Question: What do China, the Baltic and Russia have in common? Answer: seabed warfare.
There may not be any agreed definition – yet – of ‘seabed warfare’, but examples of what it might entail are increasingly making the headlines. From Baltic gas pipeline explosions and cutting of undersea communications cables to the revival of Cold War spy submarine programmes in the US and the development of Chinese underwater gliders – all evidence that the underwater space has become the new frontier.
But operating in this space remains a significant challenge as salinity, temperature, bathymetry and nature of the seabed all affect acoustic communications. Yet it is precisely communications that enable underwater operations, be it for cooperation or navigation purposes. In such context and contested space, industry and navies alike are working on the development of technologies and Concepts of Operations (CONOPS) that require thinking outside the box – or rather, the water.
Putting ‘warfare’ in ‘seabed’
The technological advances of the past decades have, unquestionably, transformed the seabed into one of the most strategic spaces of our planet. Beyond undersea communications cables, known to carry 99 percent of international data and internet traffic, and gas pipelines, which provide several countries with critical energy resources, the seabed is now also at the heart of the world’s energy transition. The offshore wind market, which continues to grow year on year, depends on the seabed not only for the cables connecting offshore wind farms to shore, but also for the rare earth materials indispensable for wind turbines’ construction.
In such context, the past decade has seen the transformation of the seabed into one of the most contested areas at sea.
In some locations, like the Baltic Sea, the main issue is the protection, or lack thereof, of critical undersea maritime infrastructure. On 26 September 2022, the Nord Stream gas pipelines, located in the Baltic Sea and supplying gas to Germany, exploded. On 8 October 2023, a leak in the Baltic Connector gas pipeline, which connects Sweden and Finland, was revealed and the pipeline was shut down. Recent reports indicate that telecommunications cables may also have been severed in the same incident.
While no definitive answer has been given as to the perpetrators of both of these attacks (the former has been successively attributed to Russia and then Ukraine, while the latter reportedly involved Russian and Chinese ships working in concert), they have nevertheless prompted NATO to significantly increase patrols in the area to prevent further incidents. On 12 October 2023 NATO and Allied forces also launched the Digital Ocean Initiative, which will enhance maritime surveillance from space to seabed.
In other areas, such as the Indo-Pacific, two different types of activities around the seabed have been the root cause of regional tensions. First, China has been significantly proactive in mapping out regional ocean floors, deploying underwater gliders in the South China Sea and hydrographic vessels in the Indian Ocean. Second, China’s interpretation of and/or respect for the United Nations Convention of the Law of the Sea (UNCLOS) has been at the centre of multiple regional diplomatic incidents.
UNCLOS stipulates that, within their territorial sea (up to 12 nautical miles from the coast), coastal states regulate any activity undertaken on the seafloor and have the power to refuse innocent passage if some activities are deemed to prejudice the coastal state’s defence or security – including research or hydrographic surveys. As such, over the past decade, China has been busy building artificial islands that aim to significantly extend its territorial sea and Exclusive Economic Zone (EEZ), where UNCLOS also grants multiple rights. The Asia Maritime Transparency Initiative counts 20 Chinese outposts alone in the contested areas of the Spratly Islands, the Paracel Islands and the Scarborough Shoal. Over the last months, there have also been multiple reports of altercations between Chinese ships and Filipino coast guard and navy vessels.
Thinking outside the water
For centuries the underwater domain was the prerogative of submarines. “These systems were solitary hunters that received an initial order and then went off on their mission,” Thierry Petit, operational expert at Naval Group, told Armada International. Communication with the world above the surface, if any, was minimal. Today, submarines have company. In addition to divers, mostly employed for mine warfare and covert missions, Unmanned Underwater Vehicles (UUV) are becoming an important feature of the underwater space.
As seabed warfare becomes a critical focus for several navies across the world, this trend is set to continue. In fact, taking example from the Oil & Gas (O&G) industry, these navies are looking at UUVs and Remotely Operated Vehicles (ROV) to extend their Maritime Domain Awareness (MDA) capabilities.
“This has transformed the underwater battlespace from one where platforms did not want to communicate and be found to one where communication has become critical to MDA,” Ioseba Tena, commercial director at Forcys, told AMR. A sentiment echoed by Petit, who added: “In the underwater domain we continue to talk extensively about platforms, such as submarines, UUVs, buoys, but these only have an added value if they can communicate while retaining stealth.”
Yet communicating in the underwater domain remains challenging. Acoustics continue to represent the primary means for underwater communications, but salinity, water temperature, pressure, bathymetry and seabed composition all contribute to affecting range and bandwidth. This translates into a constant operational compromise: low frequencies allow longer ranges, typically up to 27 nautical miles (50km) but severely limit the quantity of information that can be transmitted; higher frequencies enable higher bitrates but at much shorter ranges (generally over 5nm/10km).
