By: Ryan Neuhard, Columnist
Photo by: Navy Times
Improvements in submarine detection capabilities are eroding the stealth that US submarines rely upon for survival.[[i]] Advances in instrument sensitivity, data processing, robotics, seabed infrastructure, and communications technology underpin these improvements.[[ii]] As these capabilities begin to expose US submarines to anti-submarine forces, the United States may need to reconsider how it designs, equips, and deploys its submarine fleet.
Advances in instrument sensitivity and data processing are making it possible for anti-submarine forces to pick out increasingly subtle signatures from background noise. Key instruments include passive sonars, active sonars, synthetic aperture radars, and magnetic anomaly sensors. [[iii]] These sensors detect submarine noise emissions, hull material, surface wakes, and magnetic field disturbances. More powerful computers and data processing algorithms capitalize on these sensors’ increasingly granular data by refining data and identifying obscure patterns. [[iv]]
The development of robotics, seabed infrastructure, and underwater communications are now providing opportunities to integrate these capabilities into large detection networks. These networks can incorporate mobile unmanned underwater vehicles, fixed seabed and buoy sensors, and potentially independent commercial infrastructure, like sensors monitoring fish stocks.[[v]] Real-time underwater communication systems can then exchange information between these sensors to pinpoint submarines and alert anti-submarine forces.[[vi]]
Among our competitors, China may be emerging as the pacing challenger. After decades of emphasizing land warfare, China is now attempting to develop its naval forces — and this includes anti-submarine capabilities.[[vii]] Much of China’s recent activity has involved building up its fleet of anti-submarine ships and aircraft.[[viii]] Perhaps more importantly, China has also begun rolling out the unmanned systems and network capabilities needed for next generation submarine detection.[[ix]] While it is difficult to track the progress of military research and development efforts, there are periodic reports of sensor and computing breakthroughs that could be applied to submarine detection, which suggests China is making progress.[[x]] This growing interest in anti-submarine capabilities aligns with the Chinese government’s broader interest in expanding China’s ability to project maritime power and pursue objectives like the Belt and Road Initiative, the South China Sea claims, and Taiwan reunification.[[xi]] Given this strategic outlook, we can expect China to continue developing its anti-submarine capabilities for the foreseeable future.
Effect on Future Operations
The United States has several options for responding to the detection problem. First, the United States can develop future submarines designs that further reduce sound emissions, sound and radio wave signatures, and magnetic field disturbances. Second, the United States can outfit submarines with additional defensive countermeasures to make them more resilient to attack when exposed. Third, the United States can shift submarines from a frontline role to a standoff role.
Current submarine designs emphasize sound dampening and hydrodynamics. These designs help reduce the sound emissions and surface disturbances that alert passive sonars and active radars. Developing even quieter propulsion and engine designs can help submarines stay ahead of improving passive sonar systems, while drag-reducing designs can help submarines reduce wake and evade active radar. [[xii]] However, these design priorities do not address the submarine’s visibility to active sonar or magnetic anomaly sensors. To defeat active sonar, submarines can experiment with hull shapes and coatings that improve the absorption or deflection of sound waves. [[xiii]] To defeat magnetic anomaly sensors, future designs can reduce the amount of magnetic materials used in a submarine’s construction or attempt to use magnetic cloaking techniques to reduce a submarine’s signature. [[xiv]]
The United States can also anticipate an increase in detection and outfit submarines with better means to defend themselves. Countermeasures can include improved jammers, decoys, and interceptors, as well as unmanned support vehicles and counterattack capabilities. Improved jammers and decoys can disable or divert anti-submarine weapons’ homing systems, while interceptors can destroy the weapons before they reach the submarine. [[xv]] Unmanned underwater vehicles can be used to form a defensive perimeter around the submarine to detect and neutralize approaching threats before they come into range of the submarine, much like an aircraft carrier’s escort ships. The submarine can also expand their torpedo and missile armaments, at the expense of long-range land-attack weapons, in order to better retaliate against air, surface, and subsurface threats.
