The first electronic ballistic chronograph was invented by Kiryako ("Jerry") Arvanetakis in the 1950s. As consulting engineer under contract by NACA (later NASA), he was asked to find a way to accurately measure the velocity of various projectiles fired at hyper-velocities into a variety of engineered materials in anticipation of manned space flight. His first design was an open rectangular frame of square aluminum tubing with a screen of fine copper wire at both ends. Breaking the first wire started charging a capacitor, breaking the second wire stopped it. Measuring the accumulated voltage and knowing the rate of charge the elapsed time could be accurately calculated.
I never heard of that one. I would be surprised if it were more accurate than 2% or so because charging a capacitor is just not a very good method. The astable flip flop using vacuum tubes as a time base is much better and was available in the 1950s. All chronographs since 1960 used a crystal oscillator as the time base. Worked better and cost less.
