Navy operations require connectivity among a diverse set of platforms, including submarines, surface ships, aircraft, and shore sites. The links among these platforms support a wide range of applications, including command and control, battle management, the dissemination of common operational and tactical pictures, sensor-data dissemination, the tracking and engagement of time-sensitive and other targets, and many other C4ISR functions.
The capability of Russia and China to disrupt American military wireless and satellite communications using electronic warfare has been rising. One of the measures Defense Department is taking is to develop a rapidly deployable high speed backup data network . DARPA has developed a network of “radio relay mounted on sea buoy”, deployed from ships or planes, that are tethered together by fiber optic cables to create data network.
DARPA’s Tactical Undersea Network Architecture (TUNA) program recently completed its initial phase, successfully developing concepts and technologies aimed at restoring connectivity for U.S. forces when traditional tactical networks are knocked offline or otherwise unavailable. The program now enters the next phase, which calls for the demonstration of a prototype of the system at sea.
One of the challenge was to supplying power to floating buoy nodes on the open sea. The University of Washington’s Applied Physics Lab (APL) developed a unique concept called the Wave Energy Buoy that Self-deploys (WEBS), which generates electricity from wave movement. The WEBS system is designed to fit into a cylinder that could be deployed from a ship or aircraft. Another challenge is to develop very-small-diameter fiber-optic cables that are designed to last 30 days in the rough ocean environment—long enough to provide essential connectivity until primary methods of communications are restored.
“Phase 1 of the program included successful modeling, simulation, and at-sea tests of unique fiber-cable and buoy-component technologies needed to make such an undersea architecture work,” said John Kamp, program manager in DARPA’s Strategic Technology Office. “Teams were able to design strong, hair-thin, buoyant fiber-optic cables able to withstand the pressure, saltwater, and currents of the ocean, as well as develop novel power generation concepts.”
Having now entered its second and final phase, the program is advancing to design and implement an integrated end-to-end system, and to test and evaluate this system in laboratory and at-sea demonstrations. As a test case for the TUNA concept, teams are using Link 16—a common tactical data network used by U.S. and allied forces’ aircraft, ships, and ground vehicles.
The Tactical Undersea Network Architectures (TUNA) program seeks to develop and demonstrate novel technology options and designs to for existing tactical data networks in a contested environment using small diameter optical fiber and buoy relay nodes. “SATCOM has its limitations. Signal isn’t always available, and there are constraints on the speed and volume of communications.” “The goal of the DARPA’s Tactical Undersea Network Architectures (TUNA) program is to ensure that US forces retain an information advantage even in contested environments where potential adversaries may attempt to disrupt other communication channels,” said LGS Innovations CEO Kevin Kelly.
One of the important component of U.S. Navy’s, maritime strategy is “All Domain Access”. One of its five pillars is Assured command and control, which requires US communications networks to operate reliably and securely in the face of enemy jamming and hacking.
Navy is also developing optically tethered communications buoys for communications with military satellites, a retrievable tethered fiber optic buoy for communications and surveillance between submarine and satellite. Navy is also developing an integrated Network of distributed and netted sensors with unmanned underwater vehicles (UUVs), submarines, and surface and aerial platforms. The objective is to gain situational awareness of the undersea battlespace to locate and engage threats rapidly in littoral areas. The network elements shall be connected by mobile ad hoc network of wireless nodes that can function cooperatively and spontaneously without a fixed infrastructure.
In September, the Defense Advanced Research Projects Agency awarded a $1.9 million contract to LGS Innovations, a networking and communications solutions company, for phase one of the tactical undersea network architectures (TUNA) program. The company has two partners for the project: Linden Photonics, which specializes in high-strength fiber optic cables, and Tethers Unlimited, a private aerospace company. The team aims to “develop the world’s strongest neutrally buoyant undersea cable” for the network, an LGS press release said.
Tactical Undersea Network Architectures (TUNA)
The Tactical Undersea Network Architectures (TUNA) program seeks to develop and demonstrate novel optical-fiber-based technology options and designs to temporarily restore tactical data network connectivity in a contested environment.
