John S. Foster Jr., a physicist who helped develop the U.S. nuclear arsenal and shaped national security in the Johnson and Nixon administrations, guiding billions of dollars in research and development as a top Defense Department official, died April 25 at his home in Santa Barbara, California. He was 102.
The cause was congestive heart failure, said his son John S. Foster III.
A second-generation physicist who espoused what he called a “radical but realistic” approach to scientific innovation, Dr. Foster grew up in Montreal, where his father ran a radiation laboratory at McGill University and introduced him to Nobel Prize-winning physicists Niels Bohr and Ernest Lawrence, the founder of what is now Lawrence Livermore National Laboratory in California.
Located 40 miles east of San Francisco, the federally funded lab is where much of the country’s nuclear stockpile was developed and conceived. Dr. Foster launched his career at the lab with backing from Lawrence, helping devise more compact, high-yield nuclear weapons in the early years of the Cold War.
One of those devices, nicknamed Cleo, was detonated in 1955 in Livermore’s first successful nuclear test. Compared to Little Boy, the 9,000-pound atomic bomb dropped on Hiroshima a decade earlier, Cleo was light as a feather — small enough that each of its two parts could be stored inside “a reinforced Samsonite suitcase” and transported to the government’s Nevada testing site in the back of a station wagon, according to Dr. Foster’s biographer, Livermore physicist Tom Ramos.
Working under the program name Robin, Dr. Foster and his team later developed a design approach that resulted in “the ultimate fission weapon, the prototype used to build the country’s modern stockpile,” Ramos wrote in “Call Me Johnny,” a 2019 biography that took its title from Dr. Foster’s nickname.
Dr. Foster also worked on nuclear warheads designed for the Polaris, the Navy’s first submarine-launched ballistic missile, and served as Livermore’s director from 1961 to 1965, when he was tapped to become the Pentagon’s director of defense research and engineering.
By then, the Vietnam War was escalating, and China was conducting its first nuclear tests. The United States was also facing an ongoing nuclear threat posed by the Soviet Union. Dr. Foster spent the next eight years guiding the development of missiles, bombers and warheads; advocating for the Pentagon research budget in front of Congress; and offering scientific advice to Defense Secretary Robert McNamara and his successors, including former Republican congressman Melvin Laird during arms control talks with Russia.
Profiling Dr. Foster upon his appointment, Washington Post reporters Howard Simons and Chalmers M. Roberts wrote that he was “a persuasive personality — intent, dedicated and chock full of imaginative ideas. Ruggedly handsome, he is inclined to pace the room like a panther as he talks.”
He was also treated with skepticism, they noted, by some scientists who considered him a hawk on defense issues. Dr. Foster had joined physicist Edward Teller, known the father of the hydrogen bomb, in unsuccessfully opposing the Senate’s 1963 ratification of the Partial Nuclear Test Ban Treaty. The researchers argued that it would endanger the country’s security, notably by preventing the U.S. from working on an antiballistic missile.
At the Pentagon, Dr. Foster was credited with championing the development of early unmanned aerial vehicles, precursors to today’s military drones, and with guiding research into MIRVs, ballistic missiles that can carry multiple warheads, not just one. He also promoted the use of nuclear safeguards known as permissive-action links, which are intended to prevent the weapons from being armed or detonated by the wrong person.
Critics said that while trying to boost Defense Department research, Dr. Foster could be overly gloomy in his pronouncements on Soviet advances. Addressing the House Armed Services Committee in 1973, while trying to secure $8.7 billion in research funding, he warned that Russia may be a few years from a major breakthrough, one that was not “simply another beeping basketball in space.”
“What happens,” he asked, “if the Soviet Union is first to succeed in developing a laser system which can knock our airplanes out of the sky?”
Yet even Dr. Foster’s detractors acknowledged that he was “especially effective” in arguing for the Defense budget, as military affairs reporter Michael Getler put it in 1972, before Dr. Foster left to work in the defense industry.
“In the long-term defense of this country,” Dr. Foster had told The Post, “our research and technology base has a place second in importance only to the national will to survive.”
The older of two sons, John Stuart Foster Jr. was born Sept. 18, 1922, in New Haven, Connecticut, where his father was teaching at Yale. Both his parents were Canadian: His father, John Sr., developed radar technology during World War II and was elected a fellow of Britain’s Royal Society. His mother, Flora Curtis Foster, was a former music teacher and singer.
The family settled in Westmount, Quebec, an enclave of Montreal, where Dr. Foster showed an aptitude for science and engineering while building radios, tinkering with the family car and learning glass blowing so that he could make his own test tubes. His younger brother later followed him into physics, as did Dr. Foster’s son John.
Aided by his father’s scientific connections, Dr. Foster got a job during World War II conducting radar research at Harvard. He later traveled to Italy as a technical adviser with the U.S. Army Air Forces, helping airmen fine-tune their radar equipment, according to his family.
Dr. Foster returned to Montreal to complete his college education at McGill, where he was also a champion gymnast and ski-jumper. He received his bachelor’s degree in 1948, then married Barbara Anne Boyd Wickes, known as Bobbie, and headed west to study physics at the University of California at Berkeley.
There he worked under his father’s friend Lawrence at the Radiation Laboratory, or Rad Lab, now known as Lawrence Berkeley National Laboratory. Dr. Foster was mentored by Luis Walter Alvarez, a Manhattan Project veteran who later received a Nobel Prize, and became friends with physicist Hugh Bradner, who was credited with inventing the neoprene wetsuit in the 1950s. Early photos and advertisements for the suit show Dr. Foster gamely modeling the garment, standing on dry land wearing flippers and, for one picture, a pair of oversize diving gloves.
After receiving his PhD in 1952, Dr. Foster became one of the first physicists to work at the Rad Lab’s new branch in Livermore, which became an independent institution in 1971. He was later elected to the National Academy of Engineering and received the Enrico Fermi Award, one of the government’s highest scientific honors, in 1992.
Dr. Foster was a vice president at TRW Inc. and remained involved in national security issues for decades, serving on the President’s Foreign Intelligence Advisory Board, chairing the Defense Science Board and participating in blue-ribbon panels that reviewed the country’s nuclear stockpile. Until recently, he was still visiting Livermore to meet with staff.
“When he wasn’t going to the lab,” his son John said, “he was going to a safe house in an undisclosed area in Santa Barbara,” getting updates about defense research. “I believe he still had, up until he died, an active security clearance,” John added.
Dr. Foster’s wife Bobbie died in 1978. He was later married for 36 years to Frances “Franny” Schnell Parker, who died in 2015. A son from his first marriage, Scott, died later that year. In addition to his son John, survivors include two other children from his first marriage, Susan Duffy and Bruce Foster; nine grandchildren; and many great-grandchildren.
While still in college, Dr. Foster bought a used Vincent HRD motorcycle for $600. He and Bobbie later hopped on the bike and hit the road, driving 3,000 miles from Montreal to Berkeley so that he could start graduate school. He continued to ride the motorcycle for a few more years, John said, until Lawrence saw it at the laboratory and learned it was Dr. Foster’s.
“Get rid of it,” the physicist told him. “The mean free path is too short.”
Lawrence was offering advice, and also telling a physics joke. As John explained it, “Mean free path is the average distance a particle goes before colliding with another particle.”
Dr. Foster sold the bike.
