This document presents the Department of Defense’s (DoD) roadmap for developing and employing unmanned aerial vehicles (UAVs) over the next 25 years (2000 to 2025). It describes the missions identified by theater warfighters to which UAVs could be applied, and couples them to emerging capabilities to conduct these missions. A series of Moore’s Law-style trends are developed to forecast technological growth over this period in the key areas of propulsion, sensor, data link, and information processing capabilities. The result is a roadmap of capability-enhancing opportunities plotted against the life spans of current and projected UAVs. It is a map of opportunities, not point designs - a descriptive, not a prescriptive, future for UAVs.
This study does not necessarily imply future officially sanctioned programs, planning, or policy. Further, the conclusions at the end of this study (section 6.5) are not currently funded or programmed within the military Services’ plans. This section is not direction to any DoD organization to pursue any specific course of action. It is merely intended to highlight opportunities in the broad areas of technology, operations, and organizations, that the Services, industry, or other UAV-related organizations may wish to consider when developing plans and budgets for future UAV activity.
The U.S. military has a long and continuous history of involvement with UAVs, stretching back to the Sperry/Curtiss N-9 of 1917. UAVs have had active roles in the Vietnam conflict (3435 sorties), Persian Gulf War (over 520 sorties), and in the ongoing Balkan operations, providing critical reconnaissance in each. With recent technologies allowing more capability per pound, today’s UAVs are more sophisticated than ever. As the military’s recent operational tempo has increased, so too has the employment of UAVs. Over the past decade, the Department of Defense has invested over $3 billion in UAV development, procurement, and operations, and will likely invest over $4 billion in the coming decade. Today, the DoD has 90 UAVs in the field. By 2010, this inventory is programmed to grow to 290, with UAVs performing a wider variety of missions than just reconnaissance.
New capabilities projected for UAVs over the next 25 years include:
- Silent flight as fuel cells supplant internal combustion engines in some systems.
- 60 percent gains in endurance due to increasingly efficient turbine engines.
- Rotorcraft capable of high speeds (400+ kts) or long endurance (24+ hrs) while retaining the ability to hover.
- Endurance UAVs serving as GPS pseudo-satellites and airborne communications nodes to provide theater and tactical users with better connectivity, clearer reception, and reduced vulnerability to jamming.
- Faster cruise missile targeting due to more precise terrain mapping by high altitude UAVs.
- Self-repairing, damage compensating, more survivable UAVs.
- Significantly speedier information availability to warfighters through onboard real-time processing, higher data rates, and covert transmission.
The advantages offered by UAVs to the military commander are numerous and often subject to debate. These advantages accrue most noticeably in certain mission areas, commonly categorized as "the dull, the dirty, and the dangerous." In an era of decreasing force size, UAVs are force multipliers that can increase unit effectiveness. For example, due to its vantage point and multiple sensors, one hovering unmanned sentry could cover the same area as ten (or more) human sentries ("the dull"). The threat of nuclear, biological, or chemical (NBC) attacks on the U.S. or its military forces abroad will likely remain a key national security concern for the next 25 years, prompting the need for means to conduct operations in their aftermath. UAVs could reconnoiter contaminated areas without risk to human life ("the dirty"). In a climate more demanding of lossless engagement, UAVs can assume the riskier missions and prosecute the most heavily defended targets. Unaccompanied combat UAVs (UCAVs) could perform the high-risk suppression of enemy air defenses (SEAD) missions currently flown by accompanied EA-6s or F-16s ("the dangerous"). In such a role, UAVs would be potent force multipliers, directly releasing aircraft for other sorties.
Finally, and most fiercely debated, is the potential cost advantage offered by UAVs. Serious comparisons of manned versus unmanned system acquisition costs tend to show little advantage for the latter (the adjusted costs for reaching first flight for the U-2 in 1955 and the RQ-4/Global Hawk in 1998 were roughly the same). Likewise, any savings in procurement costs cited for UAVs by deleting the cockpit, its displays, and survival gear is typically offset by the cost of similar equipment in the UAV ground element. However, with innovative concepts of operation, UAVs may offer increased efficiencies in operations and support costs due to the reduced need to actually fly pilot proficiency and continuation training sorties. Such reductions in UAV O&S costs offer the potential for life cycle cost savings if adopted and managed correctly within the overall weapon system tasking tempo directed by the Defense Planning Guidance.
UAVs will play a major role in the increasingly dynamic battle control that will evolve in the 21st century. There will be micro air vehicles as well as behemoths. UAVs will stay airborne for weeks or months and longer, fly at hypersonic speeds, sense data in revolutionary ways, and communicate their data at unprecedented rates. Challenges, such as providing an adequate C3 infrastructure to capitalize on unmanned as well as manned operations, remain to be overcome. However, the decisions made now will lay the foundation for how far and how fast these advances are implemented. Only our imagination will limit the potential of UAVs in the 21st century.
