He was hired in 1957 by General Electric at its Knolls Atomic Power Laboratory in Schenectady, N.Y., where he performed tests on atomic power plants that were being developed for Navy submarines and surface ships. In 1965 he joined the United Nuclear Corporation in White Plains, N.Y.; he later worked at Nuclear Energy Services in Danbury, Conn.
While immersed in high-level calculations for nuclear power plants, Dr. Buck was also helping to build the sandwich business. He even donated his own kitchen table to outfit the first shop, at a strip mall in Bridgeport.
The day the shop opened, on Aug. 28, 1965, he and Mr. DeLuca sold out of their foot-long subs, which they topped with Pete’s secret salad dressing and sold for 69 cents (about $6 in today’s dollars). Subway’s foot-long subs today range in price from $5.50 to $8.95.
Dr. Buck said it took 15 years for the business to become profitable. But the two opened additional shops anyway, Mr. DeLuca told Fortune magazine, to “create the image of success.” They earned enough for Mr. DeLuca to go to college after all, at the University of Bridgeport. He graduated in 1971.
Through a relative, Dr. Buck met Haydee Piñero, the daughter of Jesus T. Piñero, the first native-born governor of Puerto Rico. They married in 1955 and had three children. They later divorced, and Dr. Buck married Carmen Lucia Passagem, who died in 2003.
Dr. Buck is survived by two sons, Christopher, from his first marriage, and William, from his second; and five grandchildren.
Mr. DeLuca died in 2015.
Dr. Buck was a major philanthropist, especially in the field of education and health care. He also donated a 23.1-carat ruby, named the Carmen Lucia ruby after his wife, to the gem collection at the Smithsonian Institution’s National Museum of Natural History.
But mostly, he kept a low profile. He drove an old car, The Wall Street Journal reported, and ate at least five Subway sandwiches a week.