I'm sorry if this should be elsewhere but I didn't think it required a dedicated topic but I have a short question.
How do friendly surface ships communicate with or avoid firing on ultra stealthy friendly subs?
This may seem obvious but surely any communication method from the sub would give them away and if we can track them by conventional methods then we should assume the enemy can as well so are surface ships just warned that a friendly sub is in the vicinity?
In fairness, this is a very technical / specialist & very secretive technology. Speaking about specifics in open fora would be detrimental to sovereign nations security.
However, it may be more prudent to look at the bigger picture & some of the mechanics of the actual act.
I started with everyone's friend, Google. I entered the following query :
"How do warships communicate with submarines ?"
...& wikipedia provided what I would consider to be logical & credible data that is deemed 'open source'
Communication with submarines - Wikipedia
From a personal opinion, I'd take it that ANY surface combatant during peacetime or wartime, who discovered ANY submarine, would treat it as hostile. I'm sure that specific nations have very specific codes to differentiate friend from foe, no doubt including communication with 'home base' to get confirmation if one of their own subs was in close proximity to their area of operation.
I's also recommend reading 'fiction' by the likes of Tom Clancy, such as "The hunt for Red October", as this used to be mandatory reading for submariners. I'm led to believe that is was not just because the volumes Mr Clancy has written / co-authored are great reading while submerged for months at a time, but because some of the technical content within them was considered to be 'trade-craft', giving the submariners specific insight on the scenarios laid out in the books.
SA