B53 Strategic Free-Fall Bomb
W53 Warhead
Mk 53 Strategic Free-Fall Bomb

On 25 October 2011, the Department of Energy's National Nuclear Security Administration announced that the last B53 bomb had been dismantled at the Pantex Plant near Amarillo, Texas. The dismantling of the last B53 marked the end of a program that had started in the 1980s and expanded with the retirement of the weapon in 1997.

The B53 "hydrogen" bomb, with a gross weight of some 10,000 pounds, had a yield in the megaton range and could be set to air burst, contact burst, or "laydown" (delayed action detonation). The weapon contained about 300 pounds of high explosive surrounding a uranium pit. It was equipped with 5 parachutes: one 5 foot pilot chute, one 16 foot chute, and 3 48 foot chutes. If for some reason a free-falling delivery was required, the parachute "can" could have been blown out, thereby jettisoning all chutes.

The B53 hydrogen bomb was first produced in 1962 as the Mk 53 and was designed to be carried internally by B-47, B-52, B-58, and B-70 aircraft. The weapon was designed to penetrate deep bunkers and other hardened facilities. In 1968, the weapon was redesignated as the B53. The Mk 6 re-entry vehicle installed on the Titan II ICBM contained a W53 warhead, which was basically the same as the B53 bomb. The B53 bomb served a critical role in the nation's nuclear deterrence through the end of the Cold War.

Air Force regulations prohibited air transport of nuclear weapons containing conventional high explosives (CHE), (i.e., B53, W62, W78) unless ground transport was not feasible. Air transport of CHE weapons required approval by the Secretary of the Military Department or the Commander of the Unified or Specified Command or their designated representatives.

A decision was made in the 1980s to begin dismantling the B53 bombs, which utilized obsolete technology. B53 bombs, however, remained in active service until 1997. At the time it was retired, the B53 was the oldest, the largest and the most destructive weapon in the US nuclear arsenal. Though retired at that time, the bombs remained in storage, until they could be dismantled through a program run by the US Department of Energy's National Nuclear Security Administration.

The dismantlement program was not without difficulties. Beyond the difficulties presented by its massive size, often described as being similar to that of a minivan, the B53 disassembly was complicated by its use of older technology developed by engineers that have long since retired or passed away. The dismantlement required the creation of many complex pieces of tooling, as well as development of new procedures, to allow for the safe disassembly of the B53.

With the help of Los Alamos and Sandia National Laboratories, where the weapon was designed, Pantex studied and designed a fully compliant way to dismantle the aging B53 using the NNSA's Seamless Safety for the 21st Century (SS-21) program. The last bomb was dismantled on 25 October 2011 at Pantex Plant near Amarillo, Texas.