Navies historically have tried to procure surface combatants that can meet all the threats they must face, but the increasing cost of permanent-fit platforms has meant that even the most well-funded naval forces need to look at other options. A popular alternative is mission modularity, but while it can be useful in its proper place, overreliance on such an approach can lead into dangerous waters.
Why Make Fleets Modular?
The allure of mission modularity derives from its apparent simplicity. A navy acquires standard hulls with spaces or bays for installing mission modules—self-contained capability packages (often in something like a ruggedized shipping container) that hook into the hull’s systems and change its operational mode. The ship provides the basic services (such as power, water, and data exchange) and the module brings the capability, be it minesweeping, antisubmarine warfare, or uncrewed surface vessels. Once an operation is over, the ship can enter a friendly port to be reconfigured for a new mission by swapping out one or more of those modules.
In addition, the modules themselves can be upgraded with new or improved technology without modernizing an entire ship—the design and construction of the hull is decoupled from that of the modules.1 Exploring these emerging module technologies also reduces risk—creating or upgrading a module requires fewer resources, so a promising capability can be tested in the field without a bigger commitment to a new platform.
There also are more prosaic benefits around logistics and crewing. The maintenance burden can be shifted ashore, with modules being updated and maintained while off the ship without bringing the whole platform into port for the duration. Modules also can be stored safely when not in use and easily transported to where they are needed using existing infrastructure, particularly if they are within something akin to a shipping container.
A complex mission-module crew also can be trained ashore and deployed with their module rather than spending long deployments at sea with a particular ship. Furthermore, if mission modularity is implemented through standardized packages across a fleet, this can reduce sustainment costs, simplify personnel training, and streamline supply chains—all effects that could be scaled with standardization across allied fleets, such as within NATO.
Not All It Seems
Despite this seemingly overflowing basket of benefits, there also are significant potential downsides to a mission-modular approach that should not be overlooked by naval planners.2
The point of a modular approach is not to optimize a design for a particular requirement, but rather to attain acceptable performance over a wide range of requirements to give options.3 However, well-designed modular capacity needs to take into account the feasibility of the approach. While one theoretically could create a module version of just about any naval capability, not all will be worthwhile on a practical level. For example, consider an antiair system. While it would be possible to containerize a system such as Sea Viper, the ship hosting it would need to take on many modules that would all need to link into her command-and-control, power, and data systems. In addition, adding a radar component to an extant hull could cause problems with topweight given the need for a high mounting spot.4 A mine countermeasures capability is a better candidate, as it requires fewer modules and can easily provide access to the sea for smaller vehicles.5
If there is a push for mission modularity without considering feasibility, capabilities may be shoehorned into a modular package to their detriment. A compromised capability may be accepted just to fit in with a wider fashion for modularity, or because acquisition is solely focused on modules. The relative low-cost and flexibility of mission modules when compared with permanent-fit surface combatants is particularly enticing during times of budgetary restriction, and the temptation to solve every capability requirement with a mission module may prove to be too much.
A proper modular approach requires deep consideration of interoperability to fully realize the benefits in terms of flexibility and logistics. Rigorous and exacting requirements need to be set from the top down on module size, interfaces, command and control, and a host of other factors (a problem compounded if interoperability is extended to allied nations). This is a tough ask, as anyone who has ever tried to get a defense bureaucracy to make a decision will know. However, too much focus on interoperability can cause its own problems. If everything must be compatible with everything else on an open-architecture basis, one may be expecting too much of the defense industrial base, at least without a rise in bid prices for module-based contracts. The need to fit in with overarching requirements also may have a stifling effect on research and development—if your company’s new or improved capability cannot fit into the standard module structure and will thus not even be considered for acquisition, what is the point in developing it?
It also is important to remember that previous attempts at general-purpose platforms have not covered themselves in glory. The U.S. Army spent billions of dollars on Future Combat Systems—a program that was to include eight crewed vehicles with a common engine, chassis, and other components—before it was canceled in 2009.6 The commonalities intended for the Joint Strike Fighter also have not come to pass, with the final three F-35 variants sharing only around 20 percent of their parts because of their diverging operational needs.
Simplicity appears to be key—one of the most adaptable platforms in the U.S. arsenal is the B-52 Stratofortress, which has kept its relevance for more than six decades by essentially being a gigantic flying box. The more complex a platform, the more problematic a multimission approach becomes, and the more missions will be adversely affected by a failure in any one platform program.7
Step Away from the Panacea
Mission modularity is an enticing prospect. What navy would not want to be more flexible, more adaptable, and more mission ready? While it has become cliché to describe the world as one of shifting sands and unprecedented threats, it is true, and navies and their sister services need to respond to this reality in a context of tighter budgets and fast-paced technological developments.
Modularity provides an answer that is easy to cling to, but navies may do so at the expense of wider and deeper conversations about force structure. The easiest choice to deal with a problem is to put out a contract for a new module, particularly when the alternative is reassessing wider acquisition decisions or investing in a larger number of permanent-fit hulls. If any new threat or capability requirement is brushed aside as another job for the modules, naval planners risk missing the bigger picture, which may lead to a fleet underprepared to meet an adversary or working with compromised capabilities. Mission modularity has its place within a modern fleet, but it is not a panacea.
