Theodore Taylor

Los Alamos scientist who later campaigned for the abolition of nuclear weapons

Lennox Miller, athlete and dentist: born Kingston, Jamaica 8 October 1946; married (two daughters); died Pasadena, California 8 November 2004.

Lennox Miller, athlete and dentist: born Kingston, Jamaica 8 October 1946; married (two daughters); died Pasadena, California 8 November 2004.

While it was not unusual for the pioneer scientists of the wartime Manhattan Project to turn against the atomic bomb, such conversions have been much rarer among those who chose to begin work on the bomb after Hiroshima and Nagasaki. The American physicist Theodore Taylor was one of those exceptional characters.

He stumbled into the post-war Los Alamos National Laboratory almost accidentally in 1949 and found he had a genius for conceiving new designs and refining old ones, so that he is now widely credited with designing both the smallest of all fission weapons and the most destructive.

By the mid-1960s, at the age of just 41, he was a senior scientist at the Pentagon with responsibility for oversight of the entire US nuclear arsenal, and then he experienced an epiphany. At that time, he would say later, the stockpile contained 37,000 weapons, and he was suddenly overwhelmed by "the craziness of what we were doing".

He resigned and devoted the rest of his career to campaigning for what he saw as the only way to avoid catastrophe: the outright abolition not only of nuclear weapons but also of nuclear energy production. He wrote books, worked as a consultant and attached himself to a variety of organisations pressing for the same ends. More than once he was arrested for taking part in civil disobedience protests at nuclear installations.

Born in 1925 in Mexico, where his father was national head of the YMCA, Taylor was a scientific prodigy at school. For all his gifts, however, he was physically clumsy and socially awkward, and he ran into difficulties during his PhD research at Berkeley. As an alternative, a colleague recommended him for a post at Los Alamos in New Mexico, the main US atomic bomb design laboratory.

"Within a week I was totally immersed in nuclear weaponry," he would write. So young and so brilliant, he proved the embodiment of the dictum that creating new nuclear weapons is more art than science. A friend, the great physicist Freeman Dyson, would say of him that he showed they could be designed freehand.

In this fashion, during the 1950s, he conjured up the "Davy Crockett", an atomic bomb that weighed just 50lb, and also the "Super Oralloy", a plutonium fission weapon with an explosive yield equivalent to a modest H-bomb. On several occasions he saw his creations exploded at US test sites in Nevada and the Pacific. "It was my bomb and my idea, and the thrill of seeing something the size of the bomb that destroyed Hiroshima - it was a cause for celebrating."

He would say later that he believed he was born with an addiction to designing nuclear bombs, an addiction that affected others too. "It's incurable. The only thing that can be done is to control it. The only control is total abstinence."

Among his most exotic assignments for the government was Project Orion, which has since acquired the aura of a science-fiction adventure. This was a scheme to create a huge, long-distance space vehicle that would be powered by ejecting nuclear bombs in space and riding the energy waves they created.

It is generally accepted that the physics were largely sound even if the cost would have been prohibitive. "I used to have a lot of dreams about watching the flight," Taylor said. "The first flight would be the most spectacular thing that humans had ever seen."

As a campaigner against nuclear weapons he brought exceptional authority to the cause, warning of the ease of proliferation, the dangers of the spread of nuclear energy production and the threat from terrorists. In 1986, when Mordechai Vanunu brought secrets of the Israeli nuclear weapons programme to London to The Sunday Times, it was Taylor who authenticated the information and confirmed that Israel was a fully-fledged nuclear power.

He also brought passion to the cause. He once wrote:

It troubles me more deeply than I can express that my country continues to be prepared, under certain conditions, to launch nuclear weapons that would kill millions of innocent bystanders. To me, this is preparation for mass murder that cannot be justified under any conditions. It must therefore be considered as human action that is out-and-out evil.

Taylor was married for 44 years, to Caro Arnim, whom he credited with never allowing him quite to forget the moral implications of the bomb during his weaponeering days.

Brian Cathcart