VictorInThePacific
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Joined: 10/30/2008
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quote:
Maneuver doesn't work very well against close range shots (think submarine shooting BOL from a sonar contact), very high speed missiles, very slow speed ships (think convoys or phibgrus), or missiles that are capable of re-attack.
In case 3 below, the above points are relevant and important. Case 3 is to be understood to apply only in certain situations.
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The best way to defeat anti-ship missiles is to ensure that they never get launched. The second best way is to shoot them down in flight. But there is a third way, which involves maneuvering the target ship, even though the missile always moves at least 20 x as fast as the ship.
Evading anti-ship missiles by maneuver:
1) Evasion to gain distance.
If the target ship moves at maximum speed directly away from the missile, it may be able to move beyond the maximum missile range before the missile arrives. This is why no one ever fires missiles at maximum range. This concept is actually built into the launch restrictions of certain missiles in Harpoon.
2) Evasion to gain time.
If the target ship moves at maximum speed directly away from the missile, the missile will arrive later than if the ship were stationary. This gives any defending SAM launchers more time to respond (more fire cycles), and this may be critical. Without doing an exact calculation for the specific situation, this process should be a standard response to any incoming missiles, unless there are only a few missiles, in which case you just swat them aside, or there are far too many missiles, in which case it doesn’t matter what you do.
3) Evasion to gain angle.
If the incoming missile has been launched by bearing only, then it will not change its course to track a maneuvering ship until it is about 5 nm from the original position of the ship, although this can be set differently. The first step is to determine if this case applies. Harpoon does not give you a good mechanism to do so, but it is not impossible. If this case does apply, the affected ship should move at maximum speed perpendicular to the course of the missile.
There are too many unknown variables to analyze this case completely. Only a few representative cases will be considered. The main thing I will consider is when the ship has moved 5 nm from its original position. A 20 kn ship will need 15 min; a 30 kn ship will need 10 min. At this point , the ship will be 7 nm away from the missile activation point, which is less than the 10 nm maximum, but that’s not important. However, the ship is now 45 degrees away from the missile flight path, and that can be very important. I am assuming that the missile cannot attack a target at 45 degrees.
How much time does the ship have to execute this maneuver? If the missile travels at 600 kn (Mach .9) and is detected 200 nm away from the ship, then it needs 20 min to arrive, so ships of any speed will be able to evade by angle. If the missile speed is doubled (to 1200 kn) or the detection distance is halved (to 100 nm), then the arrival time is halved (to 10 min). Now the fast ship should still be able to evade by angle. The slow ship, maybe not.
Harpoon does not consider many things that exist in real life. For example, SAM launchers generally don’t have a 360 degree field of fire, and the actual maneuver direction will be restricted in real life. I will let someone else analyze whether this is a problem or not.
< Message edited by VictorInThePacific -- 4/30/2009 2:23:07 AM >
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air defence - threat axes - 
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