How fighter jets lock on, and how the targets know (2014)
gizmodo.com
gizmodo.com
VTOL VR taught me about "Radar Notching". The article briefly mentions how radar can actively detect the doppler shift of targets. If you think about it, the doppler shift of the ground would be neutral, right? Or roughly the speed of the aircraft. So lets say you've been locked on by a fighter at high altitude and they've fired a radar seeker at you. Your backdrop is the ground, it can pick you out because you're moving so fast. So what you do is bank your aircraft to fly at a 90 degree angle to the oncoming missile. Now your doppler shift is the same as the ground and you blend in, the radar filters out the ground because of it's expected speed, which is now the relative speed you are moving. You get "notched out", and the missile will lose track.
Surely they can't use this poor of an optimization strategy? If the target is moving perpendicular to you, you want to point slightly ahead of the target so you intercept them as quickly as possible.
https://en.wikipedia.org/wiki/Constant_bearing%2C_decreasing...
So as you track, you can measure where it is, and how fast it's apparently moving in those two degrees of freedom - so you know x, y, dx and dy (and I guess you know higher degree deltas too).
To hit it (assuming it's in front of you) all you need to do is make control inputs to bring dx and dy to zero - you don't care what x and y are. If dx and dy are zero, if you're faster than the thing you're tracking, you're going to hit it - that's constant bearing, decreasing range.
Making control inputs to bring x and y to zero as well as dx and dy is a harder problem! You need to control four degrees of freedom to do that.
And making control inputs just to try to bring x and y to zero without controlling dx and dy is a good way to miss the target completely - obviously if you get x and y to 0 but dx and dy are nonzero, the target is going to move away from zero, requiring more control input, which might increase dx or dy, causing you to need even stronger control input...
So the upshot is: you don't have to back out the target's absolute trajectory, figure out its true velocity and your own relative velocity, determine range to target and offset where you're pointing to compensate for time of flight - just get it to stay on the same bearing from your perspective, and you're done.
Constant bearing is possible, but if you are tracking behind, above, or below the target then you don't get any advantage, taking a longer route than direct/pure chase. The missile needs a mechanism to estimate the target motion rather than only it's relative bearing. That isn't simple. Many manpads instruct the user to aim ahead so that the missile locks into a lead path, but accidentally aim up/down/behind and they will lock into a lagging approach.
Historically, I don't think any missile designed to target aircraft has ever been fielded which use the strategy you suggest. (lots of air to ground missiles do) It works fine if the target is flying straight and level, and you fire from directly behind them. But if the target has even a shallow turn towards you, the rate at which the missile will need to increase its rate of turn will increase exponentially as it closes with the target. If the target is aware it's being shot at and from what angle, all it takes to avoid the missile is to keep it at your 3/9 o'clock positions (steadily turning towards it) and it will miss every time.
The first generation of radar guided air to air missiles in the 1940s use beam riding. The missile would attempt to keep itself between the target and the shooter.
The first generation of (infrared) AIM-9 Sidewinder missiles in the 1950s used a mechanical system to perform proportional navigation; it spun the sensor at a fairly high rate of speed, causing it to act as a gyroscope. The sensor was pointed towards the target on an internal gimbal. But since the sensor was a gyroscope, if corrections had to be made, this meant the target was not at a continuous bearing. So the same corrections were sent to both the gimbal and the missile's control surfaces.
These days, everything just has a microcontroller in it, so there's no need to design such electro-mechanical Rube Goldberg contraptions to get proportional navigation to work.
The underlying principle of proportional navigation, which is what the first few generations of IR missiles use to navigate, is constant bearing decreasing range. If a missile maintains absolute bearing to a target, it will collide with that target. The first generation AIM-9, which was the first useful IR missile, didn't aim "slightly ahead" of its target, it pointed itself at the exact point where it would collide with its target, assuming the target was moving at constant speed in a straight line.
