by Michael Puttré and Kenneth B. Sherman
Jul. 1, 2001

 

The A-10 was designed around the GAU-8/A 30mm cannon for ground attack, the F-14 was designed to carry the Phoenix missile for long-range air defense, the Mirage IV was designed to carry the AN-22 60-kiloton nuclear bomb for strategic strike. All of these aircraft would carry other payloads, some originally, some as afterthoughts. But in each case, there was a specific primary purpose for the platform in mind when the engineers sat down.

The dynamic between platform and payloads in the world of unmanned aerial vehicles (UAVs) is less clear. In general, the tactical UAVs in service today were designed as jacks-of-all-trades, rather than as mission specialists. This is because military UAVs are just emerging from the awkward, one-off, bicycle shop phase of existence. They haven't turned the tide in any wars, but their presence has been felt on the battlefield and the exploits of a few have found their way onto the war story circuit. Remember when those Iraqi soldiers surrendered to a Pioneer during the Gulf War? Or how about the one when those Israeli Mastiffs fooled the Syrians into turning on their radars in 1983...?

No Richtoffens or Rickenbackers, though. As a result, makers of UAV platforms still find themselves flogging existing designs to potential buyers gussied up with new payload options. Typically, these payloads are reengineered versions of equipment that originally flew on helicopters or airplanes, or perhaps never even flew at all. All this makes the UAV marketplace seem more like a barnstormers' fly-in than the staid, modern world of aerospace systems procurement.
 

"The result of integrating different applications to an already defined airframe will most probably lead to suboptimal results," said Peck Pawelleck, director of strategic marketing for Bodenseewerk Geraetetechnik GmbH (BGT) (Ueberlingen, Germany), a division of Diehl VA Systeme. "Indeed, from my point of view the current approach is doomed to fail - or less heroic: it neglects lessons from history. Still, the approach is understandable: aircraft manufacturers are used to building airframes around pilots - now they think the only thing they have to change is to remove the g-limitation. By the way, as long as the military decision makers started their career as aircraft operators there is no perceived need to change."

In Pawelleck's view, current methods for defining military applications for UAVs are hampered by preoccupation with the UAV platforms themselves. It is much easier to state interest in "Global Hawk," for example, and then try to find possible applications (which will then probably lead to customer-specific revisions) instead of designing a capability to monitor remote areas of interest for round-the-clock surveillance under a defined military scenario. The latter method would give industry the opportunity to come up with innovative solutions that may or may not involve "strategic" UAVs, or UAVs at all. "In the Global Hawk example it might give room for presenting alternate solutions which can be deployed close to the area of operation, require less endurance, are much less price intensive, and fit much better into European environments," he said.

On The Shelf

Fitting an existing UAV platform with a brand new payload can push the bounds of engineering, particularly if the payload application is not something the UAV was originally intended to perform. Recently, Avitronics (Centurion, South Africa) received an order from a foreign customer for a UAV-based system for locating search, tracking, and fire-control radars. The requirement was that the payload be fitted to a Seeker II UAV from Kentron, a division of Denel (Pty) Ltd. (Centurion, South Africa). Avitronics developed its Electronic Surveillance Payload (ESP) using its Emitter Location System airborne ELINT package as a base. The Seeker II is a slender UAV in a pusher configuration with a fixed, tricycle undercarriage. The payload bay is accessible via a "hood" that runs the length of the fuselage forward of the wings. As an observation/reconnaissance vehicle, the Seeker II typically has a sensor attachment located between the rear landing gear struts, near the center of gravity, where a gimbaled turret for electro-optical equipment might be installed. However, since the landing gear would interfere with ELINT antennas, this location was unsuitable for the application. As a result, Avitronics designed the ESP antenna to be mounted on the nose of the aircraft.