Executive Summary * Table of Contents * List of Figures * List of Tables * 1.0 Introduction *2.2 Developmental UAV Systems *
2.2.4 Tactical Control System *
2.3.2 Concept Exploration UAV Systems *
4.1.1 Capability Requirements *
4.2.1 Capability Requirements *
4.2.2 Imagery Intelligence (IMINT) *
4.2.3 Signals Intelligence (SIGINT) *
4.2.4 Measurement & Signatures Intelligence (MASINT) *
5.1.2 Aircraft vs. Satellite Support *
5.1.3 Forward Operating Locations *
5.2 Operational Concepts Development *
5.3 Reliability & Sustainability *
6.2 UAV Roadmap for 2000-2025 *
6.3 Comparative Costs of Manned vs. Unmanned Aircraft *
6.3.3 Operations & Support Costs *
Appendix …………………………………………………………………………….. A1
Figure 2.4-1: DoD Annual Funding Profile for UAVs. *
Figure 2.4-2: Timeline of Current and Planned DoD UAV Platforms. *
Figure 3.1-1: IPL Priorities link to UAV Missions. *
Figure 4.1-1: UAV Platform Requirements. *
Figure 4.1.2-2: Specific Fuel Consumption Trends. *
Figure 4.1.2-3 Mass Specific Power Trends. *
Figure 4.2-1: UAV Payload Requirements. *
Figure 4.2.3-2: Forecast of Amount of Bandwidth Continuously Processable. *
Figure 4.3-1: UAV Communications Requirements. *
Figure 4.3-2: Airborne Data Link Data Rate Trends. *
Figure 4.4-1: UAV Information Processing requirements. *
Figure 4.4-2: Autonomous Control Level Trend. *
Figure 4.4-3: Processor Speed Trend. *
Figure 5.1-1: UAV Operations Requirements. *
Figure 5.3-1: Israeli UAV mishap causes. *
Figure 5.4-1: Relative Demand in Actual vs. Simulated Flight Training. *
Table 2.2.3-1: Summary History of Recent UAV Programs. *
Table 2.4-2: Classes of Worldwide Military Reconnaissance UAVs. *
Table 3.2-1: UAV Mission Areas *
Table 3.2-2: CINC/Service UAV Mission Prioritization Matrix--2000 *
Table 3.2-3: SOCOM UAV Mission Prioritization Matrix--2000 *
Table 4.2.2-1: Operational Performance of Current EO/IR sensors. *
Table 4.2.3-1. Proposed UAV SIGINT Demonstration Program. *
Table 4.2.4-1. Potential UAV MASINT Sensing Applications. *
Table 4.2.4-2: Bacteriological Agent Detection Schemes. *
Table 4.4.4-1: Future Processor Technologies. *
Table 4.5-1: Comparison of Service Laboratory Initiatives with CINC Requirements. *
Table 6.1-1: Operational Metrics. *
Table 6.3.1-1: Manned vs. Unmanned Aircraft Development Costs. *
Table 6.3.2-1: Manned vs. Unmanned Procurement Costs. *
Table 6.4.2-1: Status of FAA and NATO UAV Flight Regulations. *
The purpose of this roadmap is to stimulate the planning process for US military unmanned aerial vehicle (UAV) development over the period from 2000 to 2025. It is intended to assist Department of Defense (DoD) decision makers in developing a long-range strategy for UAV development and acquisition in the forthcoming Quadrennial Defense Review (QDR) and beyond. It addresses the following key questions:
- What requirements for military capabilities could potentially be filled by UAVs?
- What platform, sensor, communication, and information processing technologies are necessary to provide these capabilities?
- When will these technologies become available to enable the above capabilities?
This roadmap is meant to complement ongoing Service efforts to redefine their roles and missions for handling 21st century contingencies. The Services see UAVs as becoming integral components of the future Army’s Brigade Combat Teams (BCTs), the Navy’s DD-21 destroyers, and the Air Force’s Aerospace Expeditionary Forces (AEFs). As an example, the Army’s current "Transformation" initiative envisions each BCT having a reconnaissance, surveillance, and target acquisition (RSTA) squadron equipped with a UAV system, reflecting the initiative’s emphasis on reducing weight, increasing agility, and integrating robotics.
The approach used in this document is to:
- Identify requirements relevant to defining UAV system capabilities from the most comprehensive, authoritative sources of warfighter needs. Link these requirements to capabilities needed in future UAV platforms, sensors, communications, and information processing.
- Develop a series of forecasting trends ("Moore’s Laws") for the next 25 years for those technologies driving UAV platform, sensor, communication, and information processing performance. Define the timeframe during which the technology to address these requirements will become available for fielding.
- Synthesize an integrated plan ("Roadmap") for UAV development opportunities by combining the above requirements and technology trends.
