Unless somewhere in the SH4 settings that may be changed ALL torpedo tube doors close automatically by default after a torpedo is fired in approx 1 second real time.
Nightmare if your running 1.4 then you can not keep all six doors open at one time in the bow nor the four aft.
Unless you have changed it in the SH4 settings ( if thats possible ? ).
What they did in 1.3 was fix the door so they would
close as that some were not closing and flooded tubes were not letting new torpedoes to be slid into said tubes.
People were complaining about not being able to load torps and I was one of them.
You can set looking right at a DD and hit that
Q key all you want and that DD will never hear it, at least in the Sim/Game of SH4. Although he may charge you like a bull it wasn't the torp doors that ticked him off.