W47 (nuclear weapon)
The W47 was a thermonuclear warhead of the United States for the Submarine-launched ballistic missile UGM-27 Polaris . It was the first US warhead with a non-spherical Teller-Ulam design . It represents one of the greatest leaps in the development of US nuclear weapons towards lightweight weapons with high explosive power.
history
The story of the W47 warhead begins in the summer of 1956 on a study on submarine warfare organized by the United States Navy at Nobska Point (Woods Hole, Massachusetts ). This was attended by Edward Teller , who was instrumental in the development of the Teller-Ulam design for thermonuclear weapons and the establishment of the Lawrence Livermore National Laboratory . A Naval Ordnance Test Station employee discussed the possibility of building lightweight missiles with a range of 1,000 to 1,500 nautical miles (1,800 to 2,700 km). With the nuclear weapons technology of that time, however, these could only have carried warheads with low explosive power. Teller then suggested with the words "Why use a 1958 warhead in a 1965 weapon system?" ("Why use a warhead from 1958 on a weapon from 1965?") Proposed the development of a new type of compact nuclear weapon with an explosive power of about 1 MT which could be carried by the new missiles.
Teller's memories of the events are cited as follows: 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!"
( "The Navy asked if we could build a nuclear explosive device of this and that size and this and that explosive power. What they wanted was a small, light nuclear warhead with about 1M of explosive power. Everyone in the briefing, including representatives from Lot Alamos said it couldn't be done - at least in the near future, but I got up and said, "We in Livermore can deliver it in 5 years and it will have a megaton of explosive power." On the one hand, the Navy went happily away and the program was approved. On the other hand, when I came back to Livermore and told them what work was waiting for them, people's hair stood on end. They said, "What have you done? We can make such a small explosive device don't get a megaton out, not in five years! " )
In the spring of 1957, the US Navy formulated its request for a solid-propelled, underwater-launchable missile. In late 1957, the first positive test results of the LLNL's new warhead design were available from the Nevada Test Site . The US Department of Defense then initiated a program to deploy the new weapon system until 1960. More positive tests took place in the Pacific in the summer of 1958, just a short time before the test moratorium of 1958-1961 came into effect. During the period of the test moratorium, the warhead design was further improved with the help of computer models.
In April 1960, production began with the EC47 (EC - Emergency Capability), operational prototypes. In July 1960, the Navy received its first 16 warheads, and in November 1960 the USS George Washington (SSBN-598) set sail for the first deterrent patrol. After the test moratorium had expired, the USS Ethan Allen (SSBN-608) carried out the only test of a complete operational strategic weapon system in the USA on May 6, 1962 and fired a Polaris A1 as part of Operation Dominic Frigate Bird . The W47-Y1 warhead detonated successfully with 600 kT explosive force and an explosive force-to-mass ratio of 1.84 kT / kg. The variant W47 Y2 was tested on June 12, 1962 in a parachute-delayed drop from an airplane (Dominic Harlem). The warhead detonated at 1.2 MT, which corresponds to an explosive force-to-mass ratio of 3.42 kT / kg. Furthermore, the variant W47 Y2 with a doubled explosive force of 1.2 MT was introduced a short time later and the Polaris A2 was also equipped with the warhead. A total of 1,060 warheads were built by 1964, but never more than 300 were operational at the same time. The warhead was plagued by severe reliability problems and had to be improved frequently. In 1966, 75% of all W47 Y2s were not operational, they were overhauled by October 1967. The last W47 were retired in November 1974.
The innovations in the design of lightweight, compact thermonuclear strategic weapons introduced with the W47 are the basis of all modern US nuclear weapons to this day.
design
The warhead is based on the Teller-Ulam design . The new thing about the design of the W47 was that instead of a spherical plutonium core, an oval, melon-shaped core was used, i.e. i.e., it was not spherical. The chemical warhead that led to the implosion no longer had to be detonated at several dozen points, but only at two points. This "primary", called Robin, was also used in the W38 and W45 warheads. The warhead was housed in an Mk1 re-entry head. Beryllium was used as a heat-resistant material for this. The W47 Y2 with 1.2 MT explosive force weighed only about 313 kg (with Mk.1 about 410 kg), while the Mk3 bomb dropped over Nagasaki in 1945 weighed almost 4,700 kg with 0.02 MT explosive force.
Data
| Explosive device | EC47 | W47 Y1 | W47 Y2 |
|---|---|---|---|
| status | retired | ||
| former operator | United States Navy | ||
| developer | LLNL | ||
| Start of development | 1956 | ||
| Start of production | April 1960 | June 1960 | n / a |
| End of production | June 1960 | n / a | July 1964 |
| number of items produced | 1,060 | ||
| design | Teller-ulam , two-tiered, not spherical | ||
| Mass W47 without Mk1 | n / a | about 313 kg | about 327 kg |
| Length W47 without Mk1 | 1.16 m | ||
| Diameter W47 without Mk1 | 0.45 m | ||
| Explosive power | 600 kT | 1.2 MT | |
| Carrier system | Polaris A1 | Polaris A1 , Polaris A2 | |
| Number per carrier | 1 | ||
| Scattering circle radius | ka | ||