Such a roadmap could potentially be used in a number of ways, to include:
- Evaluating the technologies planned for incorporation in current UAV programs for underachieving or overreaching in capabilities
- Defining windows of feasibility for introducing new capabilities in the near term on existing systems or for starting new programs.
- Identifying key enabling technology development efforts to support now for use in the far term for inclusion in the Defense Technology Objectives, the Joint Warfighting Science and Technology Plan, and the Defense Technology Area Plan.
Like its highway namesake, this roadmap is descriptive, not prescriptive, in nature. It describes the options of routes (current and future technologies) available to reach a number of destinations (mission needs). It neither advocates specific UAV programs nor prioritizes the requirements, as this is the responsibility of the Joint Requirements Oversight Council (JROC) and the Services. It does, however, identify future windows when technology will become available to enable new capabilities, linked to warfighters’ needs, to be incorporated into current or planned UAV programs.
Many of the technologies discussed in this study are currently maturing in Defense research laboratories. The roadmap’s span of 25 years was chosen to accommodate the usual 15 years required to transition a demonstrated laboratory capability into an operationally fielded system, followed by 10 years of spiral development of the system until the ultimate derivative is in production, or production ends. This constitutes one (the next) generation of aircraft and payload technology.
The information presented in this study is current as of 31 December 2000.
This chapter provides condensed descriptions of current Defense Department UAV efforts as background for the focus of this roadmap—requirements and technologies for future UAV capabilities. It categorizes the Department’s UAVs as operational (those currently operated by field units), developmental (those undergoing evaluation for eventual fielding with such units), and other, which includes residual assets withdrawn from service with fielded units, concept exploration platforms, and conceptual UAVs undergoing definition. Detailed descriptions are available in the Defense Airborne Intelligence, Surveillance, and Reconnaissance Plan (DAISRP) and at the websites listed with specific systems below.
The Air Force RQ-1 Predator began as an Advanced Concept Technology Demonstration (ACTD) in 1994 and transitioned to an Air Force program in 1997. It takes off and lands conventionally on a runway and can carry a 450 lb payload for 24+ hours. Operationally, it is flown with a gimbaled electro-optical/infrared (EO/IR) sensor and a synthetic aperture radar (SAR), giving it a day/night, all-weather (within aircraft limits) reconnaissance capability. It uses both a line-of-sight (C-band) and a beyond-line-of-sight (Ku-band SATCOM) data link to relay color video in real time to commanders. Since 1995, Predator has flown surveillance missions over Iraq, Bosnia and Kosovo. The Air Force operates two squadrons of Predators, and is building toward a force of 12 systems consisting of 48 aircraft. Initial Operating Capability (IOC) is anticipated in 2001. www2.acc.af.mil/library/factsheets/predator
The Navy/Marine RQ-2 Pioneer has served with Navy, Marine, and Army units, deploying aboard ship and ashore since 1986. Initially deployed aboard battleships to provide gunnery spotting, its mission evolved into reconnaissance and surveillance, primarily for amphibious forces. Launched by rocket assist (shipboard), by catapult, or from a runway, it recovers into a net (shipboard) or with arresting gear after flying up to 4 hours with a 75 lb payload. It currently flies with a gimbaled EO/IR sensor, relaying analog video in real time via a C-band line-of-sight (LOS) data link. Since 1991, Pioneer has flown reconnaissance missions during the Persian Gulf, Bosnia, and Kosovo conflicts. The Navy currently fields three Pioneer systems (one for training) and the Marines two, each with five aircraft. Pioneer is to be replaced by the Fire Scout Vertical Takeoff and Landing Tactical UAV (VTUAV) beginning in FY03.
http://uav.navair.navy.mil/pioneer
The RQ-5 Hunter was originally intended to serve as the Army’s Short Range UAV system for division and corps commanders. It takes off and lands (using arresting gear) on runways and can carry 200 lb for over 11 hours. It uses a gimbaled EO/IR sensor, relaying its video in real time via a second airborne Hunter over a C-band line-of-sight data link. Hunter deployed in 1999 to Kosovo to support NATO operations. Although production was cancelled in 1996, seven low rate initial production (LRIP) systems of eight aircraft each were acquired, four of which remain in service: one for training and three for doctrine development and exercise and contingency support. Hunter is to be replaced by the Shadow 200 (Tactical UAV, or TUAV) starting in FY03. www.redstone.army.mil/jtuav
The Air Force RQ-4 Global Hawk is a high altitude, long endurance UAV designed to provide wide area coverage (up to 40,000 nm2 per day). It successfully completed its Advanced Concept Technology Demonstration (ACTD) and its Military Utility Assessment in June 2000. It takes off and lands conventionally on a runway and carries a 1950 lb payload for 36 hours. Global Hawk carries both an EO/IR sensor and a SAR with moving target indicator (MTI) capability, allowing day/night, all-weather reconnaissance. Sensor data is relayed over line-of-sight (X-band) and/or beyond-line-of-sight (Ku-band SATCOM) data links to its Mission Control Element (MCE), which distributes imagery to up to seven theater exploitation systems. ACTD residuals consist of four aircraft and two ground control stations. The Air Force has budgeted for two aircraft per year starting in FY02; IOC is expected to occur in FY05.
