How can flares attract LOBL IR missile?

[Ronny]

there are two kind of infrared guided missiles: -The LOAL (lock on after launch) meaning even if the missile seeker see nothing while it on the rail, it can still search around and find target after launch.
-The LOBL ( lock on before launch) meaning the missiles seeker must see and lock on to target before the pilot press the launch button. The missile can’t find target on its own.
My question is that: if LOBL missiles can’t find target on its own after launch. Then how can flares deceive them?. Wouldn’t they just remaining locked to the original target regardless of what appearing in the field of view?

 

[TomS]

there are two kind of infrared guided missiles: -The LOAL (lock on after launch) meaning even if the missile seeker see nothing while it on the rail, it can still search around and find target after launch.
-The LOBL ( lock on before launch) meaning the missiles seeker must see and lock on to target before the pilot press the launch button. The missile can’t find target on its own.
My question is that: if LOBL missiles can’t find target on its own after launch. Then how can flares deceive them?. Wouldn’t they just remaining locked to the original target regardless of what appearing in the field of view?

The flare ignites as it leaves the dispenser, so the missile initially sees it in the same cell or bit of its scan pattern as the locked-on target. But as the flare moves away from the aircraft, the missile has to "decide" whether to keep tracking the flare or the aircraft. If it follows the flare, when the flare expires the missile may not have a big enough search pattern to find the aircraft again.

(Same basic idea as range-gate pull off for radar seduction jamming)

 

[Scott Kenny]

The flare is also usually hotter than the engine exhaust, so that helps draw the seeker. Less effective against dual-freq UV/IR seekers, and marginally effective against Imaging IR.

 

[Ronny]

The flare is also usually hotter than the engine exhaust, so that helps draw the seeker. Less effective against dual-freq UV/IR seekers, and marginally effective against Imaging IR.

I think you misunderstand my question.
it specifically about LOBL missiles

 

[Ronny]

The flare ignites as it leaves the dispenser, so the missile initially sees it in the same cell or bit of its scan pattern as the locked-on target. But as the flare moves away from the aircraft, the missile has to "decide" whether to keep tracking the flare or the aircraft. If it follows the flare, when the flare expires the missile may not have a big enough search pattern to find the aircraft again.

(Same basic idea as range-gate pull off for radar seduction jamming)

so technically speaking, a LOBL missile can still find target by itself if just launched before seeker acquire target?

 

[Scott Kenny]

I think you misunderstand my question.
it specifically about LOBL missiles

Right. But because the flare starts at the same place as the missile exhaust and is hotter than the missile exhaust, the flare can easily draw off a simple IR seeker. Early Sidewinders even tracked on the sun!

so technically speaking, a LOBL missile can still find target by itself if just launched before seeker acquire target?

Not exactly. It needs a starting lock to know where to guide on.

 

[green.nova343]

LOBL could theoretically be launched without achieving a lock...but their accuracy is going to be abysmal (as in making the Vietnam-era early Sidewinders & Sparrows look like they're a sharpshooter's preferred weapon). The mechanism for them to acquire a target if launched without a lock would be the same method that allows them to attempt to reacquire a target after losing target lock, but it's not going to be that reliable. Basically, if there's something pretty much in front of them, it could technically lock onto it...but unlike in the movies,

What you need to remember is that the heat-seeker on a LOBL missile is just that: a seeker head that looks for a source of extreme heat. For nearly every target, that's going to be the engines, which is why only the latest generations have been "all-aspect" missiles; the first few generations required you to be behind your potential target before firing the missile. But at the ranges they are fired at, you're not seeing the plane...you're seeing a relatively small point with a high temperature. That seeker head might see the target as a single pixel, or maybe a 3x3 section (9 pixels total). A flare is much, much smaller than the aircraft, but its high temperature will make it show up against the sky...& as the flare's trajectory moves it away from the aircraft, the missile has to figure out which heat source to follow. Problem is, once the flare drags it off course, it's going to be nearly impossible for the missile to reacquire the original target -- technically possible, especially if the pilot foolishly maneuvers back into view of the missile seeker, but not probable.

Lobbing a LOBL missile without a prior target lock might work if you're shooting at a group of targets, but the days of massed formations of aircraft are pretty much gone. And to be honest, I'm guessing that part of what makes a LOAL missile work is that its preprogrammed search pattern allows it to lock on after launch...although my concern would be making sure that the launch platform maneuvers away in time to avoid being within that search pattern (since they tend to not have IFF systems to prevent "blue-on-blue" incidents).

