Miniaturization

The miniaturization was achieved by employing shapes and nuclear materials in dramatically different ways than the diagrams of hydrogen bombs published in textbooks, magazines and newspapers for decades.

The early plutonium implosion bombs were spherical, and the the fission primarys of hydrogen bombs have been depicted as spheres by the popular press ever since. But in 1957, workers as Livermore scientists devised a more efficient football-shaped implosion configuration.

The secondary was depicted also depicted in initial public schetches as a sphere, when in fact some of the early hydrogen bombs used cylindrical secondaries. When Howard Moreland published his landmark Progressive article in 1979, he depicted a cylindrical secondary, and the secondary has been almost universally portrayed as a cylinder ever since. In fact, the secondary of modern H-bombs is spherical. The advantage of a spherical secondary is higher compression.

The spherical hydrogen capsule is surrounded by a layer of weapons-grade uranium, which also explodes, in a process is referred to as "fission-fusion-fission."

A remarkable set of improvements occurred from 1952 to 1956 in the physics, design, and engineering of the primary stage of a nuclear weapon. The diameter of the primary stage decreased by more than a factor of three and weight decreased by more than a factor of 30. Collectively, these improvements allowed the United States to rapidly expand the flexibility and utility of its nuclear stockpile.

The improved stockpile made possible multiple delivery platforms, including ballistic missiles and tactical applications, and facilitated the shift of national policy from massive retaliation and targeting of cities and populous areas to a flexible response strategy designed to deer and counter Soviet war-fighting capabilities.

In about 1953, John Jackson initiated research on programming languages at Los Alamos. Also, Mark Wells and collaborators started, long before it was fashionable, an impressive development of a high-level programming language and operating system, eventually known as Modcap. Such language development was critical since the computer's potential could not be realized without a convenient way to communicate with it.

By 1957, with the advent of MANIAC II, the first modest experiments on man-machine interactions were started in which the programmer could direct the computer during the course of a programmed calculation. These experiments played an essential role in the discovery of the so-called universal functions, which are now becoming so important for the analysis of chaotic behavior. The main use of these developments was, of course, weapons simulation, especially for thermonuclear weapons.

Beginning in the late 1950s, delivery systems, such as ballistic missiles, governed design changes in nuclear weapons. Nuclear weapons had to be reduced in size to fit into the much smaller spaces of nose cones. Although nuclear weapons had always been constrained in size by the lift capacity of bombers, the constraints imposed by missiles were much more stringent. Miniaturization of weapons became a dominant theme in nuclear weapons development throughout the 1960s.

An important application of the hydrogen bomb came through a plan for placing such explosives in rockets carried by submarines. This development made it impossible for the Soviets to attack the United States and prevent retaliation. Indeed, rocket-delivered explosives are hard to shoot down, and the submarines that carry them are hard to locate.

The early secondaries were cylindrical, because the original goal was to make the largest possible multi-megaton explosion with a device whose diameter was more tightly constrained than its length, in order to be dropped from a bomber.

But when the goal became to fit a warhead in the nosecone of the Polaris missile, length and diameter were of comparable dimensions. The Polaris warhead, the W47, which was tested in 1958 and deployed in the 1960s, contained the first spherical secondary, an arrangement which was soon to become the standard design.

The proposal Teller made succeeded because of the excellent work of John Foster at Livermore, who designed a small and efficient non-spherical primary fission bomb, and Carl Haussmann, who designed a small and efficient spherical secondary hydrogen bomb. The resulting nuclear explosives were more than ten times as powerful as those used during the Second World War, but the use of thermonuclear reactions made them flexible enough to become practical explosives carried by submarines.

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. For the Polaris missile warhead, Livermore scientists changed the shape from a cylinder to a sphere in 1958, a configuration that that has been standard since.

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.

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 US strategic nuclear weapons. They set the tone and stage for the modern nuclear stockpile.