SARH launch warning on RWR.

[MrTUX]

Hi again guys,

 

I have a question for you experts on this subject :

 

Once I shift from scan to STT the target's RWR notices the difference with the beaming pulse(i guess) so it signals the enemy's radar lock.

 

I don't understand why when I fire the SAHR the target gets the launch warning since the missile itself is getting tracked passively by the attacker's radar(no other radar signals depart from the launched missile).

 

I found some posts here and there in this forum about this subject, but were mainly off-topics and not really clear to me.

 

I' d like to learn more on these Avionics/Systems, but when i try to google this stuff i get lazy and confused .

 

So any of you can explain how IRL the RWR works to detect a missile launch ?

 

Hope that what i wrote makes sense:huh:, and correct me if something that i stated is wrong

 

Thanks!

[GGTharos]

Nope. Those who know won't tell you the details you seek, the rest if us can only give you some suggestions, so here goes.

 

Assumptions:

- Your RWR has spherical coverage (for simplicity's sake)

- You don't have an MWS (RWR is the only warning equipment)

 

So, the bandit goes STT on you and your RWR does the following (and may be more!):

 

1. Classify the signal. (STT/Lock)

2. ID the signal (Say, MiG-29)

3. Compute signal azimuth

4. Compute signal relative elevation, if the antenna placement permits

5. Compute the signal power to determine lethal zone if known

 

At this point, you could trigger a missile launch warning based on 5. Maybe that's all the information you get. BUT.

 

What happens when the other guy is operating his radar? Maybe some or all or more than the below:

 

1. Radar locks on in STT and creates a track file.

2. PRF is usually automatically switched to HPRF

3. Pilot pulls trigger.

4. The radar begins tuning the missiles if necessary.

5. The radar may now switch the waveform for guidance. Or not.

6. The radar generates a missile uplink signal to send data to the missile.

7. The missile launches.

 

So now, our RWR may use 5 or 6, if either of those is done. If the missile uplink signal is known, and it's coming from the radar that locked you (it is transmitted through the radar antenna usually, at least for fighters), then trigger the missile launch warning.

 

A lot of SAMs typically have a different search and track radar, and when the TR locks onto you, it really has only one reason to do so, so you may as well just trigger the launch warning. Some SAMs also have a separate missile uplink or guidance waveform that the RWR can detect, so again, more cues.

 

RWR capability and the issuing of a missile launch warning depends heavily on the hardware and software capability, as well as the specific Air Force's philosophy regarding such warnings.

 

Does that help?

 

So any of you can explain how IRL the RWR works to detect a missile launch ?

Edited January 8, 2015 by GGTharos

[Sealpup]

There is also the possibility that some radars change their modulation characteristics to something more compatible with the missile seeker-head when an SARH is launched, and the RWR picks up on the change.

[MrTUX]

 

5. The radar may now switch the waveform for guidance. Or not.

6. The radar generates a missile uplink signal to send data to the missile.

 

So now, our RWR may use 5 or 6, if either of those is done. If the missile uplink signal is known, and it's coming from the radar that locked you (it is transmitted through the radar antenna usually, at least for fighters), then trigger the missile launch warning.

 

Yes Thanks:thumbup:!, this part in particular, because if I got it right it's what actually changes in the radar emission, i.e. , something that the RWR can detect.

 

But is it something variable, so the RWR might not be able to detect an incoming SARH missile immediately(or at all)?

 

Thinking about this makes me wonder on ARH missiles as well, and on how their 'Pitbull' activation is seen from a RWR point of view.

 

Maybe in game it is all more simplified, I guess it would be a nightmare to code all of this:lol:

[GGTharos]

It's always possible that the RWR may not be able to detect a missile launch. In practice it seems not to be the case though.

 

Again, you could trigger a missile launch warning simply on the fact that: Radar in STT + Radar inside lethal range.

 

As for ARH, well ... it's a different radar. If that radar goes STT on you, it only means one thing usually.