 

[HoHun]

LOBL could theoretically be launched without achieving a lock...but their accuracy is going to be abysmal (as in making the Vietnam-era early Sidewinders & Sparrows look like they're a sharpshooter's preferred weapon).

It's my impression that an analysis of the early, Vietnam-war era Sidewinders relatively poor performance came to the conclusion that this was partially owed to many launches actually being performed outside the valid launch envelope of the missiles, which would imply that they were either launched without a (solid) lock or in a situation where they wouldn't be able to maintain the lock after launch.

Which, if I remember correctly, was partially attributed to alterations of the seeker head (meant to improve its performance), which directly affected the Sidewinder's audio signal (which was a pretty straighforward derivative of the seeker head signals and thus changed with the seeker head design iterations), which wasn't properly communicated to or factored in by the pilots.

Unfortunately, I don't recall the source for the above statements ... I'm a bit outside my primany area of expertise here, I'm afraid.

That seeker head might see the target as a single pixel, or maybe a 3x3 section (9 pixels total).

With regard to the early Sidewinders, they didn't actually have an imaging sensor, but (if I understand it correctly) only a single IR-sensitive detector, which was partially covered by a rotating mask that covered 180° with a pattern of opaque lines, while the other 180° were clear. Depending on the position the image of the heat source had on the detector wafer, there was a phase difference between the position of the shutter motor and the detector signal, given the direction of the heat source from the central axis.

I'm not entirely certain how the angular distance from the central axis was measured ... it would seem possible that the ratio between obscured and clear parts would provide the required information.

What happened when two heat sources of roughly equal strengths were projected onto the sensor would depend a lot on the processing (analogue) circuitry, and as far as I am concerned, I could only guess

Regards,

Henning (HoHun)

 

[green.nova343]

It's my impression that an analysis of the early, Vietnam-war era Sidewinders relatively poor performance came to the conclusion that this was partially owed to many launches actually being performed outside the valid launch envelope of the missiles, which would imply that they were either launched without a (solid) lock or in a situation where they wouldn't be able to maintain the lock after launch.

Which, if I remember correctly, was partially attributed to alterations of the seeker head (meant to improve its performance), which directly affected the Sidewinder's audio signal (which was a pretty straighforward derivative of the seeker head signals and thus changed with the seeker head design iterations), which wasn't properly communicated to or factored in by the pilots.

Unfortunately, I don't recall the source for the above statements ... I'm a bit outside my primany area of expertise here, I'm afraid.



With regard to the early Sidewinders, they didn't actually have an imaging sensor, but (if I understand it correctly) only a single IR-sensitive detector, which was partially covered by a rotating mask that covered 180° with a pattern of opaque lines, while the other 180° were clear. Depending on the position the image of the heat source had on the detector wafer, there was a phase difference between the position of the shutter motor and the detector signal, given the direction of the heat source from the central axis.

I'm not entirely certain how the angular distance from the central axis was measured ... it would seem possible that the ratio between obscured and clear parts would provide the required information.

What happened when two heat sources of roughly equal strengths were projected onto the sensor would depend a lot on the processing (analogue) circuitry, and as far as I am concerned, I could only guess

Regards,

Henning (HoHun)

Correct, it wasn't pixeleted per se (but I figured it would be kind of an analogous without having to delve too deeply into it). Your description, though, also gives a better justification for why so many of the early Sidewinders kept on "chasing the Sun" (because even at nearly 94 million miles it's hard to find too many heat sources hotter than the Sun in the daytime).

As for firing it outside of its envelope...if they weren't getting a good lock-on beforehand, then it proves that it's not impossible to get a lock-on after launch with a LOBL missile, but it's going to take a lot of luck on the pilot's part.

I'm still not 100% sold on the whole LOAL idea...how do you keep the missile from tracking onto the target that your wingman has already fired on -- or worse, from tracking on your wingman?

 

[Hanz2k]

I'm still not 100% sold on the whole LOAL idea...how do you keep the missile from tracking onto the target that your wingman has already fired on -- or worse, from tracking on your wingman?

1. Data link to update missile post launch with current target vector.
2. Use helmet cueing system. And update via data link.
3. Shoot with search cone / FOV in mind.
4. Use brain and do not use weapon in potential blue on blue scenario.

