Frederick L. “Dick” Ashworth, the weaponeer in charge of the atomic bomb dropped on Nagasaki, Japan, at the end of World War II, died Saturday at age 94 during heart surgery at an Arizona hospital.

Ashworth, who retired in 1968 as a Navy vice admiral, was assigned to the Los Alamos-based Manhattan Project that developed the world’s first atomic bomb. He was a member of the B-29 bomber crew that dropped the second atomic bomb on Japan on August 9, 1945, assigned as the weaponeer – the person in charge of the bomb.

A self-penned obituary he wrote last year included but one short paragraph about Ashworth’s role in the Nagasaki mission. He described himself as “a member of the crew of the Army Air Force’s B-29, ‘BocksCar,’ responsible for the successful functioning of the ‘Fat Man’ atom bomb during the attack on Nagasaki, Japan.”

Ashworth, in an August talk to a Los Alamos historical group about the mission, said it was “fraught with problems,” including clouds that hid the primary military target, the potential for a crash landing with the bomb aboard and low fuel after the bomb exploded.

Army General Leslie R. Groves, who oversaw the Manhattan Project, “insisted on having someone in that airplane who had a technical background on the bomb, what it was supposed to do, what it was like when you were trying to monitor the various components of the bomb while in flight,” Ashworth said. “And make decisions, more importantly.”

The crew heard a radio report while returning to base that the Japanese had approached the Swiss embassy about surrender, he said.

“That gave us a pretty good inkling that maybe, by golly, the war might be over,” he said.

Ashworth was born in Beverly, Mass., and graduated from the Naval Academy in 1933. He did military liaison work with the Atomic Energy Commission and commanded the Navy’s Sixth Fleet, then based in France.