A History of Mission Modularity
The originator of the mission- modularity concept was the Royal Danish Navy, with its Standard Flex (StanFlex) system. First conceived in the early 1980s, the StanFlex system was adopted in the Flyvefisken-class corvette, with slots for four modular packages ranging from antisurface missiles to minelaying to oceanographic survey.1 The driver for StanFlex was money—the Royal Danish Navy needed to replace 22 warships of three classes, but it could not afford to do so on a one-for-one basis, so it came up with the idea of building 16 multirole modular vessels (later cut to 14). It further developed this concept with the Absalon-class flexible support ship, which carries five StanFlex modules and has open deck space for containers or vehicles.2 In 2012, the Royal Danish Navy commissioned the first Iver Huitfeldt–class frigate, which has six StanFlex bays but no container space, bringing the number of ship classes able to use StanFlex modules to nine.
In the U.S. Navy, mission modularity came in the form of the littoral combat ship, both variants of which were designed with dedicated bays for modules in bespoke containers. The modularity was limited to three mission packages: antisubmarine warfare, mine countermeasures, and surface warfare against small boats. The modules were designed for quick installation and removal to allow for speedy hull reconfiguration, with open-architecture principles to facilitate future technology upgrades. While modularity was not the reason for the littoral combat ship’s troubles, no serving ship in either variant ever had its modules swapped out to reconfigure its mission.3 The three mission types also had conflicting needs in terms of survivability and maneuverability and with the overall stated requirement for high speed. Unlike a surface warfare ship, a minesweeper does not need to move quickly (and, indeed, speed may be more of a liability than an asset in such missions), and submarine hunting tends to benefit from larger hulls with quiet engines and embarked ASW aircraft.4 The littoral combat ship is a jack of all trades but a master of none.
The United Kingdom will begin its foray into mission modularity with the two frigate classes currently being constructed under the Global Combat Ship program. The Type 26 frigate can carry up to 11 containerized modules to support a variety of missions, as well as embarking a range of crewed and uncrewed air, surface, and underwater vehicles.5 The design is shared with Australia and Canada for their own procurement as the Hunter-class frigate and the Canadian surface combatant, respectively. The Type 31 frigate, or general-purpose frigate, is based on the design of the Iver Huitfeldt class and involves mission modularity as a more primary component. It will carry up to six containerized modules under its flight deck as part of a concept delightfully known as the Persistent Operational Deployment System (PODS), with capabilities including command and control, precision strike, equipment repair, and uncrewed vehicle launch.6
The Second Sea Lord outlined the Royal Navy’s vision for “podular” design in 2021, describing mission modularity as “the nirvana of capability flexibility” and envisaging PODS as a way to create standardized, interchangeable packages that put the capability in the module, not the hull.7 The Royal Navy’s 2022 Maritime Operating Concept expands on this, introducing the idea of a “Protean Maritime Force” that relies on interchangeable systems rather than platform optimization.8 This forms the backdrop to the forthcoming acquisition of the Type 32 frigate. Although a formal requirement for the program has not yet been issued, BAE Systems has put forward a concept known as the adaptable strike frigate. While the ship would be roughly the same size as a Type 31, the aft section could carry a wide range of capability modules, with a focus on autonomous/automated processes.9
Other European navies are also acquiring ship classes with modularity at their core. Forthcoming vessels with mission modular capability include: the Italian Pattugliatori Polivalenti d’Altura–class multirole offshore patrol vessel, which can carry up to 13 module containers in two mission bay areas; the German F126 multirole frigate, which carries similar containerized capabilities; and the Spanish F110 frigate, which carries mission modules including uncrewed vehicles and medical support.
1. RADM Søren Torp Petersen, RDN, Standard Flex 300: The True Multi-Role Ship (Danish Ministry of Defence, 1992).
2. Ron Pudduck, Jon Goodwin, and Richard Burston, “NATO Industrial Advisory Group (NIAG) Mission Modularity Studies,” INEC Conference Proceedings (2020).
3. Emma Salisbury, “Lessons from the Littoral Combat Ship,” War on the Rocks, 15 November 2021.
4. Joshua Hampson, “The Downside to Speed,” Niskanen Center, 27 September 2016.
5. George Allison, “The Type 26 Could Be the Most Capable British Warship in Decades,” UK Defence Journal, 16 June 2020.
6. Royal Danish Navy, “Think Differently: Persistent Operational Deployment Systems,” 2020.
7. VADM Nick Hine, RN, “When Is a Box Not a Box?” speech delivered at DSEI, 15 September 2021.
8. Royal Danish Navy, Maritime Operating Concept (2022), 10.
9. BAE Systems, “Adaptable Strike Frigate,” (2022).
1. Richard Logtmeijer et al., NATO Mission Modularity Cost-Benefit Analysis (Defence Research and Development Canada), October 2020.
2. See also Emma Salisbury, “Priors and Prejudice: Planning the U.S. Navy’s Future,” War on the Rocks, 24 June 2022.
3. Norbert Doerry and Philip Koenig, “Modularity and Adaptability in Future U.S. Navy Ship Designs,” (Washington, DC: Naval Sea Systems Command, 2017).
4. Raymond McConoly, “Sea Viper Is the Turning Point for the Anti Air Warfare,” Naval Post, 30 June 2021.
5. David Manley, “The NATO Drive to Mission Modularity,” conference paper for Warship 2018: Procurement of Future Surface Vessels, London, 11–12 September 2018.
6. Christopher Pernin et al., Lessons from the Army’s Future Combat Systems Program (Santa Monica, CA: RAND Corporation, 2012).
7. Joshua Hampson, “Modularity and Acquisitions,” Niskanen Center, 18 May 2016.
