Communications relay grows with expansion of UAV missions
Shifting role offers another way to put antennas in the sky and lower burden on limited satellite resources
- By David F. Carr
- Aug 03, 2009
The ability to loft a communications relay antenna over any battlefield and keep it there for hours or even days is emerging as yet another mission for unmanned aerial vehicles, robotic tools that are steadily gaining attention as spy planes and attack aircraft.
One reason for a heightened focus on communications relay capabilities is the growing importance of operations in Afghanistan, where line-of-sight, ground-based radio is often blocked by mountainous terrain. In comparison, Iraq was a more hospitable environment in which the U.S. military could test concepts of network-centric warfare. Operations in Afghanistan have been more dependent on satellite connectivity, with its lower bandwidth and higher latency.
“If one part of your organization is on one side of a mountain and the other part of your organization is on the other side of the mountain, today you might have to use a satellite to talk to each other,” said Army Col. Raymond Jones, program manager for the Airborne and Maritime/Fixed Station portion of the Joint Tactical Radio System (JTRS). UAVs offer another way to put antennas in the sky, lowering the demand for limited satellite resources, he added.
Operating as a communications relay is already a routine, albeit secondary, mission for the Army’s Shadow UAVs, which in 2008, the service began outfitting with radio antennas mounted in wing extensions as standard equipment.
Meanwhile, the Air Force has developed a Battlefield Airborne Communications Node for use on high-altitude UAVs such as Global Hawk, which, until now, has been used primarily as a surveillance and signals intelligence plane. Northrop Grumman, maker of Global Hawk, won a $25.7 million contract to develop the node back in 2005. The Air Force is using it operationally aboard Bombardier BD-700 business jets but plans to transition to flying it on the Block 20 version of Global Hawk, with its surveillance payload removed to allow the craft to operate as a dedicated communications node.
Northrop Grumman officials declined to comment for this story, and the Air Force did not respond to a request for comments by press time. However, members of the Northrop Grumman teams that are developing the Fire Scout unmanned helicopter for the Army and Navy recently updated the military on their progress. The helicopter includes a communications relay element.
“This has been one of the key roles all along, in the context of Future Combat Systems — the capability for Fire Scout to be a flying router for the network to sustain connectivity to everyone and maintain information dominance,” said Mike Howell, business development manager for Army systems at Northrop Grumman.
Howell said UAV-based communications have been used in past conflicts — for example, to relay around mountainous terrain during the U.S. intervention in the Balkans — but those solutions were relatively limited.
The experiments that led to the Shadow’s communications relay design date to the 1980s and 1990s, said Steve Reid, vice president of unmanned aircraft systems at Textron.
At the time, AAI, now part of Textron, had obtained the manufacturing rights to the Israeli Pioneer UAV, which became a favorite of the Navy and Marine Corps. AAI developed a communications payload for the Pioneer, but loading it on the craft meant displacing the main surveillance and reconnaissance payload.
By the time AAI revisited the concept, lighter and more powerful equipment made it possible to add a communications relay to Shadow without detracting from its other missions, Reid said. At that point, the main challenge was to find the easiest way to add that capability to the UAV’s design. An initial approach that required the equipment to be mounted on pods beneath the wings hurt the Shadow’s performance and endurance.
In 2007, AAI came up with the idea of fitting the radios into six-inch extensions at the end of each of Shadow’s wings. “It’s quite elegant in its simplicity and doesn’t detract at all from the aerodynamics of the aircraft,” Reid said.
The wing extensions were deployed as an upgrade kit for Shadows used in Iraq and Afghanistan and are flying on most of the aircraft today, Reid said. The next-generation Shadow is being designed with a broader wingspan to boost endurance and will have the communications gear built in from the beginning, he added.
Communications relay is being treated as a secondary mission, with that equipment coming along for the ride while the Shadows pursue their primary mission of reconnaissance and intelligence gathering, Reid said. Commanders in Afghanistan might put more emphasis on the communications relay mission when doing their flight planning, he added. But if that becomes a primary mission for UAVs, it might make sense to use another type of aircraft.
Smaller UAVs such as Textron’s Aerosonde are being designed for more endurance, partly so that swarms of them could function as airborne routers. By staying aloft for as long as 24 hours, they could offer enhanced connectivity over a battlefield or disaster response zone where communications have been knocked out.
Another aircraft that has been proposed for that sort of mission is the Zephyr, developed by the British firm QinetiQ. The 66-pound, battery-powered UAV can recharge itself using solar cells.
“The concept is for Zephyr to fly weeks, if not months, over a geostationary area,” said company spokesman Douglas Millard. That would allow it to function like a low-flying geostationary satellite. Zephyr’s flight record is 3.5 days aloft.
QinetiQ has also been collaborating with Boeing on the design of the Defense Advanced Research Projects Agency’s Vulture UAV, which has a design goal of being able to stay in the air for five years at a time.
Airborne antennas can also be deployed on other platforms, such as tethered balloons, but they can be more quickly positioned by an aircraft, and UAVs can easily be programmed to fly circles over a mission area.
“Right now, I would say it is used more so in special operations and things like that than by regular Army,” said Joe Miller, director of JTRS programs at General Dynamics. However, the success that special operations troops have had with the technology will encourage the military to deploy UAV-based communications more broadly and routinely, particularly over difficult terrain, he added.
In addition to developing radios for JTRS, General Dynamics has an established product that’s already providing UAV-based connectivity on UHF satellite bands, he said.
“Afghanistan has really highlighted this issue and problem,” Miller said. As warfighters wind their way through the mountains on the border with Pakistan, “they can’t afford to leave those guys isolated.”
David F. Carr is a special contributor to Defense Systems.