Naval engineers are honing in on their goal of developing a “swarm” of small unmanned aerial vehicles (UAV) with the capabilities needed to carry out key reconnaissance and other missions but at a cost low enough to make them effectively expendable.

The Smart Warfighting Array of Reconfigurable Modules (SWARM) UAV project at the Naval Surface Warfare Center Carderock Division (NSWCCD), has already assembled a fleet of 10 lightweight units designed to be used in a cooperative fashion. Efforts are directed to maintain the low cost philosophy, which will result in a per vehicle production cost of $2,000.

Deborah A. Furey, SWARM UAV project manager at the Maryland research facility, summarized the undertaking this way: “These vehicles operate as a group, functioning together as a ‘swarm’ of aircraft. This operational model requires the vehicles to function as individual units while being a part of a larger functioning organization operating to achieve a common mission goal. The UAVs communicate relevant information and can reconfigure themselves, autonomously changing direction in response to sensor input to achieve the mission at hand.

“For example, if you have 100 aircraft collecting sensor input over a field of operation and five of them have engine failure or are shot out of the sky, the rest can reconfigure themselves to collect the required data and complete the mission,” Furey continued. “The important thing is that they are considered low-cost and expendable. The vehicles need to be low cost to support the swarming concept, where hundreds will fly together and where individual unit losses won’t significantly undermine the value of the total asset, both economically and militarily.”

In creating swarming aircraft, developers are not only exploring an ancient military tactic that is attracting increased attention from modern military theoreticians, but also filling out the UAV spectrum and giving new options to commanders for accomplishing missions while preserving lives and resources.

Swarming—defined as small, maneuverable fire units able to converge quickly from different directions on a common target—has a venerable military history. But some experts also see the approach as ideally suited to the age of information warfare, with two Rand Corp. researchers last year proposing the concept of the “battleswarm” based on networked maneuver units.

The application of swarm theory to unmanned vehicles has also attracted considerable interest among military researchers, who are intrigued by the idea of enabling groups of vehicles to sense and respond automatically, without having to be controlled individually by operators on the ground. The Office of Naval Research’s Autonomous Intelligent Networks and Systems project, for example, has conducted swarm-related research with small UAVs for surveillance operations in Iraq.

One important element to this aspect of swarm research lies in developing the most effective software routines needed to enable autonomous operations of the group, specifically the development of cooperative behavior algorithms. Other researchers continue to experiment with a variety of approaches, which include models based on potential fields and on pheromones, which are the chemicals secreted by ants and other insects to convey messages to others in their group.

Cost Crunching

The NSWCCD team, however, has focused less on complex control issues than on the practical aspects of designing an aircraft that can fly, be controlled and carry out military functions—and be produced for about the cost of a big-screen television. Indeed, according to former NSWCCD official and SWARM founder Vince Castelli, the $2,000 cost goal—roughly, about the price of an “expendable” Navy sonabouy—was always the most important aspect of the design process, around which limits on performance would have to be accepted.

Developers of the project, which is currently sponsored by the Defense Advanced Research Projects Agency (DARPA), also wanted to ensure the UAV could be easily used within a military environment and reconfigured to meet changing mission requirements.

“It’s a military aircraft in terms of the fuel it uses and its ability to be integrated into a field unit,” said Furey. “This aircraft was designed to be compatible with the military, and therefore is logistically easier to deploy with field units and existing military assets. For example, the weight of one aircraft is less than 20 pounds, so that one person can carry, assemble and launch it. The size is such that it can fit through a watertight door on a Navy ship. Its engine operates on JP-5 fuel, which is already in the field. This UAV was designed to be compatible with the existing military.”

The unit that emerged from the design process can be produced at the cost goal in large-scale production, developers predict. It has a takeoff weight of 18 pounds, which includes a four-pound payload of sensors or other equipment. In flight tests, it has stayed aloft for more than two and a half hours.

Key components of the UAV include:

• A thin-walled thermoplastic airframe that is light in weight and constructed to provide the needed structural rigidity.

• A 0.75 hp engine that operates on standard military fuel (JP-5/8) rather than highly volatile fuel used in model airplanes, which would have required its own supply chain and storage facilities.

• An onboard alternator that powers the on-board electronic equipment. A battery option is also available.

• An avionics unit with accelerometers, gyros and computers needed to fly the craft and determine its location through the Global Positioning Satellite system.

The full SWARM UAV concept calls for the development and implementation of low-cost surveillance and sensor systems. This follows the philosophy of expendability, in that the sensors and UAV would be a low-cost system that could be used and considered expendable.

In looking ahead to the potential uses of SWARM UAVs, Furey focused on the military intelligence, surveillance and reconnaissance advantages of such low-cost aircraft.

“The swarming UAV concept is appropriate for many applications requiring data collection on both a large and small scale,” she said. “Several units can be used to survey and map a route for troop movements. Equipped with cameras, a formation of UAVs can fly over the desired route at a specific spacing and altitude to collect mapping information at the required resolution for path finding. Alternatively, for path monitoring, a pair of UAVs can accompany a convoy for force protection applications. The UAV would fly ahead of the convoy to monitor the path for safety.”

To be sure, many of these missions could also be carried out by existing UAVs, which are high-dollar assets and in high demand. But with an individual price goal of a fraction of current UAVs, these small, easy-to-use aircraft could be ideal for situations in which commanders did not want to risk scarce resources.

“The small size of these UAVs makes them available to the individual troop units. These systems can be assigned to small groups of soldiers, making the usefulness of UAVs accessible to all scales of missions. For example, foot soldiers in Afghanistan may need to get an immediate visual over the hill. Getting one of the currently fielded units, which are often in high demand, is not always feasible or cost effective. Instead, you can send a SWARM group or a single UAV,” Furey explained.

“These small, low-cost military UAVs offer a significant asset that can be used to further the capabilities of field units. In addition, this novel swarm technology may have applications with Navy ships at sea or law enforcement organizations such as the Border Patrol. Swarming technologies offer a new way to approach mission design, mission risk and mission requirements.”