 

[green.nova343]

1. That...kind of sounds like you have to have somewhat of a lock on the target prior to launch, but from the onboard sensors instead of the missile seeker.
2. Sounds a lot like the movie/TV show Blue Thunder, although again you're having to depend on the onboard sensors to get a lock (or hope that the helmet cue system can do the trigonometry to give a decent target vector.
3. This would probably work the best, although I would think the search cone/FoV is going to be somewhat limited. They always seem to tout it as "you can target something flying next to you", but I suspect it's more like "you can target something 20-30 degrees off your boresight instead of having to be pointed directly at it".
4. That's hopefully a given...but in the stress & split-second decision-making process that goes on in a furball, training can only do so much.

 

[Hanz2k]

1. That...kind of sounds like you have to have somewhat of a lock on the target prior to launch, but from the onboard sensors instead of the missile seeker.
2. Sounds a lot like the movie/TV show Blue Thunder, although again you're having to depend on the onboard sensors to get a lock (or hope that the helmet cue system can do the trigonometry to give a decent target vector.
3. This would probably work the best, although I would think the search cone/FoV is going to be somewhat limited. They always seem to tout it as "you can target something flying next to you", but I suspect it's more like "you can target something 20-30 degrees off your boresight instead of having to be pointed directly at it".
4. That's hopefully a given...but in the stress & split-second decision-making process that goes on in a furball, training can only do so much.

I have no idea what you want to accomplish. LOAL is a fact. For Active Radar missiles is mandatory as they have 200km or more range and there is no way puny radar in missile perform any LOBL. For modern IR missile it is nothing impossible as well. More over - for true stealth fighter it is mandatory to shoot missile from a bay, so just expect all missiles doing LOAL with fighter datalink providing initial guidance. Thx.

 

[green.nova343]

I have no idea what you want to accomplish. LOAL is a fact. For Active Radar missiles is mandatory as they have 200km or more range and there is no way puny radar in missile perform any LOBL. For modern IR missile it is nothing impossible as well. More over - for true stealth fighter it is mandatory to shoot missile from a bay, so just expect all missiles doing LOAL with fighter datalink providing initial guidance. Thx.

Which missiles have these super-long ranges that you're claiming? And I don't mean experimental missiles (like the AIM-260), I mean actual missiles, since you're claiming LOAL is a current fact. Even the AIM-120D is only estimated to have a 160km range, still less than what you claimed. But even then, I would imagine that (as with 99% of all air-to-air missiles) that range is for head-on engagements...not firing at a target 90 degrees or more to either side. And even with beam-forming, the APG-77 is still limited to a 120-degree view...& I highly doubt it can "bend" the radar beyond the 90-degree limitation the antenna would have (else the AEGIS ships wouldn't need 3-4 separate arrays for 360-degree coverage in ships).

Again...just because the pilot can see a target from his cockpit doesn't mean he knows exactly how far away it is, what its heading is, or how fast it's going...all of that data being critical for a LOAL missile to be able to steer itself in the right direction (because no way in hell that the radar onboard the LOAL missile is going to have anywhere near the range or discrimination capabilities of the radar on the launch platform). Too far off-axis, & you aren't going to waste the LOAL missile because it won't have enough info to go after the target.

And unless in this case LOAL means "we get the steering data from an AWACS so that we don't have our own radar even turned on, so that the target doesn't know it's being painted until the onboard seeker turns on like the AIM-54 Phoenix used to do", it's a complete waste to even use that capability, especially if your opponents don't have 200+ km-range missiles to respond with. Which is probably why the 2 specific examples I found of LOAL missiles were ASRAAM (25+ km range) & AGM-114L Longbow Hellfire (~8km range)...because in a dogfight, or attacking targets at an offset, LOAL would be more crucial than in long-term sniping.

 

[Ronny]

Which missiles have these super-long ranges that you're claiming? And I don't mean experimental missiles (like the AIM-260), I mean actual missiles, since you're claiming LOAL is a current fact. Even the AIM-120D is only estimated to have a 160km range, still less than what you claimed.

I can think of a few:
For air to air missile: AIM-54, R-37, Meteor, PL-17
For surface to air missile: SM-6, 40H6E, CIM-10
For air to surface missiles: JSM, JASSM, LRASM, AARGM-ER, SLAM-ER, RBS-15, Brahmos, ASM-3

because in a dogfight, or attacking targets at an offset, LOAL would be more crucial than in long-term sniping.

LOAL basically mean the seeker doesn’t need to lock on target before launch, it is an absolutely compulsory requirement for extended range missile

 

[Scott Kenny]

It's my impression that an analysis of the early, Vietnam-war era Sidewinders relatively poor performance came to the conclusion that this was partially owed to many launches actually being performed outside the valid launch envelope of the missiles, which would imply that they were either launched without a (solid) lock or in a situation where they wouldn't be able to maintain the lock after launch.

