Pilotless aircraft proliferate through the military spectrum

May 1, 1998
As unmanned aerial vehicles begin joining the military services, designers increasingly look to COTS and open-systems architectures to get the most out of onboard sensor processing and limited-bandwidth air-to-ground data links

As unmanned aerial vehicles begin joining the military services, designers increasingly look to COTS and open-systems architectures to get the most out of onboard sensor processing and limited-bandwidth air-to-ground data links

By John Rhea

The unmanned aerial vehicle (UAV) business is sorting itself out into two general categories: tactical systems to provide real-time battlefield data for deployed forces, and the top-of-the-line strategic systems for the upper-command echelons. Common to all, however, will be powerful and inexpensive sensors, onboard processors, navigation subsystems, and data links - many of them derived from manned aircraft and increasingly dependent on commercial off-the-shelf (COTS) information-processing technology.

The logic for using COTS data processing on UAVs is compelling, maintains Robert Finkelstein, president of Robotic Technology Inc. of Potomac, Md.: much data must be processed onboard the aircraft because UAVs typically have limited-bandwidth air-to-ground data links for their sensor data and command and control instructions. Tactical UAVs, such as the Pioneer, Hunter, and Outrider, in fact, are limited to 10 to 20 MHz data links while the long-range, medium-altitude Predator and long-range, high-altitude Global Hawk and DarkStar offer somewhat more with C- and Ku-band satellite and terrestrial-line-of-sight communications.

The situation is analogous to the evolution of spacecraft, Finkelstein explains. The original satellites were unable to do much onboard processing because their primitive computers were so limited. As a result, early satellites had to transmit a lot of raw data back to Earth, which required large communications payloads and large, expensive antennas on the ground.

Today`s powerful microprocessors have already overcome that limitation for spacecraft - witness the proliferation of low-cost receivers for the Global Positioning System (GPS) - and will be essential for UAVs to meet military needs. Not only must UAVs process sensor data rapidly and with minimal ground equipment, but they also will need narrow bandwidths and data encryption to counter interception or jamming.

Lt. Col. Ted Mouras, the deputy systems manager for UAVs at the U.S. Army Training and Doctrine Command (TRADOC) at Fort Huachuca, Ariz., calls himself "the user`s rep." He spells out the UAV dichotomy. "The larger platforms are for more-capable [opposing] armies so you can interdict them," he says, "but the lower echelons at the brigade level need tactical UAVs that are cheap and expendable."

Among the larger platforms is the Global Hawk, which made its first flight Feb. 28 under another demonstration funded by the U.S. Defense Airborne Reconnaissance Office (DARO) and managed by the Defense Advanced Research Projects Agency (DARPA). Global Hawk costs more than $10 million, including avionics. Among the tactical UAVs is the Outrider, which Mouras says will cost less than $350,000 with payload. At this price, and assuming current tests proceed satisfactorily, Mouras sees UAV operations shifting down to the squad level, including cavalry scouts and special operations.

In addition to improving military reconnaissance, Mouras says the benefits of UAVs could trickle down to other defense operations. For example, he says, a tube-launched, optically tracked, wire-guided anti-armor round - better known as TOW - costs $8,000 to $10,000, including command and control. UAVs could help Army leaders use these munitions more effectively by determining wind and other atmospheric conditions, Mouras points out.


The infrared sensors for all UAVs and synthetic aperture radar for the long-range medium- and high-altitude UAVs are well defined and should become increasingly common across the UAV spectrum. The same is true for guidance, which employs readily available satellite- and inertial-navigation systems operating in tandem.

Yet all airborne vehicles - particularly UAVs - need dense, high-power computation at the front end for sensor fusion, notes Barry Isenstein, vice president for advanced technology at Mercury Computer Systems in Chelmsford, Mass.

The processing power that today`s UAVs require is where a COTS solution is particularly attractive. COTS is suited to the somewhat tolerant operating environment of the larger vehicles, and to the severe cost constraints of tactical UAVs.

