RCS Changes to Phoenix/Missiles seem to be a bit excessive - Missiles being intercepted by Aim120

[GGTharos]

1 hour ago, okopanja said:

Please consider that at time zero when AIM-54 gets launched, AIM-120 were already in flight. At that moment: range between AIM-54 and launching aircraft is practically 0 from the point of AIM-120. Now lets consider the speed: the between 2 is virtually zero. At the same time the missile accelerates and range is increasing. The aircraft changes its aspect and speed radically. You could argue that AIM-120c sees aircraft as one large chaff protecting nice hot target called AIM-54 (it really gets slower and stay behind).

 

No, absolutely not.   You would have to nail the exact time when the AIM-54 is accelerating through M1.

 

1 hour ago, okopanja said:

However, you made me take a closer look into the video, and this time I used HD from the start. I think we are discussing the wrong scenario here: too me it looks like it's actually AIM-54 that intercepts AIM-120c in both cases. You can see that AIM-120c tracks nicely in both encounters the aircraft and actually does not react to AIM-54 which changes it speed and aspect from the aircraft. AIM-54 in contrast never points to aircraft but immediately to AIM-120. Am I wrong?

 

Not sure, but really neither scenario should happen.   There is a very very narrow possible exception but it would be when the missile and aircraft are relatively co-speed still, and the aircraft has turned away so as to make the missile match the gates better, right as the incoming missile starts scanning.  It's a very unlikely scenario and you only need an RCS/return strength filter to avoid that one as well.

[okopanja]

52 minutes ago, GGTharos said:

No, absolutely not.   You would have to nail the exact time when the AIM-54 is accelerating through M1.

Well if it was AIM-120c targeting AIM-54 and Tomcat separation, I would not need to nail the exact time, since this is already the case.

 

53 minutes ago, GGTharos said:

Not sure, but really neither scenario should happen.   There is a very very narrow possible exception but it would be when the missile and aircraft are relatively co-speed still, and the aircraft has turned away so as to make the missile match the gates better, right as the incoming missile starts scanning.  It's a very unlikely scenario and you only need an RCS/return strength filter to avoid that one as well.

I could not agree more with you on this, something is really fishy with AIM-54 accuracy.

 

While AIM-120 is fairly large, AIM-54 should never achieve the 80% 4/5 kills here (the one were it missed was probably aerodynamically impossible, if it was fired on a tad more distance I am sure it would have been 5/5). Who needs stealth when you can shot down incoming missiles at will?

[KenobiOrder]

On top of everything that has been said so far I seriously doubt that modern fighter radars would generally allow missiles to show up at all. As it does in DCS, it clutters the radar screen and makes it vastly more difficult to achieve adequate SA. Because of the way this is implemented at the moment the second everyone starts shooting the radar turns into nightmare where its hard to tell if the new targets suddenly appearing on the screen are missile or just new contacts you didnt see before etc.

 

-Right now missiles can be detected throughout their flight path. It seems extraordinarily unlikely that anyone would want a fighter radar displaying mach 3-4 targets with closure speeds impossible from any valid target, such as a enemy plane. In fact IIRC Ive seen radar manuals where the max target speed is far below this.

 

-The RCS of the missiles seems excessive, especially rear aspect. Why is my radar capable of detected a AIM-54 or Aim-120 as it closes in on the target 20-40nm away? Its difficult for the DCS radars to detect aircraft that are nose cold at those ranges...much less missiles.

 

 

[GGTharos]

6 hours ago, KenobiOrder said:

On top of everything that has been said so far I seriously doubt that modern fighter radars would generally allow missiles to show up at all.

 

How would they know?  What's the difference between an AAM and a supersonic AShM that you want to shoot down?  Or a MiG-25/31 going mach 3?

 

6 hours ago, KenobiOrder said:

As it does in DCS, it clutters the radar screen and makes it vastly more difficult to achieve adequate SA. Because of the way this is implemented at the moment the second everyone starts shooting the radar turns into nightmare where its hard to tell if the new targets suddenly appearing on the screen are missile or just new contacts you didnt see before etc.

 

Oh no, combat is messy.

