The Wac Corporal, America’s first sounding rocket, started life in World War II, when reports of the German missile programs reached the California Institute of Technology. Caltech rocket workers had originally entered the missile business with a sounding rocket in mind, so the Wac Corporal was justified as a developmental “little sister” version of the Corporal missile.
The rocket could carry 25 pounds of meteorological and cosmic ray instruments to an altitude of over 40 miles.
An Aerojet liquid propellant motor, originally designed for the jet assisted take-off of aircraft, was selected, as its low thrust would be easy on scientific instruments. To simplify the design, the Wac was fin stabilized. This required high speed at the time of release, so a solid booster and long launch tower were used.