SANTA FE, N.M. — Frederick L. "Dick" Ashworth, the weaponeer aboard the B-29 that dropped the atomic bomb on Nagasaki, Japan, in 1945, has died at 93.

He died Saturday while undergoing heart surgery in Phoenix, family friend Glen Smith said.

Ashworth, who retired in 1968 as a Navy vice admiral, was assigned to the Los Alamos-based Manhattan Project that built the atomic bomb.

Three days after the bombing of Hiroshima, he was aboard the bomber that dropped a weapon nicknamed Fat Man on Nagasaki on Aug. 9, 1945. Ashworth was assigned as the weaponeer, responsible for arming the bomb during the flight. Estimates of the death toll in Nagasaki range from 60,000 to 80,000.

Ashworth, in an August talk to a Los Alamos historical group, said the mission was "fraught with problems," including clouds that hid the city of Kokura, which was the primary target, the potential for a crash landing with the bomb aboard and low fuel after the weapon exploded.

The weather over Kokura was so bad that the B-29 — named Bock's Car after its usual commander, Frederick Bock — flew on to Nagasaki.

Ashworth said that during the return flight, the crew heard a radio report that the Japanese had approached the Swiss about surrender. "That gave us a pretty good inkling that maybe, by golly, the war might be over," he recalled.

Japan surrendered unconditionally on Aug. 15.

Ashworth was born in Beverly, Mass., and graduated from the U.S. Naval Academy in 1933. After the war, he did military liaison work with the Atomic Energy Commission and commanded the Navy's Sixth Fleet, then based in France.

He is survived by his wife, Ercie Bell Ashworth; three sons; three grandchildren; and one great-grandson.

Services are scheduled for tomorrow at Santa Fe National Cemetery.