Chaff and R27(E)R

[Sweep]

I really do wonder here, what needs fixing?

 

Just the seeker going after chaff outside seeker FOV thing?

 

Am I missing something?

[Capn kamikaze]

I've never seen any reference to any mention of a gyroscope whether it be electromechanical[unlikely size weight and complexity] pizo[MEMS again unlikely as its not exactly accurate enough] or ring laser.

 

Just one little nitpick with that, piezo gyros are not MEMS, those are two entirely different technologies, MEMS gyros are far superior to piezo gyros, and MEMS suffer far less drift than piezo, they would easily be usable in an INS system, especially in the short flight time of a missile.

[pr1malr8ge]

Just one little nitpick with that' date=' piezo gyros are not MEMS, those are two entirely different technologies, MEMS gyros are far superior to piezo gyros, and MEMS suffer far less drift than piezo, they would easily be usable in an INS system, especially in the short flight time of a missile.[/quote']

 

Capn, I did a bit more research on Mems, and yes you're right. Miniaturized FOG has way much better drift loss then that of Piezo and I thought at that time Piezo was part of the mems category. I still wonder though if MEMS gyros will be able to take the abuse associated with the High G A2AMs endure. It may be better suited then that of a RLG.

[Capn kamikaze]

To be fair MEMS can use piezo material in their construction, but not in the way that a traditional "Piezo gyro" uses it, eg in the tuning fork MEMS system uses it. It's important to distinguish the two classes of systems, a MEMS system can use piezo material, but just using piezo material in a gyro does not necessarily make it a MEMS gyro/accelerometer.

 

Good point about the G factor, not sure about that, but from a purely accuracy and drift POV MEMS would definately be up to the job, it is used in flight stabilisation and nav systems in low G applications, just consider all the drones that everyone is about to get on the 25th....

[*Rage*]

Nothing. I'm tired of all this and with the DCS stuff. See you in the spring, if something new. I turn to other things in my free time...

 

You had such faith before! Lift your spirits comrade!

[pr1malr8ge]

To be fair MEMS can use piezo material in their construction, but not in the way that a traditional "Piezo gyro" uses it, eg in the tuning fork MEMS system uses it. It's important to distinguish the two classes of systems, a MEMS system can use piezo material, but just using piezo material in a gyro does not necessarily make it a MEMS gyro/accelerometer.

 

Good point about the G factor, not sure about that, but from a purely accuracy and drift POV MEMS would definately be up to the job, it is used in flight stabilisation and nav systems in low G applications, just consider all the drones that everyone is about to get on the 25th....

 

the "RC" market uses Piezo only gyros or so thats what I have seen when I was flying RC Helicopters. I'm sure there might be some diff tail lock gyros availible that isn't piezo but I'm sure they cost deniro.

 

Again, last time I truly looked into the GryoMarket has been some time ago. Things costs etc may have went down considrably. I remember the cost of my first Gyro when I was learning how to fly RC Helis [quite flying them because they are a PITA and cost too much to fix] and that thing cost well over 200 bucks and this was early 2000's

[Capn kamikaze]

LOL we have a common hobby, I've been flying RC helis for the last 19 years, and piezo gyros are old hat, most heading hold gyros, I am tempted to say all now, are MEMS sensors, especially flybarless controllers.

 

Roughly just after 2000, maybe 2003-4 is when MEMS started to get on the market IIRC, the cost has come down a LOT since then.

[Fri13]

Well according to some sources that could be the case for the R-27R - i.e. that for an R-27R launched from a MiG-29 the datalink range is some 25 km - if you compare this with published range figures for the R-27R(up to some 70 kilometers against a non-manouvering target), it would seem that the missile could outrange the datalink reach by a fairly large margin :)

 

Isn't the datalink in the radar beam?

 

Meaning, the launching aircraft (Su-27S/Mig-29 in this case)

1. will first get the lock with radar for target direction, speed and distance with enough data in given time period to estimate where it is in next X seconds.

 

2. feed the trajectory to the missile computer prior the launch.