The spinning sensor that you mention was on a gimbal, it wasn't pointing along the boresight. The spinning caused it to act as a gyroscope, so it would maintain its orientation in absolute space. The gimbal would track the sensor so that it was pointing at the target, and the same inputs were fed into both the gimbal and the missile's control surfaces. Therefore, if the bearing was changing, that would cause the missile to maneuver in such a way that the bearing would stop changing. If the bearing wasn't changing, the missile would not maneuver. This is all you need to do to point the missile at the exact point where it will intercept a non-maneuvering target.
As a first order approximation, the assumption of a constant speed straight line target is a useful one, given the technological limitations of the time.
https://en.wikipedia.org/wiki/Proportional_navigation
https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_r...
https://qph.fs.quoracdn.net/main-qimg-a0e376f321a658b5d99e25...
The principal use is to break missile lock. It's less useful for disguising position, especially against opponents with AEW&C and data link. Breaking lock means reducing the doppler return to below the range gate threshold, and changing bearing to escape the Kalman filter that is predicting your position based on prior kinematics.
With modern data links it's now possible in principle to provide target tracking updates from a different sensor (like IRST) or even a completely different aircraft. If done correctly the target won't even realize a missile is on the way until it's too late to evade.
At closer range there is still the UV flare of the missile solid rocket burn, but detecting it depends on weather and aspect.
Flying perpendicular to that bearing will thus (hopefully) result in both sets of radar electronics filtering you out.
Should the two bearings diverge at some point, I'd recommend notching against the one armed with the explosive warhead with your name on it.
You need to "Notch" or beam against the missile itself if it's an Active Radar Missile or Fox-3. The jet's radar isn't good enough for terminal guidance. However if the firing jet is close enough it can maintain a pulse STT which cannot be notched and the missile will stay in Semi-Active mode and follow your beam to the target.
However in a Beyond Visual Range fight usually you can't stay nose on to the enemy since he will be firing his own missiles. Most missiles will be fired in Active mode (Fire and Forget) followed by evasive maneuvering once they enter their terminal phase and "Go Active." TWS launched active missiles will usually go active within some pre-calculated distance based on target size.
Newer missiles probably use better guidance but they are all pretty freaking secret. Computer vision would make for some seriously effective datalink guided missiles. But the kind of computers you can stick in the front of a 335lb solid rocket propelled tube that pulls 10-20Gs is very limited. Mostly just: "Go after jet shaped hot thing" or "Go after metal thing that moves fast."
We haven't really seen that level of air combat in real life though. Typically you would only see fights like that in a symmetric situation. (EG: India vs. Pakistan, China vs. Russia) Most jets shot down by AAMRAMS from the US are 3rd generation fighters sold to second world countries. Typically we require visual ID and warnings in rules of engagement making BVR impossible.
What VTOL VR does is use the VR environment to make an interactive cockpit. Rather than you memorizing a huge list of bindings, you just interact with the cockpit the way the pilots would. That memorization aspect is why I never really got into falcon 4 or DCS. And as a first mil sim flight game, if you have a headset, that's my recommendation.
Falcon BMS example: https://www.youtube.com/watch?v=_mU2d3PbD78
https://ieeexplore.ieee.org/document/1631867
https://www.researchgate.net/profile/Jp-Molinie/publication/...
I don’t know much about stealth though so I could be completely wrong.
In any case, you are right that OTH skywave radars like the Nostradamus usually have a pretty good chance to detect stealthy planes. However due to the frequency bands involved such detections are typically more of the "there is something in this cubic kilometre" type and not of fire-control quality. You need much more accurate systems to actually guide a missile. Still, it is pretty cool. There are also "passive" systems which use the reflections of waves from normal civilian radio stations and a phenomenal amount of signal processing to determine the position of thousands of targets simultaneously, although I'm not aware of any in active service yet. Like fusion power, this type of "multistatic" radar seems to be perpetually 30 years away from practical use.
Source: Used to be a weapons engineer for the Dutch Navy, at one point specializing in advanced radar systems.
