W76-2 / W76 Mod 2
The W76 warhead used on the Trident-II is a two stage hydrogen bomb, as are most modern nuclear weapons. The detonation of a relatively low yield implosion fission device - the primary - creates an intense burst of X-rays which in turn drives the implosion of the much higher yield fusion device - the secondary. The yield of the fission primary is "boosted" by the introduction of a small amount of radioactive gaseous Tritium [an isotope of hydrogen]. Without this gas, the yield of the fission primary is insufficient to ignite the fusion secondary - the bomb is a fizzle, with a yield of "only" a few kilotons. For comparison, the modernized B61-12 aircraft bomb hasyield options of 0.3, 1.5, 10 and 50 kilotons.
On 04 February 2020 the Pentagon announcd that the U.S. Navy had fielded the W76-2 low-yield submarine-launched ballistic missile (SLBM) warhead. In the 2018 Nuclear Posture Review, the department identified the requirement to “modify a small number of submarine-launched ballistic missile warheads” to address the conclusion that "potential adversaries, like Russia, believe that employment of low-yield nuclear weapons will give them an advantage over the United States and its allies and partners. This supplemental capability strengthens deterrence and provides the United States a prompt, more survivable low-yield strategic weapon; supports our commitment to extended deterrence; and demonstrates to potential adversaries that there is no advantage to limited nuclear employment because the United States can credibly and decisively respond to any threat scenario".
Russian Deputy Foreign Minister Sergei Ryabkov said that the appearance on the US strategic carriers of low-power charges means US assumption of a limited nuclear war. “The appearance on the strategic carriers of the United States of low-power charges means that the arguments previously voiced in declarative form on the American side about the possibility of using such means in a hypothetical conflict are already embodied in metal, in products. This is a reflection of the fact that the United States really lowers the nuclear threshold, which they allow themselves to conduct a limited nuclear war and victory in such a war," the diplomat said.
The former head of the 4th Central Research Institute of the Ministry of Defense (the institute dealing with the development and use of nuclear weapons) Vladimir Dvorkin believes Russia, most likely, by now has no more than 1,500–2,000 tactical nuclear weapons. These are about 200 updated B61 American munitions deployed in Belgium, Italy, the Netherlands, Germany and Turkey.
The Nuclear Posture Review released by the Pentagon in February 2018 called for a new low-yield submarine-launched ballistic warhead, which the Trump administration says is needed to deter Russia from using a similar low-yield tactical nuclear weapon to achieve escalation dominance in a military conflict fought with conventional weapons. The low-yield submarine-launched weapon requested by the Donald Trump administration by dialing back its explosive yield, according to the acting head of the Department of Energy weapons agency. “A low-yield submarine-launched ballistic missile warhead capability, deemed the W76 Mod 2, will be fielded by configuring a small number of existing ballistic missile warheads for primary-only detonation,” acting NNSA Administrator Steven Erhart said 22 February 2018 at the ExchangeMonitor’s annual Nuclear Deterrence Summit.
In the framework of the new United States nuclear strategy, the Pantax enterprise in Texas produced the first low-power nuclear warhead W76-2 to re-equip some of the Trident II (D5) intercontinental ballistic missiles on strategic nuclear submarines, a spokesman for the US National Nuclear Security Administration said 15 February 2019. As it became known from informed sources, speaking at a specialized conference on nuclear deterrence, a spokesman for the management, John Evans, said that by the end of February there would be a final check of the product design. According to him, after that, the Directorate will be able to begin preparing for the dispatch of the warhead to the naval forces.
In late January 2019, the US National Nuclear Security Administration officially announced that the production of low-power W76-2 nuclear warheads built from the more powerful W76-1 had already begun. The first batch of new warheads will go to the US Navy until the end of September. “The Directorate is working to equip the navy with the initial number of W76-2 warheads necessary for operational capabilities by the end of the fiscal year 2019 (ends on September 30, IF),” the agency said then.
The number of warheads is not officially disclosed. It is noted only that it will be small. According to reports, by September at least 20 such warheads can be produced. In the current fiscal year, $ 65 million was allocated for the creation of new warheads. The next fiscal year, management requested $ 60 million.
The new 5-6 kiloton warheads, which is one third of the power dropped on the Hiroshima American bomb, will only be re-equipped with a portion of Trident II (D5) intercontinental ballistic missiles that are armed with nuclear-powered missile submarines of the US Navy. According to representatives of the Navy, the associated nuclear tests will not be required, since new nuclear weapons are created on the basis of the W76 thermonuclear warhead, which was produced in the 1970s-1980s. Its capacity is 100 kilotons. These warheads, along with even more powerful W88 (475 kilotons) are equipped with Trident II (D5) ballistic missiles.
The Pentagon is also planning to create low-powered nuclear warheads for sea-based cruise missiles, which will be installed on attack submarines and surface ships.
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