 

3. Release the missile that first initiates its own INS and trajectory after launch parameters and stabilize itself for guidance.

 

4. Platform is transmitting the command guidance updates to missile INS via the radar beam that is used to "paint the target"?

 

 

5. Platform is receiving echoes from the target and updates the radar beam commands after echo has been processed.

 

Meaning that every datalink command update is "old data", and the delay is how long the radar takes to travel from radar to target, echo back to the radar and get processed and then transmitted again?

 

 

So, as I am just totally speculating, guessing and just throwing something up.

 

The inertial navigation updates for missile via datalink (radar beam?) doesn't mean to be long distance ones because they are there only to change missile path when it has enough energy to do so and if the target trajectory has changed radically from the previous ones.

 

And if the datalink is the radar beam, then logically the datalink range is always the same as the radar range is, and it is actually even longer for the missile than launching platform, because the missile is after longer period of the time, much closer the target than the launching platform is, even when the missile has a smaller seeker than the launching platform, it can pickup the radar and hence datalink from the target, even when the launching platform doesn't see anything.

 

But at that point the datalink missile receives, is obsoletely invalid because it is way too old.

BUT at that point missile should already be in homing phase, where it would ignore the datalink and head on the largest reflection it sees.

 

 

 

So am I assuming correctly that the radar beam from the launching platform is the datalink? Isn't that the thing what RWR recognize as launch and alarms the target pilot from the launch?

If the radar isn't the datalink, is there a radio transmitter in the aircraft that would transmit the updates to missile? And then that would logically mean that the missile would need to have a radio transceiver in its rear fins/around rocket motor that can receive the datalink?

[pr1malr8ge]

 

Meaning that every datalink command update is "old data", and the delay is how long the radar takes to travel from radar to target, echo back to the radar and get processed and then transmitted again?

The data that is sent is computed trajectory. I.e. if nothing changes [the aircraft is maintaining its current flight path either turning or going straight etc.] it will be Here when the the missile arrives at terminal guidance.

 

 

that the missile would need to have a radio transceiver in its rear fins/around rocket motor that can receive the datalink?

D/Mlink antenna is in the rear or at least it is in the aim120 from the technical drawings I have seen.

 

 

 

Edited December 12, 2015 by pr1malr8ge

[ShuRugal]

I really do wonder here, what needs fixing?

 

Just the seeker going after chaff outside seeker FOV thing?

 

Am I missing something?

 

It's a couple things adding up. SARH missiles are currently having a plethora of problems tracking the target. The biggest issue at the moment is that the DnD-Style "Roll to check chaff resiliency" mechanic current makes it possible to evade an R-27R/ER at any range just by spamming chaff.

 

This is unrealistic for a couple reasons:

 

1) Fighter radars and missiles are designed with a certain measure of chaff-resistance, mainly by building a track of the target and ignoring deceleration rates that are impossible for a plane to perform (chaff tends to stop dead in the air within a second or two). In the specific case of the R-27, the missile's mid-course guidance comes via m-link (one-way datalink) from the parent aircraft. The Su-27 generates the updates for this link based on its track of the bandit.

 

2) Since chaff stops moving so quickly, at close ranges and/or flanking aspects, there will quickly become enough angular separation between the parent aircraft that the chaff is either no longer illumated, or moves out of the missile's FoV. This, again, is also somewhere that chaff-rejection programming should tell the missile to ignore the chaff, because a fighter can't go from 1200 km/hr to 10 km/hr in under three seconds without turning into a grease stain.

 

3) the Su-27 is equipped with an EOS targeting system to supplement the radar. in STT mode, the EOS can also track the target based on IR signature. Even a rudimentary tracking program should be able to recognize the difference between a fighter with both radar and IR signature, and a cold bundle of chaff (or the other way around, in the event of flare launch). This would allow the Su-27 radar to be kept on target based on IR sensor returns, further improving chaff-resistance at close range.

