An odd thing in my patrol

[Captain Norman]

I was leaving the port of St. Nazaire in the beginning of my patrol, and I was taking the exact same route I always take out of it, and trust me, I didn't hit anything coming out of it, but suddenly my u-boat was rocked by an explosion, and I took pretty bad damage to the stern torpedo room and the engines, which I was able to fix. Im interested in knowing how this happened. Is it possible I hit the fire key and fired a torpedo, cause the only thing I can think of is a torpedo exploding in the tube, or near the stern of my ship, but I dont know if thats possible.