Source: People's Liberation Army Daily, China Military Trumpet
Author: Cui Qiang, Zhou Shangxian, Tang Lu
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At the end of last year, Russia added two more nuclear submarines to the ranks. It is said that the two submarines belong to the Boreas-class and Yasen-class, respectively, and are equipped with "Bulava" submarine-launched ballistic missiles.
Submarine-launched ballistic missiles are ballistic missiles that are carried and launched by submarines, usually equipped with nuclear warheads. The relatively good concealment of the launch and the tremendous destructive power have made the SLBM the main force of the second nuclear strike. Therefore, the development and movement of SLBMs can easily "stir up waves".
In June 2022, the U.S. Ohio-class strategic nuclear submarine launched four Trident II.D5 missiles. Shortly thereafter, Russia announced that the latest backbone of its sea-based nuclear forces, the Boreas-A-class strategic nuclear submarine, had test-fired the Bulava missile.
Not only the military powers, but also the progress of other countries in the field of SLBMs are also under great concern. In particular, in recent years, some countries have successively used conventionally powered submarines to successfully test-launch submarine-launched ballistic missiles, which has become a hot topic in the international arena for a while. Why are SLBMs so much in the spotlight?
An important support for the strategic strike force
As we all know, there are three main types of nuclear strikes: land-based intercontinental ballistic missiles, sea-based submarine-launched ballistic missiles, and air-based strategic bomber strikes, which together constitute the "nuclear triad." When a country has a three-in-one nuclear strike capability, it means that it has a comprehensive nuclear deterrent capability.
Looking at the composition of the nuclear strike forces of the major nuclear powers, it can be seen that the proportion of sea-based submarine-launched ballistic missiles is not low.
According to open information, the deployment rate of US strategic nuclear warheads on SLBMs has exceeded 60 percent, and this proportion is increasing year by year, while Britain and France have deployed all their strategic nuclear warheads on SLBMs.
There are many reasons why various countries attach so much importance to sea-based strategic nuclear forces, but the most important point is that they are more likely to form a second-strike nuclear capability.
Second-strike capability, in simple terms, refers to the ability of a country to use nuclear weapons to counterattack after being attacked by an enemy nuclear attack. This capability consists mainly of two parts: the ability to preserve some or most of the strategic nuclear forces in the event of an enemy nuclear strike, and the ability to use them to carry out effective retaliatory strikes. According to relevant theories, if a country has the capability of a second nuclear strike, it can effectively deter and deter the adversary, so that it does not dare to carry out strategic nuclear strikes.
Compared with land-based and air-based nuclear strike methods, sea-based SLBMs are more likely to form a secondary nuclear strike capability, and the reason why they are usually carried by nuclear submarines comes from the fact that they are usually carried by nuclear submarines. The characteristics of cruising on the seabed with the submarine for a long time and being able to launch at any time give the submarine-launched ballistic missile a unique advantage.
Good concealment. Submarines have always been known as "ghosts of the deep sea". With its strong endurance and large diving depth, it is difficult for strategic nuclear submarines to be detected by the enemy once they are deployed in advance. The unique concealment brings about a relatively strong survivability, which provides the conditions for the formation of a secondary nuclear strike capability.
High mobility. Strategic nuclear submarines can cruise in the deep ocean for several months, which means that they can theoretically reach any sea area and have a range that can cover any country or region, making it twice more difficult for the enemy to defend.
It is less affected by the size of the territory. Generally speaking, countries with larger territories have greater strategic room for maneuver and a stronger ability to organize a nuclear counterattack. Countries with smaller territories are at a relative disadvantage in the nuclear power game. The emergence of SLBMs has broken the limitation of territorial area, and this is the main reason why Britain and France have deployed all their strategic nuclear warheads on SLBMs.
There are certain differences in the development paths and levels of different countries
With the emergence and development of nuclear weapons, nuclear submarines, and ballistic missiles, the two camps led by the United States and the Soviet Union were keenly aware of the strategic value of SLBMs and threw themselves into this strategic wrestling.
In September 1955, the Soviet Union successfully launched a ballistic missile from a submarine for the first time, but with a conventionally powered submarine, the launch was also on the surface, and the missile had a range of 150 kilometers, so it was only symbolic.
