Anyone involved in the study or practice of naval warfare can attest to the prowess of submarines. While neither the flashiest nor most “visible” components of a navy, submarines are unique in their ability to provide access to contested regions. While surface ships are easy to spot and detect, modern submarines have proven very difficult to track. This means they can infiltrate areas that are heavily defended by anti-access/area denial (A2/AD) defenses much more easily than a surface fleet can. This article will focus on the Virginia-class nuclear attack submarine specifically.
Surface combatants often have a hard time balancing defense and offense. If a surface vessel devotes too many launch tubes to defense, it will find itself unable to strike effectively. Conversely, if too many tubes are used for offensive missiles, the vessel may find its defenses overcome in a large scale attack. The more sophisticated and proliferate anti-ship missiles become, the more space must be devoted to defensive armaments, leading to a shortcoming in offensive firepower.
Submarines offer a solution. Impervious to anti-ship missiles and generally difficult to eliminate, submarines have little need for defensive armaments. As such, submarines are able to allocate space to other critical systems such as propulsion and offensive weaponry. However, most of the world’s submarines are unable to take full advantage of their stealth because of limited offensive armament. The US Virginia-class nuclear submarines currently only carry 12 Tomahawk missiles in two 6-missile tubes. Thus, Virginia-class submarines could provide a stealthy, highly mobile missile platform, but often do not carry a large missile armament.
In addition to the Tomahawks, these boats have heavyweight torpedoes for engaging surface ships and other subs, the primary task of hunter-killer submarines. While these torpedoes are highly lethal against ships and other submarines at close range, they are of no use against shore-based systems or vessels at long range. In response to attack submarines’ shortcomings in long-range missile firepower, the US Navy has decided to field the Virginia Payload Module (VPM). The VPM is a hull module which will be spliced into future Virginia-class nuclear attack submarines, adding extra payload space which can be used for missiles as well as other large-diameter cargo.
Giving Virginia-class boats missile capabilities is not a new concept. As mentioned, boats of the class already carry 12 Tomahawk cruise missiles in six-missile tubes. However, there are important distinctions to be made between the future VPM module and the current six-missile tubes. Most importantly, the current six-missile tubes are outside of the Virginia’s pressure hull. This means they cannot be accessed or serviced while the boat is underway, which precludes them from carrying any sort of advanced payload which may need to be maintained or inspected. Conversely, VPM tubes are fitted inside the pressure hull, allowing for easy access while underway. Second, the Virginia’s current six-missile tubes lack commonality with other submarine tubes already in use by the US Navy. The VPM tubes, on the other hand, are the same diameter as Ohio-class’s launch tubes, providing commonality. This means that the VPM tubes can carry the same loadouts as the four Ohio-class boats which have been converted into guided missile submarines. The VPM program also establishes a standard diameter for future US Navy payload tubes to use.
The increased missile armament will be welcome in intensive combat. But, the VPM’s payload configurations extend far beyond offensive missiles alone. Remarkably wide in diameter and accessible while underway, the VPM modules could be used for a myriad of other payloads, including unmanned undersea vehicles, or UUVs. UUVs are essentially underwater drones which can be launched from submarines, surface ships or planes. Like their aerial counterparts, UUVs vary greatly in size and capabilities. The smallest ones can be easily launched from a rigid-hulled inflatable boat and possess relatively low endurance. The largest require a large ship or submarine for launch and can operate autonomously for days, giving them remarkable capacity to patrol and gather information.
UUVs are increasingly sought after by commanders at sea. Currently, the US subsurface forces are falling short of their force requirements by significant margins, a problem exacerbated when submarines are utilized to do low-intensity operations. The submarine force also desires unmanned systems which can carry out risky missions without risking the loss of a manned boat. These two issues can be addressed through the usage of a UUV: the UUV is deployed to perform repetitive or dangerous tasks not ideal for the manned submarine, freeing up the manned boat to perform more demanding or less risky missions. In an era of budget crunches and shipbuilding fund shortages, UUVs seem like the ideal solution.
Current UUVs are launched from torpedo tubes, the small size of which limits complexity and endurance. The VPM allows for the employment of more sophisticated large-diameter UUVs by providing a cavernous space in which the UUV can be stowed, as well as offering access to the complex UUVs, which will likely require servicing and reprogramming while at sea. As large-diameter UUVs will likely prove the most useful in future operations, the VPM will be necessary to facilitate their launch and recovery.
By offering such a versatile payload addition to the Virginia-class boats, the VPM is an archetype of sorts for the US Navy’s engineering philosophy. VPM fits into the Navy’s “distributed lethality” program, as it places more offensive missiles on submarines, diversifying and bolstering the Navy’s pool of cruise missile platforms. It also facilitates the more mundane but increasingly common tasks: surveillance, asymmetrical duties, etc. While high-end and lower-end capabilities often cannibalize each other’s budgets, VPM shows how the two can co-exist in a single versatile package. Further, this sort of of dual-use solution is one the Navy will increasingly find itself compelled towards as adversaries evolve and budgets remain strained; VPM is likely just the start of a trend towards modular and versatile systems in the US Navy.