January 13, 2024: South Korea has become the seventh nation to use Sea Launched Ballistic Missiles or SLBMs. The second version of the KSS-III submarines feature a number of firsts. They were non-nuclear, the first non-nuclear submarines that not only use Air Independent Propulsion or AIP but do so using lithium ion instead of lead-acid batteries. With this AIP system the KSS-III submarines can operate submerged for about three weeks. These subs also have ten Vertical Launch Cells or VLS filled by Hyunmoo 4-4 SLBMs with a range of 800 kilometers. North Korea is developing similar technology, but the north can only manage to build crude imitations of what the South Korean created. South Korea is far wealthier and technically advanced than the north. Both Koreas produce weapons that work often enough to do some damage and kill people. The South Korean weapons do this more reliably and effectively. North Korea is content to be able to say, “We have that too.”

South Korea joins six other nations, the United States, Russia, France, Britain, China, and India that also have SLBMs and submarines to launch them from. The United States was the first nation to develop SLBMs and install them in nuclear powered submarines. The South Korean SLBMs have conventional warheads and are launched from non-nuclear submarines. South Korea is developing nuclear weapons, after not doing so for many years to appease the United States.

The Americans have pioneered the development of SLBMs and still have the most advanced and reliable models. This is the UGM-133A Trident II D5 SLBM, which has consistently set records for successful test launches. So far there have been nearly 180 of these test launches and very few failures. The 172nd successful test flight took place in 2019. No other strategic ballistic missile has been as reliable. The 58 ton, 13.58 meter long, 211cm 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, and 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 needs 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, since 2010 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 developing a new SLBM is very expensive and the current Trident SLBM is superior to whatever anyone else has. A new SLBM would not be as reliable initially and would be a lot more 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 own 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 needed 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 or 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. Mod 2 achieves its lower yield by eliminating the second stage of nuclear detonation, which 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, like 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 with many more higher yield warheads. This capability addresses the question of what options an American president has short of a major nuclear response. It was suggested that some SLBMs be equipped with conventional high explosive warheads 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 or 14 and type of nuclear warheads carried by each missile. Trident has a range of from 8,000 to over 12,000 kilometers depending on how many nuclear weapons are carried in the last 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 are already in service, mounted on Trident SLBMs.

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.

Since 2010, 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 were 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 on 336 missiles. That would have 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 failure rate for test launches of Russian rockets is eight percent, half of Bulava's development test launches 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.

American military planners have always assumed 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 or 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. China finally had a usable SLBM by 2022.

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 with 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.

Each Trident II costs about $65 million and entered service in 1990. Some of them are fired every year, to ensure that the current configuration of hardware and software still works as it is supposed to, and to give the launch crews on the subs some experience with the real thing. The Trident II needs some major upgrades. For example, the guidance system uses 1980s era electronics, and is becoming impossible to maintain. That's because many key components are not manufactured anymore, and supplies of these spares are running out. So the U.S. Navy is developing a new guidance system, using current components, and a design that makes it easier to substitute future, and more powerful, components for those that become obsolete. The United States has 18 Ohio class SSBNs, each of them carrying twenty Trident II SLBMs.

Russia has been developing a missile similar in design to the Trident II and has had lots of problems. While the similar Russian Bulava is less reliable, it is using more modern components than the Trident II. But there is something wrong with the basic Bulava design, and the way it is put together. Half of the first 14 test launches failed. The original Trident SLBM, the Trident I, had a failure rate of 13 percent while in development during the 1970s. The 48 ton, 18 meter long Bulava costs about the same as the Trident II. Russian leaders insist that the Bulava will eventually succeed. But insiders say that, if you use the same criteria as for a successful Trident II launch, only two of the 14 Bulava tests were successful. While overall, out of over 5,000 Russian ballistic missile tests had a failure rate of eight percent, the Bulava uses a lot of new technology, for the Russians and the development is being done by a workforce much depleted by the best people leaving for more lucrative jobs in the private sector. In contrast, test firings of older Russian ICBMs, built before the Cold War ended in 1991, have been much more successful than Bulava.