Born in Evanston, Illinois, on November 26, 1901, "Deke" Parsons graduated from the Naval Postgraduate School at Annapolis in 1929 with an emphasis on ordnance. While at the Office of Scientific Research and Development (OSRD), he was Vannevar Bush’s assistant on the combat use of proximity fuses.

In March 1943, Capt. Parsons joined the Manhattan Project as leader of the Ordnance Division. Except for the uranium physics and metallurgy, the gun assembly of "Little Boy," the uranium bomb, was mostly an ordnance problem entrusted to Capt. Parsons. After the reorganization in August 1944, Parsons was also entrusted with transforming the uranium and plutonium bombs into combat weapons.

Capt. Parsons was also the head of Project Alberta, which oversaw the various responsibilities necessary for the actual delivery of the bombs. These included modifying the aircraft to accommodate the bombs, supervising field tests, developing fuses, selecting and advance bases for assembly and delivery.

Capt. Parsons was a member of the crew of the Enola Gay, since the Little Boy bomb was armed in-flight due to its unstable design.

He continued to be involved with nuclear issues for the rest of his career. In 1946, he worked to organize Operation Crossroads, a series of nuclear tests in the Pacific.

He eventually rose to the rank of Rear Admiral. On December 5, 1953, he died from a heart attack at Bethesda, Maryland.