The long-range, high-altitude Global Hawk from Teledyne Ryan Aeronautical in San Diego, for example, weighs nearly 9,000 pounds (all weights expressed as empty weight), and is about the size of a small corporate jet. At the other end, the 300-pound Pioneer from the joint venture of AAI Corp. in Hunt Valley, Md., and Israel Aircraft Industries in Lod, Israel, does not have to do as much, but it does have to be affordable.

The situation boils down to the need for a system architecture for each UAV that will provide the necessary analog-to-digital interface between the sensors and the computational assets and hierarchical input/output connections to get the best out of computers and sensors, explains Jack Berenholz, principal packaging engineer at Mercury.

"One-size-fits-all doesn`t work well," he says. The good news is that power dissipation is not linear with processor speed, Berenholz adds. A 250 MHz Motorola PowerPC microprocessor dissipates 3 1/2 watts, not much more than the 1 1/2 watts of the vintage Intel 8086, which operated at only 1 MHz. Still to be determined is the form factor, with PCI, VME, and all the other contenders in the running.

Another technology issue that developers must address for UAVs is stabilization, says Brad Ganther, president of Graflex Inc. in Riviera Beach, Fla., a division of Lenzar Optics Corp.

The primary role of a UAV is surveillance, he says, which in turn is directly related to the performance of the stabilized sensor package. This package generally includes a high-resolution TV camera with a long-range telephoto zoom lens, a forward-looking infrared sensor package for night operations, and a laser rangefinder/designator. These subsystems mount onto a stabilized platform.

Ganther maintains that stabilization is the key to making these subsystems effective for surveillance, and furthermore that the cost is not prohibitive. Stabilization platforms for UAVs with a 27X zoom capability run around $5,000. Also, using a gyro-stabilized platform allows the UAVs to fly higher in order to get a better view of the battlefield.

The requirements for surveillance at increasingly longer ranges has also precipitated requirements for specialized TV zoom lenses, he adds. These lenses are compact, rugged, lightweight, and capable of military and sophisticated commercial applications. Los Angeles authorities, for example, are using the stabilization packages for an infrared sensor to handle law enforcement and traffic control. Other applications include tracking radar and video fire control systems.

End of an era

DARO officials in Washington, the arm of the Pentagon overseeing UAV development and acquisition strategies, have a master plan that calls for the phaseout of the Pioneer UAV. This aircraft really is a pioneer, since U.S. Navy and Marine Corps officials first fielded it in 1986 and saw it give service during the Persian Gulf War in 1991.

The Pioneer phaseout depends on the successful development of the two follow-on tactical UAVs - the 1,200-pound Hunter from TRW Avionics & Surveillance Group in San Diego, and the 400-pound Outrider from Alliant Techsystems in Hopkins, Minn. U.S. Army officials have begun operating Hunter for training and payload demonstrations. Defense will make a decision this year whether to place Outrider in full-scale development.

Beside Global Hawk at the upper end is DarkStar, a project of the Lockheed Martin Skunk Works in Palmdale, Calif. DarkStar is a stealthy, long-range, high-altitude UAV. Of the two, Global Hawk has greater endurance (as long as 38 hours) for use as a wide-area surveillance platform. The 4,000-pound DarkStar, meanwhile, has a projected endurance time of 12 hours, and would be used against heavily defended areas because of its stealth feature. Both have maximum operating altitudes of about 50,000 feet.

Straddling the two camps is the 1,200-pound Predator from General Atomics Aeronautical Systems in San Diego. Predator flew six months after General Atomics received the initial contract in January 1994. A year after the first flight Predator began supporting NATO forces in Bosnia, flying more than 550 missions and more than 3,300 flight hours for reconnaissance missions. As a result, DOD officials ordered full production last August.

The Predator momentum continues this year with an a $71.5 million contract announced in March from the Naval Air Systems Command for 18 aircraft, two ground stations, two lots of spares, and two lots of ground support equipment, bringing the total number of Predators to 53.