US submarines could also shift from frontline combat and surveillance roles to backfield coordination and host roles. A recent report from the Center for Strategic and Budgetary Assessment outlined what this transition might look like and drew parallels to the role of today’s aircraft carriers. [[xvi]] In the future, submarines could avoid operating in high-risk waters accessible to enemy forces and instead serve as a mothership for smaller, more expendable unmanned underwater vehicles that could conduct the high-risk, frontline missions. The submarine could also serve as a communication hub for processing and distributing information gathered by the unmanned vehicles’ sensors. The Navy’s recent experiments with submarine-launched unmanned vehicles and the Navy’s unmanned vehicle-related requirements for future attack submarines suggest that the United States may already be moving toward this model of operations. [[xvii]]
As US competitors continue developing and fielding advanced submarine detection capabilities, the United States will need to develop innovative submarine designs, countermeasures, and doctrine, in order to maintain its advantage. This is an opportunity. By embracing new technologies and operational concepts, US submarines can chart a path toward a new era of submarine operations.
[[i]] Bryan Clark, “The Emerging Era in Undersea Warfare,” Center for Strategic and Budgetary Assessment, 22 January 2015, accessed 21 March 2018, http://csbaonline.org/research/publications/undersea-warfare.
[[iii]] Carlo Kopp, “Evolving ASW Sensor Technology,” Defence Today, December 2010, accessed 22 March 2018, https://www.ausairpower.net/SP/DT-ASW-Sensors-Dec-2010.pdf.
[[iv]] Bryan Clark, “The Emerging Era in Undersea Warfare,” Center for Strategic and Budgetary Assessment, 22 January 2015, accessed 21 March 2018, http://csbaonline.org/research/publications/undersea-warfare.
Example of algorithm enhancing passive radar capabilities:
Wentao Fan, Xinhua Zhang, and Biao Jiang, “A New Passive Sonar Bearing Estimation Algorithm Combined with Blind Source Separation,” Institute of Electrical and Electronics Engineers, 29 July 2010, accessed 21 March 2018, http://ieeexplore.ieee.org/abstract/document/5532922/.
[[v]] Application of networked unmanned underwater vehicles:
Paolo Braca, Ryan Goldhahn, et al. “Distributed Information Fusion in Multistatic Sensor Networks for Underwater Surveillance,” Institute of Electrical and Electronics Engineers, 12 May 2015, accessed 21 March 2018, http://ieeexplore.ieee.org/document/7105827/.
Application of fixed sensor networks:
Steven Stashwick, “US Navy Upgrading Undersea Sub-Detecting Sensor Network,” The Diplomat, 4 November 2016, accessed 21 March 2018, https://thediplomat.com/2016/11/us-navy-upgrading-undersea-sub-detecting-sensor-network/.
Concern about “inadvertent detection by non-military sensors”:
Bryan Clark, “The Emerging Era in Undersea Warfare,” Center for Strategic and Budgetary Assessment, 22 January 2015, accessed 21 March 2018, http://csbaonline.org/research/publications/undersea-warfare.
[[vii]] “Although progress in anti-submarine warfare (ASW) is less pronounced, there are indications that the PLA(N) is committed to addressing this gap… Over the next decade, China is likely to make gains in ASW, both from improved sensors and operator proficiency.”
Ronald O’Rourke, “China Naval Modernization: Implications for U.S. Naval Capabilities — Background and Issues for Congress,” Congressional Research Service, 13 September 2017, accessed 25 March 2018, 2-5, 95-96, https://fas.org/sgp/crs/row/RL33153.pdf.
[[viii]] Franz-Stefan Gady, “China’s Navy Inducts 2 More Sub Killer Stealth Warships,” The Diplomat, 30 December 2017, accessed 25 March 2018, https://thediplomat.com/2017/11/chinas-navy-inducts-2-more-sub-killer-stealth-warships/.
Ankit Panda, “China Deploys Advanced Anti-Submarine Warfare Aircraft to South China Sea Air Base,” The Diplomat, 26 July 2017, accessed 25 March 2018, https://thediplomat.com/2017/06/china-deploys-advanced-anti-submarine-warfare-aircraft-to-south-china-sea-air-base/.
[[ix]] Ankit Panda, “China Unveils New Unmanned Surface Vehicle, Claimed to Be the World’s Fastest,” The Diplomat, 18 December 2017, accessed 25 December 2018, https://thediplomat.com/2017/12/china-unveils-new-unmanned-surface-vehicle-claimed-to-be-the-worlds-fastest/.