 

6 hours ago, KenobiOrder said:

-Right now missiles can be detected throughout their flight path. It seems extraordinarily unlikely that anyone would want a fighter radar displaying mach 3-4 targets with closure speeds impossible from any valid target, such as a enemy plane. In fact IIRC Ive seen radar manuals where the max target speed is far below this.

 

There are valid Mach 3-4 targets out there.  You probably don't want to miss them.

 

6 hours ago, KenobiOrder said:

-The RCS of the missiles seems excessive, especially rear aspect. Why is my radar capable of detected a AIM-54 or Aim-120 as it closes in on the target 20-40nm away? Its difficult for the DCS radars to detect aircraft that are nose cold at those ranges...much less missiles.

 

Sure, but that's a different issue.

[Gierasimov]

On 8/12/2021 at 11:12 PM, DoorMouse said:

yeah.... im pretty sure this is a bug and not an intended design feature. Its a problem for the 120 shooter too, you can use this to stuff their missiles at will. 

 

It was discussed some time ago in the DCS Missiles thread (Russian) and it was mentioned ED sees no problem in that. 

Since several updates back I was able to kill R77s with AIM120 / AIM9X with 100% probability. So, if ED feels shooting down R77 is appropriate, I don't see why Phoenix would be not. New era for DCS. go hunt those missiles now. 

As far as Phoenix goes, I wish Hornet had it, would serve nicely in lieu of TALD.

[DoorMouse]

This is absurd.  Air to Air missiles intercepting eachother is not in any way realistic or intended - this is a bug.  

And as a point of clarification, a tomahawk cruise missile is TWICE the size of a phoenix missile and will have an even larger RCS due to the wings.... and it is incredibly challenging for missiles to intercept those.  Having SD10's intercept Phoenixes or 120's is complete nonsense. 

[KenobiOrder]

5 hours ago, GGTharos said:

How would they know?  What's the difference between an AAM and a supersonic AShM that you want to shoot down?  Or a MiG-25/31 going mach 3?

Most super sonic Ashm dont move at mach 3-4, and they are significantly larger. Given that they have a similar shape to air to air missiles, they almost certainly have a larger RCS. So there are multiple ways you can discriminate these targets. Unless you think a PL-12 has the same RCS as a Mig-25.

 

5 hours ago, GGTharos said:

Oh no, combat is messy.

You dont say?

 

But its not material in any case. The way TWS is picking them up is clearly plain wrong for example. As you know, TWS systems dont just display every hit they get. They take at least two (and as I know you are aware, many real systems we have info on take more than that) frames before they upgrade a target to a track and display in on the radar screen. Yet in DCS the radar immediately displays AAMs such that you can basically see them coming of the launch rail. And there is a issue of acceleration too boot. No jet accelerates like a AAM, so if the TWS system would very likely continue to see many such missiles as False Alarms because their statistical distance from the first detection (if its coming of the rail for example) would be wildy beyond any reasonable maneuver gate.

5 hours ago, GGTharos said:

There are valid Mach 3-4 targets out there. 

What jet other than a SR-71 does mach 3-4? A mig-31 doesn't quite get there, and again you could just discriminate by RCS. Off the top of my head and cant think of a single valid target that is going to have around a -10db RCS and also is flying at those speeds.

 

5 hours ago, GGTharos said:

Sure, but that's a different issue.

How is that a different issue. Its directly related to the excessive detection of air to air missiles. If the RCS were reduced to more reasonable levels, this issue would be greatly reduced.

Edited September 28, 2021 by KenobiOrder

[GGTharos]

19 minutes ago, KenobiOrder said:

Most super sonic Ashm dont move at mach 3-4, and they are significantly larger.

 

Being larger only theoretically changes detection distance, nothing else.  This is assuming they don't have any RCS reduction features.   And sure there are mach -3-4 AShMs out there, even old ones.

 

19 minutes ago, KenobiOrder said:

Given that they have a similar shape to air to air missiles, they almost certainly have a larger RCS. So there are multiple ways you can discriminate these targets. Unless you think a PL-12 has the same RCS as a Mig-25.

 

So what?  Again all it changes is detection distance.  I've never heard of the radar discriminating by RCS.   Last I checked it's literally all about detecting whatever's in the air and outside of the doppler filter and above the noise floor.

