FEATURE ARTICLE

June 2005

The Future May Belong to Unconventional Designs, Missions

By Joe Pappalardo

Unmanned aerial vehicles spying on enemies may be commonplace above today’s battlefields, but there is a future generation of unconventional designs with added functions that, experts predict, almost certainly will displace current drones from their lonely, lofty perches.

From prototype aircraft designed like insects to vehicles that react and respond with human-like behavior, there is a new world of UAVs coming from Pentagon-funded research laboratories. Evolving missions and advanced decision-making capabilities also will likely transform the way unmanned systems are employed.

Researchers are looking beyond fixed wing and rotorcraft designs. For example, there are several research tracks to create disposable unmanned craft.

One UAV would be launched from a P-3 Orion aircraft by being fired from a sonobuoy chute. The retractable wings would unfold in flight, allowing the pilots to steer the drone close to any target of interest while maintaining a safe altitude. “You could launch four or five of these and engage multiple targets,” said David Ludwig, UAV project officer for the Office of Naval Research, which is testing the product, dubbed the sonobuoy-launched UAV. “When you launch this, you’re not getting it back, so it has to be low cost.”

A demonstration of the SL-UAV, dropped from a P-3, is scheduled for September, he added.

A similar program, but one that is not progressing with such promise, is a wingless UAV that could be fired from an existing M260 rocket tube on a helicopter wing to provide a fast look at a target or assess battle damage. The Army’s aviation applied technology directorate has slowed the funding of this program, noted Keith Arthur, leader of manned and unmanned teaming efforts at AATD, without providing details on the problems.

Another effort is proceeding in building battery and other UAV components into the structure of the craft. At the Naval Research Laboratory’s multi-functional materials branch, scientists are testing small UAVs with lithium polymer batteries incorporated into the wings. Other UAV efforts include ways to make fuel tanks double as struts and other structural parts.

Perhaps the strangest effort is an attempt to replicate animal motion in small UAVs. Run out of another NRL shop, scientists have been studying the biomechanical designs of grasshoppers, flies and other invertebrates to form the foundation of future indoor flying vehicles.

“We’re not a production house,” emphasized James Kellogg, the principal investigator of micro air vehicles with NRL’s tactical electronic warfare division. “We’re learning the basic technologies... We’re not out to build a mechanical bird or a mechanical bug.”

Mimicking nature is a difficult, but worthwhile approach because of the physics of tiny flying objects. “Why would anyone want to do a flapping wing?” Kellogg asked. “If you want to get a very small vehicle to the size of a dragonfly, down to six inches, the aerodynamics are not the same. Rotors and propellers become very ineffectual. ”

Thanks in part to a decade of breakthrough research from entomologists, the dynamics of insect flight are better known and certain aspects can be incorporated in robotic design. For example, research is continuing inside NRL to perfect a UAV powered by a mechanism resembling a sideways V, with aerodynamics similar to a grasshopper’s wings or falling maple seed. Prototypes have been flown, and a second generation of the craft, dubbed Samara, is being tested currently, Kellogg said. The specifics of this project have not been cleared for public release, he added.

Other UAV designs incorporate clapping wings, including the “biplane insectoid travel engine” or BITE-Wing. The craft has no fixed lifting surfaces, but instead has a shape of two connected tongs, facing away from each other. These reversing-camber flapping wings open and shut. During their cycle the wing pairs clap against each other and separate, producing positive pressure to the rear, and forward-directed negative pressure that increases thrust. Because the two beams are of equal mass and move in opposition, the BITE-Wing is dynamically balanced in flight.

One aspect of this design that is favored by the researchers is the ability for BITE-Wing to crawl as well as fly, which gives an indoor craft the ability to land, perch and observe from a good vantage point. The BITE-Wing is able to inchworm along the ground. It flaps like a scallop through water.

These projects may appear outlandish, but when Kellogg’s lab designed the first prototypes of the Marine Corps’ now-popular Dragoneye, it would have been hard to imagine their proliferation on today’s battlefield.

Yet steep challenges for tiny UAVs remain. Scientists need to develop small, but powerful energy sources, and they must find a way to overcome the limited sensor payload of these tiny platforms.

Other Pentagon projects with unique UAV designs are considered much closer to fielding. One highly anticipated project, involves unmanned aircraft with ducted fans, which feature propellers housed within the fuselage. A ducted fan is more efficient than a conventional propeller of equivalent size because they are quiet and have a high thrust-to-weight ratio that is needed for slow flying and hovering.

The Defense Advanced Research Projects Agency is working on miniature aerial vehicles using a ducted fan design, and two remain frontrunners for inclusion with the Future Combat System vehicles and equipment. One, called the Micro Air Vehicle, is a man-portable version meant for platoon-sized deployment, while the other, Organic Air Vehicle II, is designed to be launched from a FCS vehicle, said Paul Eremenko, program manager.

“Unlike most flying systems, these are designed to operate in an urban environment, where wind gusts are unpredictable,” Eremenko said.

Gas-powered MAVs were flight tested on a tether earlier this year. Further research and a military assessment by the 25th Infantry Division is to be completed in fiscal year 2006.

Moving from gasoline to diesel is one key to these craft’s success, and to that end DARPA is funding research into small heavy-fuel engines. In October, the agency selected RCV Engines Ltd and GS Engineering to pursue ideas for this challenge. “None of the large companies seemed interested,” Eremenko noted. A final design will be chosen during this summer, he added.

Beyond design, the behaviors of future UAVs also will be advancing. The emphasis on “smarter” unmanned aircraft means giving them a wider slate of jobs and more autonomy.

One new role, in an idea first put forward by troops in the field, is using unmanned aircraft to deliver supplies to front line troops. Unmanned aircraft “might be an ideal support mechanism,” predicted Dyke Weatherington, deputy of the UAV planning task force at the office of the secretary of defense.

High on the list of possible applications that soldiers want to see delivered from above are medical kits to troops stuck in hot spots, he said, as well as re-supplies of batteries, water, blood and plasma.

Thomas Yost, team leader for UAV programs at the U.S. Army Research Development and Engineering Command, said that this unmanned logistical support role is an “immediate focus area” for research. Also on this list is the idea of teaming unmanned with manned aircraft, which would make it possible to communicate with UAVs from the cockpit as a pilot would with a wingman, issuing orders rather than directly controlling the UAV.

The key shared by most advanced UAV functions is programming them to take care of themselves with minimal direction.

Old functions will benefit from improved programming, such as collision avoidance systems and tracking multiple moving targets. But with autonomy comes new functions, such as conforming aerial routes to maintain coverage along a winding road and forming airborne communication networks. If a communications link were severed because of maneuvers on the ground, the pack of communications craft in the air could reconfigure to self-heal the breach.

Likewise, UAVs could be programmed to avoid a major quandary coming from the Iraqi theater: confliction problems with other UAVs. Autonomous unmanned aircraft might be able to position themselves at optimal spots out of each other’s paths. “You want them to move out of the way themselves,” Arthur said. However, he noted that the difficulty of the problem has discouraged investigation into a solution. “Nobody has put a lot of money into this.”

Back To Top