5 ms·

Radar is also very good at distance measurement so I guess this won't work for a real life rocket fired at a fighter jet. Because it's so easy to defeat this tr

Radar is also very good at distance measurement so I guess this won't work for a real life rocket fired at a fighter jet. Because it's so easy to defeat this trick in the software.

oehpr 5y ago
I'm to understand that tricks like this are much less effective against more modern A2A missiles, so you might be right.
sandworm101 5y ago
A missile will generally not care about distance. What matters is direction/angle. Distance is irrelevant. Just keep pointing at the target and eventually you will get there, assuming you are faster. So the direction to the strongest reflection, or greatest doppler shift, or combination of both, will suffice to get the missile to the target even without range data.
- wyager 5y ago
  > Just keep pointing at the target and eventually you will get there 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.
  - klodolph 5y ago
    Yes, even old ordnance like the Sidewinder, which entered service in the mid-1950s, would aim ahead of the target.
  - jameshart 5y ago
    ‘Pointing at’ in this case means maintaining a constant bearing to target, with decreasing range. If anything it’s easier for a moving guidance system to achieve that than to point at the target.
    - giva 5y ago
      Link for clarification: https://en.wikipedia.org/wiki/Constant_bearing%2C_decreasing_range https://en.wikipedia.org/wiki/Constant_bearing%2C_decreasing...
      - sandworm101 5y ago
        Except that, in the case of a missile, you cannot assume decreasing range. We assume that the missile knows to aim ahead of the target, but determining which way is ahead and which behind is tricky. If it is chasing a hotspot, a single point, getting that wrong means worsening your approach. A strait/boresight approach might not be ideal but it avoids the question over which offset is ahead and which behind the target.
        thrill 5y ago
        Continuously pointing directly at the target tends to result in the missile being unable to generate the needed turn rate at the conclusion of the intercept. If the missile has a large warhead, that might not matter so much, but air-to-air missiles tend to be small.
        Animats 5y ago
        Yes. So one strategy is to aim at a point midway between the target's current position and its projected position. This puts the missile on the target's tail, which is a good attack position when the target evades.
        jameshart 5y ago
        If you're a missile seeker, all you have as input is a two-dimensional forward view of where in your forward cone the target is - either deflection and azimuth, or x and y offset - it's like a dot on a scope. Let's assume cartesian x and y input for simplicity. 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.
  - sandworm101 5y ago
    It can be easier in terms of getting to a far away target, of maximizing range, but pointing strait has an advantage. As the target moves forwards the missile will be dragged behind, which reduces the relative angle at intercept, reducing the targets ability to make a last second maneuver. An direct approach IR missile can literally fly up the tailpipe of a fast target.
- nradov 5y ago
  That was true for earlier radar guided missiles. The latest ones are smart enough to account for distance and calculate an energy optimized intercept course rather than just pointing straight at the target.
  - sandworm101 5y ago
    Missile systems. Such complex approaches are calculated and controlled by the launching platform. A radar-guided missile will normally not "see" the target on its own until long after launch, until near endgame. Whether the actually missile has the brains to make such calculations is different than whether the entire system has the ability.
    - dvtrn 5y ago
      The missile knows where it is by knowing where it isn’t.
      - avereveard 5y ago
        Say derivative without saying derivative
      - ryanmarsh 5y ago
        By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation.
      - raviolo 5y ago
        For the confused (or to get more confused!): https://youtu.be/bZe5J8SVCYQ https://youtu.be/bZe5J8SVCYQ
        dangerboysteve 5y ago
        after a minute, I was expecting a reference to the Turbo Encabulator.
  - 5y ago
angry_octet 5y ago
Notching definitely works, it is used routinely in air combat. It is more effective at greater range because it's hard to maintain the same distance to a radar that is closing on you. 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.

Radar is also very good at distance measurement so I guess this won't work for a real life rocket fired at a fighter jet. Because it's so easy to defeat this trick in the software.

oehpr 5y ago

I'm to understand that tricks like this are much less effective against more modern A2A missiles, so you might be right.

sandworm101 5y ago

A missile will generally not care about distance. What matters is direction/angle. Distance is irrelevant. Just keep pointing at the target and eventually you will get there, assuming you are faster. So the direction to the strongest reflection, or greatest doppler shift, or combination of both, will suffice to get the missile to the target even without range data.

wyager 5y ago
> Just keep pointing at the target and eventually you will get there 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.
- klodolph 5y ago
  Yes, even old ordnance like the Sidewinder, which entered service in the mid-1950s, would aim ahead of the target.
- jameshart 5y ago
  ‘Pointing at’ in this case means maintaining a constant bearing to target, with decreasing range. If anything it’s easier for a moving guidance system to achieve that than to point at the target.
  - giva 5y ago
    Link for clarification: https://en.wikipedia.org/wiki/Constant_bearing%2C_decreasing_range https://en.wikipedia.org/wiki/Constant_bearing%2C_decreasing...
    - sandworm101 5y ago
      Except that, in the case of a missile, you cannot assume decreasing range. We assume that the missile knows to aim ahead of the target, but determining which way is ahead and which behind is tricky. If it is chasing a hotspot, a single point, getting that wrong means worsening your approach. A strait/boresight approach might not be ideal but it avoids the question over which offset is ahead and which behind the target.
      - thrill 5y ago
        Continuously pointing directly at the target tends to result in the missile being unable to generate the needed turn rate at the conclusion of the intercept. If the missile has a large warhead, that might not matter so much, but air-to-air missiles tend to be small.
        Animats 5y ago
        Yes. So one strategy is to aim at a point midway between the target's current position and its projected position. This puts the missile on the target's tail, which is a good attack position when the target evades.
      - jameshart 5y ago
        If you're a missile seeker, all you have as input is a two-dimensional forward view of where in your forward cone the target is - either deflection and azimuth, or x and y offset - it's like a dot on a scope. Let's assume cartesian x and y input for simplicity. 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.
- sandworm101 5y ago
  It can be easier in terms of getting to a far away target, of maximizing range, but pointing strait has an advantage. As the target moves forwards the missile will be dragged behind, which reduces the relative angle at intercept, reducing the targets ability to make a last second maneuver. An direct approach IR missile can literally fly up the tailpipe of a fast target.
nradov 5y ago
That was true for earlier radar guided missiles. The latest ones are smart enough to account for distance and calculate an energy optimized intercept course rather than just pointing straight at the target.
- sandworm101 5y ago
  Missile systems. Such complex approaches are calculated and controlled by the launching platform. A radar-guided missile will normally not "see" the target on its own until long after launch, until near endgame. Whether the actually missile has the brains to make such calculations is different than whether the entire system has the ability.
  - dvtrn 5y ago
    The missile knows where it is by knowing where it isn’t.
    - avereveard 5y ago
      Say derivative without saying derivative
    - ryanmarsh 5y ago
      By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation.
    - raviolo 5y ago
      For the confused (or to get more confused!): https://youtu.be/bZe5J8SVCYQ https://youtu.be/bZe5J8SVCYQ
      - dangerboysteve 5y ago
        after a minute, I was expecting a reference to the Turbo Encabulator.
- 5y ago

angry_octet 5y ago

Notching definitely works, it is used routinely in air combat. It is more effective at greater range because it's hard to maintain the same distance to a radar that is closing on you. 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.