 

And yes, the game is simplified: If STT + trigger is pulled, RWR = Danger Will Robinson, Danger!

[TAW_Blaze]

I imagine available intelligence on enemy equipment may also play a part in how things are set up.

[MrTUX]

Thanks for the replies!

 

At the moment in game a SARH fired in STT immediatly triggers a launch warning on the target, would be nice to have like a 10% margin of detection error/delay for RWR.

 

It would be closer to reality and make SARHs more dangerous, wouldn't it?

[GGTharos]

No, I don't see why it would be. 10% of what, anyway?

 

Modern RWRs work quickly and error rates are on the order 0.1%-3%, and that's just a conservative guesstimate which also depends on electronic battlefield circumstances. ED won't be implementing such a thing any time soon, if ever, AFAIK.

 

 

Thanks for the replies!

 

At the moment in game a SARH fired in STT immediatly triggers a launch warning on the target, would be nice to have like a 10% margin of detection error/delay for RWR.

 

It would be closer to reality and make SARHs more dangerous, wouldn't it?

Edited January 8, 2015 by GGTharos

[fltsimbuff]

I've always assumed that for SARH it would be similar to IR where the missile is detected via MWS. I've seen this simulated in that past (in things like the harpoon series) where extreme BVR missiles like the Phoenix would go undetected until they either turned on their terminal guidance or were seen visually or via IR.

 

However, as GGTharos alluded to, there will likely be a change in signal for missile guidance. Even if the launching aircraft doesn't directly communicate with the missile after launch, consider that in the case of multiple launches against different targets, each active track will have to have some difference in signal so each missile knows which target belongs to it.

[*Rage*]

If the rwr gave a launch warning every time STT lock + lethal range was detected it would change alot of the current multiplayer BVR dynamic.

[GGTharos]

That's just one warning trigger possibility. Again, you don't get the option to choose in the game, but in RL these set-ups are based on the fighting philosophy.

 

You could well trigger just based on STT. Or might not trigger a warning at all. On the other hand, if you do trigger a warning, why not use the best info you have - ie. the missile uplink.

[ff4life4]

I haven't been shot at by a MiG-21 yet, but I have killed su27s and f15s in multi with it. However I usually use the R-3r SAHR, and some f15s have reported to me that they haven't received any warning at all before they were hit. Is it changed for the Mig21 for the Stt + trigger pull warning?

 

Anyone been shot at by a mig-21?

Edited January 8, 2015 by ff4life4
wording

[GGTharos]

If true, it sounds like a bug. Though frankly if a MiG-21 locks on, seriously, just pop the CMs. He can't be that far.

[ff4life4]

One other question... for SAHR missiles, does it simply just pick the the reflected radar signals from the target aircrsft. Or does the radar send an uplink signal to the SAHR, similar to how a radar gives updates to aim120

[fltsimbuff]

My understanding of missiles like the Sparrow and Phoenix were that they simply locked onto the reflected track from the fighter radar prior to launch and followed that reflection toward the target. I am fairly sure there was no data link. That could be different with newer missiles though.

[ff4life4]

I don't think the Phoenix followed the beam that far. IIRC it would climb up very high and cruise at like 80k feet and use its active radar as it came down. More like an aim 120

[fltsimbuff]

Yes, the crazy thing with the Phoenix was its use of all the propellant in the first few seconds of flight, and then gliding down on top of the target at range. The terminal active guidance had a limited range. It only turned it on in about the last 10nm or so.

[GGTharos]

Phoenix never did that. There are some interesting anecdotes regarding how Phoenix worked exactly for its mid-course, but terminal was active.

 

As for sparrow, it depends on the sparrow version. The ones we're concerned with (MH for the eagle, P when the 18C comes out), use a missile uplink.

 

My understanding of missiles like the Sparrow and Phoenix were that they simply locked onto the reflected track from the fighter radar prior to launch and followed that reflection toward the target. I am fairly sure there was no data link. That could be different with newer missiles though.

