Pilotless Planes

The Los Angeles Sheriff's Department got plenty of attention in the spring when it announced plans to use Unmanned Aerial Vehicles to help them search for criminals and missing persons. Those plans underscore a dramatic surge in UAVs, which are playing an increasingly important role in their primary function in military applications.

Drones are seeing dramatic growth in Afghanistan, Iraq and other regions where the military wants surveillance information. As the U.S. focuses on what it calls network-centric warfare, UAVs play a key role in intelligence gathering. Developers are responding by making UAVs more versatile, using technologies like Ethernet and field programmable gate arrays so operators can easily alter drones for specific missions.

Their growing role is underscored by the wide range of unmanned planes now in use. "There are a great number of UAVs out there, more than 18 different versions are being used in various theaters today," says Robert McKee, platform and operational units program manager at Mitre Corp.

The tests in Los Angeles are among many trials being run by police forces in places as far away as Israel. Many say law enforcement is only one of the civilian applications where UAVs are being examined. "We're seeing more interest for civil applications like border patrols and firefighting," says Doug Fronius, Navy Fire Scout program manager at Northrop Grumman.

As this potential market emerges, developers continue to come up with new techniques making it possible to do more surveillance without putting humans where they might be in harm's way. As in the past, the military is pushing the technology. "We're working on UAVs that can hover, as well as fly, so they can sit outside a window," says Robert Leheny, DARPA's deputy director.

As more drones are used, developers are making sure they can adapt to take on new roles. That can mean anything from adding new types of sensors to carrying missiles or bombs. "When the Predator was built, designers had no clue that the Air Force would want to put firepower on it. That highlights the need for adaptability," says Glen Logan, senior systems engineer for the Open Systems Joint Task Force.

In drones we trust

One of the many reasons for the increased use is that drone designs have improved greatly. Early versions were not overly dependable, but today's models are quite trustworthy. "Ten to 20 years ago, UAVs were considered, to some degree, expendable, trading reliability for cost. Today, they want systems as reliable as manned platforms," Fronius says.

Technical improvements also continue to augment the cost and safety issues that originally made UAVs attractive. Today's systems are far more versatile, operating autonomously or responding to user commands. "Hunter has the option of full manual control or it can be pre-programmed," says Drew Telford, chief technologist for Hunter UAV at Northrop Grumman.

The success of drones is helping speed up development. As the market shows signs of expansion, boardmakers are paying more attention, coming up with new designs. "We're doing a variety of modules that have extended temperature ranges so they can go into UAVs," says Rodger Hosking, vice president of Pentek Inc. of Upper Saddle River, NJ.

Need for networking

As the aerospace and defense industries become more comfortable designing with commercial off-the-shelf technologies, design engineers are turning to standards to gain the same benefits standardization brings throughout the electronics industry.

"We want to be able to adopt new technologies, coming close to plug-and-play. The backbone of GlobalHawk is Fast Ethernet," says Ed Walby, business development director for Northrop Grumman's High Altitude Long Endurance Systems.

Ethernet provides a standard interface that can easily and affordably be added to any new technologies, making it simple to add and remove elements over the long lifetime of the craft. The speed of Ethernet also makes it possible to use one bus for many systems. Earlier UAVs often used several different buses dedicated to various technologies, making it more difficult to share and transmit data quickly.

Heavy issues

Two of the critical design parameters for drones are versatility and mission duration. Like other aircraft, UAVs have fairly long lifetimes, so engineers have to come up with ways to make sure that new technologies can be integrated as they become available. While users will be adding new elements to vehicles, there's also a push to make them lighter so they can fly longer.

Though electronics are, by nature, lighter than engines and fuel, they account for a large portion of the overall weight of these aircraft, which don't carry much beyond equipment such as radar, cameras, storage, a variety of sensors, and systems that do some processing on this data. "Every ounce you can take off the electronics translates to more fuel for longer missions," Leheny says.

Keeping weight down can be a real challenge, however. Though drones are generally smaller than fighter jets, operators often want them to carry as much gear as the large Airborne Warning and Control Systems that are carried by large bombers.

"UAVs like GlobalHawk have a lot of radar systems, yet the amount of weight they can handle is far less than an AWACS carrier. Because of the weight and size constraints, there's a big push to use FPGAs to do a lot of signal processing," says Mike Jadon, director of product marketing, Micro Memory LLC of Chatsworth, CA.

FPGAs aren't just desirable because of their speed. "FPGAs let you put several discrete parts and logic chips into one part," says Randy Robertson, vice president of engineering at Honeywell Aerospace. They also make it simpler to upgrade systems such as radios, since the hardware can be reprogrammed almost as easily as software can be altered.

As design engineers attempt to do more with faster chips and denser boards, they run into the cooling dilemma that plagues most system developers. Though UAVs often operate in cool, upper atmospheres, many often idle for lengthy periods in desert airports while they're checked out and prepared for action.

Radar systems are a particular problem. Many of these radar systems run extremely hot, so engineers are looking at ways to use liquid cooling without sacrificing replaceability. To help keep small radar systems running for long periods, the VMEbus International Trade Association is developing packaging that integrates electrical connections and leak-proof liquid cooling pipes that are encased in metal housings. "With cans, it's much easier to change out liquid-cooled modules," says Ray Alderman, executive director of VITA, headquartered in Fountain Hills, AZ.

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