 

 

If DCS was correctly simulating these effects, then a defending pilot would be required to not only spam chaff, but to maneuver himself into a relative position that allows him to negate the chaff-resistant features of his opponent's aircraft (IE: make high-G turns to disrupt track building, chose a hard hot or cold aspect to place his aircraft in-line with his chaff bundle, etc). The attacking pilot would then need to maneuver his own bird to try and regain a favourable position/radar picture.

 

This problem is the kissing-cousin of another missile tracking problem that has been plaguing the R-27 for ages, and that is ground-clutter susceptibility. At one point, a few patches ago, it was so bad that I had an AI Su-25 "dodge" my missile simply by "notching" against the sky. No chaff, no maneuvers, just turned 90 degrees and kept flying straight. Unloaded my entire payload, and finally killed him with guns.

[Fri13]

Ray tracing isn't necessary other than for checking LOS. You'll almost always have a better/faster algorithm running off of tables to calculate RCS etc, compared to ray tracing.

 

Naturally, you could make even that more complex. One of the big 'radar things' is the radar cell - I haven't seen any sim model that, nor am I terribly surprised. It is not trivial to code, and it is probably not trivial to make the AI deal with it either (though not impossible in either case).

 

 

 

There wouldn't need to be any ray tracing used for the simulation.

 

Simple things like a "2D sprite" like modeling that is build by some random radius circles that are linked to each other and they get enlarged and finally "phased" depending all kind various elements like wind direction and speed, time etc.

 

For a calculations it would fairly simple thing to really do. Each sphere has X diameter and it will transmit X percentage back. The chaff would have a "tail" and it could spread out in basic chain that each circle gets bigger in time, but same time its reflecting power fades.

 

It shouldn't be too much asking to just change the "chaff chain" in a fairly low updates like every 500ms as it would be enough to be kept alive for short period of times before it is grown bigger and then updated less often like every 5-10 seconds.

As the chaff would stay up in the air for long periods, as the metal sheets doesn't just "vaporize" or "stop emissions" like flares do when they are consumed (burn out).

 

If DCS can already calculate the radar range, engagement range etc as spheres, visualize those in the F10 map and in KA-50 ABRIS as 2D circles, then it should be able to add a few more to the simulation, that get changed over time (like "chaff chain" of 7 circles morf in time to 2-3 big circles that just flow and fade away in time).

 

Sorry for my "über MS paint skills" but I am not on my computer.

 

 

This would mean that the chaff isn't just for quick counter measure against missile, but it will have affects to SAM and every other radar on the air for that area. The chaff will continue reflecting the radars echoing signals back to anyone that has the radar cone at the direction, blocking the radar "seeing" what is on "other side" (like the invisible mountain between aircrafts).

 

It would as well force players to consider WHEN to chaff and how much. As filling the air full of chaff would result to situation where there are just "invisible mountains" everywhere and pilots would need to get closer or use other means to "see".

 

It would be as well problem for SAM, AWACS and GCI as they would not be able see what is going on.

 

 

And this would create a new reason to have "Dynamic Weather" as the "clouds" of the chaff could float around for long period of times.

[DarkFire]

I really do wonder here, what needs fixing?

 

Just the seeker going after chaff outside seeker FOV thing?

 

Am I missing something?

 

I was going to post a lengthy paragraph about the issues currently affecting SARH missiles, but ShuRugal nailed it spot-on. Lack of out-of-FOV chaff rejection, pure probability-based chaff rejection and apparent severe issues with background clutter rejection all contribute to the R-27(E)R's dismal performance at present.

[Fri13]

The data that is sent is computed trajectory. I.e. if nothing changes [the aircraft is maintaining its current flight path either turning or going straight etc.] it will be Here when the the missile arrives at terminal guidance.

 

 

D/Mlink antenna is in the rear or at least it is in the aim120 from the technical drawings I have seen.

 

Thanks!

 

I have been under believe that guidance data is transmitted on the radar beam and that the missile radar receiver gets it as echo from the target.

 

But.... isn't the missile in a way then "beam rider" as it needs to fly inside the radar beam to receive the guidance commands?