[fltsimbuff]

Phoenix never did that. There are some interesting anecdotes regarding how Phoenix worked exactly for its mid-course, but terminal was active.

 

As for sparrow, it depends on the sparrow version. The ones we're concerned with (MH for the eagle, P when the 18C comes out), use a missile uplink.

 

Do you happen to have any sources more specific than "SARH" for the mid-course updates?

 

I have not been able to discern whether there is a data link, or it just "rode the beam." Semi-active radar homing has been used to refer to both the beam-riding variety and missiles receiving data via a guidance link, as that still relies on the aircraft's radar track.

 

Using a guidance link usually requires that the launching aircraft track both the missile AND the target in order to provide accurate updates. As the AWG-9 could track 24, but only display 16 tracks at a time it is possible it could reserve some tracks for the missiles, but given the arc the Phoenix takes to 80,000-100,000 feet it seems it would be pretty "inconvenient" for the radar antenna to have to re-position to track the missile at that altitude.

 

The Phoenix did have a certain autonomy, but used SARH to intercept the target prior to activating its terminal active guidance very close to the target.

[ff4life4]

Well I know for the Mig-21 there are 2 missiles available. One is the RS-2US which is a beam rider which looks backward to follow the radar similar to how the vikhr follows the laser.

 

Then you have the R-3r, which is a SAHR and it simply picks up the reflected energy from the painted aircraft.

 

And then from what GG said earlier some later SAHR missiles don't follow the painted energy but receive an uplink signal from the aircrafts radar

 

Edit: point being there are many different ways that missiles receive guidance.. not to mention the data link system used with the 120

 

Also I'd be really interested in knowing how the Phoenix could keep any contact with radar if it was soaring at 80k feet.. far above the shooter aircraft. I'd really expect that the Phoenix used a datalink system similar to the aim120

Edited January 8, 2015 by ff4life4

[fltsimbuff]

Edit: point being there are many different ways that missiles receive guidance.. not to mention the data link system used with the 120

 

Also I'd be really interested in knowing how the Phoenix could keep any contact with radar if it was soaring at 80k feet.. far above the shooter aircraft. I'd really expect that the Phoenix used a datalink system similar to the aim120

 

Unfortunately so little data made public (probably for good reason). The Phoenix was produced in 1966 (but didn't go into service until the F-14 was put in service), so it's less than a decade newer than the Sparrow.

 

That is a good question on how it could see any returns, or receive anything from the controlling radar considering the altitude. I assume some energy would be scattered from the target, but probably not enough to detect it at range. I'd be really interested in any declassified data that might be available on how this guidance worked, considering it has been retired from service.

[GGTharos]

Do you happen to have any sources more specific than "SARH" for the mid-course updates?

 

For the Phoenix? Not really. I had a weapons manual hanging around somewhere but I can't find it any longer.

 

I have not been able to discern whether there is a data link, or it just "rode the beam." Semi-active radar homing has been used to refer to both the beam-riding variety and missiles receiving data via a guidance link, as that still relies on the aircraft's radar track.

 

The Phoenix is no beam-rider, and realize that 'riding the beam' is a specific type of guidance that is not SARH, and further impossible to use with a lofting trajectory if you only have a single antenna for guidance. Phoenix was rumored to use SARH-to-ARH guidance, using 'reflections of the targets from afar to update position', but this sounds very, very fishy - even down-right incorrect.

 

Using a guidance link usually requires that the launching aircraft track both the missile AND the target in order to provide accurate updates.

 

It most certainly does not. Some systems do that (NIKE for example) - they have a missile tracking (and command) radar. On the other hand, pretty much every modern missile has an INS, so it knows it's own position. All you need to do is send it the target position.

 

As the AWG-9 could track 24, but only display 16 tracks at a time it is possible it could reserve some tracks for the missiles, but given the arc the Phoenix takes to 80,000-100,000 feet it seems it would be pretty "inconvenient" for the radar antenna to have to re-position to track the missile at that altitude.

