November 2, 2016
Technological Disjunctures and the 21st Century Destroyer
The future of surface warfare requires cooperation across borders.
By Danny Lam
What are those major technical changes? The largest break comes from cheap and plentiful computing, networking and communications as a result of the commercial, off-the-shelf (COTS) revolution that began in 1990s. Electronics that have gained processing power with every generation of Moore’s law have become an enabler for across many domains. Increases in processing power have enabled sensors that can detect and tease out targets from the sea of noise. Weapons systems that are smart, accurate, countermeasure-resistant, and plentiful have replaced tonnage as the metric for effectiveness.
Finally, sensor- and software-enabled automation of navigation, propulsion, and even damage control have decreased the need for large crews. Technological changes also drive manning requirements. Up until recently, military vessels required much larger crews than comparable civilian vessels. Demands that are difficult to automate like damage control, at sea maintenance, operations and repairs of complex weapons systems and defense against low tech threats required large crews. Extensive automation of these functions enabled the USS Zumwalt (DDG-1000) to operate with a crew of about 140. An impressive reduction for a vessel with greater capabilities than several Oliver Hazard Perry-class frigates, but with a crew less than a single one, and less than half the crew of a Arleigh Burke-class destroyer. Lower manning requirements in turn translate into lesser requirements for cabins, sustainment, and spare crews.
Collectively, these changes brought about by electronics have been no less dramatic than the change from sail and black powder to steam, director fire control, sonar, and radar. Perhaps less appreciated is the coming shift away from guided missiles. Kinetic energy weapons with chemical propellants dominated much of the history of modern warfare. Today, lasers, rail-guns, and microwave weapons—science fiction in the 20th century—are maturing technologically. Lasers, microwave devices, and integrated circuits are now manufactured in mass quantities for consumer applications. This vast commercial volume has driven technologies faster than military applications could ever have in the past decades.
Proliferation of directed energy weapons and electronics technologies goes to the heart of a modern vessel: the nature of the demand for energy. For much of the 20th century, vessels were powered by machines that converted thermal energy (derived from fossil fuels or nuclear reactors) into mechanical energy to move the vessel, and a small amount of electricity for the rest. The advent of directed energy weapons and large radar arrays now favor an all-electric drive train. Rather than propulsion being the largest consumer, weapons systems will in the future be larger. Energy (however produced) in the form of electricity can be quickly and easily distributed and stored to be shared among competing demands for weapons, propulsion and sensors.
Traditional drivetrains based on either steam or gas turbines, diesel or CODOG, cannot offer the flexibility found in all-electric ships like the Zumwalt-class destroyers, and their staggering 58 megawatts of exportable power—out of a total of 78 MW—when cruising at 20 knots. The need to generate, distribute, store, and dynamically allocate electricity favors 4,000-volt circuits compared to the present 400-volt power bus. Energy storage devices for directed energy weapons are presently occupying substantial amounts of space. Such changes are difficult and costly to retrofit or implement in existing designs.
Unmanned air, surface, and subsurface platforms are likewise revolutionizing the endurance, reach, and persistence of a naval vessel. Unmanned aircraft are a game changer for smaller vessels. Rather than fielding one or two helicopters that have endurance measured in hours or parts of a day limited by crew fatigue, ships with unmanned platforms are limited only by weather and their fuel (or aerial refueling) capacity up to their required maintenance interval. Applying this to unmanned surface and subsurface craft, and it is apparent that many traditional destroyer missions like antisubmarine warfare can be more effectively handled by highly persistent and capable UxVs launched from a frigate or destroyer, rather than using a manned helicopter.
The mission of modern warships has also changed. Sea control, the historical primary mission for a navy, can no longer rely solely on carrier strike groups armed with short-range fighters. Carrier groups have been vulnerable to nuclear attack by ballistic missiles at least since the 1960s. While one can argue a plausible case for Russia or China exercising restraint in crossing the nuclear threshold in attacking an American carrier group, can that same calculation be made for a North Korean or Iranian regime fighting for its survival? As an alternative to a few, high-value carrier groups that are attractive targets, an alternative may be smaller and more numerous vessels that are substantially capable of using unmanned platforms to perform the same sea control function.
