Hartshorn, the son of a railroad mechanical engineer, worked as an apprentice for the New York, New Haven, and Hartford Railroad while attending Tufts University in Boston. In 1942 he joined the Army, becoming a second lieutenant in the 729th Railway Operating Battalion. He was injured in March 1945 by a V-1 cruise missile in Antwerp, and also experienced V-2 ballistic missile bombardment. In the summer of 1945 Hartshorn was involved in organizing rail transport for the thousands of tons of V-2 and other missile data and parts shipped back to the United States.
After the war, he returned to school, graduating in mechanical engineering from Tufts in 1946. He worked at various mechanical construction jobs before joining Convair in San Diego in September 1953. Hartshorn was immediately assigned to Plant Engineering Design, where he was tasked with estimating the costs of major facilities that had never been built before - intercontinental rocket production facilities, test stands, launch pads, and missile silos. He soon was Chief of Design for Plant Engineering, continuing in that position throughout the life of the Atlas missile program.
In 1966 Hartshorn was promoted to General Dynamics' corporate office as Manager of Facilities. He conceived and led the construction of an unprecedented General Dynamics facility at Charleston, South Carolina, for fabrication of 35-m-diameter, 700 metric ton aluminium spheres for liquid natural gas transport ships. He also designed and built General Dynamics nuclear submarine frame and hull construction and engineering facilities at Quonset Point, Rhode Island. He retired in 1986.
Birth Place: West Haven, Connecticut.