Military planners say they are making headway on a means to quickly restore tactical data links, should they become disrupted.
Through the Tactical Undersea Network Architectures (TUNA) program, the Defense Advanced Research Projects Agency (DARPA) seeks to develop a rapidly deployable undersea network. The agency says a first phase drew promising ideas from a range of heavy-hitting vendors, and it expects to wrap up solicitations in January in anticipation of further developments and practical demonstrations.
Phase I brought together a veritable who's who of military contractors, with participation from Raytheon BBN Technologies, Northrop Grumman Systems Corporation Information Sector, LGS Innovations, Harris Corporation, and Lawrence Livermore National Laboratory, among others.
The outcome of hurling that much brainpower at the issue? "The short answer is, it is a hard problem, but it is technically feasible," said John Kamp, the TUNA program manager.
The problem has to do with disruption of tactical networks, something that can occur through enemy attack, force of nature or diverse other causes. As a solution, DARPA proposes a system of lightweight undersea fiber-optic cables, strung together between buoys.
While satellite connectivity can come to the aid of a distressed data network, SATCOM has its limitations. Signal isn’t always available, and there are constraints on the speed and volume of communications. Fiber optic is a robust alternative, but it, too, faces challenges, especially in an undersea scenario.
"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," Kamp said.
Phase I looked at three elements of the equation. Some vendors focused on systems design, including integrated network and system architectures, deployment concepts, information assurance, and reconfiguration and restoration. Others looked at the design of the buoy nodes meant to connect the tactical data network to the undersea fiber-optic network.
Other teams considered the fiber-optic cable systems, with efforts to develop small-diameter, lightweight unpowered optical fiber technologies capable of surviving deployment and operation in the ocean for at least 30 days.
LGS Innovations fell into this group of vendors, looking specifically at ways to make a cable that would be neutrally buoyant — that is, a cable that would float in the water at any given depth.
The company ultimately came up with a fiber slightly larger in diameter than a human hair. 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.
Floating is critical in the tactical scenario. First, a broken cable floating near the surface, supported between buoys, is easier to fix than one lying on the ocean floor. Floating cable can be cheaper, too, since you need less of it if you don’t have to drape it up and down miles of hills and valleys at the sea bed.
"If you could create a neutrally buoyant fiber, you’d need a much shorter length of fiber," Kelly said.
While TUNA is looking specifically at ways to restore disrupted connectivity, Kelly foresees the eventual product having ever broader applicability, as, for instance, in the rapid deployment of tactical networks.
"What if the U.S. military needed to set up operations on the three islands in the middle of the Pacific and there is no optical fiber connecting them?" he said. "Now they could very quickly deploy that network, put it in place, and when they were finished they could roll it up and take it away."
The solicitation for Phase II asks vendors to take the next step, to "develop and demonstrate an integrated, end-to-end, scaled network prototype" for the system. Convinced of TUNA’s viability, planners say they now want to see it put to the test.
