A 77-year-old retiree, known as an eccentric genius but in declining health, played an unexpected role over the last year in designing the nation's new hydrogen bomb.
Seymour Sack, a legend among nuclear weapons designers, was called in from his home in the hills above Berkeley into his old offices in a high-security zone of the Lawrence Livermore National Laboratory.
Sack's role illustrates the predicament facing the U.S. nuclear weapons complex in an era without nuclear testing: Its newest hydrogen bomb springs from a 25-year-old design whose architect ventures out of his house as seldom as he can.
"I do as little as possible these days," Sack said. "I'm not feeling too well."
If the new bomb enters production and is deployed atop missiles on nuclear alert, as the Energy Department hopes, it will have to navigate a careful path through serious technical issues and political attacks.
The Navy will have to be convinced that the bomb will blow up reliably without a new test to prove it. And Congress will have to be persuaded that thousands of existing bombs will become obsolete. And arms control advocates who fiercely oppose the program will have to be outmaneuvered.
But the bomb, known as the reliable replacement warhead, has progressed much further and faster than any new nuclear weapons program since the end of the Cold War.
On Friday, the Livermore lab was selected over Los Alamos National Laboratory to design the weapon and begin a 12-month effort to assess its cost, schedule and scope. If all goes well, the new weapon could be mounted on missiles aboard the Navy's Trident submarines by 2012.
Livermore won the competition with a warhead design based on something Sack developed in the 1980s. At the time, most nuclear bombs were designed to be as small and light as possible, and that made them less reliable.
Defense and Energy department officials now say those aging weapons might not work at some point and should be substituted with the reliable replacement warhead. But without a new test -- the U.S. swore off nuclear testing in 1992 -- the new weapon would have to go on alert status.
Sack contends the design, tested in the 1980s, is still reliable.
"You will end up with a very reliable weapon," he said in an interview Friday. "It doesn't matter that the tests were done 25 years ago."
When Sack was given the prestigious Enrico Fermi Award in 2003, his low-profile role in the world of nuclear arms was finally recognized.