 

19 minutes ago, KenobiOrder said:

They take at least two (and as I know you are aware, many real systems we have info on take more than that) frames before they upgrade a target to a track and display in on the radar screen.

 

Yes, the track system in DCS isn't great, but it's not true that the hit won't be displayed on screen.  Position and closure is known from a single pulse or at least a single train of pulses for the doppler.

 

19 minutes ago, KenobiOrder said:

No jet accelerates like a AAM, so if the TWS system would very likely continue to see many such missiles as False Alarms because their statistical distance from the first detection (if its coming of the rail for example) would be wildy beyond any reasonable maneuver gate.

 

If you can build a track for a MiG-25 you can build one for an AAM.  Sure, it would take time to build the track but not as long you may think.  I agree though it won't be anything close to instant.

 

19 minutes ago, KenobiOrder said:

A mig-31 doesn't quite get there, and again you could just discriminate by RCS.

 

You will never discriminate based on RCS if you don't have to.  Give up on that made up idea.  The first order of EW in some cases is to change the RCS of a target to be bigger than it appears.  Heck, chaff does that.

 

19 minutes ago, KenobiOrder said:

Off the top of my head and cant think of a single valid target that is going to have around a -10db RCS and also is flying at those speeds.

 

All you need is a little ECM to drop the SNR.  So what if you can't think of it?

 

19 minutes ago, KenobiOrder said:

If the RCS were reduced to more reasonable levels, this issue would be greatly reduced.

 

That I agree with.

[KenobiOrder]

25 minutes ago, GGTharos said:

Being larger only theoretically changes detection distance, nothing else.  This is assuming they don't have any RCS reduction features.   And sure there are mach -3-4 AShMs out there, even old ones.

And this can be used to discriminate against unwanted targets. At 25miles the return from a missile (if a get one at all) is going to be weaker than he return from a Mig-25 head on. If you combine the weak return at the given range with the other information, you have everything you need to eliminate most targets.  And regarding mach 4 AShms, I dont know of any, stuff like the P700/800 dont move anywhere near that fast. But if there are systems like this thats completely fine, Radars are optimized across their entire design for certain kinds of targets. There are other systems that can engage cruise missiles.

 

31 minutes ago, GGTharos said:

I've never heard of the radar discriminating by RCS

This happens in tracking loops all the time to discriminate against chaff, and unless DCS is wrong, the Flankers radar shows this in search. I am even fairly certain that you yourself pointed out that AIM-120s going pitbull could use RCS as part of their gate to find the right target. In any case, RCS discrimination is quite doable

 

33 minutes ago, GGTharos said:

the doppler filter and above the noise floor.

I know of at least one example, Mig-29A that has velocity limits for closing targets. Fairly certain this sort of thing is built into the choice of operating frequencies and the PRF of the radar. For a given PRF and given frequency spectrum being emitted, only a certain range of velocities is going to remain suitable. For example a high PRF may no longer be a high prf if the shift is so dramatic that the phase shift is ambiguous.

 

40 minutes ago, GGTharos said:

Yes, the track system in DCS isn't great, but it's not true that the hit won't be displayed on screen.  Position and closure is known from a single pulse or at least a single train of pulses for the doppler.

Sure, but the hits can be turned off, at least in the hornet. And that is why i was referring to the TWS tracks not the hits.

 

42 minutes ago, GGTharos said:

If you can build a track for a MiG-25 you can build one for an AAM.

Sure, but this creates problems for the accuracy of the TWS tracking gates if you expect to be able to detect both of these kinds of targets across their entire practical performance envelope. Missiles do things fighters cant do, so if you widen your correlation gates to include missile type maneauvers and performance, you are going to degrade your ability to reject false alarms and make accurate correlations between various tracks from frame to frame. Which is part of why I doubt this is done, especially on fighters who main design target was not a cruise missile.

 

Also I know you said you agree it should not be as fast, but I want to reiterate that is my main point about it. If the hits setting is on, sudden missile tracks would be hits and not new track files, which provides and measure of discrimination by itself. And if hits was off, you wouldnt see them, at least not at that moment shortly after coming off the rail.

 

50 minutes ago, GGTharos said:

The first order of EW in some cases is to change the RCS of a target to be bigger than it appears.  Heck, chaff does that.

