John T. "Chick" Hayward, 90, a retired Navy vice admiral who was a decorated aviator and who participated in the Manhattan Project, which developed the atomic bomb, died of cancer in Atlantic Beach, Fla., on May 23.

He enlisted in the Navy in 1925 by lying about his age, and he graduated from the U.S. Naval Academy at Annapolis in 1930. In the early part of World War II, he flew dozens of bombing missions in the South Pacific before participating in the Manhattan Project.

Adm. Hayward joined the Manhattan Project at the China Lake Naval Ordnance Test Station in California in 1944. He helped develop the implosion components of the bomb dropped over Nagasaki, Japan, on Aug. 9, 1945.

He was not involved in the development of the atomic bomb dropped on Hiroshima three days earlier.

After the war, he went to Japan to study the aftereffects on Nagasaki and Hiroshima. In 1946, he was in charge of the first attempt to photograph a nuclear explosion on the Bikini atoll at 800,000 frames per second.

In the early 1950s, he helped plan atomic weapons laboratory work at Los Alamos and Sandia. He also worked on the foundation of the Livermore Laboratory program in 1952 in close collaboration with Edward Teller.

Over the years, he had worked on systems for ground- and air-launched rockets and became a pioneer in the development of weapons used to fight submarines.

He also commanded the first nuclear-powered task force in naval history, leading the aircraft carrier Enterprise.

Adm. Hayward served as president of the Naval War College in Newport, R.I., from 1966 until retiring from active duty in 1968. He later worked for General Dynamics as a vice president for international programs.

His Navy decorations included two awards of the Distinguished Service Medal and the Silver Star, the Legion of Merit, the Distinguished Flying Cross and the Air Medal.

Adm. Hayward was born in New York. As a youth, he was a batboy for the New York Yankees baseball team.