The buoy nodes interconnect the tactical data network and manage the undersea fiber optic network. They function as relays and energy sources, and should be rapidly deployable from existing platforms such as Navy ships, submarines, and aircraft and have “plug, play and operate” functionality with tactical data and undersea fiber optic networks.
The first phase will involve modeling, simulations, scaled component technology development, and limited testing. An expected second phase will implement an integrated, end-to-end, scaled network prototype, with at-sea testing.
The prototype TUNA system will consist of the following minimum subsystems:
- An operational planning and management system;
- A scaled small diameter optical fiber ocean network deployable by commercial vessels or unmanned vehicles;
- Common interfaces that enable both network scale-up and the extension to non-TUNA systems; Link-16 or a representative tactical network with the information assurance needed for operations; and
- A capability for reconfiguration and restoration in the event of fiber failure.
TUNA emphasizes concept and technology development in three technical areas: system design, small fiber optic cable systems, and buoy nodes.
TA1: System Design
(System Design): TA1 seeks proposals for system designs and studies aiming to develop novel system architecture designs that integrate a military tactical data network into a rapidly deployable temporary undersea network. Proposers may offer integrated network and system architectures, deployment concepts, and concepts of operation and employment for the TUNA system.
“As soon as you put something underwater, that makes it automatically harder. You’ve got pressure, you’ve got things that swim in the ocean, you’ve got vessels. There are forces in the ocean. It’s a hostile environment. It will break everything it can,” said John Kamp, the TUNA program manager.
TA2: Lightweight, buoyant unpowered optical fiber technologies
TA2 seeks proposals for lightweight, buoyant unpowered optical fiber technologies capable of surviving deployment and operation in the ocean for at least 30 days.
Proposals are sought for innovative approaches that improve the survivability of small-diameter cables while reducing the volume and weight. Examples include methods to control cable buoyancy, reduce tension and shear loads on deployment, methods to reduce fiber losses, novel joining and repair technologies, and protective coatings. Specifically excluded are systems with an outside diameter greater than 2 mm, unmodified commercial fiber systems, and low-data rate.
Under the $1.9m contract, LGS will be responsible for the delivery of model simulations, design, and analysis, as well as scaled development and technology demonstration over a period of 15 months.LGS Innovations is collaborating with Linden Photonics and Tethers to develop the neutrally-buoyant undersea cable for an undersea fibre optic based network.
One of the main challenges “is the development of an undersea micro cable that simultaneously possesses small size, high strength, low optical loss and neutral-buoyancy, and is producible in long cable lengths,” Beyers said in an email. . To date, most undersea cables are big, heavy and expensive, he noted.
The cable LGS has proposed is based on a commercial offering by Linden Photonics called “strong torpedo fiber optic cable,” Beyers said. LGS proposed changes in design and fabrication that would enable the product to better meet the military’s needs, he said. The cable uses a highly resistant liquid crystal polymer to improve strength.
Effectively, it’s a glass tube doctored with rare-earth minerals that are amenable to conducting light without distortion, then encased in nylon and Teflon and Kevlar to strengthen it, to keep it from stretching or bending or getting severed. “But the real engineering is in placing the right amount of air bubbles in all of that mixture, so that you get something that floats,” said LGS’s CEO Kevin Kelly.
TA3: Buoy nodes
Makai has been selected for a DARPA Phase 1 contract that is focused on developing cable related components of the buoy node; a subsystem of the overall TUNA program.
Initially, Makai’s work will be focused on modeling the hydro-mechanics of the small diameter fiber optic cable and buoy relay nodes under realistic dynamic, time varying, 3D environmental scenarios. Based on the modeling results, Makai will design and develop the hardware for an innovative inter-buoy cable management system to minimize tensile loads on the inter buoy cables as well as potential entanglement issues.
DARPA envisions a second phase to implement an integrated end-to-end network prototype, and to test and evaluate this system in a laboratory setting, simulations and at-sea demonstrations.