At 10 kg, the ESP controller, which sits inside the bay, is well within the Seeker II's 50-kg payload limit, the necessity of locating the antenna array on the nose of the UAV forward of the nose wheel introduced the problem of balancing the aircraft in flight. Avitronics engineers responded with a tetrahedron shape with low band (0.5 to 6 GHz) and high-band (6 to 18 GHz) antennas arranged to cover 240 degrees azimuth and 70 degrees elevation in three sectors that only weighs 6 kg. The design fulfilled the operational requirement for its ESM mission while not interfering with the Seeker II's flight performance.

Although the technical aspects of the ESP on the Seeker II were well served by Avitronics' solution, the necessity of using a particular platform is something of a concession. Another industry expert said a disadvantage of fixed, nose-mounted sensors is that the target must be kept within the UAV's forward hemisphere, which imposes restrictions on its flight operations. This disadvantage is less pronounced for "standoff" applications, such as using ESM to determine electronic orders of battle, because the border is generally well defined. The burden then is on the mission planners to choose mission waypoints and routes that keep the target area within the sensors' arc of coverage. Nevertheless, a fixed, nose-mounted sensor would be hampered were it called upon to perform more "tactical" applications requiring frequent maneuvers or involving targets in unknown locations.

BGT's Pawelleck said that such integration issues do not necessarily lead to the conclusion that payload must come first. "Instead, the definition of missions and required capabilities in prospective scenarios should come first. This brings a systems perspective that has due regard for specific requirements for both payload and airframe, which are interrelated."

Peter Lloyd, sales and marketing manager at Roke Manor Research Ltd. (Hampshire, UK), a research and development firm specializing in communications and sensors, agreed that in a perfect world neither the payload nor the UAV comes first, since the mission and its goals come first. Roke Manor Research has carried out work for both the UK Ministry of Defence (MoD) and major UAV manufacturers that includes systems engineering studies of UAVs. In these studies, the company attempts to first define the customer's mission goals and expected scenarios, then defines sensor options and consequential data processing and datalinks, then defines support equipment, and only then is there an analysis of UAV options and performance.

The above can be described as a best-case approach to UAV platform and payload specification, acquisition, and integration. In the past, UAV operators typically had to make do with what was available, because of the dearth of options in the marketplace. More often than not, UAV platforms were begged or borrowed and payloads kluged together from components initially designed for other purposes. However, most industry observers would agree that UAVs are hot commodities these days - at least hot in the world of low rate initial production.

What Is That Thing?

The big question about UAVs is, what are you supposed to use them for? (see chart) According to the US Department of Defense's "UAV Roadmap," in 2001 "UAVs compose 0.6 percent of the US military aircraft fleet, i.e., there are 175 manned aircraft for every unmanned one in the inventory. For every hour flown by military UAVs, manned military aircraft fly 300 hours. UAVs currently suffer mishaps at 10 to 100 times the rate incurred by their manned counterparts. UAVs are predominantly relegated to one mission: reconnaissance. Before the acceptance and use of UAVs can be expected to expand, advances must occur in three general areas: reliability, survivability, and autonomy. All of these attributes hinge on technology."

Israel is arguably the world leader in practical, day-to-day UAV operations. According to Colonel Nir Barkan, Israeli Air Force, commander of 200 Squadron, a UAV unit, his mission is target acquisition, bomb damage assessment, and joint missions with ground and air units; missions that have been flown routinely since the squadron's formation in 1971. Barkan's squadron, based at Palmachim, south of Tel Aviv, is equipped with IAI-MALAT Searcher II and Silver Arrow Hermes 450 UAVs (see JED , June 2001) that can all be fitted with optical and thermal imaging cameras, and laser target designators. The payloads are interchangeable between UAV platforms, the main differentiator being the duration of the mission: Searcher II has an endurance of about 12 hours while Hermes 450 has an endurance of up to 20 hours.

