Research from first hand sources indicated about 1:30 to 2 minutes to be a reasonable figure for loading a torpedo into the tube on a 637 sub. The 45 seconds comes from the game originally being compressed into a half-scale environment where the flow of time becomes about 2x realtime.
We know that the Novembers could reload the entire nest of 8 tubes in about 15 minutes, which works out to slightly under 2 minutes per tube. Type XXI could reload its 6 tubes in 10 minutes, which is comparable performance using power-loading equipment. This performance is also in line with every other sim, from Fast Attack through DW.
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