Unmanned Air Vehicles - A revolution of sorts?

The immense potential offered by unmanned air vehicles owes much to the convergence of information technology with advances in the science of flight, but large hurdles remain

Peter La Franchi/CANBERRA

Within the first decade of this new century, the long-awaited promise of a revolution in civil and military aerospace operations driven by unmanned air vehicles (UAVs) looks likely to come to fruition, but in forms few observers would have suggested even a decade ago, and with challenges no-one foresaw.

The superhighway leading to that revolution is already under construction through a variety of UAV demonstration and development programmes. While these are predominantly military, the UAV revolution and its potential has not gone unnoticed among civil operators, with emerging commercial and scientific concepts and applications promising to take UAV technology into far broader realms.

Military interest alone has resulted in UAV technology undergoing major generational shifts as defence planners have sought to integrate the growing potential of unmanned systems with the wider changes now shaping how future conflicts could be fought.

These include the emergence of the concept of "network-centric warfare", where operations are no longer conducted solely within the realms of topography, but instead within sensor-to-shooter information networks. Within such architectures, UAVs are no longer seen as stand-alone assets with interesting capabilities. Instead, they will operate as information nodes within a larger system of systems.

Major milestones

There is no doubt military UAVs are becoming more mature. In the past year, go-ahead has been given for the first of a new generation of vertical take-off and landing unmanned air vehicles (VTUAV) for the US Navy, and this year will see the planned first crossing of the Pacific by a UAV (see Northrop Grumman Global Hawk technical description and cutaway drawing on PP26-32). The first demonstration of an unmanned combat air vehicle (UCAV) is to commence in the USA in the second quarter of this year.

Serious work is under way within several armed forces on concepts for unmanned airborne early warning and anti-submarine warfare aircraft, and even submarine-launched UAVs.

In both the civil and military sectors, work is under way on concepts for unmanned transport aircraft, ranging from freighters to rival today's converted airliners to rotary-wing assault transports that would deploy robotic artillery or establish forward fuel depots.

Ideas for hybrid systems continue to blur the lines, whether it is the concept of "hunting packs" of armed and unarmed UAVs operating autonomously behind enemy lines, or the exploitation of endurance capabilities developed for the military to meet civil and scientific needs.

The first demonstrations of commercial broadband telecommunications-relay services using high-altitude endurance (HAE) aircraft, albeit manned, took place midway through last year. Limited operational services, again using manned aircraft initially, are planned to become available by late this year. Unmanned platforms are expected to begin hosting such services for military and civil users by mid-decade.

In addition, planning began last year among the West's diplomatic community for unmanned endurance systems to be used as part of internationally co-ordinated relief operations after natural disasters, with key decisions on a way forward to be made in March.

Converging technologies

Much of the UAV revolution now evident in conceptual thinking and product development is characterised by the convergence of a broad array of technologies. This has had an impact not only on air vehicle design, but also in the critical areas of system control, navigation and payload capabilities. The most significant of these convergences involves commercial information technology, which can now provide the ability to leverage the raw data output provided by UAV sensors into a coherent real- and near-real-time command and control architecture.

While unmanned system capabilities are being widely explored through military exercises and battlelab demonstrations, nowhere has the potential became more apparent, perhaps, than in the actual operation of UAVs such as the USAir Force's General Atomics Predator during NATO's Bosnia and Kosovo campaigns.

Yet despite its potential, UAV technologystill has many hurdles to overcome:

Available communications bandwidth remains a key obstacle to the widespread integration of UAVs into military information networks. The immaturity of available technology continues to plague development programmes. Real-time extraction of information from sensor data still demands massive computer power and new approaches to signal processing. UAV project management is still an evolving branch of military acquisition practice in most nations, including the USA. Civil and military users face key challenges in the development of appropriate doctrine and concepts of operation. There is still no common approach to the certification of UAVs for operation in civil airspace despite more than five years of activity and active pressure from potential users. Development costs remain a major barrier to the emergence of civil UAV systems, while the market economics of commercial operations are still in a state of infancy.

What is clear is that, if the coming UAV revolution is to be fully exploited, whether by civil or military users, a breakthrough is needed to deal with the host of underlying issues and challenges.

Changing definitions

The looming revolution in applications has seen an evolution of UAV classes over the past decade, with further changes almost certain. This is particularly likely among military users where the convergence of surveillance and combat systems has already seen a blurring of the definitions of what constitutes a guided weapon as opposed to a UAV.

This includes missiles which have operational characteristics more akin to those of a UAV, and missiles capable of performing as a UAV simply through substitution of the warhead for a sensor or decoy emitter.

Past approaches to classifying UAVs have been based on characteristics such as the vehicle's function, range or survivability. No single approach is without its criticisms, as much generated by the ability of systems to perform multiple roles as by the problems inherent in trying to impose order on a dynamic development environment.

Current functional classification approaches used by the military are based on an initial split between support and combat UAVs. Existing UCAV sub-classifications include fighter and strike systems, while support UAVs can be further differentiated into reconnaissance, target and transport platforms.

