The U.S. Navy UGM-133A Trident II D5 SLBM (Sea Launched Ballistic Missile) set another record on May 9th when it made its 172nd successful test flight. No other strategic ballistic missile has been as reliable. The 58 ton, 13.58 meter (44 feet) long, 211cm (83 inch) diameter Trident II has not had a test failure since 2016, when a British D5 test was aborted after a problem was detected in the guidance system, That was attributed to a problem with the test warhead, which replaces the combat warhead (containing nuclear weapons). The test warhead monitors all of the SLBM systems and continually transmits that “telemetry” data back to a ground station so that the exact cause of each test failure can be determined and fixes made.
Sometimes the telemetry data confirms that an older component is in need of an update. The Trident is a complex system with three separate stages and a warhead with up to 14 nuclear weapons aimed at different targets. For example in the last decade over $200 million was spent to upgrade and test the Mk 6 guidance systems in over 400 Trident missiles. The original guidance systems were 1980s technology and some of them were twenty years old as well. The upgraded guidance systems are more accurate, reliable and easier to maintain, but they are another complex item that each test launch evaluates for reliability and performance.
Production of the Trident II D5 ended in 2005 because disarmament treaties are reducing the number of SLBMs the U.S. and Russia could have on their SSBNs. The U.S. and Britain (the two nations that use the D5) have enough missiles to keep their SSBNs equipped as well as allowing for regular test launches of randomly selected missiles. In 2005 it was believed the existing supply of missiles would last until the D5 was replaced with a new design in the late 2030s. Production of the D5 could resume earlier if need be and that may happen because a new SLBM would be expensive.
The Trident had two failures during its 49 development test launches, but since then it has been the most reliable SLBM to ever enter service. Such reliability is a crucial aspect of weapons, just like range and accuracy. Each Trident II costs about $65 million and first entered service in 1990. Two or three of them are fired every year, to ensure that the current configuration (of hardware and software) still works as it is supposed to. Britain has complete control over its D5 SLBMs and sometimes modifies the ones they use. However, most D5 maintenance and storage is carried out in a single U.S. Navy facility because it is cheaper and more reliable that way. Even telemetry data from a successful test provides indications of changes that must eventually be made and sometimes that means a lot of missiles have to be modified quickly. That process is best carried out in a central facility.
The nuclear warheads are not included in test launches and are monitored while installed on D5s carried by SSBNs on combat patrols. That monitoring data indicated that the older W76 warheads were in need of some updates and upgrades as well. Such updates and upgrades are a small part of the cost of maintaining each warhead as well as the entire SLBM. Both warheads and missiles are complex systems with a lot of electronic, chemical and mechanical components that eventually age to the point of failure or unreliability.
The latest upgrade of the W76 entered production in 2019. This new model is the W76 Mod 2 and several hundred will be produced. This is a lower yield (explosive power) version of the standard W76, which was originally built to provide 100 kilotons (equivalent to 100,000 tons of conventional explosives) of blast effect. The new W76-2 is a minor modification of the current W76 Mod 1 design. The Mod 2 achieves its lower yield by eliminating the second stage of the nuclear detonation (that basically amplifies the yield). The result is a warhead with a yield of 5-10 kilotons. This provides the option to respond to some kinds of nuclear attack (like a few ICBMs aimed at the United States that are intercepted) with a low-yield nuke to demonstrate that actions (firing nuclear armed missiles at the U.S.) have consequences and that now it is time to talk rather than face a much more devastating nuclear response (many more higher yield warheads). This capability addresses the question “what options do I (an American president) have short of a major nuclear response.” It was suggested that some SLBMs be equipped with a conventional (high explosive) warhead for “demonstration of willingness” purposes. It was pointed out that using a high explosive warhead on an ICBM just demonstrates that you were willing to pay a lot to deliver a non-nuclear warhead.
One of the common differences in each Trident is the number (8-14) and type of nuclear warheads carried by each missile. Thus the Trident has a range of from 8,000 to over 12,000 kilometers depending on how many nuclear weapons are carried in the last (top) stage. While the W76 is an old design it is not the only warhead used by Trident SLBMs. There is also the W88 warhead. These were designed in the 1980s and 400 were manufactured in 1988-89. The W88 has a yield of 475 kilotons and American SSBNs carry one or more missiles armed with the W88. The W76-2 warhead will equip one or two missiles on each SSBN with the rest of the missiles having the standard W76. Since the current SLBMs normally carry no more than eight warheads, the ones carrying the W76-2 might just have one warhead. The first W76-2 warheads will be in service (mounted on Trident SLBMs) in the early 2020s.
