Peter Grining, a long-time Harpoon correspondent, wrote in asking about the ESM cross-fix rules in SITREP #21. While the cross-fix article provided a quality level for targeting. It didn’t include BOL targeting. In fact, the entire issue of SSM targeting needs to be reviewed, and treated like torpedoes, but with slightly different rules. In response to his question, here’s one solution:
The first thing to recognize that the best solution is an actual detection - a known target location. The second thing to recognize is that the missile doesn’t care how good the solution is - as far as it’s concerned, it’s going to look where you tell it to look and that’s all it can do. So once it has been fed into the missile, there’s no such thing as a “Good” or “Bad” solution. It becomes a hit modifier. What is the chance of the missile being positioned so that the target is dead center in its seeker cone?
The solution quality degrades with range/time, which affects missiles that don’t have midcourse targeting, or missiles where the feature isn’t used (the helo was shot down). It’s the reason antiship Tomahawk never worked at extremely long ranges, even with good targeting. By the time the missile got there, the target could be anywhere. It’s also a hidden strength of missiles like the Moskit. Speed helps penetrate the defenses, but also means its chance of finding the target is greatly increased.
And the quality of the ESM system matters. This affects the angular width of the uncertainty area, but it also affects the TMA calculations of target course and speed. For medium and long-range shots, this is vital. So a good solution will stay good longer, because it has a more accurate starting point, and a better prediction of the target’s course and speed. A bad solution, like a bad hamburger, will go bad more quickly. A BOL launch at anything but a short-range target becomes little more than a guess.
And target speed matters a lot. A slow mover is a lot more predictable than a 30+ knot warship. Luckily for the shooter, warships don’t go banging around at high speeds all time.
Let’s declare that a detection is an “Excellent” Solution. Even the best sensor, tracking a noncooperative target under operational conditions, will have some error.
| ESM Cross-Fix Table (using ESM generations) | |||
|---|---|---|---|
| Angle | 1st Gen | 2nd Gen | 3rd Gen |
| 0-20° | Poor | Fair | Fair |
| 21-45° | Fair | Good | Excellent |
| 46-90° | Good | Excellent | Excellent |
TMA solutions and ESM cross-fixes go directly to this table.
| Antiship Missile Solution Modifier Table | |||||
|---|---|---|---|---|---|
| Flight Time (tac turns) | Excellent (detection) | Good | Fair | Poor | BOL |
| 1 | -0 | -0 | -5 | -10 | -10% |
| 2-3 | -0 | -5 | -10 | -20 | -25% |
| 4-8 | -5 | -10 | -20 | -30 | -40% |
| 9+ | -10 | -20 | -30 | -40 | -60% |
Missiles with midcourse targeting use the top line (1 turn) no matter what the flight time, as long as the link is available. The turn counter starts once the link is lost.
Apply this Solution Modifier to the chance of a hit on the Antiship Missile attack Table.
Example
A US task force uses 2nd Gen ESM to cross-fix the location of an Iranian frigate. The angle between the two cross-bearings is 35°, so it is a Good solution. They fire four Harpoon 1C missiles (3rd Gen seeker). The missiles reach the target on the second Tactical Turn after they are launched, so this is a -5% Solution Modifier. The frigate has a Small signature and 2nd Generation decoys, so the Harpoon IC has a 60% chance to hit, minus 5% more for the Solution, for a net chance of 55%.
These rules should drive the shooter into improving his solution and positioning himself for a shot, instead of just letting fly.
These rules are not an official change yet. If you use them, please let me know how they work.
BT
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© Copyright 2002 by Larry Bond and Clash of Arms.
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