capability and price inflation. Two tier navies (destroyer/cruiser + frigate) is able to moderate the power inflation of their frigates, in contrast.

 

[nlalyst]

I know how TVM works. It won't be called TVM if its command guidance. It means Track Via Missile and that means radar data from the missile takes priority. You're talking about range? Its about rate of closure, not range. Rate of closure is best calculated from data from the missile related to the target, than a ground station observing the missile from afar along with the target from afar.

We first need to establish which guidance law is used.

For example, proportional navigation homing can work with just angle data. It won't compute the most optimized path to target, but it will work. That's how IR missile home.

You do not 'refine' weak data with strong data, you disregard the weak data and rely only on the strong data. In this case this is not about the range resolution towards both the missile and the target, but the rate of closure between the missile and the target. Pulse compression is also an issue with earlier seekers due to the complexity of the circuit involved; CW is preferred because of its simplicity and reliability. The overall size of the circuits are much smaller and this matters especially to the bulkier Soviet era circuitry.

If a monopulse doppler tracking radar is able to track a target, then it may obtain the following: angle data, range data, and doppler shift (relative speed), in a single pulse. Instead of discarding this data, what is done, I think, is to fuze this data with data obtained from the missile seeker.

AIM-7M has a monopulse seeker. Its still a CWI. People toss around the word PD because it sounds cool but they don't really know what it means, and they don't want to bother knowing the difference between CW and PD. That's one reason when they see a Slotted Array antenna they call it PD, even if slotted arrays can be used for both.

As I previously pointed out, Raytheon documentation explicitly mentions pulse doppler guidance:
Guidance System: Raytheon semiactive on either continuous wave or pulsed Doppler radar energy

On the synchronization of pulses between the tracking/illuminating radar and the missile:


Therefore, a PD TVM system would not be anything new. If you read up on the various upgrades made on the Patriot radar, you can find that pulse doppler functionality comes up several times.

 

[Zichan]

Would anyone chime in on the divergence of NATO and PLAN SAM guidance on AEGIS like ships?

PLAN seems to prefer active guidance for its SAMs, whereas even the latest NATO AEGIS ships under construction like the Spanish F110 frigate retain dedicated semi active radar illuminators.

 

[BoraTas]

Would anyone chime in on the divergence of NATO and PLAN SAM guidance on AEGIS like ships?

PLAN seems to prefer active guidance for its SAMs, whereas even the latest NATO AEGIS ships under construction like the Spanish F110 frigate retain dedicated semi active radar illuminators.
View attachment 109600

NATO countries have a lot of semi-active guided missiles in inventories. They have to have those illuminators if they are not willing to discard most of their current inventories. China's naval modernization started in an era active-radar guided missiles were becoming common. Thus no need for backward compatibility exists. Active radar guidance is simply a superior solution. It increases how many missiles you can use to engage a target. It also increases ECM resistance and even **range.

**: Higher resolution homing means a smaller warhead is needed thus more space for fuel and less post-burnout mass.

 

[Zichan]

NATO countries have a lot of semi-active guided missiles in inventories. They have to have those illuminators if they are not willing to discard most of their current inventories. China's naval modernization started in an era active-radar guided missiles were becoming common. Thus no need for backward compatibility exists. Active radar guidance is simply a superior solution. It increases how many missiles you can use to engage a target. It also increases ECM resistance and even **range.

**: Higher resolution homing means a smaller warhead is needed thus more space for fuel and less post-burnout mass.

Thanks for your reply.

What I find curious is that the primary loadout or the F110 frigate will be ESSM v2 which is an active homing SAM.

It seems that SPG-62 illuminator will be used only for cooperative engagement?

I don’t think active homing increases ECM resistance: the ship borne illuminator can paint the target with much larger Rf power at short to medium ranges, plus it acts as a bistatic radar where both the ship and the missile track the target which can be useful against VLO targets. This can be even more powerful if several ships paint the target each with an illuminator from different angles greatly increasing the probability that some of the RF bounces back to the missile receiver.