It's not about been totally hidden (sans a cloaking device that is never going to happen) it's about been less detectable after all.
If the distance the stealth platform can see you from is greater than the distance you can reliably detect them from you are already dead - the missile simply hasn't arrived yet.
Everyone is probably already arming space to the teeth. I guess it's better than mutually assured destruction?
Put a few hundred missiles in orbit, give them enough spare fuel to travel a decent distance on their own, and you have a pretty substantial worldwide strike capability.
Apparently it’s hard to fully shield weapons grade material
The ICBM can hit anywhere (instead of just where the orbit track happens to pass), in less time (or at most the same time, since deorbiting takes around half an orbit) with a better mass fraction (since it doesn't have to reach orbit and then deorbit afterwards) while being more accurate (you know exactly where the launch platform is, while satellites are harder to locate) and less vulnerable (you can harden an ICBM silo far more effectively than a satellite).
Really, it's hard to think of something that satellite anti-ground weaponry does better.
There is a lot of icbm detection. Unplanned rocket launches could lead to global nuclear annihilation. What happens if something seems to deorbit above the US? How much early warning and procedure is there?
Especially if you want to deliver conventional munitions to a non-nuclear power, a system like this seems better than an ICBM.
If you want to hit something with a conventional warhead in a non-peer state without warning, why not use a stealthy cruise missile instead?
I am not advocating weapons in space btw. Just pointing out what the advantages are.
https://en.wikipedia.org/wiki/Kinetic_bombardment
Possible, though problematic.
There might already be stealth sats in orbit.
A curious case was the Zuma satelite [1].
Classified payload. Ostensibly failed to detach from the payload adapter, as claimed by anonymous sources... Lot's of speculation that this was a media charade to sow confusion about a stealth sat.
http://www.projectrho.com/public_html/rocket/spacewardetect....
Just because it's physically challenging to avoid having some blackbody emissions or whatever doesn't mean you can't evade modern sensors in practice.
Wikipedia isn't a reliable source for this stuff. Look at the basic physics involved.
To me, this seems to imply you could make a useful system today with orders of magnitude less transmit power.
An army consisting exclusively of F-35 vs old generation jets could decimate all enemy jets without losing a single F-35.
It's the same with modern tank vs old tanks. Those old tanks can't penetrate the armor of modern tanks.
https://abcnews.go.com/blogs/headlines/2012/07/f-22-fighter-...
> while the planes own the skies at modern long-range air combat
In fact I would say if such an encounter were ever to happen, due to rule of engagements, a dogfight would be more likely than a BVR engagement (and likely to end without a single shot fired).
The F-35 can see and shoot down the F-16 with radar-guided missiles in BVR well before the latter is even aware the F-35 is in the area.
Dogfighting is minimally relevant to modern air combat for nuclear-armed nations. Things would have to be going extraordinarily badly in a war for the brass to start deciding to send their exceedingly expensive fifth-gen stealth fighters into dogfight coin tosses.
Hell, even an A-10 is a surprisingly effective dogfighter against modern fighters. The fighters have speed but the Warthog has an extremely tight turning radius and far better low-speed maneuverability, both of which allow it to stay inside the opponent’s “bubble” (the area inside which a turning jet can’t ever manage to point its nose). If the A-10 can keep it to a one-circle fight it will win handily. A fighter will often have to rely on a “boom and zoom” tactic (where it disengages, gains distance, and turns back around for a guns pass) but that can be quite low probability of kill and still be relatively risky if the A-10 has friendlies in the area feeling it location information.
But just like the situation already being discussed, this is for all practical purposes completely irrelevant. A flight of F-16s would engage and destroy a flight of A-10s from miles away with AMRAAMs and it would never have a chance to transition to an up-close dogfight.
what's stopping the f-16 from turning around and going cold as soon as it hears a lock or senses enemy radar?