Reconnaissance UAVs previously were generically classified as tactical or strategic. This second category has now been generally supplanted by classifications based on endurance. Medium-altitude endurance (MAE) systems fly at 20,000-40,000ft (6,100-12,200m) for 24-48h at ranges of around 500km (270nm), while high-altitude endurance (HAE) systems generally operate at 40,000-65,000ft for similar durations, but at ranges of up to 5,000km.

Examples of the MAE category include the European Aeronautic Defence and Space (EADS) Eagle, Frontier Systems A160 Hummingbird rotorcraft, General Atomics Predator and Silver Arrow Hermes 1500. Representative HAE systems include EADS' planned SAROHALE/Fregate system and the Northrop Grumman Global Hawk.

Both MAE and HAE systems can be further differentiated in terms of endurance. The medium-altitude, long-endurance (MALE) UAV is best illustrated by Israeli Aircraft Industries' (IAI) Heron, which has carried out missions of more than 50h at altitudes up to 35,000ft.

High-altitude, long-endurance (HALE), or high-altitude, long-operation (HALO), systems generally operate above 65,000ft with missions lasting beyond 48h at ranges beyond 5,000km. While most representative air vehicles are still in early development, mainly for scientific purposes, examples include Aurora Flight Sciences' Perseus, the Aerovironment Helios solar-powered flying wing, and the ScaledComposites/Angel Technologies Proteus "optionally manned" aircraft.

Tactical conundrum

The general category of tactical systems covers a vast array of air vehicle types, from UAVs capable of operating at ranges up to 200km with up to 16h endurance at altitudes up to 20,000ft, down to aircraft with an endurance of less than an hour at ranges below 10km and altitudes measured in hundreds of feet.

Generally accepted military sub-classifications of tactical UAVs tend to be based on existing land-force command structures, with more capable systems usually operated at the higher divisional or corps levels, while less capable vehicles reflect lesser brigade, company, platoon and unit requirements.

The US Department of Defense (DoD) groups systems operated at the corps, divisional and brigade level under the general category of tactical UAV. This category includes the cancelled IAI/TRW Hunter and AlliantTechsystems Outrider UAVs as well as the AAI Shadow 200 now under development.

Tactical systems used by lower echelon land- force units are generally grouped under the equally broad sub-category of short-range UAVs, based on a maximum range of up to 50km and an endurance of around 2h. Representative systems range from the hand-launched AeroVironment Pointer and Codarra Advanced Systems Spectre, both essentially based around miniature sailplanes, and BAI Systems' Dragon Drone family and the Silver Arrow Micro V.

The coherence of the tactical category is further complicated by the recent emergence of micro unmanned air vehicles with wingspans less than 250mm (10in). Examples include the Lockheed Martin Sanders (now BAE Systems) MicroStar and the MLB Trochoid.

The boundaries of the tactical UAV classification are being pushed further out by the desire for increased endurance from brigade- and divisional-level systems, which, at the same time, are required to operate at ranges of only around 5km.

Shift to small

In parallel, the warfighter requirement for increased situational awareness in the immediate tactical vicinity, often areas of 1,000m2 or less, appears to be driving a general shift in short-range system development towards small to micro-scale UAVs, and a general move away from new investment in systems dedicated to monitoring areas in the 20-50km range.

This particular segment of the short-range market was previously dominated by systems intended mainly for use in artillery spotting roles, with early generation systems either derived from target drones or using purpose-built air vehicles with technical limitations which meant that most have been unable to meet higher order requirements. Notwithstanding, a significant number of new systems emerging from second- and third-world manufacturers are targeting this segment to provide their domestic defence forces with their first experience in fielding UAVs.

While UAVs have generally been single-role vehicles, one of the key characteristics of emerging systems is the ability to provide far greater capability within a single air vehicle type. A single HAE UAV, for example, can now simultaneously carry out radar surveillance over a large theatre, with either radar spot beams or electro-optical sensors watching targets of interest, while monitoring hostile force emissions with onboard signals intelligence systems.

At the same time, the air vehicle can also be equipped with an airborne data-relay terminal enabling communications with covert forward- deployed ground forces or unattended ground sensors. Or the UAV could carry small air-to-ground munitions to destroy mobile missile launchers and other time-critical targets, in doing so further blurring the boundaries of unmanned system classification.

This expansion of capability is, in turn, having a direct impact on the traditional air power concepts of reach, penetration and time on station. UAV development continues to expand the options for maintaining pervasive air power within a theatre of operations, without the accompanying necessity of placing air crews at risk. This also enhances the political and cultural acceptability of their use.

Unique concerns

Despite the apparent advantages, deciding when to choose an unmanned solution is still an emerging science for military planners. The traditional military evaluation of manned platforms is a complex process based on the analysis of aspects such as cost, performance, survivability, air vehicle flexibility or utility and, in the case of strike platforms, lethality.

In the context of UAVs, however, the analytical process for the evaluation of their utility is not as clearly defined, particularly with regard to the unique political concerns that complicate direct comparisons between the effectiveness of manned and unmanned aircraft.

At the forefront of these concerns is the concept of acceptable expendability, which holds that a UAV can be used to apply air power in higher risk operations because of the lower cost and attendant lower risk of loss of life compared with using a manned platform.