The first UAV that 200 Squadron used was the IAI-MALAT Scout, which had an endurance of only six hours. As the legs and heft of the platforms increased, it was both possible and practical to carry payloads other than the early day and night EO/IR imagers. Payloads now include advanced models of such equipment, mounted in stabilized turrets. Israeli Aircraft Industries' (Tel Aviv, Israel) TADAM division makes a variety of Multi-mission Optronic Stabilized Payloads (MSOP) for day/night missions. These have automatic video trackers and a variety of sensor combinations. IAI's Elta division makes a Synthetic Aperture Radar (SAR) that can be carried by UAVs, significantly expanding a platform's capabilities. The Electrooptics Industries Ltd. (Elop) subsidiary of Elbit Systems Ltd. (Haifa, Israel) (whose Silver Arrow subsidiary makes the Hermes 450) has developed a number of stabilized payloads suitable for UAV use. Most intriguing is a laser target designator, which transforms the UAV from an observer to an actual participant in the kill.

As early as 1988, the governments of the United States and Israel have worked on cooperative programs for the development of UAV payloads. These programs specified interest in stabilized payloads for day and night surveillance, target tracking and identification, and laser designation and range finding. The products currently fielded by IAI and Elbit may be seen as descendents of these agreements, either directly or indirectly. While the US has shown itself an enterprising user of UAVs, with notable deployments in the Gulf War and the Former Yugoslavia, latter-day interest has tended toward the larger, high-flying, very long endurance systems, culminating in Global Hawk. Moreover, advocates of UAVs in the US seem to be enamored of exotic, expensive jet-powered combat UAVs that don't have hope of being fielded before the decade is out, if ever. Meanwhile, Israel has remained on the path of continuous, incremental improvement of tactical and medium endurance systems with pedestrian pusher propeller configurations, carrying ever-more capable payloads on ever more complex missions. In May, the French military selected IAI's Eagle medium altitude UAV - with EADS as prime - over a General Atomics bid with its Predator UAV. In a separate award, France elected to procure Sagem's Sperwer UAV over an EADS offer, with Sagem also expected to provide the optronics payload.

This is not to say that US-built platforms, led by General Atomics' Predator and AAI's Shadow 200, are not attracting their share of advanced payloads. US forces modified at least one Predator during Operation Allied Force to carry a laser target designator (and Yugoslav forces reportedly succeeded in downing about 20 UAVs during the conflict, which has caused some to question the wisdom of fitting advanced payloads on "expendable" platforms). General Atomics has developed its Lynx Synthetic Aperture Radar for use on the Predator on the slightly smaller I-GNAT UAV, from which the Predator was derived. Lynx is an outgrowth of the Ku-band SAR technology developed at the US Department of Energy's Sandia National Laboratories over many years.

According to General Atomics, weight savings was the key engineering challenge in adapting the SAR payload for use on UAVs. The original Sandia SAR weighs 220 kg, where Lynx weighs about 50 kg. Lynx could also equip GA-ASI's Prowler II UAV - which can carry a payload of about 45 kg - by slightly reducing the radar range while retaining its resolution. Lynx uses an offset-fed dish antenna mounted on a three-axis gimbal within a radome, and is designed to perform as much like an optical system as possible from the user perspective. Current capabilities include coherent change detection in near-real time, allowing it to detect very small changes in the scene from one pass to another over the same area. Images are transmitted to the ground station via datalink on a store-and-forward basis. In addition, Lynx has a moving-target indication (MTI) mode.

In US service, the Predator has four sensors on board. Three are located in a Versatron/Wescam Skyball containing a variable zoom (16-160mm) day camera, a 955mm Spotter camera, and an Infrared camera. The fourth sensor is a Tactical Endurance Synthetic Aperture Radar (TESAR). This combination of sensors allows it to collect intelligence day or night, in clear or cloudy weather. The US Army describes TSAR as a strip-mapping SAR that provides continuous variable-resolution imagery from 1 meter to 0.3 meter (1 foot). The focused imagery is formed on board the Predator aircraft, compressed and sent to the Predator Ground Control Station over a Ku band data link. The imagery is reformed and displayed in a scrolling manner on the SAR workstation. As the imagery scrolls by, the operator has the ability to select 1k-by-1k image patches for exploitation at the Predator Data Exploitation, Mission Planning and Communications (DEMPC) workstation. The imagery is also recorded continuously on data tapes.

