Career Start December 1941 in Manila driving a Porpoise.
The Porpoise has four conning towers available, the second tower (first upgrade) is available January 1943.
The third tower (second upgrade) is available April 1943.
It took several missions during 1943 to actually get it.
on the last two 1943 missions, we took damage, including hull damage, and attained a mission rating of two in each.
And so, it continues to play out in the US Pacific portion of SH4 that a conning tower upgrade requires multiple, consecutive missions with damage incurred and a mission rating greater than 1. It seems, and I stress seems, that a mission rating of three disqualifies the upgrade. Twos and ones along with consecutive missions with some hull damage seem to cause the upgrade.
Next upgrade is August 1944 and it appears to be just a paint job.
__________________
there are only two things in the world: submarines and targets.
Fortis et stabilis et fidelis, semper
------------------------------------------------------------
Silent Hunter 4 1.5 Gold Edition on CDROM
LAA enabled
Dell XPS with 32 GB Ram running Win10