While this is a key driver behind current military interest in UAV systems, how the argument would hold up, say, in the case of a surveillance UAV experiencing a technical failure and crashing into a crowded marketplace in a potentially hostile country remains to be seen.

Allegations that Serbia used short-range tactical UAVs as part of its "ethnic cleansing" operations in Kosovo suggest that unmanned systems can quickly be characterised in less than humane terms if players on either side of a conflict deem it politically useful.

Political acceptability also stands as a barrier still to be crossed before unmanned combat air vehicles can be deployed, with the distinction between a UCAV and a cruise missile still hotly debated within the context of the interpretation of existing international arms control agreements controlling such weapons.

The choice of future unmanned combat air vehicle missions will also be a political determination. Sending a UCAV to destroy a remote radar site is a relatively clear-cut mission compared with using it to attack a surface-to-air-missile battery protecting a command bunker in a heavily populated urban area.

Not surprisingly, the issues raised by the weaponisation of UAVs and the emergence of UCAV concepts has prompted an increased interest in optionally manned aircraft or, in the case of development work by Dassault and others, the notion of a manned "controller aircraft" flying alongside unmanned platforms during operations against potentially sensitive targets.

Development dangers

Choosing a UAV can also be heavily influenced by the perils associated with changing political priorities, and the ever-present technical risks inherent in developmental programmes. The DoD, for example, has launched no fewer than 17 UAV development programmes in the past 20 years at a cost of some $6-7 billion. To date, however, only two systems, Pioneer and Predator, have been accepted into operational service, while three others - the USAir Force's Global Hawk, US Army's Shadow 200, and US Navy's Northrop Grumman Fire Scout VTUAV - are in various stages of development.

The cancelled projects, totalling at least $5 billion in accumulated expenditure, include the Amber, Aquila, Compass Cope, Compass Dwell, Condor, DarkStar, Hunter, Outrider, Raptor and at least one still-classified project.

Overcoming obstacles

Not surprisingly, the military's dismal track record has been a major source of discouragement to the wider adoption of UAV systems by the civil sector, although clearly it does not present a permanent obstacle.

In contrast to the plethora of military approaches, there are relatively few well-thought-out concepts for UAV operations in the civil sector. There is also a lack of a widely accepted civilian methodology to assess UAV utility equivalent to that used by the military. Notwithstanding, the developing interest in UAVs among civil users involves many development drivers that parallel those shaping military systems, though with divergences in other areas.

What contrasts most significantly between military and civil concepts for UAV applications is that the desire for cost savings is the main factor driving commercial operators towards unmanned solutions.

In turn, this emphasises low-risk approaches, which also means less funding will be available for development programmes unless they are underwritten by government agencies or, in some instances, by defence departments as an investment in dual-use technologies with potential military applications.

Civil utility

So far, the lead in civil UAV development has largely come from the scientific and research sectors. Development work by NASA, for example, has stemmed not only from its desire to explore alternative flight concepts for manned systems, but also from the demands of the US agency's Earth science mission.

Unsurprisingly, this has placed NASA in a unique position to exploit UAVs, particularly in the development of endurance systems as low-cost surrogates for satellites in remote sensing roles, and for carrying out upper atmosphere research within the atmosphere itself.

While the air vehicle requirements for the civil endurance mission have close parallels with military concepts, there remain clear areas of difference. For military endurance UAVs such as the Global Hawk, missions generally require deployment into a distant theatre (reach), followed by extended loiter (time on station), then a return to an operational base.

For a civil endurance system, such as the Aerosonde commercial meteorological monitoring UAV, the endurance mission is primarily aimed at providing low-cost controlled flight operations across vast distances between ground control stations, carrying a relatively simple payload and with no loiter requirements.

In the case of commercial endurance platforms such as the Scaled Composites/Angel Technologies Proteus, intended for use as an atmospheric telecommunications relay platform, range capability is largely a byproduct of the requirement to carry a heavy payload to high altitude and to loiter over the same geographical point for long periods.

Civil requirements for both reach and time on station are emerging, particularly for remote area science missions, but also through the development of concepts such as the US Department of State's Project Peace Wing proposal to use endurance UAVs to monitor civilian disasters in third-world nations.

Civil requirements corresponding to the military tactical unmanned air vehicles see strong emphasis being placed on imagery generation. This is particularly the case in emerging concepts for UAVs to support law enforcement, search and rescue and, customs tasks. Other unique drivers are also emerging, however, from sectors such as media and entertainment, where VTUAVs are being explored for use as television camera platforms in place of manned helicopters.

One characteristic of this segment of the market is that potential civil users are more likely to prefer developed and mature UAV systems. Accordingly, as civilian applications develop, a major market may emerge for leased UAV services. A related market may also develop for UAV operator training services, possibly in a form similar to the pilot training academies used by both civil and military trainees alike.

Regardless of how civil concepts develop, the biggest challenge to the proliferation of UAVs will remain their cost effectiveness. In that regard, many an investor will be looking at military programmes to provide guidance on future decisions in what has been, thus far, a tumultuous industry irrespective of its long-term potential.

Source: Flight International