What Predator has going for it besides service in Bosnia (also shared by Pioneer) is an open-system architecture that turns it into a family of UAVs. This family includes the tactical-endurance Gnat with infrared and synthetic aperture radar, as well as electronic countermeasures; the 450-pound Prowler tactical UAV with autonomous flight capability, which shares the common ground control station and data link with Predator and Gnat; and a high-altitude (45,000-60,000 feet) research UAV known as Altus, which is operational with NASA, the Department of Energy, and the Navy.

System commonality

In a way, Predator represents a microcosm of the trends emerging within the UAV industry: commonality of payload subsystems and ground support equipment in order to reduce costs and ease the logistics burden. This enables migration toward both ends of the spectrum: smaller tactical UAVs like Gnat and high-altitude operations like Altus.

Nonetheless, DARO officials plan to mix and match five UAV types to do the whole reconnaissance job by the year 2010: Global Hawk and DarkStar for the long-range, high-altitude mission; Predator as the long-range, high-altitude airborne communications node, and large numbers of tactical UAVs.

This strategy envisions UAVs taking over much of the airborne reconnaissance that manned aircraft now perform. The plan calls for the long-range, high-altitude UAVs with image intelligence and signals intelligence to replace the U-2; the DarkStar to penetrate heavily defended areas, Predator for medium-altitude missions, and tactical UAVs to augment the low- and medium-altitude tactical platforms. Predator and Outrider are to be upgraded by 2010.

Another issue that DARO officials are addressing is how to get air-tasking messages to the troops in the field in time to respond to rapidly changing situations. This originally took 72 hours during Predator`s first deployment to support NATO, but a real-time system has since been developed to enable a tactical commander to direct the vehicle and its sensors by telephone while watching the downlinked video. The imagery is then disseminated through the Joint Broadcast System to theater and international command and control facilities to permit near-real-time control of the UAV from virtually any location.

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No, it`s not the B-2 bomber. This artist`s rendering depicts a new generation of unmanned combat air vehicle that may be able to outperform manned aircraft on some missions, and will place the human pilot out of harm`s way.

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The lightweight Outrider UAV features a ground-control system that operators can run using laptop personal computers.

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The AAI Corp. Pioneer unmanned aerial vehicle is one of the workhorses of the U.S. pilotless aircraft fleet, has seen action in several conflicts, and has been operated from a variety of platforms, including U.S. battleships.

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The 400-pound Outrider from Alliant Techsystems (pictured above) is a tactical UAV that will cost less than $350,000 with payload. Defense officials will make a decision this year whether to place Outrider in full-scale development.

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This U.S. Army technician adjusts the sensor payload for the Alliant Techsystems Outrider UAV. The payload, which includes forward-looking infrared sensor, comes from the Tamam subsidiary of Israel Aircraft Industries.

Pilotless fighter aircraft set to take center stage

By J.R. Wilson

By 2010, leaders of the U.S. Air Force and Navy will be operating with dramatically fewer fighter and attack aircraft at their command than at any time in the second half of the 20th Century. Still, circumstances already have demonstrated that the end of the Cold War has brought more - not fewer - military deployments and even greater demands on America`s diminishing military forces.

With that in mind, officials of the Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., and the U.S. Air Force are sponsoring an Advanced Technology Demonstration (ATD) leading to a fly-off of Unmanned Combat Air Vehicle (UCAV) prototypes in 2002.

DARPA officials selected four contractors April 16: Boeing Co. of Seattle; Lockheed Martin Corp. of Bethesda, Md.; Northrop Grumman Corp. of Los Angeles; and Raytheon Co. of Lexington, Mass. The exact amounts of those contracts, according to DARPA officials, will be negotiated individually, but the total funding projected through 2002 is $120 million.

DARPA officials seek to demonstrate the technical feasibility of UCAVs for suppression of enemy air defense and other deep-strike missions that would be the most hazardous for 21st-century manned aircraft. If all goes well with the demonstration, UCAVs would begin moving to the field around 2010 as a "force enabler" within the emerging global command and control architecture.

DARPA officials envision a UCAV that costs less then one-third as much as the Joint Strike Fighter, and with a lifecycle cost that is 50-to-80 percent less than a current tactical aircraft.