Either way, if the enemy turns and flees, from your perspective you’ve won the engagement. Whatever their purpose in the area was (SEAD, strike, air superiority, etc.) has been subverted.
Maybe ... in the air ... if the numbers are the same ... if all of those F-35s are able to fly ... if the other side doesn't have a significant SAM capability ... if if if. In a realworld battle between armies the air-to-air capacity of fighters is a small part of the battle. Most will try to defeat the other's aircraft using ground assets, missiles/manpad. Ideally you take out aircraft in their hangars. A single well-placed artillery shell can take out a dozen F-35s in a hangar. A single frogfoot can destroy any F-35 that is low on fuel/ammo/speed after engaging a couple flankers. Realworld combat is messy. A pack of crows can take down an eagle.
During the Sri Lankan civil war about 10 years ago, the Tiger rebels had acquired Zlin Z 43s, modified them to carry several bombs [1], and were bombing targets left and right, including the country’s capital.
The populace was increasingly pondering why the country’s well-trained air force, with modern fighter jets with years of scrambling experience [2] could never seem to shoot these slower planes down. In fact, there were no confirmed kills during the conflict.
It was later revealed that the rebels knew the capabilities of the enemy Chengdu J7 and MiG 29 interceptors, and had modified their own aircraft engines with anti-IR capabilities [3]. Complex IR jamming equipment was suspected, but the country’s PM later said that the rebels had simply redirected the exhaust fumes from the back of the aircraft to the front, throwing “unlockable” heat signatures [4].
By the end of the war, the rebels had actually “won” the war in the skies by destroying over 30 aircraft and losing 2, despite ultimately losing.
[1] https://en.m.wikipedia.org/wiki/Zl%C3%ADn_Z_43
[2] The government’s prized jet fighters were stationed in the capital, about 400 km from the main conflict zone. In 2000, the rebels launched a devastating offensive and the government held on by a thread due to their ability to scramble ground attack craft to battles in 7 minutes. It’s said that had they lost that battle, all hopes of winning the war would have been lost.
[3] http://www.sundaytimes.lk/081102/Columns/sitreport.html
[4] https://www.dailynews.lk/2020/01/18/local/208783/slaf-most-e...
It must obviously be more complicated than that but that should be doable nowadays?
Or, for that matter, hull? These aircraft have many layers of material between the traditional tensioned skin of the aircraft and the outside air.
Stealth coated airplanes are supposedly flying very slow on missions to avoid infrared detection.
It will probably still not do anything against astronomy grade infrared sensors.
Radar is a huge field and HN's simplistic view is humorous.
These aircraft don't just fly around and let you take your sweet time killing them.
If you manage to lock one you have to deal with this as well:
https://en.wikipedia.org/wiki/Radar_jamming_and_deception
Some of these are quite sophisticated, example:
>Digital radio frequency memory, or DRFM jamming, or Repeater jamming is a repeater technique that manipulates received radar energy and retransmits it to change the return the radar sees. This technique can change the range the radar detects by changing the delay in transmission of pulses, the velocity the radar detects by changing the Doppler shift of the transmitted signal, or the angle to the plane by using AM techniques to transmit into the sidelobes of the radar. Electronics, radio equipment, and antenna can cause DRFM jamming causing false targets, the signal must be timed after the received radar signal. By analysing received signal strength from side and backlobes and thus getting radar antennae radiation pattern, false targets can be created to directions other than one where the jammer is coming from. If each radar pulse is uniquely coded it is not possible to create targets in directions other than the direction of the jammer
"Find the F35 and you're dead" is just wrong and simplistic. Head to head anti-air fights aren't what's gonna happen. The F-35 in every mission it's supposed to do is going to go heads up against multiple different detection platforms.
This is so incredibly wrong.
I bet that there are people on this platform who have never had a conscious thought about radars, also there are ones who design radars for a living. And the whole gamut in between.