 

Meaning if the missile will take a totally different trajectory, away from LOS between platform and target, and the platform has target locked (focused beam to target), can't the missile simply fly outside of the LOS and this way lose totally the guidance if target changes trajectory?

[ShuRugal]

But.... isn't the missile in a way then "beam rider" as it needs to fly inside the radar beam to receive the guidance commands?

 

To an extent, but the thing with any radio transmitter is that there is no such thing as a "tight" beam. The center of the beam, where the signal is strong enough to paint a target with, may only be a few degrees wide, but the radar energy will be detectable from basically anywhere in front of the dish when within the range that a missile will fly.

[Fri13]

My knowledge is drawn almost from these videos:

 

[ame]https://www.youtube.com/watch?v=d5T1vPmA-l4[/ame]

[ame]https://www.youtube.com/watch?v=IiSswJ2Oqng[/ame]

[ame]https://www.youtube.com/watch?v=xHiWojxaYaQ[/ame]

[ame]https://www.youtube.com/watch?v=WfLWS-ZT240[/ame]

[ame]https://www.youtube.com/watch?v=OAFdiadkLKs[/ame]

 

But I must say... let's not be so serious:

[ame]

[/ame]

 

And I must say, I find the chaff in DCS to be totally different than any of these videos presents that era chaff working (50-60's).

 

Like when I am flying toward or away (front or behind chaff) the AA uni like ZSU-23-4 that use narrow radar beam to calculate distance to the target (if I remember correctly, the beam was something like 3.6 degrees http://fas.org/man/dod-101/sys/land/row/zsu-23-4.htm), it should be fooled by then as the reflections coming at it would give totally wrong readings and so on firing solution to be wrong.

 

But like that, isn't it so that the system basically just use radar automatically to lock on the target without user requiring to keep "needle on target" (tracking target manually)?

Meaning even then a basic chaff would fool the system for wide variation of angles?

[Fri13]

To an extent, but the thing with any radio transmitter is that there is no such thing as a "tight" beam. The center of the beam, where the signal is strong enough to paint a target with, may only be a few degrees wide, but the radar energy will be detectable from basically anywhere in front of the dish when within the range that a missile will fly.

 

Yes, but if it is true that ie. SPO-15 was designed so that its sensitivity is about 120-130% from the radar max range, then it means that when you are outside of the focused beam area, there is already bigger difference than the radar dish is emitting around the beam and the transmitted power, as it can be just around 5-10% of the power in focused beam.

 

But at shorter ranges the signal is already more powerful (in inverse square rule) unless it is controlled (to optimize the power so only focused beam keeps the detectable power).

[Fri13]

What I haven't yet understood is what does "radar lock" really mean? Like what does it mean when aircraft is "locked" and then it suddenly isn't because chaff is a released?

I get the "invisible mountain" as chaff works like a smoke blocking line of sight.

And I even get that chaff reflects more energy toward radar so missile will reject the original target and fly trough the chaff cloud (this was presented in one Russian weapons sale presentation, I tried to find it without luck) as it was bigger target. And in that sense chaff works as flare. The flare is "hotter" than original target so missile will fly at it (before multicolor seekers etc) and that way the chaff cloud is redlectring stronger signal so missile chooses it.

 

But what really happens on launching platform? Isn't it enough for it just keep pointing the target that is continuing the trajectory or even just point the radar at the direction (BVR) as missile will then pick the strongest echo source?

So why does missiles go dumb (ballistic) when platform loses the "lock"?

Why doesn't the platform just continue emmiting radar at the area like flashlight in the darkness hoping that when someone with reflectors comes to light beam it gets visible to platform too?

[GGTharos]

The signal is transmitted on the sidelobes; it isn't really likely that the missile will stray far anyway: Proportional navigation will cause it to somehow be more or less along the LOS to the target.

 

But.... isn't the missile in a way then "beam rider" as it needs to fly inside the radar beam to receive the guidance commands?