In terms of range, yes ARH can be better if it’s aimed at over the horizon targets, however the missile will be inherently heavier as it needs to carry a battery and additional power circuitry to sustain RF radiation. Why do you say that ARH has higher resolution?

EDIT:
Apparently, ESSM v2 can also be guided semi-actively. Therefore, the dedicated illuminators can be used to provide illumination against particularly tough targets.

 

[BoraTas]

Thanks for your reply.

What I find curious is that the primary loadout or the F110 frigate will be ESSM v2 which is an active homing SAM.

It seems that SPG-62 illuminator will be used only for cooperative engagement?

I don’t think active homing increases ECM resistance: the ship borne illuminator can paint the target with much larger Rf power at short to medium ranges, plus it acts as a bistatic radar where both the ship and the missile track the target which can be useful against VLO targets. This can be even more powerful if several ships paint the target each with an illuminator from different angles greatly increasing the probability that some of the RF bounces back to the missile receiver.

In terms of range, yes ARH can be better if it’s aimed at over the horizon targets, however the missile will be inherently heavier as it needs to carry a battery and additional power circuitry to sustain RF radiation. Why do you say that ARH has higher resolution?

EDIT:
Apparently, ESSM v2 can also be guided semi-actively. Therefore, the dedicated illuminators can be used to provide illumination against particularly tough targets.

In ARH you have both the emitter and receiver close to the target. Semi-active is passive from the perspective of the missile thus resolution is limited by gain.

Most semi active missiles are of SAGG type. In that arrangement, the missile acts according to the judgement of the launcher unless the link is jammed. Missile's seeker data and judgement is transmitted to the launcher and the launcher compares that with its own data and does the final decision. Then the decision is sent to missile. The missile acts on its own judgements only if the launcher is not returning or disengages. Active works the same too but now you have an extra seeker on board. That increases resolution and makes jamming the missile seeker much harder.

And a distant radar isn't going to compete with even the tiny radar on the missile. Power requirements scale by the power of 2.

 

[Zichan]

In ARH you have both the emitter and receiver close to the target. Semi-active is passive from the perspective of the missile thus resolution is limited by gain.

Most semi active missiles are of SAGG type. In that arrangement, the missile acts according to the judgement of the launcher unless the link is jammed. Missile's seeker data and judgement is transmitted to the launcher and the launcher compares that with its own data and does the final decision. Then the decision is sent to missile. The missile acts on its own judgements only if the launcher is not returning or disengages. Active works the same too but now you have an extra seeker on board. That increases resolution and makes jamming the missile seeker much harder.

And a distant radar isn't going to compete with even the tiny radar on the missile. Power requirements scale by the power of 2.

Hmm.

Resolution is not fundamentally different between ARH and SARH. The receivers on both systems can achieve equal angular resolution: this is a function of antenna size, number of antenna receive elements and wavelength. In both cases, the missiles are much closer to the target than the radar on the launch platform and that’s what really matters. Modern missile receivers use monopulse techniques to track the target, regardless of ARH or SARH.

“distant radar” really depends on the relevant parameters. I once did a back of the envelope calculation and concluded that the SPG-62 illuminator likely out-powers the SM-6 active seeker up to 200km from the ship, at which point ARH delivers more RF on target. This is because the ship based illuminator is probably on the order of 100 times more powerful in emitted RF, plus it has a much larger antenna 2.3m in diameter which can create a significantly narrower beam (higher gain) than the small missile antenna at the same wavelength.

EDIT:
The Constellation class frigates will have the AEGIS combat system, but will not be equipped with dedicated illuminators according to current information, the first for a USN AEGIS ship.

 

[Zichan]

Continuing from above:

However, the under construction FLTIII Burkes are equipped with dedicated SPG-62 illuminators, as are the new Maya class Aegis ships for the JMSDF. I doubt both navies would be installing illuminators on brand new high end ships if there weren’t additional advantages to them, existing stockpiles of ancient missiles notwithstanding. Especially the JMSDF, which does not have as big missile stockpiles as the USN, and the latter also finds it difficult to populate all the VLS cells in the fleet.