Stealth is still 80% of shaping. Specular reflection can be reflected away from the radar receiver. In the resonant scattering region, where the signal amplitude matches the object sizes, you remove radar return by removing all parts that are a similar size to the wavelength, like the tail. Coatings and Absorbers reduce radar even return more but only after the shaping works.
If you can get radar into an angle that the shape was designed for, or transceiver and receiver are in separate locations stealth advantage decreases dramatically.
Chinese are probably the first to deploy long-range air-to-air missiles that have dual sensors. Both radar and IR. (Stunner missile has that already, but it's ground-to-air missile). Traditionally IR is used only in short-range missiles. You direct the missile to approximate position and then it uses IR and radar together to remove stealth.
So what happens when the dual seekers give different results? If there were three seekers then you could ignore one, but with only two you cannot check one against another. What if the radar says turn left but the IR says turn right? Having two seekers may make the target's life easier: defeat either seeker and you defeat both.
Small errors count. A few degrees off and your missile doesn't get to the target. Any averaging will probably result in a miss. In such cases a single sensor would be better, or two different sensors on two different missiles.
This comes up in all manner of flight systems. Take altitude. If one sensor says you are at 1000feet and another says 10,000, the one thing everyone should agree is that you aren't at 5500. One of the sensors is wrong and needs to be ignored, but how do you pick between the two?
What did the sensors say one minute ago? There's no reason this has to be Markovian.
For example, the Kalman Filter tells you the weight to apply to each new sample and the last estimate to make a new estimate. These weights are optimal if the measurement errors have a Gaussian distribution with zero mean. In many practical systems they are usably good even when that assumption does not perfectly hold.
In your example the new measurement that was less consistent with the last fused estimate would be downweighted by a KF.
And when deployed against a jamming target that it well aware of gaussian distributions and how to game them? When deployed against a jammer that is very good at pretending to not be a jammer? An aware jammer will feed you good results, just enough to convince your gaussian distribution (capture) and them move it off of onto a false path (seduction) resulting in you following a false signal (miss) or cause you to fall back into search mode (delay=miss). The game is different when the thing you are trying to measure is actively trying to deceive you.
The dual-mode terminal guidance on the Chinese missile may be a response to the fact that the US has very good countermeasures for IR terminal guidance. IR guidance is cheap but it may not be reliable against some advanced targets.
In contrast, the AIM-120D has bidirectional data link, so it can feed it's RADAR picture back to the launch platform.
The fact that Radar + IR is a spoken of as somewhat novel either tells me the defense industry parasites are way behind or the public intel is just several decades behind.
But given the speeds I can see the problem being more difficult that I think.
Another approach is to passively listen for reflections of cell tower or FM radio signals. Stealth aircraft do not reflect much radio energy straight back at the source, but they do reflect it in other directions.
VHF is inherently too inaccurate for a lock either. It just scales with how big the radar is.
I believe it was possible to pickup the Russian Duga system.
These are still a source of interference on the amateur bands. You can find more info on that at https://www.iaru-r1.org/spectrum/monitoring-system/iarums-r1...
[1] https://en.wikipedia.org/wiki/Active_electronically_scanned_...
An AESA radar that can track up to 5 targets for example might still be limited to a single target with a low RCS because more of the array has to be focused on it.
He didn’t talk much about the war but one of things he told me was that while he was that their aircraft had several stubby antennae around the aircraft that monitored the radar from ground to air weapons.
He said they had various jamming equipment and would send back radar signals out-of-phase so that ground radar would receive strong signals where they should be weak to throw off the targeting.
He said at one point over Cambodia his equipment was overloaded by being locked on by multiple Chinese made weapons.
Later analysis showed at least 3 different “Firecan” radar locked on.
Luckily they were not fired upon.
Edited to add that Wikipedia shows that Fire Can as Russian made. But my father did state he thought they were Chinese made
Right now it just seems like aiming reticule edge detection
The homing is probably done exactly like graphics, with ray tracing.
I love those in DCS.