Yes and tracking loops can reject this. A sudden jump in SNR above a threshold is an indication of a countermeasure.

 

54 minutes ago, GGTharos said:

All you need is a little ECM to drop the SNR

Sure Jamming could do that. So dont apply that set of discrimination parameters in the presence of a jammer. But what A2A missile Jams?

 

56 minutes ago, GGTharos said:

So what if you can't think of it?

Ok what example would you give? An SR71? That still would not explain a mach 4 target however. Also there are ways you could allow for such a target without over saturating other modes, like letting some other submode such as VS have different parameters.

 

1 hour ago, GGTharos said:

That I agree with

[LetMePickThat]

1 hour ago, GGTharos said:

I've never heard of the radar discriminating by RCS.   Last I checked it's literally all about detecting whatever's in the air and outside of the doppler filter and above the noise floor.

 

This isn't relevant to the subject at hand, but AESA radars do sometimes have RCS-based discrimination features. 

Also, technically, aren't blade counting and other radar-return identification features a form of RCS discrimination?

[GGTharos]

They are micro-doppler extraction which is a whole technique sitting upon another technique ... most of the discrimination I've heard of for detection is just be out of the notch and be above noise floor, nothing more.  For locking on, you'd use doppler and range gates, for keeping track you might start looking at RCS discrimination in the event you had a sudden RCS bloom (not reduction).

 

A bunch of missiles have size switches but AFAIK this sets fuze sensitivity and maybe seeker activation range.  If there's any RCS discrimination going on there I don't know.  There could be thresholds but given that RCS is variable IRL, I think they'd be fairly large bins.

[Airhunter]

Ok, all of what ED is doing is wrong and stems from some random document they found where detecting and shooting down missile was described. Like GGThanos has said, this simply isn't how even older missiles are programmed to work because if they worked in this manner the Pk would be much lower and glide decoys would be the primary way of defense. There is exactly 0 chance where a Phoenix matched the doppler and range gate of a hot aspect Tomcat at the same time, at the expected range. We actually know the physical properties of the Phoenix and its radar dish so a fairly good RCS estimate for x-band can be calculated rather easily. Right now however, I see people defending S300's and SA-11's with AMRAAM's online with ease. An active missile you just fired on a fighter should not be switching targets onto the missiles the enemy fighter has fired on you, even when active - unless it somehow happens literally at the moment of separation in a window of less than 1s. where it won't really matter. 

[okopanja]

Minor observation: smaller RCS would mean lesser reflection, however with doppler the higher the speed the more contrast between target and background, hence higher speed would likely make an object more detectable.

 

Also: find me an officer who wishes to see less. They would always prefer more visibility.

[nighthawk2174]

Having missiles hit other missiles isn't that big of a stretch its the main radar detecting them (and their current RCS values) I have an issue with.  

 

2 hours ago, KenobiOrder said:

And this can be used to discriminate against unwanted targets. At 25miles the return from a missile (if a get one at all) is going to be weaker than he return from a Mig-25 head on. If you combine the weak return at the given range with the other information, you have everything you need to eliminate most targets.  And regarding mach 4 AShms, I dont know of any, stuff like the P700/800 dont move anywhere near that fast. But if there are systems like this thats completely fine, Radars are optimized across their entire design for certain kinds of targets. There are other systems that can engage cruise missiles.

I know of at least one example, Mig-29A that has velocity limits for closing targets. Fairly certain this sort of thing is built into the choice of operating frequencies and the PRF of the radar. For a given PRF and given frequency spectrum being emitted, only a certain range of velocities is going to remain suitable. For example a high PRF may no longer be a high prf if the shift is so dramatic that the phase shift is ambiguous.

The F14 specifically has a switch to display targets with a closure high closure rate, allowing for the radar to display targets up to a 4000kt closure rate.  Normally its only up to 1200kts of closure, up to 1800 if you put another switch into the up position. @GGTharos

 

[DGC338]

With typical missile RCS of ~0.5m2 what range would you expect to pick one up?

[JayRoc]

F14 is not in a notch...couldnt replicate it. But stuff like this happens alot since the update.

[DoorMouse]

Any response at all on this from the team?