www2.acc.af.mil/library/factsheets/globalhawk
Fire Scout is a vertical take-off and landing (VTOL) tactical UAV (VTUAV) currently in Engineering and Manufacturing Development (EMD). Fire Scout can remain on station for at least 3 hours at 110 nm with a payload of 200 lbs. Its Modular Mission Payload (MMP) consists of a gimbaled EO/IR sensor with an integral laser designator/rangefinder. MMP data is relayed to its ground control station and to remote data terminals in real time via a Ku-band LOS data link, with a UHF backup for control.
The Army selected the RQ-7 Shadow 200 (formerly the TUAV) in December 1999 to meet its Close Range UAV requirement for support to ground maneuver commanders. Catapulted from a rail, it is recovered with the aid of arresting gear. It will be capable of remaining on station for 4 hours at 50 km (27 nm) with a payload of 60 lbs. Its gimbaled EO/IR sensor will relay video in real time via a C-band LOS data link. Eventual procurement of 44 systems of four aircraft each is expected with IOC planned in early FY03.
Table 2.2.3-1: Summary History of Recent UAV Programs.
First Number Number in
System Manufacturer Lead Service Flight IOC Built Inventory Status
RQ-1/Predator General Atomics Air Force 1994 2001 54 15 87 ordered
RQ-2/Pioneer Pioneer UAVs, Inc Navy 1985 1986 175 25 Sunset system
BQM-145 Teledyne Ryan Navy 1992 n/a 6 0 Cancelled ‘93
RQ-3/DarkStar Lockheed Martin Air Force 1996 n/a 3 0 Cancelled ‘99
RQ-4/G’Hawk Northrop Grumman Air Force 1998 2005 5 0 In E&MD
RQ-5/Hunter IAI/TRW Army 1991 n/a 72 42 Sunset system
Outrider Alliant Techsystems Army 1997 n/a 19 0 Cancelled ‘99
RQ-7/Shadow200 AAI Army 1991 2003 8 0 176 planned
Fire Scout Northrop Grumman Navy 1999 2003 1 0 75 planned
The Tactical Control System (TCS) is an open architecture, common interoperable control system software for UAVs and supported C4I nodes currently in Engineering and Manufacturing Development (EMD). TCS will provide five scalable levels of UAV vehicle, sensor, and payload command and control, from receipt of secondary imagery (Level 1) to full control of the UAV from takeoff to landing (Level 5). It will also provide dissemination of imagery and data collected from multiple UAVs to a variety of Service and Joint C4I systems. IOC for TCS will coincide with the fielding of the Navy and Marine Fire Scout and with the Army Shadow 200 Block II upgrade.
http://uav.navair.navy.mil/tcs
Approximately 50 hand-launched, battery powered FQM-151/Pointers have been acquired by the Marines and the Army since 1989 and were employed in the Gulf War. Most recently, Special Operations Command Europe (SOCEUR) employed one system (3 aircraft) in Europe, and the Army acquired six systems for use at its Military Operations in Urban Terrain (MOUT) facility at Ft Benning, GA. Pointers have served as testbeds for numerous miniaturized sensors (e.g., uncooled IR cameras and chemical agent detectors) and have performed demonstrations with the Drug Enforcement Agency, National Guard, and special operations forces. http://uav.navair.navy.mil/smuav
The Army’s Night Vision Electronic Sensors Directorate (NVESD) operates four Sentry UAVs (acquired in 1997), four Flight Hawk mini-UAVs, three Camcopters, and a Pointer system as testbeds for evaluating various night vision sensors and employment concepts.
2.3.2 Concept Exploration UAV Systems
Service laboratories have developed a number of UAVs tailored to explore specific operational concepts. The Marine Corps Warfighting Laboratory (MCWL) is currently exploring three such concepts. The first, Dragon Warrior (or Cypher II) was intended to perform over-the-shore, fixed-wing flight, then land, remove its wings, and convert to a hovering design for urban operations. This effort was transferred to the auspices of the NVESD in late 2000, and the MCWL is now proposing a refined version of its Dragon Warrior concept. Neither has yet flown.
www.mcwl.quantico.usmc.mil/images/downloads/dragonwarrior
A converted K-Max helicopter is being used to explore the Marines’ Broad-area Unmanned Responsive Resupply Operations (BURRO) concept of ship-to-shore or ship-to-ship resupply by UAV. It has been flying since early 2000.
