Sub-Launched Nuclear Weapons

How reliable are the W-76 warheads? Now that the land-based missiles are largely retired, the W-76 is our main nuclear warhead, but it may not be as reliable as we think:

Dr. (Richard L.) Morse (Los Alamos National Lab) specialized in scientific explanations for the complex flows that curl through the extraordinarily hot gases known as plasmas, which lie at the heart of an exploding nuclear weapon. His main goal was to help scientists develop a giant laser that, in lieu of an atomic match, would fire on a tiny radiation case surrounding an even tinier pellet of hydrogen fuel, releasing a burst of nuclear energy. Heat from such miniature hydrogen bombs was envisioned as one day being used to make electricity.

But Dr. Morse found that nature had erected tricky barriers to that goal. In particular, he documented how a form of turbulence known as Rayleigh-Taylor instability (named after the physicists Lord Rayleigh and Geoffrey Taylor) could perturb the expanding plasma of the very hot radiation case, forming waves, ripples and whorls that blocked ignition of the thermonuclear fuel. He also found that extremely small variations in the case were responsible for the onset of turbulence, making it hard to eliminate.

In 1996, Dr. Morse brought similar analyses to bear on the W-76's thin case, arguing that it would probably fail. He said that for decades, officials had swept the issue under the rug and that Mr. Cremer, the designer, had struggled with the problem.
In an interview, Dr. Morse said he was soon "disinvited" from the evaluation and left Los Alamos for Sandia National Laboratories in Albuquerque. But he added that concerns about the W-76 only grew.

Dr. Beckner (National Nuclear Security Administration) disagreed. He said the joint review found that the W-76 "looks like a pretty good weapon."

...At a secret meeting in March 2004 at Los Alamos, Dr. Morse led four critics who laid out their concerns to lab and federal officials, including Dr. Beckner. Dr. Morse characterized the discussion as acrimonious.

"It was a verbal mud-wrestling match," he recalled. The lab and federal officials "would not be candid with us. We told them things they didn't know. It was very, very disappointing."

In contrast, Dr. Beckner said the meeting and subsequent analyses left him with "high confidence that this nuclear weapon is a good design, was built properly and will function if required."

In early July, news reports in New Mexico began to describe the dispute, and the director of Los Alamos days later scheduled a secret lab symposium to review the "technical challenges" to understanding how radiation cases act in the first microseconds of a nuclear blast, according to a synopsis of the planned meeting.
As the number of news reports grew, officials denied that there was any problem with the W-76. They cited a history of detonations of the weapon at the Nevada Test Site.

In late November, the dependability issue emerged nationally as Congress approved a small budget item that began a new weapons design effort known as the Reliable Replacement Warhead program. Its goal is to have weapons scientists design a new generation of nuclear arms that are more reliable and more durable, reversing the cold war trend of making small, lightweight, powerful weapons. If possible, the effort is to proceed without nuclear testing.