The W76 is the standard nuclear weapon used on SLBM ballistic missiles carried by American SSBNs. In 2011 Britain decided to use the W76-1 upgrade to the older W76 nuclear warhead, as older generations of nuclear warheads are updated before they become dysfunctional from old age. Previous to this, Britain had used its own nuclear weapons designs for these warheads, although the current British SLBM warhead is believed to be similar to the American W76, but with some different features (like selectable yield, or how big a nuclear explosion there will be).
Over the last decade, the U.S. has produced 2,000 W76-1 warheads. This is a minor upgrade of the original W76 and has the same yield of 100 kilotons. Upgrading these older W76 warheads was not easy. For example, American efforts to refurbish the elderly W76 nuclear warheads was held up by difficulties in manufacturing several components. The warheads were originally manufactured between 1978 and 1987. Since that time it was discovered that the necessary details for manufacturing some of the unique components had been lost. One of those items, a chemical codenamed Fogbank, could not be created with surviving documents. This problem was eventually overcome, but then similar problems were discovered with some other components. This sort of thing was largely the result of manufacturing details being so highly classified. Normally, manufacturing details for older items can afford to be a little vague, because unclassified components have lots of similar items either still in production, or many people and documents you can consult to quickly reconstruct the needed materials and process details. Not so with highly classified components for nuclear weapons.
All this W76 activity got started because the earlier ones were fast approaching the point where they would be useless. Nuclear warheads have a lot of components (explosives, various exotic chemicals and electronics) that degrade over time. The W76 had been “the oldest warhead in service” for a long time. In 2007 the nuclear weapons industry proposed a new warhead design for the D5 missiles. This involved replacing 3,000 W76 warheads that equipped 336 missiles. That would cost about $100 billion. The navy preferred to refurbish the W76s and save a lot of money, rather than coming up with a new design.
While the U.S. has had some problems managing all this, other nations have often done far worse. For example, the latest Russian SLBM, the Bulava, is having an awful time when it comes to testing. While the overall (out of over 5,000 of them) failure rate for test launches of Russian rockets is eight percent, half of Bulava's development test launches have failed. The U.S. Trident had a failure rate of 13 percent while in development.
The 48 ton, 56 foot long Bulava costs about the same as the Trident II. The Bulava SLBM is a little shorter than the land-based Topol M missile it is based on so that it could fit into the missile tube on the submarine. Thus Bulava has a shorter range of some 8,000 kilometers. Bulava has three stages and uses solid fuel. Currently, each Bulava carries a single 500 kiloton nuclear weapon, plus decoys and the ability to maneuver. The warhead is also shielded to provide protection from the electromagnetic pulse of nearby nuclear explosions. Take away all of these goodies, and the Bulava could be equipped with up to ten smaller (150 kiloton) warheads. But the big thing is still trying to defeat American anti-missile systems. First Bulava has to get the bugs out. Russian SLBMs have long been plagued with development problems. Think of it as a tradition the Russians are still trying to lose.
It's always been assumed, by American military planners, that Russian ICBMs and SLBMs were less reliable. But even with that, enough of them would work, and kill millions of Americans, and cripple the economy for over a decade, if there were ever a nuclear attack. Russia finally figured out what was causing most of the failed test launches and fixed the problems. The Bulava is still less reliable than the Trident but both are more reliable than the Chinese SLBMs.
The Chinese JL (Julang) 2 SLBM has failed most of its test launches. The 42 ton JL-2 has a range of 8,000 kilometers and would enable China to aim missiles at any target in the United States from a 094 class SSBN cruising off Hawaii or Alaska. Each 094 boat can carry twelve of these missiles, which are naval versions of the existing land-based 42 ton DF-31 ICBM. China had lots of problems with the JL-2, which was supposed to have entered service by 2008, but kept failing test launches. Then, in 2018 came rumors of a JL-3 that worked. There were apparently some successful JL-3 test tests in late 2018 and early 2019. If true China may have a usable SLBM by the early 2020s.
The main reason for the success of the American SLBMs is the better tech to start with and using solid fuel from the beginning. The first SLBM was the U.S. Polaris A1, which entered service in 1961 preceded by about five years of development. Polaris was a two-stage solid fuel missile. The Polaris A1 weighed 13 tons, had a range of 2,200 kilometers and a one-ton warhead. In 1972 the 29 ton Poseidon SLBM entered service with a range of 5,900 kilometers. In 1979 the 33 ton Trident I entered service with a range of 7,400 kilometers and finally the 59 ton Trident II in 1990 with a range of up to 12,000 kilometers. Each generation of SLBM was more reliable and accurate and could carry more warheads.
When the Cold War ended there were hopes that SLBMs and ICBMs could be eliminated or at least have their number greatly reduced. Complete elimination has so far proved impossible to implement. Reducing the number of missiles and nuclear weapons on them has been accomplished. Also reduced was the amount of money spent on developing new missiles and nukes. No one was willing to cut the development budget to zero so work continues at a slower pace.