John L. Stewart worked as an electrical engineer for the Army's Jet Propulsion Laboratory between 1949 and 1951. While at JPL, Stewart was directly involved with research and development, construction, and testing of ballistic missile projects, including the 'Corporal', 'Sergeant' and 'Hermes' missile projects. The 'Corporal' was the first ballistic missile developed by the United States. Controlled by a command guidance system, the surface-to-surface missile had a range of approximately 75 miles at about Mach 3. It was eventually replaced by the 'Sergeant' missile. 'Hermes' was the Army program which involved testing operations using captured V-2 rockets.