Which, if I remember correctly, was partially attributed to alterations of the seeker head (meant to improve its performance), which directly affected the Sidewinder's audio signal (which was a pretty straighforward derivative of the seeker head signals and thus changed with the seeker head design iterations), which wasn't properly communicated to or factored in by the pilots.

Unfortunately, I don't recall the source for the above statements ... I'm a bit outside my primany area of expertise here, I'm afraid.

From reading about Taildog/SRAAM, the problem was mostly that the pilots were firing as soon as they got a missile lock, while the locked target was not inside the engagement envelope. Usually, crossing too fast, such that the target was out of missile FOV before the missile finished leaving the launch rails.

Your description, though, also gives a better justification for why so many of the early Sidewinders kept on "chasing the Sun" (because even at nearly 94 million miles it's hard to find too many heat sources hotter than the Sun in the daytime).

As for firing it outside of its envelope...if they weren't getting a good lock-on beforehand, then it proves that it's not impossible to get a lock-on after launch with a LOBL missile, but it's going to take a lot of luck on the pilot's part.

No, they were getting locks, just that they couldn't tell what the missile had locked onto. In addition to shooting as soon as they heard the lock-on growl, instead of the missile growling only when the target was in the NEZ.

I'm still not 100% sold on the whole LOAL idea...how do you keep the missile from tracking onto the target that your wingman has already fired on -- or worse, from tracking on your wingman?

Datalinks and IFF.

 

[green.nova343]

I can think of a few:
For air to air missile: AIM-54, R-37, Meteor, PL-17
For surface to air missile: SM-6, 40H6E, CIM-10
For air to surface missiles: JSM, JASSM, LRASM, AARGM-ER, SLAM-ER, RBS-15, Brahmos, ASM-3

LOAL basically mean the seeker doesn’t need to lock on target before launch, it is an absolutely compulsory requirement for extended range missile

AIM-54 hasn't been in service, and required lock-on from the AWG-9 before launch. Aside from being "roughly 20 ft long", there are no actual stats for the PL-17 (aside from China's claims about its range...which without verification are as useful as a wetsuit on a duck).

I'll give you the Meteor & the other missiles...except...they're not using IR seekers. That's the question that OP had, whether flares would disrupt IR-guided LOAL missiles they way they can disrupt LOBL missiles.

Nor have you addressed the concerns I raised about preventing a LOAL missile in a close-range situation from locking onto a wingman or another allied aircraft (or even your own AEW platform, if you're shooting at an enemy fighter that's near it). The active seekers on every missile you mentioned won't care if the target is friendly or not...their active radar seekers will just see a target in front of them. And I have yet to find any information that indicates that the missiles you listed above -- especially the woefully obsolete & long-retired ones like Phoenix & Bomarc -- for the missile to distinguish the target after launch. That's a separate signal that has to be sent out...& just because you don't get a valid IFF return signal doesn't mean that the target is an enemy target either.

Don't get me wrong: if it works, it sounds like great technology. But I'm not convinced that it's actually as "foolproof" as it's made out to be. We've seen too many overhyped claims with military hardware over the decades to blindly accept every single sales pitch from the manufacturers as being 100% accurate.

 

[Ronny]

AIM-54 hasn't been in service, and required lock-on from the AWG-9 before launch.

LOBL mean the seeker on the missile must acquire target before launch
LOAL mean the seeker on the missiles does not need to see target before launch
Whether the sensor of the aircraft can acquire the target or not is irrelevant

That's the question that OP had, whether flares would disrupt IR-guided LOAL missiles they way they can disrupt LOBL missiles.

I think you misunderstand my question. My question is how can flare deceive LOBL missile if the seeker can’t acquire/lock target after launch

 

[Flame2512]

My question is how can flare deceive LOBL missile if the seeker can’t acquire/lock target after launch

A simplified way of thinking about it is that (without any flare rejection technology being implemented) an IR missile will simply track the strongest IR source it can see, hence IR missiles (early ones at least) have a habit of locking onto the sun if they are pointed too close to it.

When ab aircraft drops a flare it will ignite and produce a strong IR source right next to the aircraft. As the missile will be looking directly at the aircraft in order to track it the missile will inevitably see the flare. The flare will then move away from the aircraft, and because it is a stronger IR source than the aircraft, the missile's seeker will be attracted towards the flare and start following it instead of the aircraft. Eventually the distance between the flare and the aircraft will become great enough that the missile can no longer see the aircraft at all.