The US Army's Communications-Electronics Command (CECOM) at Ft. Monmouth (NJ) is nearing decision on a SIGINT payload for its TUAV (see "EC Monitor"). The SIGINT mission is about halfway down the list its Top 10 list of priorities (see chart). Reconnaissance tops the list, much as it did when the US first started thinking seriously about UAVs. This is less the result of a lack of imagination or innovative spirit among Army planners as it is the fact that this mission has yet to be fully realized. Currently, the Army has contracted with AAI Corp. (Hunt Valley, MD) for low-rate initial production of the Shadow 200 UAV. The current value of the contract is $83.6 million. In concept, the Shadow 200s will equip brigade commanders, giving them organic reconnaissance capability. They would be towed and launched from hydraulic catapults and recovered with the assistance of arrester gear (how very Navy). AAI hopes to receive a full production contract in the fall for as many as 36 UAVs, with a total value of over $300 million.

Scott Martin, manager of EW business development at Rockwell Collins (Cedar Rapids, IA), is excited by the potential of the UAV payloads market, describing it without irony as "explosive" (see sidebar, "UAV or Missile?"). Rockwell Collins' focus is on electronic attack (comm jammers) and signals intelligence (SIGINT) payloads. "Smaller, cheaper, lighter, and faster: These are common themes that will not go away," Martin said. "Our comm suites are on Global Hawk and we are shrinking our current jammers for small, UAV applications. We have a quick reaction capability as well as a philosophy that requires us to leverage off existing programs."

Nevertheless, Martin said that existing programs and existing UAV platforms will probably remain in the driver's seat as far as payload development is concerned. There is not yet a consensus in procurement circles on the tactical UAV's proper role in modern warfare, and therefore expensive development programs for these "lesser" systems will likely remain in the shadow of Global Hawk.

The Post Unmanned Age

According to BGT's Pawelleck, much of the difficulty in the UAV payload-platform relationship stems from the latter's unfortunate - and completely incidental - resemblance to manned aircraft. This sort of thing happened before: when tanks were treated like cavalry because people rode on them and they want fast and early aircraft were treated as artillery spotters because they were up high. The fact that UAVs are described in relation to their populated predecessors can be something of a sticking point for developers and operators alike.

"All current UAV platforms and their prospective successors are remotely piloted vehicles: More or less the pilot has just been 'degraded' to a ground-based operator," Pawelleck said. "What is still lacking is a real abolishment of manned piloting functions. This results in the issues of autonomous behavior (not to be mistaken for preprogrammed behavior). The real challenge for future UAV can be found in substituting a manned pilot by using means of artificial intelligence."

Autonomy is based on situational awareness. The system must be aware of the operational context to enable true decision-making. Again, sensors must collect the inputs for this awareness. But the requirements are different from just taking stable high-resolution IR/EO or SAR pictures. "From my point of view this autonomy aspect currently is the main hurdle for solutions in regard of 'see & avoid' functions related to the issues of flying UAV in controlled airspace," Pawelleck said. "Getting the UAV reacting to the unforeseeable needs more than just linking the sensors with the autopilot. Thus, all current attempts fall short."

There are signs that the pilot/operator may soon be out of the loop. Col Barkan of Israel's 200 Squadron says his unit currently has specialist pilots for UAV takeoff and landing and operators that handle the mission flight. IAI is working on automatic landing systems for UAVs, to remove what is statistically the most hazardous aspect of UAV operations - the human element. Barkan - a veteran operator himself - said he is wary of automatic landing systems, but would use them if they were reliable. Perhaps the revolution in UAVs will come once the "unmanned" moniker is removed and the aerial vehicles are viewed as new, revolutionary platforms on their own.

 

 

 

Copyright 2001 eDefenseonline.com & Horizon House Publications