In July 1960, the USS George Washington nuclear submarine test-fired the "Polaris" A1 ballistic missile from underwater, hitting a target at a distance of 1,800 kilometers, marking the entry of submarine-launched ballistic missiles on the stage of history.
The U.S. submarine-launched ballistic missile model is the "Trident" II.D5, which is carried on the Ohio-class strategic nuclear submarine, and is the third generation of U.S. submarine-launched ballistic missiles, which entered service in 1990, with a maximum range of more than 11,000 kilometers, a circular probability error of 90~120 meters, and a maximum of 14 nuclear warheads. An Ohio-class nuclear submarine can carry 24 Trident missiles. This type of missile has been in service for more than 30 years, during which it has been continuously upgraded, but it has not been replaced. According to foreign media reports, the first boat of the Columbia-class of the new generation of US strategic nuclear submarines is scheduled to enter service in 2031 and begin combat duty, when it will still be equipped with "Trident" II.D5 missiles.
After the collapse of the Soviet Union, Russia inherited most of its strategic nuclear forces, and on this basis, developed the Bulava submarine-launched ballistic missile. The "Bulava" missile has been in service since 2013, with a range of more than 8,000 kilometers, and can carry 6~10 independently guided nuclear warheads, as well as 10 hypersonic warheads, and the warheads can also be equipped with decoys to deceive enemy anti-missile systems. A Boreas-class nuclear submarine is capable of carrying 16 Bulava missiles.
France began to develop submarine-launched ballistic missiles in the 60s of the 20th century. In 1969, the country successfully tested the M1 submarine-launched ballistic missile underwater. After decades of development, the French submarine-launched ballistic missile in service is the M-51 type, which is carried on the Triumph-class strategic nuclear submarine. The maximum range of the M-51 missile is 8000~10000 kilometers, the circular probability error is less than 400 meters, and it can carry 6~12 sub-warheads.
Although Britain has had sea-based nuclear forces since the late 60s of the 20th century, it has always used American-made submarine-launched ballistic missiles. At present, the Avantgarde-class strategic nuclear submarines in service in the United Kingdom are equipped with Trident II missiles.
In the 90s of the 20th century, India began to develop sea-based nuclear forces, and its submarine-launched ballistic missiles were named the "K" series, which were mainly developed from the "Agni" series of land-based ballistic missiles. The first "K-15" missile has been tested underwater since 2008, and in 2018, it was successfully tested on the enemy-destroyer-class ballistic missile nuclear submarine with a range of 700 kilometers. At the beginning of 2020, India announced the successful test launch of the "K-4" missile, with a range of 3,500 kilometers. According to foreign media reports, India has begun to develop the "K-5" submarine-launched ballistic missile, which is expected to have a maximum range of 6,000 kilometers and can carry four nuclear warheads.
Of course, the launch of submarine-launched ballistic missiles with nuclear warheads from nuclear submarines is now not the only form of formation of sea-based strategic forces. According to the analysis of some experts, the use of conventional submarines to launch submarine-launched ballistic missiles or the use of submarine-launched ballistic missiles to carry conventional warheads may become an option for some countries in the future under certain conditions.
The DPRK and the ROK have also developed submarine-launched ballistic missiles. Since 2015, North Korea has successfully test-fired its Polaris series of submarine-launched ballistic missiles from conventional submarines. According to foreign media analysis, the "Polaris-5" missile, which can carry multiple warheads, which North Korea publicly displayed in early 2021, has an estimated range of 5000~6000 kilometers. In September 2021, South Korea also test-fired its "Hyunmoo-2B" submarine-launched ballistic missile from the conventional submarine Dolsan Anchang-ho, which has a range of 500 kilometers when carrying about 1,000 kg of warhead and up to 800 km if it carries a 500-kg warhead.
Although the difficulty of research and development is great, it is difficult to prevent its continued development
Since its inception, SLBMs have been developed for more than 60 years, and only a handful of countries have possessed them. In addition to the strategic value that determines that its development is restricted by various factors, more importantly, its research and development is difficult and the threshold is high. Most SLBMs are developed from land-based ballistic missiles, but the process of "turning around" from ground launch to water launch can be described as difficult.