Dragon Eye is a mini-UAV (2.4 foot wingspan and 4 lbs weight) developed as one potential answer to the Navy’s Over-The-Hill Reconnaissance Initiative and the Marines’ Interim Small Unit Remote Scouting System (I-SURSS) requirement. Its design is still evolving; the first prototype flew in May 2000. Each of the three Marine Expeditionary Forces will evaluate ten Dragon Eyes (30 total) during 2002. www.mcwl. quantico.usmc.mil/images/downloads/dragoneye)
The Counter Proliferation ACTD, sponsored by the Defense Threat Reduction Agency (DTRA), envisions deploying several mini-UAVs (Finder) from a larger Predator UAV to conduct point detection of chemical agents and relay the sensor results back through Predator. Fifty Finders are to be built as part of this ACTD. www.jhuapl.edu/colloq/foch
The Naval Research Laboratory (NRL) has a history of exploring new aerodynamic and propulsion concepts for maritime UAVs. Besides the Dragon Eye and Finder projects described above, the NRL has built and flown nearly 20 original small and micro UAV designs in recent years. The Naval Air Warfare Center Aircraft Division (NAWC/AD) maintains a small UAV test and development team at Webster Field, Maryland, and operates a small fleet with nine types of UAVs. This team managed the evolution of the Exdrone into the Dragon Drone for use by the MCWL. Together, NRL and NAWC/AD operate nearly 30 models of UAVs, many of which are in-house designs.
The Defense Advanced Research Projects Agency (DARPA) is currently sponsoring five innovative UAV programs. The DARPA/Air Force X-45 Unmanned Combat Air Vehicle (UCAV) prototype contract was awarded to Boeing in March, 1999. Its public debut was in September 2000, and first flight is anticipated in the Summer/Fall of 2001. The goal of the UCAV is to perform the suppression of enemy air defenses (SEAD) mission with an aircraft that costs one-third as much to acquire as a Joint Strike Fighter (JSF) and is one-quarter as expensive to operate and support. www.darpa.mil/tto/programs/ucav
A similar DARPA/Navy Advanced Technology Demonstration (ATD) is to develop UCAV-Navy (UCAV-N) prototypes and examine concepts for an eventual carrier-based UCAV for the surveillance, strike, and SEAD missions. Its goal is to cost a third as much to acquire as a JSF and one half as much to operate and support. Two definition contracts are underway, with prototype flights possibly beginning in 2002. Neither the Air Force nor the Navy UCAV ATD is expected to lead to a fielded UCAV design before 2010. www.darpa.mil/darpatech2000/speeches/ttospeeches/ttoucav-n(scheuren)
The Advanced Air Vehicle (AAV) program is developing two rotorcraft projects, the Dragon Fly Canard Rotor Wing (CRW) and the A160 Hummingbird. The CRW will demonstrate the ability to takeoff and land from a hover, then transition to fixed wing flight for cruise. The result will be a high speed (400+ kts) rotorcraft UAV. CRW is expected to fly in late 2001. The A160 UAV uses a hingeless, rigid rotor to achieve a high endurance (24+ hrs), high altitude (30,000 ft) rotorcraft. It is to fly in late 2002.
www.darpa.mil/tto/programs/aav
Finally, DARPA was exploring four designs for micro air vehicles (MAV) - aircraft less than 6 inches in any dimension. Two, the Lutronix Kolibri and the Microcraft Ducted Fan, rely on a shrouded rotor for vertical flight, while the Lockheed Martin Sanders MicroStar and the AeroVironment Black Widow are fixed wing, horizontal fliers. The envisioned utility of MAVs is to aid the individual soldier/Marine engaged in urban warfare. The micro air vehicle program pushed the envelope in small, lightweight propulsion, sensing, and communication technologies. As of FY01, all MAV funding was put toward defining the Organic Air Vehicle (OAV) within the DARPA/Army Future Combat Systems program. www.darpa.mil/tto/programs/mav
The Services are currently funding efforts to define three UAV systems for possible fielding in the post 2010 timeframe. The Air Force’s involvement in DARPA’s X-45/UCAV ATD may, depending on its outcome, lead to an operational version (UCAV-AF) for the SEAD mission. The Navy is studying the feasibility of developing a naval combat UAV (UCAV-N) from its parallel ATD. The Navy is also in the process of defining the Multi-Role Endurance (MRE) UAV, whose performance would be in the realm between that of the tactical Fire Scout and the strategic Global Hawk. A fourth effort, the Air Force Research Laboratory’s (AFRL’s) Sensorcraft, moved from being an unfunded concept to a funded initiative in FY01; its design is to be optimized for future sensing capabilities. http://uav.navair.navy.mil/mre
Between 1990 and 1999, the Department of Defense invested over $3 billion in UAV development, procurement, and operations. It plans to invest $2.3 billion more by 2005 (see Figure 2.4-1). Projecting this rate out to 2010, DoD will likely invest $4.2 billion in UAVs in the first decade of the new century. By 2010, the U.S. UAV inventory is expected to grow from 90 today to 290 and to support a wider range of missions.
