The anniversary of the moon landing is an appropriate time to note the changing technologies involved. In particular, the moon landing would not have been possible had it not been for the analogue computer.
I worked for Electronic Associates, which made these computers for NASA. They performed calculations using physical variables such as voltage; even the best digital computers of the day were too slow to calculate the parameters needed to ensure that the craft would complete its mission safely.
Analogue computers perform arithmetic operations using large numbers of operational amplifiers, which modify the voltage of the electronic signal inputs. Operating in parallel, they can solve differential equations at very high speed. Coupled to the fastest digital computers of their day, they performed these calculations over and over again until they found the best solutions.
The equations were in this case mainly simultaneous partial differential equations in four variables - ...
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