TX-14The TX-14 was the first solid-fuel American thermonuclear bomb. Instead of using tritium, the bomb contained a stable (not radioactive) isotope of lithium called Li-6. The lightest metal, and the third lightest element, Lithium is a solid, which means that the material is stored at high density. The neutrons from the fission weapon break up the Li-6 to make the tritium. Thus the fuel is created in the same microsecond that the bomb is exploding. The fusion fuel is usually lithium combined with deuterium, called lithium deuteride. President Truman announced at the beginning of i950 that the Nation would build a hydrogen bomb, nicknamed the "Super." Liquid deuterium was used as fuel in successful thermonuclear devices tested at Eniwetok Atoll in 1952. But it was clear that a final hydrogen bomb would not be fueled by liquid deuterium, yielding a so-called "wet" bomb. Rather, it would be the light compound lithium deuteride (LiD). An experimental design, only five units were produced in early 1954. Sandia and Los Alamos forwarded a joint letter to the Division of Military Application May 22, 1952, proposing that the TX-14 be designed with the following guidelines:
- Maximization of yield to the point where escape of a manned transporting bomber was impossible (the use of an unmanned drone had meanwhile been discarded), or production of the largest yield possible in the size allowed.
- Diameter not to exceed 64 inches; length, about 20 feet; and weight, about 50,000 pounds. (This made the TX-14 comparable in length and weight to the World War II Block Buster bomb which was 27 feet long and weighed 44,000 pounds).
- Bomb to be capable of withstanding forces involved in careful handling, aircraft loading and carrying, and free or retarded fall.
- Bomb to have a capability for air-burst operation only.
The Division of Military Application forwarded this proposal to the Military Liaison Committee, which replied, June 13, 1952, that the Joint Chiefs of Staff had established a military requirement for the development of thermonuclear weapons with yields of 1 megaton and over, requesting that these weapons becompatible in size, shape and weight with delivery systems that would be available in 1954. Production facilities for thermonuclear materials would be developed immediately. It was felt that any prior production of a deliverable thermonuclear weapon by the Soviet Union would reduce the existing American lead in weaponry,and that such a shift in balance might well cause a change in Soviet policy. This factor alone provided adequate justification for an approach involving considerable technical risk and a large expenditure of funds.
Meanwhile, design work was proceeding on the TX-14, with procurement for the program being authorized September 15, 1952. Transportation of the heavy bomb from storage to airfield was a problem, since conventional equipment resulted in high wheel loadings that might damage roads and runways, and a multiwheeled, low-bed semi-trailer with pneumatic tires was developed. Sandia assumed the task of assuring weapon compatibility with carrying aircraft. The only bombers capable of delivering the TX-14 were the B-36 and the B-47. Fin clearance in the bomb bay was found to be ample in the B-36, but critical in the B-47.
Every theoretical study indicated that both aircraft could not escape from the detonation effects of free-fall thermonuclear weapons, and it was decided that a parachute would be provided to slow the rate of fall of the bomb. Ribbon parachutes were developed by Wright Air Development Center and tested, starting in late 1952. Most of these drops were made at Edwards Air Force Base, California, with a few being conducted at the Saltón Sea Test Base. Development contracts were issued for parachutes with a diameter of 100 feet. Subsequent computed down-times for this design were so great that the diameter was reduced to 80 feet. This design was later changed to a 64-foot-diameter parachute that could be reefed for different bomb weights. The system that finally evolved consisted of a pilot chute, a secondary extractionchute, and a main ribbon chute, all fitted into the afterbody of the bomb. Upon release, the pilot chute, which was attached hy a static line to the aircraft, deployed. This pulled out the secondary chute which, in turn, deployed the ribbon chute. The ribbon chute was reefed to a small diameter for 10 seconds and then opened to full size. Without this controlled deployment, the parachute would have jolted the bomb or would have been ripped away. Tests were made with both B-36 and B-47 aircraft, and the drops continued until March 1954, when releases had been made.
Much of the work on the TX-14 had been performed up to this point, under the cog-nizance of Los Alamos. Santa Fe Operations Office suggested, July 14, 1953, that the same division of responsibilities on thermonuclear weapons be made as had been previously established for fission devices, and it was proposed that an inter-laboratory committee, similar in scope to the TX-14 Committee, be set up to work out the details of this division of responsibilities. This committee, which was called TX-Theta, (the Greek letter theta stood for thermonuclear), was formed and held its first meeting October 26, 1953. Inasmuch as work on the TX-14 was well advanced, the attention of the Committee was directed largely toward other thermonuclear weapons. The vork of the Committee assumed added importance from the start, as in the meantime the Soviet Union had announced August 12,1953, that it had detonated a thermonuclear device.
Following the Soviet test of a Hydrogen Bomb in 1953 in which lithium was detected in the fallout, a "crash" program implemented for the purpose of developing a large scale lithium separation plant. Thus, when the decision was made to pursue the development of the hydrogen bomb, Y-12 at Oak Ridge was chosen as the site for the separation of lithium-6 from the more abundant lithium-7. Not unlike the earlier Manhattan Project, a massive mobilization of personnel and material resulted in operational plants in less than fifteen months. Lithium production cascades were housed in large buildings formerly used for uranium separation. Production for various separation processes started between 1953 and 1955. Emergency-capability TX-14's first entered stockpile in February 1954. The bomb was 61.5 inches in diameter and had a length of 222 inches. It was tested in April 1954 during the Castle Union nuclear test and had a yield of 6.9 Mt. Meanwhile, other thermonuclear bomb designs had progressed to the point of stockpile entry. Since their yields, nuclear economics, assembly and logisticswere better than those of the TX-14, the latter weapons were retired in October 1954 after six months of service. Part of the retired material was used in the Mk 17/24 program.
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