Figure 2.4-1: DoD Annual Funding Profile for UAVs.
A consolidated snapshot of Service UAV programs is illustrated in Figure 2.4-2, which presents a 40-year picture (1985-2025) of historical and planned U.S. UAV procurement. End dates were estimated for those programs without a planned date for withdrawal from service.
Figure 2.4-2: Timeline of Current and Planned DoD UAV Platforms.
Currently, some 32 nations manufacture more than 150 models of UAVs; 55 countries operate some 80 types of UAVs, primarily for reconnaissance. Table 2.4-2 categorizes current military uses of selected foreign UAVs to identify any mission niches not being performed by current U.S. UAVs. Systems not yet fielded are italicized in the table. Knowledge of such niches allows U.S. planners to rely on and better integrate the unique capabilities of coalition UAV assets in certain contingencies. The one niche common to a number of other countries but missing in the U.S. UAV force structure is a survivable penetrator for use in high threat environments. France and Germany have employed CL-289s with success in Bosnia and Kosovo, Russia’s VR-3 Reys may be succeeded soon by the Tu-300, and Italy’s new Mirach 150 supports its corps-level intelligence system. All are essentially jet engines with cameras attached which fly at low altitude at high subsonic speed to increase their survivability. Previous U.S. counterparts, the D-21 (a Mach 3 reconnaissance drone spun-off from the SR-71) and the RQ-3 DarkStar, relied on supersonic speed or stealth as well as high altitude for their survivability.
Table 2.4-2: Classes of Worldwide Military Reconnaissance UAVs.
Tactical Specialized Endurance
Country Over-the-Hill Close Range Maritime Penetrating Medium Rng Long Rng
United States Pointer Hunter/Shadow Fire Scout Predator Global Hawk
France Lulleby Crecerelle Marvel CL-289 Eagle/Horus
Germany Luna Brevel Seamos CL-289 under study
United Kingdom Sender/Observer Phoenix
Italy Dragonfly Mirach 26 Mirach 150 Predator
Israel Eyeview Searcher Heron
Russia R90 Shmel/Yak-61 VR-3 Reys
VR-2 Strizh
The purpose of this chapter is to identify emerging requirements for military capabilities which could possibly be addressed by UAVs. A requirement is defined here as an unmet need for a capability. The key question addressed in this section is: What are the requirements for military capabilities that could potentially be met by employing UAVs?
3.1 Warfighters’ Roles for UAVs
The primary source for identifying requirements are the Integrated Priority Lists (IPLs), which are submitted annually by each of the nine Unified Command CINCs to prioritize the warfighting capability shortfalls of each theater. They are the seminal source of joint requirements from our nation’s warfighters. Taken as a whole, IPLs offer the advantages of being "direct from the field" in pedigree, joint in perspective, enumerating worldwide (vice service- or theater-centric) requirements, and not originating from a UAV-centric forum.
Figure 3.1-1: IPL Priorities link to UAV Missions.
3.2 Requirements Association with UAVs
Despite only EO/IR/SAR sensors being operationally fielded on DoD UAVs to date, Table 3.2-1 shows a number of nontraditional payloads which perform tasks within these 15 mission areas have been previously flown on UAVs in proof-of-concept demonstrations. These demonstrations show that UAVs can be a candidate solution for certain requirements. Whenever possible, UAVs should be the preferred solution over their manned counterparts for those requirements posing the familiar three jobs best left to UAVs: the dull (long dwell), the dirty (sampling for hazardous materials), and the dangerous (extreme exposure to hostile action).
