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It's been a long time since homing missiles aimed directly at the target. The AIM-9 Sidewinder entered service in 1956, and it aimed at where the target will be

It's been a long time since homing missiles aimed directly at the target. The AIM-9 Sidewinder entered service in 1956, and it aimed at where the target will be, not where it is.

sandworm101 5y ago
Some early IR missiles do aim slightly ahead of the target's bearing, but they don't really 'know' where they or the target are located in time and space. It is one thing to tell a missile to aim 10% to the left of a target bearing (which isn't simple in 3d space) another for that missile to understand its relative position. The early sidewinder used a single IR sensor behind a spinning reticule made of slots. This wasn't a camera with multiple pixels. It was one big pixel. The "brain" would alter the missiles course according to the position of that spinning reticule and the blinking signal from the lone sensor. There was no concept of range. At best, the brain could keep the target at a specific angle. This was achieved through literally re-drawing the reticule to include a solid band at the appropriate angle. So long as the target was behind this dark band the sensor would not blink and the missile would fly strait. Should the target move, the blinking would start and the missile would turn to put it back in the blank/dead zone. https://images.app.goo.gl/N3mTpDUeeJW6W7wu9 https://images.app.goo.gl/N3mTpDUeeJW6W7wu9
- nwallin 5y ago
  You don't need to have an understanding of 3d space, positioning, range to target, trajectories etc to create an intercept course. 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/Proportional_navigation https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_range https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_r... https://qph.fs.quoracdn.net/main-qimg-a0e376f321a658b5d99e25b029c95341.webp https://qph.fs.quoracdn.net/main-qimg-a0e376f321a658b5d99e25...

It's been a long time since homing missiles aimed directly at the target. The AIM-9 Sidewinder entered service in 1956, and it aimed at where the target will be, not where it is.

sandworm101 5y ago

Some early IR missiles do aim slightly ahead of the target's bearing, but they don't really 'know' where they or the target are located in time and space. It is one thing to tell a missile to aim 10% to the left of a target bearing (which isn't simple in 3d space) another for that missile to understand its relative position. The early sidewinder used a single IR sensor behind a spinning reticule made of slots. This wasn't a camera with multiple pixels. It was one big pixel. The "brain" would alter the missiles course according to the position of that spinning reticule and the blinking signal from the lone sensor. There was no concept of range. At best, the brain could keep the target at a specific angle. This was achieved through literally re-drawing the reticule to include a solid band at the appropriate angle. So long as the target was behind this dark band the sensor would not blink and the missile would fly strait. Should the target move, the blinking would start and the missile would turn to put it back in the blank/dead zone. https://images.app.goo.gl/N3mTpDUeeJW6W7wu9 https://images.app.goo.gl/N3mTpDUeeJW6W7wu9

nwallin 5y ago
You don't need to have an understanding of 3d space, positioning, range to target, trajectories etc to create an intercept course. 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/Proportional_navigation https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_range https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_r... https://qph.fs.quoracdn.net/main-qimg-a0e376f321a658b5d99e25b029c95341.webp https://qph.fs.quoracdn.net/main-qimg-a0e376f321a658b5d99e25...