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    <p>What you are suggesting is called "Command Guidance" but there is an easier, and better way.</p> <p>The way that real missiles generally do it (Not all are alike) is using a system called Proportional Navigation. This means the missile "turns" in the same direction as the line-of-sight (LOS) between the missile and the target is turning, at a turn rate "proportional" to the LOS rate... This will do what you are asking for as when the LOS rate is zero, you are on collision course.</p> <p>You can calculate the LOS rate by just comparing the slopes of the line between misile and target from one second to the next. If that slope is not changing, you are on collision course. if it is changing, calculate the change and turn the missile by a proportionate angular rate... you can use any metrics that represent missile and target position. </p> <p>For example, if you use a proportionality constant of 2, and the LOS is moving to the right at 2 deg/sec, turn the missile to the right at 4 deg/sec. LOS to the left at 6 deg/sec, missile to the left at 12 deg/sec... </p> <p>In 3-d problem is identical except the "Change in LOS Rate", (and resultant missile turn rate) is itself a vector, i.e., it has not only a magnitude, but a direction (Do I turn the missile left, right or up or down or 30 deg above horizontal to the right, etc??... Imagine, as a missile pilot, where you would "set the wings" to apply the lift...</p> <p>Radar guided missiles, which "know" the rate of closure. adjust the proportionality constant based on closure (the higher the closure the faster the missile attempts to turn), so that the missile will turn more aggressively in high closure scenarios, (when the time of flight is lower), and less aggressively in low closure (tail chases) when it needs to conserve energy. Other missiles (like Sidewinders), which do not know the closure, use a constant pre-determined proportionality value). FWIW, Vietnam era AIM-9 sidewinders used a proportionality constant of 4.</p>
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    1. POHow to create an "intercept missile" for a game?
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    1. CO+1 for giving the answer that I was about to type in. Summary for the casual reader: if the target bearing is changing to the left, steer left. If it's drifting right, steer right. If it's at a constant bearing (other than directly behind you), you're on an intercept course. Sidenote: this also works on an entrance ramp on the highway when you're trying to merge. If you see a car at a constant bearing that's getting steadily bigger in your view, you need to make a change....
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    2. CO@Bob, actually even works when target is behind you! only issue is what the closure is... If LOS rate is zero (LOS constant and stable) then You may be getting closer to target, or furthur away, but you're on collision course. This is, actually exactly the way most air-to-air missiles work.
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    3. CO@elliot, This will not produce a collision course. It may not even produce an intercept course. When you say "travelling faster than target", I suspect you are not really talking about your speed, buit your closure on the target. Clearly, if you stop "turning towards the tgt" once you are "... faster than the tgt", then at that point you might be pointed in a completely wrong direction. But even if you meant closure, this is by no means the best collision course. And in some cases (when in lead with less than the tgt's speed ), turning towards the tgt will reduce closure even furthur.
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