W47

By shaping the plutonium pit into an ovoid [like a small watermelon, smaller than a football], Livermore weapons designers were able to dramatically reduce the size and number of explosives needed to detonate the bomb. The The W47 was the first warhead in this new generation of weapons. Although it was only half as large as the bomb that leveled Hiroshima, but it had 80 times the yield.

The Livermore-designed W38, W45, and W47 share a common primary, the "Robin."

Polaris was a turning point in nuclear weapon design. Physicist Edward Teller, a driving force behind Livermore's founding and its director from 1958 to 1960, championed the effort to develop small, efficient thermonuclear weapons that could be carried by submarine. For Polaris, Livermore designers came up with radical new designs for the primary and secondary as well as novel ways to minimize the overall mass. The result-a weapon for a reentry vehicle carried by a solid-fueled missile-fit inside a submarine and met Navy specifications for yield and weight. Polaris was a critically important breakthrough, greatly adding to the stability of the nuclear deterrent.

Researchers at Livermore had focused their thermonuclear work on the design of H-bombs that were smaller in size and yield than those of Los Alamos. The first thermonuclear test in 1954, KOON, was a fizzle. On April 6, 1954, on the Bikini Atoll, the Laboratory detonated Koon, the third in the seven-test series under Operation Castle, and the first test of a Livermore H-bomb (thermonuclear) design. The test was disappointing and persuaded designers and testers to cancel the next Livermore test, Echo. with a predicted yield of 1 megaton its actual yield was only 110 kt. The test device was name Morgenstern ("morningstar"). Beset by last-minute doubts about the design of the radiation case, Livermore physicists surrounded the railroad car-sized Morgenstern with water-filled jerry cans, hoping to prevent the neutron preinitiation that had almost caused the Mike device to fail and forced its eleventh-hour redesign. Continuing efforts and future successes led to Livermore's development of much smaller diameter "H-bomb" missile warheads later in the 1950s, which made the Polaris submarine program possible.

In the summer of 1956, a Navy-sponsored study on antisubmarine warfare was held at Nobska Point in Woods Hole, Massachusetts. Edward Teller attended the Project Nobska study. His bold input would profoundly affect the course of the Navy's Fleet Ballistic Missile Program and the future of the Laboratory. At the time, the approved program plans called for the deployment in 1965 of submarines that would carry horizontally four 80- ton Jupiter S ballistic missiles, which were large enough to carry existing thermonuclear warheads.

During Project Nobska, Frank E. Bothwell from the Naval Ordnance Test Station raised the possibility of designing ballistic missiles 5 to 10 times lighter than the Jupiter S missiles, with a range of 1,000 to 1,500 miles; however, they would be able to carry only a relatively low- yield nuclear weapon. Teller discussed the feasibility of a 1- megaton warhead compact enough to fit onto a torpedo- a radical concept. When asked whether his ideas could be applied to the Navy ballistic missile program, Teller replied with a question, "Why use a 1958 warhead in a 1965 weapon system?" He opened the door to a highly efficient deterrent system in which 16 compact missiles could be placed vertically on a submarine and launched on demand without repositioning- the Polaris program.

Teller recalled that "The Navy asked if we could make a nuclear explosive of such and such dimensions and such and such a yield. What they wanted was a small, light, nuclear warhead in the 1-megaton range. Everyone at the meeting, including representatives from Los Alamos, said it could not be done- at least in the near future. But I stood up and said, 'We at Livermore can deliver it in five years and it will yield 1 megaton. ' On the one hand, the Navy went away happy, and the program got approved. On the other hand, when I came back to Livermore and told them of the work that was in store for them, people's hair stood on end. They said, 'What have you done? We can't get a megaton out of such a small device, not in five years!"

So began a crash, three- year effort. In early 1957, the Navy issued a requirement for an underwater-launched solid- fuel missile system by 1965. By the end of the year, following successful tests of Livermore designs at the Nevada Test Site, the Secretary of Defense authorized a step- up to deploy the system by 1960, which was accomplished.

In June 1957, the Navy decided to entrust the design and development of warheads for its new Polaris missiles to the second laboratory. Meeting the Polaris challenge has often been described as Livermore's coming of age. Polaris carried the first modern, high-yield, low-weight nuclear warhead, and became an important element of the strategic stockpile. The highly integrated warhead and reentry vehicle required close cooperation between the Laboratory and the Navy, establishing a new way of doing business for both.

The summer of 1958 brought genuine breakthroughs based on ingenious proposals by Carl Haussmann, Kenneth Bandtel, Jack Rosengren, Peter Moulthrop, and David Hall of A Division and by B Division's John Foster (Lab Director, 1961- 1965), Chuck Godfrey, and Wally Birnbaum. The significance of the innovations was confirmed during tests in the Pacific only a few months before the 1958- 1961 nuclear testing moratorium began. Work continued at the Livermore and Sandia laboratories, and through the efforts of weapons designers and engineers, computer specialists, and other experts, the W47 Polaris warhead was created.

A moratorium on nuclear weapons testing went into effect on November 1, 1958. It lasted almost three years, until September 1961. Although the moratorium barred further testing of the Polaris warhead, deployment proceeded. In July 1960, the Navy accepted delivery of the first 16 warheads, and four months later, USS George Washington, the first Polaris submarine, went to sea on its first patrol with 16 armed missiles aboard. After the moratorium, the Polaris missile system provided the only full-scale operational test from launch through detonation ever conducted for a U.S. nuclear missile. On May 6, 1962, a submerged Polaris submarine launched a stockpile Polaris missile to explode a thousand miles away over the open ocean.

Polaris designers trusted their work despite changes from the designs field-tested before the moratorium and the implementation of substantial warhead upgrades. A major factor in promoting this trust was computer modeling of the extremely complex physical phenomena involved in nuclear explosions. Stimulated by their concern to understand the physics, bomb designers devised increasingly complex computer codes to model the physical behavior of nuclear weapons. That required state-of-the-art computers--the more powerful the better.

The program's remarkable achievements were demonstrated in spectacular fashion on May 6, 1962. The USS Ethan Allen, the sixth- launched Polaris submarine, fired a complete operational test of the Polaris A-1 missile system, culminating with the successful detonation of the Livermore- designed megaton- class warhead (see Year 1962).

Conceived as a highly survivable system able to counterattack in the event of a Soviet first strike, Polaris has a unique place in American nuclear weapons history. The Laboratory's innovative design and development of the W47 as part of a crash program established Livermore's reputation as a major nuclear weapons design facility. The work spurred additional innovations and provided a model for future strategic weapon development.

"This development [of Polaris] made it impossible for the Soviets to attack the United States and prevent retaliation," noted Teller. "Indeed, rocket-delivered explosives are hard to shoot down, and the submarines that carry them are hard to detect." The innovative design for the Polaris warhead was first validated in 1958. In 1960, the first Polaris submarine armed with Livermore-designed warheads took to sea, ahead of the most optimistic schedule.

The design improvements introduced in the Polaris warhead had far-reaching effects. Small, lightweight designs, whose evolution can be traced to the Polaris W47, were adopted in most subsequent U.S. strategic nuclear weapons. They set the tone and stage for the modern nuclear stockpile.