Waay back in '67, my artillery battery was issued a computer to calculate firing data. It ran on 240V @400 hz-supplied by generator. The computer itself was the size of a large suitcase. Time required to calculate firing data was 2/3 the time of projectile flight. At maximum range, time of flight could be almost 3 minutes. Enough time to get a cuppa, light a smoke and enjoy it. Five seconds before impact, we would wake up the forward observer with the radio transmission "splash".