 

Which is why missile uplink signals (specifically, mid-course updates) are sent over the radar antenna sidelobes.

 

The Phoenix did have a certain autonomy, but used SARH to intercept the target prior to activating its terminal active guidance very close to the target.

 

We don't know what the Phoenix had. That's the point. There's a lot of stuff written and a lot of talk, but it's all fishy, confusing, and thus meaningless. You really need the weapons manual to understand what's going on, and even then there might only be hints.

 

There is certainly A hint that Phoenix may have used SARH, but that same hint implies other things as well which are common to AMRAAM, too - and that little thing certainly doesn't use any SARH modes that I'm aware of.

[fltsimbuff]

It most certainly does not. Some systems do that (NIKE for example) - they have a missile tracking (and command) radar. On the other hand, pretty much every modern missile has an INS, so it knows it's own position. All you need to do is send it the target position.

 

I am not sure I would consider a Phoenix to be a "modern missile", and that's my point. I've seen no mention of an INS by any sources. At least one source I've read specifically says it does not have an INS.

 

https://engineering.purdue.edu/~mjgrant/aiaa-guidance-navigation.pdf (chart at bottom)

 

The AMRAAM on the other hand, is said to use a data link and an INS until its active radar kicks in (in some modes).

 

There is certainly A hint that Phoenix may have used SARH, but that same hint implies other things as well which are common to AMRAAM, too - and that little thing certainly doesn't use any SARH modes that I'm aware of.

 

I am not sure most people realize exactly how old the Phoenix was when it was retired. Comparing it to an AMRAAM is like comparing a B-52 to a B-2. The Phoenix used some very clever tricks to achieve its range and standoff capability, but it relied on very old tech and had a lot of shortcomings (one being poor terminal maneuvering characteristics).

 

Ultimately they could have used a method unlike any weapon before it or since to handle the "mid-course updates" so all we can do is speculate... though it is fun to speculate sometimes :)

[GGTharos]

I am not sure I would consider a Phoenix to be a "modern missile", and that's my point. I've seen no mention of an INS by any sources. At least one source I've read specifically says it does not have an INS.

 

https://engineering.purdue.edu/~mjgrant/aiaa-guidance-navigation.pdf (chart at bottom)

 

There is no way (that I can think of) for 'Predictive Flight Path' and 'No INS' to work for the phoenix missile with the AWG-9 system, unless the term 'Predictive' is being used very loosely.

 

The AMRAAM on the other hand, is said to use a data link and an INS until its active radar kicks in (in some modes).

 

Not 'said', it does, in all modes save for VISUAL.

 

I am not sure most people realize exactly how old the Phoenix was when it was retired. Comparing it to an AMRAAM is like comparing a B-52 to a B-2. The Phoenix used some very clever tricks to achieve its range and standoff capability, but it relied on very old tech and had a lot of shortcomings (one being poor terminal maneuvering characteristics).

 

And for those tricks it needs an INS ... and it wouldn't have been the first old missile of that size to have one. As for poor terminal maneuvering, there's no documentation other than hearsay to show this. Yes, missiles of the era had power limitations for their fins (and we also don't know the 54's structural limitation) - but we also need to decide whether we're talking about 54A's or 54C's, too.

 

Ultimately they could have used a method unlike any weapon before it or since to handle the "mid-course updates" so all we can do is speculate... though it is fun to speculate sometimes :)

 

There are a few things it really can't do:

 

1. Fly in the beam (it flat out doesn't fly in it)

2. Pick up a target from 90nm away, in clutter (it will be in clutter)

3. Pick up the CORRECT target from 40nm away after it has flown for a while, among a bunch of other targets ... and clutter.

 

... unless it receives some form of MCU, which requires it to use some form of INS.

[GGTharos]

I just confirmed that the Phoenix does in fact have an inertial sensor system which is part of the guidance (not control) section.

Whether that translates to a functional INS, hard to tell.

 

I also confirmed that it uses both SARH and ARH modes, but not the usage mechanism.