UCAV capabilities

Future UCAVs must be able to operate in all weather, and during the day and at night. They also must be able to operate from NATO-standard 8,000-foot runways and carry sufficient weaponry, sensors, and fuel to tactically significant ranges, knock out air defense and other non-hardened targets, perform their own battle damage assessment, fly on to and attack a secondary target or loiter over a target area as necessary, and return safely to base for refueling, reloading, and a quick return to service.

"UCAV is about affordability and effectiveness, and that`s our primary focus," says Greg Zwernemann, manager of advanced unmanned concepts for the Advanced Systems & Technology Unit of Northrop Grumman`s Military Aircraft Systems Division in Pico Rivera, Calif. "We`ve done a number of studies about trading capability to achieve an affordability goal.

The UCAV system is composed of mission control, an air vehicle, and a support system," Zwernemann says. "All three components are being considered equally. It will operate cooperatively within an environment that includes manned assets and use data from unmanned aircraft, space assets, and Joint STARS type aircraft."

Defense officials envision further cost reductions by keeping the UCAVs boxed in storage until needed, then shipping them directly to the theater and putting them into service within 24 hours with a minimum of maintenance or other logistics support. A minimum number of units would be used for training because the mission-control system also would function as a mission simulator and the actual presence of a UCAV would be irrelevant to training.

"If these things do not cost substantially less than manned fighters, they just aren`t going to happen. So we are keeping our eye on fly-away prices of $10 million or less for all applications," says Armand Chaput, who leads the Lockheed Martin UCAV design team at Fort Worth, Texas.


David Whelan, director of DARPA`s tactical technology office, says simplicity in design of the airframe, the ability to carry large numbers of small, light munitions, and keeping on-board sensors to a minimum, will combine with as many commercial-off-the-shelf (COTS) components and subsystems as possible to meet that goal. UCAVs may use such sensor-heavy systems as the Global Hawk high-altitude, long-endurance unmanned aerial vehicle for off-board cueing and targeting, officials say.

DARPA officials expect the UCAV not only to be small and light, but also to incorporate stealth and other self-defense technologies so it can operate safely over enemy territory. Requirements call for broad use of infrared and radar signature-reduction techniques.

"Low lifecycle cost technologies, long-term storage, logistics support, and maintenance requirements shall be considered as a driving signature design parameter," DARPA officials wrote to the contractors. "Signature-reduction features shall be compatible with long-term storage without degradation and/or special maintenance requirements."

Furthermore, DARPA officials wrote, the UCAV must be able to protect itself against anticipated threats with capabilities such as electronic support and countermeasures, on-board jammers, expendable countermeasures, towed decoy systems, "or other innovative methods for surviving enemy actions."

DARPA officials also want the UCAV to be difficult to see, and operate quietly to "eliminate, reduce, mask, or diffuse any or all electronic emissions to reduce the probability of detection, tracking or engagement by a threat."

While not part of the current DARPA effort, U.S. Navy leaders have an unmanned strike aircraft study of their own with Boeing and Lockheed Martin. Northrop Grumman officials have joined that effort under a cooperative research development agreement, in which they pay their own way rather than receive a contract. This same approach was taken in recent years with an F-5 avionics upgrade for the Air Force.

Sea-based UCAVs

The Navy UCAV requirement is somewhat more stringent than DARPA`s, given that Navy leaders want to launch and recover the aircraft from small surface warships and even from submarines. Most officials involved agree there will be a considerable degree of cross-fertilization between the Navy and DARPA efforts, especially in sensors, communications, guidance, control, and weaponry.

Navy officials view their UCAV as a reusable cruise missile, explains Lockheed Martin`s Chaput. "In many respects, they already have a UCAV [the Tomahawk] - it just doesn`t come back," he says. "They already have assigned a lot of their deep-strike targets to unmanned systems."

For their part, Lockheed Martin officials are looking at three concepts for sea-based UCAV launch and recovery: short-takeoff/vertical-landing aircraft; vertical-attitude-takeoff-and-landing aircraft; and vertical-attitude-takeoff-and-landing aircraft launched from submarine ballistic missile tubes.