 

Meaning if the missile will take a totally different trajectory, away from LOS between platform and target, and the platform has target locked (focused beam to target), can't the missile simply fly outside of the LOS and this way lose totally the guidance if target changes trajectory?

[GGTharos]

Is the missile even looking in the right direction to see a reflection any longer?

 

Anyway, when lock is lost, most radars (and let's keep it to the radars represented by the FC3 planes for now) will use some form of mini-raster or other memory mode to attempt to recover the target.

 

If it takes too long, the radar drops the track and returns to search mode (or possibly an AACQ/CAC mode). By this time, the missile will have already moved anywhere between one and two kilometers, and the target about half of that. Depending on circumstances, the missile might not even be in position to see that target any longer.

 

So why does missiles go dumb (ballistic) when platform loses the "lock"?

Why doesn't the platform just continue emmiting radar at the area like flashlight in the darkness hoping that when someone with reflectors comes to light beam it gets visible to platform too?

[ShuRugal]

What I haven't yet understood is what does "radar lock" really mean? Like what does it mean when aircraft is "locked" and then it suddenly isn't because chaff is a released?

I get the "invisible mountain" as chaff works like a smoke blocking line of sight.

And I even get that chaff reflects more energy toward radar so missile will reject the original target and fly trough the chaff cloud (this was presented in one Russian weapons sale presentation, I tried to find it without luck) as it was bigger target. And in that sense chaff works as flare. The flare is "hotter" than original target so missile will fly at it (before multicolor seekers etc) and that way the chaff cloud is redlectring stronger signal so missile chooses it.

 

But what really happens on launching platform? Isn't it enough for it just keep pointing the target that is continuing the trajectory or even just point the radar at the direction (BVR) as missile will then pick the strongest echo source?

So why does missiles go dumb (ballistic) when platform loses the "lock"?

Why doesn't the platform just continue emmiting radar at the area like flashlight in the darkness hoping that when someone with reflectors comes to light beam it gets visible to platform too?

 

"Locked" means that the radar set has a good return signal and is automatically tracking the strongest part of that signal. Older radar sets relied on various forms of feedback-loops, based on things like signal polarization and phase-angle. "lockbreakers" disrupt this function by sending out a signal on the same frequency that is out of phase or cross-polarized, which causes the radar dish to move away from center of signal instead of towards it.

 

Newer radars are smarter, and use computer processing to build an "image" from returns, and track accordingly. Doppler radars are even more robust in this regard, because they use more types of signal data to compile their image.

 

Chaff works by virtue of the fact that while it is sufficiently close enough to the target, the radar sees it as part of the target's RCS. Until the chaff diverges enough for the radar to see two separate targets, it has no way to discriminate.

 

So why does missiles go dumb (ballistic) when platform loses the "lock"?

Why doesn't the platform just continue emmiting radar at the area like flashlight in the darkness hoping that when someone with reflectors comes to light beam it gets visible to platform too?

 

The missile goes dumb because the current radar simulation is extremely simplified. The Su-27 actually will continue to emit, even if the radar loses the target completely in the ground notch, provided you remembered to turn on EOS and get the "EORL" lock display. In this case, even though the radar has lost your bandit in ground clutter, the EOS keeps the radar slaved on target, and keeps illuminating the target so that it can re-acquire as soon as the notch is exited.

[tflash]

I have the best results with SU-27 when I operate in a look up scenario at short range, not exceeding 5 miles. You really have to do as if your radar has no look down capabilities at all and go for a Vietnam era style pursuit. And indeed: keep the EO system on, I use HPRF on the radar. The IIR missiles are in fact simple heaters with no imaging capabilities whatsoever and the R-27ER's non-performance has been sung over emphatically already in this thread. I guess the vintage AIM-7D Sparrow was wildly superior to the R-27 as it is modelled in this game.

 

The good thing is the SU-27 is so manoeuvrable that classic dogfighting is an absolute blast! BVR and associated tactics are simply non-existent in the game with the SU-27.

Edited December 14, 2015 by tflash

[GGTharos]

I guess the vintage AIM-7D Sparrow was wildly superior to the R-27 as it is modelled in this game.