-- It is difficult to shorten the length of missiles. Limited by the space inside the submarine, the SLBM cannot be too large. The Russian "Bulava" missile was developed from the land-based "Topol-M" missile, the length of the missile body has been shortened by 9.5 meters, and the launch weight has also been greatly reduced. In this case, in order to ensure the range and load of the missile, it is necessary to borrow from composite materials. Good composite materials can not only reduce the weight of the missile body, but also have the effect of absorbing waves, making it difficult for the opponent to detect, thereby enhancing the missile penetration performance. It is very difficult to develop the ideal composite material.
- Underwater ignition and launch are difficult. The three ignition and launch methods all have corresponding technical difficulties to be overcome: First, the missile is directly ignited and launched from the launch canister, and the high temperature and high pressure generated at this time are a severe test for the hull design; second, the missile is first ejected from the launch barrel with pressure, and it is ignited and launched before it comes out of the water, and the difficulty of ignition and launch in the water is also very high; third, the missile is ejected from the launch canister first, and then ignited and launched after it comes out of the water, and this method has extremely high requirements for ignition timing and accuracy.
——It is difficult to improve the rigidity of the projectile body. Submarine-launched ballistic missiles generally need to run underwater for a certain distance after launching, and the density of water is equivalent to more than 800 times that of air. While greatly improving the rigidity of the projectile body, the weight of the projectile body cannot be significantly increased, which puts forward higher requirements for the materials used in the projectile body.
-- It is difficult to ensure precise guidance. Compared with land-based ballistic missiles, SLBMs have higher guidance requirements and mostly adopt composite guidance modes. For example, the American "Trident" II.D5 missile uses satellite + starlight + inertial joint guidance. Not to mention satellite guidance or starlight correction, even if it is a relatively simple inertial guidance system, many countries do not have the ability to develop it.
-- It is difficult to coordinate and match boats and bombs. It is not easy to operate submarines, so how to ensure the safe and reliable launch of submarine-launched ballistic missiles? In addition to strengthening the safety of the missiles themselves, the key lies in improving the degree of coordination and matching between boats and missiles, and this requires developers and users to do a lot of relevant work.
Although there are many difficulties in research and development and there are many restrictions on their use, the strong concealment and survivability of SLBMs still make SLBMs the focus of research and development in some countries, and the following trends are shown in their development:
The first is to improve the ability to penetrate defenses. In the face of the ever-upgrading missile defense systems of various countries, SLBMs may adopt more advanced full-guided multi-warhead technology, and can also effectively penetrate defenses by constantly changing their paths in flight and carrying decoy warheads to deceive the enemy. In the face of the development of sensor technology and sonar detection technology, it is likely that the range of SLBMs will be further increased to ensure battlefield survivability.
The second is to improve the accuracy of strikes. In order to form a deterrent capability for SLBMs, improving the accuracy of strikes is an important link. In the future, SLBMs are likely to use more advanced guidance means, including relying more on satellite guidance to achieve their goals, and using terminal active guidance to obtain the ability to strike moving targets.
The third is to improve the degree of versatility. The generalization of weapons can improve the battlefield support capability and the effectiveness of the use of weapons, and the development of submarine-launched ballistic missiles may also develop in this direction. The universalization rate of components between Russia's "Yars" and "Topol-M" land-based ballistic missiles and the "Bulava" submarine-launched ballistic missiles is 30 percent.
Fourth, it is necessary to improve anti-interception capabilities. Intercepting ballistic missiles in the booster stage is the focus of research and development by major powers. In order for SLBMs to form a deterrent, it is necessary to improve the anti-interception capability of the booster stage. For example, Russia's "Topol-M" and "Bulava" both use rapid-ignition booster technology, which not only reduces the infrared and laser characteristics of the missile in the booster stage, but also effectively shortens the flight time of the booster stage of the missile.
Fifth, there has been a change in the warheads carried. On the one hand, there is the low-yield nuclear warhead quantification, and some countries are trying to lower the threshold for the use of nuclear weapons, such as the United States is adding low-yield nuclear warheads to the "Trident" II missile, and the United Kingdom has also deployed low-yield submarine-launched ballistic missile nuclear warheads. This is a dangerous start, and it is likely to lead to a strategic miscalculation. For example, the United States is studying how to make the "Trident" missile carry a conventional warhead, so that it can use a submarine-launched ballistic missile in a conventional war, so that it can have both tactical strike capability and strategic deterrence capability.
(Produced by the People's Liberation Army Daily, China Military Horn)