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It's a Bug, It's a Plane, It's a Flying Circuit Board

December 2011
By George I. Seffers, SIGNAL Magazine
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The CICADA small unmanned aircraft can be deployed from larger manned or unmanned aircraft, weather balloons or precision munitions.

A small aircraft prototype aims to fly from the lab to the battlefield.

U.S. Navy researchers have built a prototypical family of small, simple and affordable unmanned aerial vehicles that warfighters can use to deploy an array of sensors, tailor for a variety of missions, and launch by ones and twos or by the thousands. Essentially a flying circuit board, the miniature craft has completed basic research and development and is ready for further technological advances and eventual battlefield deployment.

Created by the Naval Research Laboratory (NRL), Washington, D.C., the Close In Covert Autonomous Disposable Aircraft (CICADA) can be fired from a cannon, launched from a larger aircraft, dropped from a weather balloon or tossed out of the open hatch of a C-130 cargo plane. Deploying the devices by air eliminates the danger soldiers would face if placing the sensors by hand.

The prototype systems do not carry a specific payload but can be used to deploy any small sensor, including signals intelligence, acoustic or chemical and biological detection sensors. “The mission profile is as simple as it can be,” says Chris Bovais, NRL aeronautical engineer. “The CICADA is dropped from another airborne platform—manned or unmanned aircraft, weather balloon or precision munitions. It is simply a glider. There’s no propulsion system. It has a single wavepoint it can fly to, and it establishes an orbit around that wavepoint and descends in that orbit until it reaches the preprogrammed location on the ground.”

One NRL source refers to CICADA as a “dumb” sensor because of its simple design, but according to other lab officials, the genius of the system lies in its simplicity. “The concept is to make the smallest, simplest, lowest-cost air vehicle that can precision-emplace a sensor on the battlefield,” Bovais says.

The research lab has developed three versions known as Mark I, II and III. The autopilots for Mark II and Mark III are built on a single circuit board, which reduces manufacturing time, eliminates wires and harnessing and creates a surprisingly rugged airframe structure. Depending on the version, the circuit board is also the structure for the wings or the fuselage. The original version featured wings that could fold down and could be deployed by the thousands from an aircraft pod produced by Sargent Fletcher, a subsidiary of Cobham Plc, Dorset, United Kingdom. “Up to 8,900 could be loaded into an aircraft and deployed. The original concept of CICADA placed a premium on compact packing. We’re working with a different version now, but it’s a modular design, and we could go back to the original if that’s what the mission calls for,” Bovais notes.

Al Cross, who leads the NRL’s vehicle research section, adds that the initial flight may not be pretty when CICADAs are dropped in such large numbers, but that does not limit how many can be deployed simultaneously. “You’re not particularly limited in the number of vehicles you could deploy. As we saw, even though the vehicles were sometimes tumbling, they were able to right themselves fairly easily.”

Deploying a veritable swarm of CICADAs offers distinct advantages, Bovais explains. “You can quickly seed a battlespace with sensors and create that smart battlefield that everybody’s looking for. By doing a lot of sensors over a wide area, you can reduce the sensor power and size and keep the same coverage just by having more of them,” he says. “Currently, most sensors are hand-emplaced. CICADA allows for a low-cost delivery of multiple precision-located sensors without placing the warfighter in harm’s way. Seed the battlespace from the air.”

Cross echoes that point. “You don’t have to have boots on the ground to put a sensor at the intersection of a road or on a trail that you want to monitor,” he emphasizes.

The NRL has not yet networked the sensors under the CICADA program, but doing so would not be a huge technological leap. “We haven’t really explored the networking concept in detail, but we are working programs that have small flying vehicles, and sensors communicate with one another. We could see it as a logical next step to make these vehicles part of a large network” Cross says. “It would give you the ability to have them interact in coverage for a given area, and by the way, you could also have a reconfigurable network so that if one sensor dropped offline, the network could reconfigure itself and still maintain coverage over the battlespace.”

 

The CICADA Mark II unmanned vehicle is deployed from a larger Tempest unmanned airplane during a demonstration at Yuma Proving Ground, Arizona.

CICADA Mark III underwent an autonomous deployment demonstration in July and August at the Army’s Yuma Proving Ground in Arizona. For the demonstration, a disposable, high-altitude weather balloon carried a Tempest unmanned aircraft that also transported two wing-mounted CICADA Mark IIIs. The balloon itself had two CICADAs attached directly to the balloon payload box. This configuration demonstrated the high-altitude deployment of the Tempest, up to 57,000 feet, which could travel to an area of interest and then deploy two CICADAs from its wing-mounted pylons.

Meanwhile the balloon payload CICADAs could be released independently. This scenario showed the ability for a single balloon to deploy up to five aerial drones. Programmed to find their way back home, a total of 15 CICADAS were deployed from as high as 36,000 feet. They had an 87 percent success rate. “This is another potential use of CICADAs—to hang over the battlespace for a long period of time and be released when the warfighter needs them,” Bovais explains. He adds that each one was flyable immediately afterward with nothing more than a battery charge.

The system is powered by lithium polymer batteries, which can be plugged into a computer’s universal serial bus port and recharged using a cell phone charger. For high-altitude drops, the most recent version also uses a heater to keep the plane’s vital equipment from freezing. “It gets quite cold at 30,000 feet—in the minus 57 degree Celsius range. So, we have to keep the batteries and electronics healthy and working,” Bovais points out.

The Mark III system can withstand winds up to 40 knots, and the Mark I avionics have been hardened to survive 10,000 gravitational force units for a gun-launch application. Because CICADA has no propulsion system, the range and flight time vary depending on the wind speed and direction, as well as the altitude from which the system is dropped. The Mark III has a 3.5-to-1 glide ratio. One aircraft traveled 11 miles to the target from a downwind release and still arrived at the target at an 18,000-foot altitude. Then it orbited overhead and descended.

With the basic research and development now over, NRL officials are looking for industry or government partners to further develop and ultimately deploy the system. “We’ve had some interest from industry, and we’re starting discussions to begin a cooperative research and development agreement, which could potentially lead to a technology transfer. The Defense Department community has also expressed interest based on our latest demonstration,” Bovais says.

Because it is preprogrammed, the system currently has no requirement for a radio frequency (RF) link for a controller. The RF link to a user could be integrated depending on particular mission or range requirements. “Right now, we do the deployment and the drop and wait for them to show up and then watch them land. They’re kind of like our little boomerangs,” Bovais says. “But if there’s no requirement for an RF link, there’s no reason to add it. Reducing parts reduces costs.”

WEB RESOURCES
U.S. Naval Research Laboratory: www.nrl.navy.mil
NRL Factsheets: www.nrl.navy.mil/vrs/factsheets/index.php