Steven Stashwick, “New Chinese Ocean Network Collecting Data to Target Submarines,” The Diplomat, 2 January 2018, accessed 25 March 2018, https://thediplomat.com/2018/01/new-chinese-ocean-network-collecting-data-to-target-submarines/.
[[x]] Example of new Chinese magnetic anomaly sensor:
David Hambling, “China’s quantum submarine detector could seal South China Sea,” New Scientist, 23 August 2017, accessed 21 March 2018, https://www.newscientist.com/article/mg23531404-400-chinas-quantum-submarine-detector-could-seal-south-china-sea/.
[[xi]] Chinese President Xi Jinping highlighted these objectives in his recent speech at the 19th Party Congress.
Xi Jinping, “Secure a Decisive Victory in Building a Moderately Prosperous Society in All Respects and Strive for the Great Success of Socialism with Chinese Characteristics for a New Era” [The Work Report for the Chinese Communist Party’s 19th National Congress], Xinhua, 18 October 2017, accessed 25 March 2018, http://www.xinhuanet.com/english/special/2017-11/03/c_136725942.htm.
[[xii]] Example of a quieter propulsion system (an electric-drive propulsion train) to counter passive sonar:
Example of drag-reducing technology (an electromagnetic “water cloak”) to counter wake-tracking radar:
Ken Kingery, “Electromagnetic Water Cloak Eliminates Drag and Wake,” Duke University Pratt School of Engineering, 11 December 2017, accessed 25 March 2018, http://pratt.duke.edu/about/news/water-cloak.
[[xiii]] Example of improved sound-absorption coating:
Jessica Thomas, “Synopsis: Thinner Stealth Coatings,” American Physical Society, 6 January 2015, accessed 25 March 2018, https://physics.aps.org/synopsis-for/10.1103/PhysRevB.91.020301.
[[xiv]] Example of non-magnetic materials for submarine construction (Soviet Titanium hull):
Carlo Kopp, “Evolving ASW Sensor Technology,” Defence Today, December 2010, accessed 22 March 2018, https://www.ausairpower.net/SP/DT-ASW-Sensors-Dec-2010.pdf.
Example of magnetic cloaking technique:
Tushna Commissariat, “How to Hide from a Magnetic Field,” Physics World, 22 March 2012, accessed 25 March 2018, https://physicsworld.com/a/how-to-hide-from-a-magnetic-field/.
[[xv]] Example of interceptor:
Sam LaGrone, “Navy Develops Torpedo Killing Torpedo,” U.S. Naval Institute News, 20 June 2013, accessed 22 March 2018, https://news.usni.org/2013/06/20/navy-develops-torpedo-killing-torpedo.
Example of decoy capability:
“CANTO for Submarine: Anti-Torpedo Countermeasure,” Naval Group, accessed 22 March 2018, https://www.naval-group.com/wp-content/uploads/2017/01/canto-for-submarine-anti-torpedo-countermeasure.pdf.
[[xvi]] Bryan Clark, “The Emerging Era in Undersea Warfare,” Center for Strategic and Budgetary Assessment, 22 January 2015, accessed 21 March 2018, 17, http://csbaonline.org/research/publications/undersea-warfare.
[[xvii]] Franz-Stefan Gady, “Confirmed: US Navy Launches Underwater Drone from Sub,” The Diplomat, 24 July 2015, accessed 25 March 2018, https://thediplomat.com/2015/07/confirmed-us-navy-launches-underwater-drone-from-sub/.
At the Naval Submarine League’s 2016 symposium, the Navy’s Program Executive Officer for Submarines, Rear Admiral Michael Jabaley, mentioned that a key feature of the Virginia-class’s successor would be the capability to “seamlessly integrate, deploy and employ unmanned vehicles.”
Megan Eckstein, “Navy Seeking Unmanned Under-Water Advances to Field Today, to Inform Next Generation Sub Design in 2020s,” United States Naval Institute, 31 October 2016, accessed 25 March 2018, https://news.usni.org/2016/10/31/navy-seeking-uuv-advances-to-field-today-to-inform-ssnx-design-in-2020s.