At present, however, the DARPA/Air Force effort is moving forward more vigorously than is the Navy program. Originally, officials did not expect the ATD awards scheduled for the end of April until late in the year.

"They are driving to have a decision package ready to go by 2005 that would identify how the Air Force will deal with the force structure in the early years of the 21st Century," Chaput says. "My view is it will be hard to maintain the force structure unless we have a very low-cost system like UCAV."

Leaders of all four contractors say UCAVs are in the same league as stealth technology; they both represent a significant product line in the next century. Company officials also say UCAV development is a major opportunity to make maximum use of the latest computing and simulation technologies.

"We`ve already put together a simulator to conduct an operator/vehicle ratio trade study - how many vehicles can one or a team of operators control simultaneously? That same simulator will be used to develop the mission-landing algorithms and eventually will evolve into the mission-control system, where we will do the actual training of operator teams," says Northrop Grumman`s Zwernemann.

Maintaining a low-risk mindset, DARPA officials initially are looking at direct operator control of the UCAV, while evolving the system toward greater autonomy. Determining how much autonomy is best is part of the tradeoff studies.

"We feel there will be a high level of autonomy in this vehicle eventually, but the human operator will always be involved in delivery decisions and accountability for the weapons," Zwernemann notes.

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A flying wing configuration of unmanned combat air vehicle is one of several design concepts under consideration at Northrop Grumman Corp. for the DARPA competition to build a new generation of pilotless fighter aircraft for the 21st century.

COTS flight simulation tools may apply to UAVs

Some of the same simulation techniques that help aeronautical engineers design manned aircraft may be appropriate for designing unmanned aerial vehicles (UAVs).

Engineers at the Calspan Advanced Technology Center in Buffalo, N.Y., have developed simulation techniques that enable a small jet aircraft to duplicate the flight characteristics of an aircraft in design. In this way, engineers can get feedback before flight testing begins.

Now these same techniques may also be applicable to UAVs, say officials of the developer of the software tools, The MathWorks Inc. in Natick, Mass.

Calspan experts used a package known as SIMULINK, which runs on Sun workstations and personal computers, for performance flight testing and data reduction. "We program the simulation and load it into our computers on the airplane," explains Paul Deppe, an engineering test pilot at Calspan. "The computer drives the flight control surfaces to make the airplane fly like the customer`s model."

The simulation is programmed as a block diagram in SIMULINK. Another package from The MathWorks, a real-time workshop, then automatically generates C code. One of the simulations that Calspan officials conducted was for the Cessna Citation-X business jet.

Officials of The MathWorks describe the approach as a concept-to-implementation suite of design tools for rapid prototyping of control systems. These tools also have been used for radar systems and guidance and flight control, two requirements for UAVs. - J.R.

UAVs offer opportunity for simulation-based acquisition

Given the spectrum of unmanned aerial vehicles (UAVs) and the need to oversee their lifecycle from acquisition through deployment, UAVs represent an opportunity for simulation-based acquisition, according to Philippe Collard, president of Virtual Prototypes Inc. of Montreal.

The necessary tools already exist at commercial software simulation firms, he adds. All the military services have to do is integrate them into their acquisition process.

The simulation-based acquisition environment would start with the mission needs statement and the subsequent requirements documents spelling out performance, such as altitude, payloads, and range. The environment then provides the common tools so that developers, users, and system integrators would all interface with each other throughout the acquisition process.

Collard lists eight tools that would constitute simulation-based acquisition:

(1) tactical environment generator;

(2) air vehicle aerodynamic modeling and flight simulation;

(3) operator console design;

(4) operator console development (not necessarily an outgrowth of the console design tool);

(5) out-the-window scene generator;

(6) terrain database generator;

(7) model development; and

(8) sensor simulation.

"Whether viewed from a distance or close up, this process [UAV acquisition] has been more linear and open loop than circular and closed loop," Collard comments. "Even today, the parties to the acquisition process ... do not all have a common frame of reference.

"This creates a lack of continuity, or disjointedness of effort, which can enter the process at any point," he says. - J.R.

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