Got to draw the minimum long range capability somewhere. And given the existing availability of HHQ-9 family SAMs (with an effective range of about 200km or more) on 052D and 055, standardizing that minimum long range capability with UVLS canisters across the three types of ships (054B, 052D, 055) seems like a good foundation to start with.
Ok, sounds reasonable.
Then I'll add some medium/high altitude threats and some of my own thoughts. Not forcing my conclusions on you, of course, this matter will obviously depend on personal opinion.
~10-25 km - bomb release high altitude drop, drone light weapons, and everything that pops up from below the horizon;
~25-40 km - average for tactical missiles and unpowered gliding weapons with low aspect wing;
~80-90 - unpowered gliding weapons from high altitude drop (against moving target);
~100-140 - boosted gliding weapons from high altitude drop (against moving target); aerial gliding mines; modern ARMs.
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After that - currently produced air-launched light ASCMs and next-generation ARMs tend to be over 200(not all of them).
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Heavy air-launched ASCMs (both subsonic and supersonic) now aim for ~500 and more (their flight range in Lo-Lo-Lo is significantly shorter)
Long story:
Minimum self- and formation defense(
not CIWS): 20-25 km(and ~12-15 altitude) is just necessary, anything less and you'll get bombed.
Optimal Max engagement range (non-AA combatant) still looks like 150-160 km to me. It deters most types of non-determined saturation attacks against the combatant, and allows a reasonable degree of coverage for dispersed TF.
Air defense combatants: should aim at 300 at least, but the opportunity to take even longer-ranged shots against oblivious targets may be of value. Furthermore, as per onbservations, it takes both size of the missiles and their number, especially when we're trying to protect friendly positioned away from the shooter.
Problems: the outer edge of engagement is a very slippery zone, as even for the fastest naval AA missiles it takes many minutes to get there, so there is ample opportunity for a target to react. Just as (or more) valuable are maximum ranges of direct launch(w/o loft) with given Probability of kill(Pk), as well as minimum engagement ranges, time to engage, and Pk at minimum engagement ranges.