The thing is compare to radar, for IR since your aircraft already emit them from the heat the IR tracking system doesn’t need to emit anything but only to receive. So there is no way to detect that someone is « locking » you. You are already emitting your own lock from your own heat the enemy just need to have the tool to see you.
How does a fighter jet lock onto and keep track of an enemy aircraft? (2013) - https://news.ycombinator.com/item?id=8439560 - Oct 2014 (85 comments)
Also, we changed the url from https://gizmodo.com/how-fighter-jets-lock-on-and-how-the-tar... to the quora.com page it's copied from.
> A digital signal processor looks for recognizable radio "chirps" that correspond to known radars, and displays their azimuth on the scope. A chirp is a distinctive waveform that a radio uses.
These days it should be pretty easy to use pseudorandom waveforms, unique each time. LPI radars existed for a while.
I believe this is wrong, the computer actually determines what are most pertinent threats and puts it on the inner circle and puts the rest on the outer circle.
. The inner band (critical) is generally missiles in flight . The middle band (lethal) is for radars actively tracking you . The outer band is classified as non-lethal since these are radars searching for you, not actively tracking you.
> RWR also has an audio component. Each time a new radar signal is detected, it is converted into an audio wave and played for the pilot. Because different radars "sound" different, pilots learn to recognize different airborne or surface threats by their distinctive tones.
Pretty sure this is wrong too, they all emit the same tones for tracking and another tone for searching tone...
watch this: https://www.youtube.com/watch?v=MOLk_Je0NKg
https://www.livescience.com/38861-carrots-eyesight-myth-orig...
Missile launch sites are located separately from radar sites so they can’t be targeted (since they have no radar emissions themselves) and so that pilots don’t know ahead of time where to look for missile plumes for visual indicators of a launch.
All of these sites are networked so can feed information across a large region and back to a hardened command center far away. Sharing information this way allows minimizing the amount of time between a vulnerable front-line system revealing its location and launching a missile at its target. Tracking radar and missile sites can even wait to become active until a hostile aircraft is over or even past them to defeat wild-weasel style tactics.
Both tracking radar and missile sites are also often mobile so once they’ve disclosed their location by using radar and/or firing a missile, they can quickly move to a new location to avoid retaliatory strikes from anti-radiation missiles and regain the element of surprise.
Anyhow loved this article
But it's really cool to read about!
Also ABP allows some ads it deems not intrusive. Ublock origin is stricter and better in my experience.
https://www.quora.com/How-does-a-fighter-jet-lock-onto-and-k...
Edit: changed back, explained here: https://news.ycombinator.com/item?id=27488965
What a god awful website.
I've seen detergent bottles that were more apprehensive about their process of use.
War is about killing. It's an ugly fact but fact nevertheless. It seems like the world kill offends you, but it is an accurate description of the severity of what's going on.
I didn't check to see if the article referenced any sources, but it wouldn't surprise me to learn that a primary one was a conversation with an F-16 pilot.
There is no reason to assume this sort of thing only occurs among high schoolers, or in any case that a Gizmodo writer would be more likely to embark upon a serious consideration of the moral weight of aerial combat than to focus on its literal and figurative whiz-bang, wow-cool-robot aspects, of which there is no shortage.
https://www.quora.com/How-does-a-fighter-jet-lock-onto-and-k...
Edit: Quora link.
Fighter pilots are kind of the ultimate cool kids from the perspective of a milstuff nerd, and there is an unusual degree of hero worship among that cohort already.
War is terrible, but this is one of the very few situations in modern combat where there is a clear line between civilians and the combatants. Everyone engaged is a willing participant.
In this situation I'll apply Doug Stanhope's logic:
> As long as the people who kinda wanna go kill other people are going to go kill other people who kinda wanna go kill other people, you're killing all the right people and opening up all the best parking spaces.
Funny quote, but I don't think front-line infantry have the best parking spaces. That would be the flag officers.
Conscription is a thing in many countries. Not sure how many conscripts are flying, though.