Ralph E. Lapp

Ralph E. Lapp worked with the Manhattan Project, helping to create the first atomic bombs, and became an authority on radiation hazards and civil defence. He is probably best known in Britain as the author of the 1957 best-seller The Voyage of the Lucky Dragon, which did much to raise international awareness of the dangers of atmospheric nuclear testing.

Ralph Eugene Lapp, physicist and writer: born Buffalo, New York 24 August 1917; Assistant Director, Metallurgical Laboratory, University of Chicago 1943-45; Head of Nuclear Physics, US Office of Naval Research 1946-50; married (two sons); died Alexandria, Virginia 7 September 2004.

Ralph E. Lapp worked with the Manhattan Project, helping to create the first atomic bombs, and became an authority on radiation hazards and civil defence. He is probably best known in Britain as the author of the 1957 best-seller The Voyage of the Lucky Dragon, which did much to raise international awareness of the dangers of atmospheric nuclear testing.

Born in Buffalo, New York, in 1917, Lapp was studying for a physics PhD at the University of Chicago, specialising in cosmic rays, when the United States entered the Second World War. He soon found himself co-opted to his laboratory's effort, led by Enrico Fermi, to achieve the first controlled nuclear chain reaction, a key stage in the development of the atomic bomb. By the end of the war Lapp was assistant director of the laboratory.

It was at Chicago in mid-1945 that scientific doubts about the use of the weapon crystallised, and Lapp was one of 59 scientists to sign a petition to President Harry S. Truman declaring that the use of the bomb against Japanese cities could not be justified. "A nation which sets the precedent of using these newly liberated forces of nature for purposes of destruction may have to bear the responsibility of opening the door to an era of devastation on an unimaginable scale," it warned.

Lapp did not, however, drop out of military work after Hiroshima and Nagasaki, instead becoming head of the US Navy's physics research department. When the US conducted its first peacetime nuclear tests at Bikini Atoll in 1946 he was there to supervise naval data gathering and analysis and it was after this that radiation and civil defence came to dominate his interests.

From 1950, when he left government service, until late in his life, he worked as a consultant, writer and commentator in this field. While he was critical of the nuclear arms race and of what he called "the tyranny of weapons technology", he also had strong views about what he regarded as an exaggerated public fear of things nuclear and radioactive.

Once, in a television programme, he took issue with the consumer activist Ralph Nader, who asserted (incorrectly) that a pound of plutonium could wipe out humanity. A pound of air was just as dangerous, stated Lapp, explaining that the plutonium could kill millions only if it were divided into tiny quantities and injected into just the right place on each human body, and even then many deaths might not occur for decades. By contrast, a bubble of air injected into the bloodstream in the right way would kill more certainly and more swiftly.

It was a US hydrogen bomb test in the Pacific in 1954 that prompted Lapp's most famous work. A Japanese tuna-fishing boat, the Lucky Dragon, was doused in a white snow of radioactive fallout even though it was supposedly outside the danger area, and all 23 men on board became sick, one dying soon afterwards.

Seeing this as a case where public concern was more than justified, Lapp went to Japan to investigate both as scientist and writer, and the result was his most famous work.

"The true striking power of the atom was revealed on the decks of the Lucky Dragon," Lapp wrote in his conclusion:

When a man a hundred miles from an explosion can be killed by the silent touch of the bomb, the world suddenly becomes too small a sphere for men to touch the atom.

Lapp's many books include both general and technical works on radiation, a fine Time-Life educational primer called Matter, accounts of space and space travel and a number of titles on the arms race. In 1995 he published an autobiography: My Life with Radiation: Hiroshima plus fifty years.

Brian Cathcart