On this date October 11, 1968, Apollo 7, the first fully-manned Apollo mission was launched with astronauts Donn Fulton Eisele, Wally Schirra, and R. Walter Cunningham.
"The Apollo spacecraft was a big thing like a multi-engine passenger jet, compared to the jet fighter experience of the Gemini spacecraft and the experimental feeling of Mercury. By the time of Apollo, the computer was a big part of everything, and we all had to become computer gurus to fly the ship. Back in Mercury, we had a wristwatch and a wind-up clock." – Commander Wally Schirra of Apollo 7.
I have a love affair with airplanes, and submarines. When I read this quote from Commander Schirra, it reminded me of the books I have read about the early submarine commanders who would have to look through the periscope and estimate the range to the target. Estimate the targets speed and heading. They would literally line their boat up perpendicular to the targets projected course and fire their torpedoes. They were required to do math mentally in their heads with a stop watch in hand in order to determine how long it should take the torpedoes to hit their targets.
Underwater navigation wasn't much more sophisticated. It was a mental game played in your mind while issuing orders for the crew to drive the ship around and under a fleet of targets. Because of this fact many early submarine Captains would simply sail into their targets and fire their torpedoes while surfaced and then dive to avoid enemy counter measures. Later they would resurface and attack again. There was one account I read where an American submariner managed to get inside a convoy and running at almost full speed firing a torpedo every time a ship was in front or directly behind her and using the targets as a screen from the destroyers which were on the outside of the convoy.
Today computers on our desktops are so much more powerful than what the astronauts of those ships entrusted their lives to. The computers in today's submarines and electronics in the torpedoes is an entirely new level of technology.