“Depending on whether platforms will operate in coastal or blue waters, these problems will be exacerbated,” said John Camin, senior manager at L3Harris. In blue waters there are areas where the sound bends downward, impeding the propagation of sound between two points, whereas in shallow coastal waters, acoustic waves bounce around different surfaces resulting in weaker signals.
Similarly, navigation is challenging because there is no such thing as a GPS underwater. Underwater systems rely on acoustic waves to measure attitude and position. “The problem, however, is the doppler shift resulting from issues with the speed of sound underwater,” Camin explained. As sound travels, frequencies change thus affecting the accuracy of positioning. “The same issue also affects the ability of UUVs to communicate with each other as they navigate.”
“In such complex environment, developing adequate underwater communication [and navigation] systems is only possible if operational needs and profiles are well defined,” Petit concluded. This includes defining range, bandwidth, stealth and reliability for each platform and system. “It also means defining how much data should be or needs to be communicated, as well as when and how,” Tena added.
Multi-domain submarines
“Today submarines are fully integrated into the naval force, which means that communication between submarines and other platforms, such as frigates and potentially Maritime Patrol Aircraft [MPA], is not only more frequent but also both downlink and uplink,” Petit explained.
But if a submarine’s main advantage is its stealth, how can these systems safely communicate with other platforms in the naval force? Strange as it might sound, one way submarines can communicate critical information about underwater domain awareness is through SATCOMs: the submarine moves up to periscope depth, hoists the SATCOM antenna and transmits critical information to ships, MPAs and/or shore. “Currently, a submarine’s main SATCOM link works in L-band, a legacy band that is not only narrow but is also no longer a match for the satellites that now function with Ku and Ka bands,” Asaf Punis, VP global marketing and Business Development at Orbit Communications Systems, told AI. Additionally, issues of real estate space in a submarine mast have to be taken into consideration as the number of critical systems continues to increase.
To address these challenges, Orbit has been working to transform its airborne SATCOM antennas into systems that can be integrated into Unmanned Surface Vehicles (USVs) and, in the future, submarines. “The MPT30WGX is ideal, given the constraints of a submarine, because its circumference is only 11.8 inch (30cm) and it is a proven, ruggedised technology,” Punis commented. Additionally, the MPT30WGX features low power consumption, another important characteristic for a submarine. Orbit is currently looking for partners for the integration of the MPT30WGX in the mast.
Over the past few years, industry has also been working on using submarine-launched UAVs and buoys to increase the amount of data shared between submarines and other platforms, both uplink and downlink.
At DSEI 2023, for instance, SpearUAV showcased a new capsule designed to enable of the launch of the company’s Viper 750 UAV from the 4inch (10cm) signal ejector featured on most submarines and underwater platforms around the world. The capsule is programmed to either automatically release the UAV upon reaching the surface or release it at a pre-programmed/pre-agreed time. “The latter would give the submarine enough time to leave the area of operations and avoid detection, since the capsule has been designed to sink once the UAV is released,” explained Itamar Ben-Tovim, chief business development officer at SpearUAV. The UAV then enters into contact with other platforms to deliver the information.
Similarly, Naval Group has been working with Alseamar to develop submarine launched buoys that can release the information at a pre-established Radio Frequency (RF) once they reach the surface. “The same can work the other way around,” Petit told AI: at a pre-established time and place, a submarine can launch a buoy that then deploys its acoustic sensor to enable communications with a submarine or UUV.
The key, in this CONOPS, is to be able to transform acoustic waves into RF, and vice versa. It is in this context that L3Harris offers its CUUUWi (Communicating Using Underwater Ultrasonic Wireless) communication gateway. “The CUUUWi communicates at high rates with RF and then down samples the information to rebroadcast it underwater,” Camin explained.
Finally, in order to overcome the challenge that environmental issues pose to underwater communications, DSIT has developed a computer controlled acoustic communication solution. “The way we are controlling the acoustic signal is changing,” Capt. Ziv Rom, marketing/BD and Naval Warfare Systems director at RAFAEL stated: “we are now testing the underwater environment in real time to adjust the way in which we are transmitting data into the water.” To achieve this, DSIT uses a pre-determined algorithm based on a table providing information on optimal data transmission according to temperature, depth and salinity. “Using the algorithm, the computer automatically adjusts transmissions in real-time to enable longer range transmission,” Rom added. Thus far the system has been developed and integrated to enable transmission of text between submarines and surface ships as well as divers up to 5.3nm (10km).