Table 3.2-1: UAV Mission Areas
Requirements
UAV Mission Attributes Involved UAV Experience(Mission Areas) "Dull" "Dirty" "Dangerous" (UAV/Payload and/or Place Demonstrated and Year)
Imagery x x Pioneer, Exdrone, Pointer/Gulf War, 1990-91
Intelligence (IMINT) Predator, Pioneer/Bosnia, 1995-2000
Hunter, Predator, Pioneer/Kosovo, 1999
Communications x Hunter/CRP, 1996; Exdrone/TRSS, 1998
Global Hawk/ACN, Predator/ACN, ongoing
Force Protection x x Camcopter, Dragon Drone/Ft Sumner, 1999
Signals Intelligence x x Pioneer/SMART, 1995
(SIGINT) Hunter/LR-100/COMINT, 1996
Hunter/ORION, 1997
Weapons of Mass x x Pioneer/RADIAC/LSCAD/SAWCAD, 1995
Destruction (WMD) Telemaster/Analyte 2000, 1996
Pointer/CADDIE 1998; Hunter/SAFEGUARD, 1999
Theater Air Missile x x Israeli HA-10 development, (canceled)
Defense (TAMD) Global Hawk study, 1997
Suppression of Enemy x Hunter/SMART-V, 1996
Air Defenses (SEAD) Hunter/LR-100/IDM, 1998
Combat Search and x Exdrone/Woodland Cougar Exercise, 1997
Rescue (CSAR) Exdrone/SPUDS, 2000
Time Critical Targeting (TCT) x Predator w/JSTARS/Nellis AFB, 1999
Mine Counter x Pioneer/COBRA, 1996
Measures (MCM)
Meteorology and x x Aerosonde/Visala, 1995
Oceanography Predator/T-Drop, 1997
(METOC)
Counter Narcotics (CN) x x Predator/Ft Huachuca, 1995
Psychological Ops x Non-DoD UAV/leaflet dispensing, 1990’s
Post Single Integrated x x DarkStar mission (canceled)
Operations Plan (SIOP)
Forward Operating x Global Hawk/Linked Seas demo, 2000
Location (FOL)
In response to a recent Joint Staff-led, Joint Requirements Oversight Council-validated survey, Unified Command and Service staffs prioritized twelve mission areas in terms of their desirability for being performed by Predator, Global Hawk, Shadow 200, and Fire Scout; see Tables 3.2-2 and 3.2-3. Although one-to-one alignments of these 12 missions with the previously described 15 priorities from the IPLs for UAVs is inexact, the priorities of the two for concurrent mission areas are in general agreement; see the last column of Table 3.2-2 for a comparison.
Table 3.2-2: CINC/Service UAV Mission Prioritization Matrix--2000
|
Mission |
Predator |
Global Hawk |
TUAV |
VTUAV |
IPLs |
|
Reconnaissance |
1 |
1 |
1 |
1 |
1 |
|
Signals Intel |
3 |
2 |
7 |
4 |
4 |
|
Mine Countermeasures |
7 |
12 |
4 |
5 |
10 |
|
Target Designation |
2 |
11 |
3 |
2 |
- |
|
Battle Management |
8 |
7 |
5 |
7 |
- |
|
Chem-Bio Reconnaissance |
10 |
10 |
6 |
9 |
5 |
|
Counter CC&D |
4 |
5 |
8 |
11 |
- |
|
Electronic Warfare |
6 |
4 |
9 |
10 |
7 |
|
Combat SAR |
5 |
8 |
10 |
8 |
8 |
|
Communications/Data Relay |
9 |
3 |
2 |
3 |
2 |
|
Information Warfare |
11 |
6 |
11 |
6 |
- |
|
Digitial Mapping |
12 |
9 |
12 |
12 |
- |
U.S. Special Operations Command’s (SOCOM’s) priorities differed substantially from those of the other CINCs due to its unique mission requirements and are therefore enumerated separately (see Table 3.2-3). SOCOM added seven missions: psychological operations (PSYOP), covert/clandestine sensor emplacement, decoy/pathfinder, team resupply, battle damage assessment (BDA), differential GPS, and weather reporting Although all 19 SOCOM missions were prioritized for both TUAV and VTUAV, only 14 of these missions were deemed applicable to Global Hawk and 12 to Predator, explaining the lack of entries under some missions for these UAVs. Also, some SOCOM priorities, such as "day/night/all-weather surveillance," were considered to be part of the overall "reconnaissance" priority, which explains the double entries for some missions.
Table 3.2-3: SOCOM UAV Mission Prioritization Matrix--2000
|
Mission |
Predator |
Global Hawk |
TUAV |
VTUAV |
|
Reconnaissance |
- |
5 |
7,8 |
7,8 |
|
Signals Intel |
- |
7 |
15 |
11 |
|
Mine Countermeasures |
10 |
12 |
11 |
11 |
|
Target Designation |
6 |
6 |
6,14 |
6,14 |
|
Battle Management |
7 |
8 |
16 |
16 |
|
Chem-bio Reconnaissance |
1 |
1 |
1 |
1 |
|
Counter CC&D |
- |
10 |
18 |
18 |
|
Electronic Warfare |
- |
- |
19 |
19 |
|
Combat SAR |
- |
11 |
17 |
17 |
|
Communications/Data Relay |
4,11 |
3 |
4,13 |
4,13 |
|
Information Warfare |
8 |
9 |
5 |
5 |
|
Digitial Mapping |
5 |
4 |
- |
- |
|
PSYOP (broadcast/leaflets) |
2 |
2 |
2 |
2 |
|
Covert sensor emplacement |
2 |
- |
3 |
3 |
|
Decoy/Pathfinder |
- |
- |
9 |
9 |
|
Team Resupply |
9 |
- |
10 |
10 |
|
Battle Dammage Assessment |
12 |
- |
12 |
12 |
|
GPS Psuedolite |
- |
13 |
- |
- |
|
Weather |
- |
14 |
- |
- |
Aircraft achieve their operational capabilities through the integration of a number of diverse technologies. Manned aircraft rely, in some measure, on the pilot (or aircrew) to provide this integration. Lacking them, unmanned aircraft therefore require even further integration, particularly in their sensing and communication capabilities. The key question addressed in this section is: What advances in platform, payload, communication, and information processing technologies are necessary to provide the CINCs’ desired capabilities?