The new mission of sea-based ballistic missile defense (BMD) requires a large, missile-armed platform that can economically keep station within a limited area for extended periods of time, and withstand precision-guided salvo attacks on its own. Carrier strike groups, on the other hand, must move quickly and unpredictably for defense against the same attacks. Sea-based BMD has advantages over longer-range but fixed, land-based systems. Ships can moved to deal with different threats from land- to sea-based intercontinental ballistic missiles (ICBMs). Presently, only the Aegis combat management system both supports BMD and is well integrated with other BMD systems. Aegis for BMD requires physically large and heavy antennas that need high power and cooling to operate and risk destabilization of smaller vessels. Smaller, less sensitive versions fitted on existing hulls leave much to be desired in terms of capability, and in turn, require support from off-platform, networked resources to perform their mission. Moreover, anti-ICBM missiles require large “strike length” vertical launchers and sufficient quantities to defeat multiple targets and decoys, virtually ruling out smaller hulls.
Traditional sea control missions like mine hunting, submarine-hunting, suppressing piracy, search-and-rescue, and humanitarian relief require varying degrees of specialized equipment. In order to fit these requirements onto a modest hull, of perhaps 10,000 tons, some form of modularization will be required where pre-configured systems can be plugged into a hull. Modularization was pioneered by the Royal Danish Navy with the StanFlex system, and a similar concept was adopted by the US Navy for its littoral combat ships (LCSs). Newly-designed surface combatants compatible with pre-tested, stockpiled modules, uniformly used by allies, will bring major benefits.
The question of upgradeability is critical. Many systems that have been in use for decades have been superseded by improved variants. For example, Mark 57 vertical launch system (VLS) provide substantial improvements in survivability and maintainability, and are backward compatible with most munitions designed for later variants of Mark 41 VLS. Naval guns will be used for some time, but within five to ten years, conventional cannons are likely to be rendered increasingly obsolescent by directed energy weapons. A design that is readily upgradeable is thus crucial.
Perhaps the most important element of upgradeability is the ability of a vessel to readily adopt upgrades in electronics hardware, software, and network bandwidth. The Zumwalts pioneered the use of standardized ruggedized electronic modular enclosures (EME) that are protected against shock, vibration, and electromagnetic pulses, while providing power, security and cooling to the supported electronics. What’s more, should the EMEs’ protection prove inadequate, it is technically feasible to swap out the entire module for more ruggerdized versions, thus providing for both rapid technology and protection refreshes. Swappable modules are key to rapid repair of battle damage and rapid insertion of hardware upgrades.
A look at destroyer- and frigate-sized vessels “on-the-shelf” today reveal that there are really no designs that are ideally suited for this 21st century environment, or that even have many of the desirable features enumerated above. Most vessels do not have integrated power systems that can produce large amounts of exportable power. The US Navy's three Zumwalts, the only vessels with enough, are optimized for shore bombardment. These may be the easiest to convert for anti-ICBM missions, and potentially to support multiple batteries of rail guns and other directed energy weapons, for high survivability against salvos of precison weapons. The LCSs are too small and under-armed, and it is questionable that their speed is sufficiently advantageous enough to warrant the cost. There are risks that innovations pioneered on the Zumwalt—like the total ship computer environment, the EMEs, and the Mark 57 VLS—are presently found on no other vessels. They could potentially be risky dead-ends.
If an allied navy is to start from a clean sheet, the likely form factor that can support these roles will likely require at least 10,000 tons displacement. Power of nearly 100 MW, with ample space for energy storage, is conceivably necessary for multiple batteries of rail guns, lasers, and microwave weapons. At least 75 strike length VLS cells may be necessary for a mix of anti-ship missiles, air- and missile-defense missiles, land-attack missiles, and anti-submarine rockets. Extensive provisions for unmanned aircraft—that may include vertical launch— need to be considered. Such ships will still require provisions for at least one manned helicopter, and launch and retrieval of reusesable unmanned aircraft. With respect to the innovations pioneered on the Zumwalt, only the US Navy can give a clear indication as to whether the technologies have a future.
These issues speak to the need for navies to begin thinking of developing a new generation of vessels. Given the large investments required, there is a strong case to be made for a common design shared among most allied fleets. Economies can be realized if many designs can share common components including powertrains, hulls, and interchangeable features like mission modules, EMEs, and compatible interfaces for automation systems. The economics of technologically-intensive industries speak to how critical it is to have high volumes and common designs that can accommodate open source hardware and software upgrades seamlessly. The days when a major power, like even Britain or France, can afford proprietary designs may be over. The future is in sharing work with individual partners specializing in particular pieces.
Dr. Danny Lam is a defense researcher in Calgary.