Integrating UUVs
“In the present geopolitical climate, navies are already stretched, busy with multiple missions around their territorial waters, regions and/or the world and limited by budget constraints, so UUVs and ROVs are the ideal solution to try to ensure a near-constant monitoring of the seabed,” said Rear Admiral Cédric Chetaille, deputy commander in charge of seabed warfare for the French Navy, during the second edition of the Euronaval Talks on 28 September 2023.
UUVs, ROVs and USVs (surface) have already become the focus of much research & development (R&D) in the Mine Countermeasure (MCM) domain and the O&G sector over the past decade. Yet while these advances clearly represent a strong basis to build on, the CONOPS within which they have been used are quite different and, therefore, less constrained by the challenges of underwater communications and navigation.
Communications, for instance, are less problematic for MCM and O&G infrastructure protection because the systems are either tethered, in constant contact with fixed beacons or simply relay the information once the mission is over. “The difference with navies is that they need to think about how to use these systems to rapidly survey vast areas and quickly (preferably covertly) alert of any anomalous activity,” Tena explained. As such, the key question for navies is: how much do they wish to communicate, to whom and how?
Increasingly, industry leaders are working on the ability of UUVs to work in swarms and communicate with one another. This presents two challenges. First, as Dr Bruce Russell, head of mission systems at BMT, wrote to AMR: “Increasing use of UUVs will make the underwater communication frequencies potentially more congested.” To address this issue, L3Harris has developed the MASQ, a third-generation multi-channel spread spectrum technology. Emulating the technology allowing cell phone towers to process multiple cell phone individual codes at the same time, MASQ assigns each UUV a unique individual code that allows communication between multiple UUVs or between UUVs and a bay station.
Second, UUVs communication is also closely linked to their ability to position themselves within the underwater space, which is impaired by the doppler shift they experience as they navigate. One key technology on which the commercial sector depends to mitigate this issue is Ultra Short Base Line (USBL) systems. “While such technology is ubiquitous to the commercial domain, it has yet to gain more traction in the defence industry,” Tena said.
Nevertheless, some emerging concepts and solutions are also integrating USBL. French SME ArkeOcean, for example, has developed Proteus, a solution to enables UUV swarms by building on three interconnected systems. INCA UUVs drift in the ocean in swarms and share the information they gather with their large synthetic receiving antennas through the MAYA UUVs, which act as data relay with surface assets. The presence of a USBL on the MAYA is what allows INCAs to continue evolving as a swarm – possible only with constant precise positioning – by recalibrating every time the MAYA surfaces. The SEAKER is the acoustic system that enables the MAYA to dock onto the INCA.
Finally, as noted by Dr Russell, “cyber security/encryption of signals will also need to be designed into network solutions.” To this end, Sonardyne has been leading a technical programme to develop Phorcys, a high-integrity secure waveform for acoustic communications. The critical element of the programme is that the standard – Phorcys – is not classified, enabling access by multiple users; what is classified is the key necessary to decode the cryptographic keys that ensure the protocol is secure-by-design. In parallel, L3Harris is working on the SDAC (software defined acoustic communications), a next generation modem that will allow customers to use multiple protocols, including JANUS and Phorcys.
Swimming ahead
Because of the environment’s inherent complexity, underwater communications are first and foremost about tactics. Technologies, to date, are developed to facilitate those tactics as the physics of the underwater domain continue to largely constrain decision-makers to a constant compromise: range versus bandwidth.
While for now acoustics remain the communication technology of choice, often supplemented by RF through the use of surface relays, industry leaders are also exploring other options. Naval Group, for instance, is currently looking into different uses of fibre optic cables. “One option would be to have a fibre optic cable connecting the UUV to its ‘mothership’ in order to relay large quantities of data very fast at relatively long distances,” Petit said. Fibre optic cables as long as 50km are already being used for modern torpedoes. “Another option would be to exploit seabed fibre optic cables,” Petit continued. This would be a sort of undersea ‘WiFi’ that would facilitate information sharing between UUVs and cables at very close range.
As is the case in multiple military domains, the use of quantum technologies is also being explored. “Quantum technologies could be used, for instance, to better model communications paths via different means, such as acoustic/RF/optical,” Dr Russell added. Thales, on the other hand, is looking at quantum technologies to enable the development of smaller antennas with larger bands to provide ultra-low frequency communications with a longer range. “This would be key for UUVs where optimal SWAP is critical,” Marc Delorme, Director of unmanned underwater warfare and seabed warfare projects teams at Thales, told AI.
“Currently industry and navies alike are looking at communications as a niche and are developing solutions for niche applications, but underwater communication is much bigger than that,” Tena concluded. “It requires a strategy about how UUVs will communicate underwater, their interoperability, and how much information should be shared,”. In other words, seabed warfare is putting the strategy into underwater communications.
by Dr. Alix Valenti
