This paper describes the new photonic
velocimetry (PDV) technique for measuring time‐resolved projectile velocity and acceleration profiles for full flight of the launch package in a two‐stage light‐gas gun (LGG). This technique is shown to provide excellent temporal and spatial resolution in measurement. Two non‐linear acceleration stages were observed for the first time on the LGG. When the gun bore was at atmospheric pressure, a strong opacity was observed during hypervelocity projectile motion >2200 km/s.