Original sentence: November 23 1972: Vehicle serial number 7L the engines ran for 106.93 seconds after which Pogo oscillation of the first stage caused engine cutoff at 40 km altitude; a programmed shutdown of some of the engines to prevent over-stressing of the structure led to an explosion of engine number 4
Edited sentence: November 23 1972: Vehicle serial number 7L the engines ran for 106.93 seconds after which Pogo oscillation of the first stage caused engine cutoff at 40 km altitude; a programmed shutdown of some of the engines to prevent over-stressing of the structure led to an explosion of the oxygen pump on the engine number 4