 

I have a set of maneuvering target tables and graphs for the real AIM-7E/E2. It's quite significantly inferior to the R-27 as modeled.

[ShuRugal]

I have the best results with SU-27 when I operate in a look up scenario at short range, not exceeding 5 miles. You really have to do as if your radar has no look down capabilities at all and go for a Vietnam era style pursuit.

 

This, really, is the problem everyone is complaining about: It's not that R-27s have stopped working, it's that they have been reduced to Vietnam-era performance levels by the dramatic reduction in seeker performance.

 

The Su-27 is NOT a Vietnam-era fighter, it HAS look-down shoot-down capability. The R-27 family is NOT a family of 5-mile missiles (that would be the R-3).

 

The problem, as near as I can tell, is that the missile's effective range has become limited to how far it will fly before the engine rolls the dice on chaff/ground-clutter... Once chaff and/or notching has been a factor for more than a few seconds, the missile goes stupid. This behavior is forcing players to launch at shorter ranges to try and deny the target time to react in a way that abuses the current seeker modeling.

 

It's no surprise to anyone that the missile is performing brilliantly inside 5 miles... at that range, you're already inside the R-73 envelope.

[Nerd1000]

What I haven't yet understood is what does "radar lock" really mean? Like what does it mean when aircraft is "locked" and then it suddenly isn't because chaff is a released?

I get the "invisible mountain" as chaff works like a smoke blocking line of sight.

And I even get that chaff reflects more energy toward radar so missile will reject the original target and fly trough the chaff cloud (this was presented in one Russian weapons sale presentation, I tried to find it without luck) as it was bigger target. And in that sense chaff works as flare. The flare is "hotter" than original target so missile will fly at it (before multicolor seekers etc) and that way the chaff cloud is redlectring stronger signal so missile chooses it.

 

But what really happens on launching platform? Isn't it enough for it just keep pointing the target that is continuing the trajectory or even just point the radar at the direction (BVR) as missile will then pick the strongest echo source?

So why does missiles go dumb (ballistic) when platform loses the "lock"?

Why doesn't the platform just continue emmiting radar at the area like flashlight in the darkness hoping that when someone with reflectors comes to light beam it gets visible to platform too?

 

There's no functional difference between the platform and the missile where chaff is concerned, except that the platform is in a different spot and (being larger and re-usable) might have more advanced signal processing to filter the chaff out. If the radar on the plane can't tell the difference, it may end up tracking the chaff too! This was certainly the case with early radars.

[Ragnarok]

There's no functional difference between the platform and the missile where chaff is concerned, except that the platform is in a different spot and (being larger and re-usable) might have more advanced signal processing to filter the chaff out. If the radar on the plane can't tell the difference, it may end up tracking the chaff too! This was certainly the case with early radars.

 

In "High freq." mode, filter is good, and there is no confusion as long as two target (plane and chaff or other plane) are somewhat different from these three, altitude, speed and vector ranging within the 500m distance over 8 km in free space (serbian term for sky background), but calculation is slow in high aspect (180-160) so mistakes are great at switching from observing the track (lock). Often error of up to 8 km, and is often unsuccessful lock on and the correction of fixing the aerial and extended search on average 7-12s. that is problem with "high" freq. However, when the locking to give, after is all stably. But search and lock problem is within the range of 8 km, when it switches on "medium"freq.

 

In "Medium" there are disturbing false targets (from chaff on the sky, or clutter or chaff on the look down), but due to better behavior on the rapid changes in information at short distances, combat modes for close combat is always used "medium" frequency, when the interference from the chaff as possible in "look up", and in a high aspect (180-160) with clutter in look down.

 

In "inermedium" mode, because of frequent overshoot, if the target of turning defensive in "look up", at the moment of transition from Hot to Cold, lock it may break (does not mean always) if it lasts more than three cycles search by cramped cottage regime (I do not know what his name is an expression in English).

Edited December 16, 2015 by Ragnarok