Today’s UAVs compose 0.6 percent of our 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.
Enhanced reliability, a product of technology and training, is key to ensuring better mission availability of UAVs. Although today’s UAVs tend to cost less than their manned counterparts, this savings is achieved largely by sacrifices in reliability—omitting system redundancy and using components not originally developed for use in the flight environment—shortcuts which would be unacceptable if an aircrew is involved. The trade-offs involved between increased cost and extended life must be carefully weighed to avoid driving UAV costs to unacceptable levels. Technology offers some options for improving reliability today (e.g., electric versus hydraulic actuators), and more are needed for the future. Section 5.3 discusses the reliability issue further.
Survivability, a product of technology and tactics, must be improved to ensure UAVs remain mission effective. As with reliability, survivability considerations are often traded for lowered costs; higher attrition becomes a more acceptable risk without an aircrew being involved. While this plays directly to one of unmanned aviation’s strong suits—performing the overly dangerous mission—it detracts from a commander’s willingness to use UAVs when missions repeatedly fail to accomplish their objective. Section 4.1.3 examines survivability issues.
Autonomy, a product of technology and doctrine, must be developed for UAVs to expand into new roles and to grow in unmanned mission effectiveness. Increasing current limited capabilities to make time sensitive decisions onboard, making them consistently and correctly, and making them in concert with other aircraft, manned and unmanned, is critical for combat UAVs to achieve their full potential. The doctrine to allow using such autonomy in a commander’s rules of engagement (ROE) must be evolved in lockstep with the technology that enables it. Autonomy is discussed further in section 4.4.
Based on the CINC IPLs, the most desired platform capability, in the context of enhancing reconnaissance and surveillance, is increased coverage, which can be met by increasing the number, endurance, and/or sensing capability of stand-off assets. For penetrating assets, the addition of survivability features contributes to increasing their coverage capability. The following sections discuss technology-based opportunities for improving the endurance, sensing, and survivability features of future UAVs.
Figure 4.1-1: UAV Platform Requirements.
Endurance is driven by propulsion, both in terms of system efficiency (i.e., specific fuel consumption (SFC) or, for batteries and fuel cells, specific energy) and performance per unit mass (mass specific power, or MSP). SFC is the amount of fuel burned per time for the amount of power delivered by a combustion engine (i.e., pound (fuel)/hour/pound (thrust)). MSP is the ratio of the power delivered to the weight of the engine/battery/fuel cell (i.e., horsepower/pound).
Significant advances in propulsion technology have been achieved over the past decade by the AFRL-led, joint Integrated High Performance Turbine Engine Technology (IHPTET) program. Since its inception in 1988, it has increased the thrust-to-weight (T/W) ratio of its baseline small turbine class (Honeywell F124) engines by 40 percent, reduced SFC by 20%, and lowered engine production and maintenance costs by 40 percent. IHPTET concludes in 2003, but its successor, the Versatile Affordable Advanced Turbine Engines (VAATE) program, aims to improve each of these three criteria half again by 2015. If these trends can be continued through 2025, T/W will improve by 250 percent, SFC by 40 percent, and costs by 60 percent (see Figure 4.1.2-1). For UAV use, these goals may partially be met by deleting turbine blade containment rings and redundant controls, as well as reducing hot section lifetime from 2000 to 1000 hours or less. In combination, the T/W and SFC improvements provided by IHPTET should enable the number of endurance UAVs needed to provide 24-hour coverage of an area to be reduced by 60 percent, or conversely, the endurance of individual UAVs increased by 60 percent.
Figure 4.1.2-1. IHPTET and VAATE Program Goals and Trends
Figure 4.1.2-2 shows a threefold improvement in SFC has occurred from 1955 to the present day for the two dominant types of combustion engines: gas turbines (jet engines) and internal combustion engines (ICEs). Another 60 percent improvement in gas turbine SFC and 30 percent in ICE SFC should be realizable by 2025. These improvements translate directly into endurance, and therefore coverage, increases.
Using current jet fuels, SFC should not drop below a floor value of around 0.2 lb/hr-lb force, due to the maximum combustion temperature of these fuels. Lower SFC values may be obtained in the future following the introduction of new fuels such as JP-900 or endothermic JP. These developmental fuels are expected to reduce SFC floor values by another 2% (to around 0.196 lb/hr-lb force), assuming complementary advances in materials and fuel-cooling technologies, which are needed to increase combustion temperature.
Figure 4.1.2-2: Specific Fuel Consumption Trends.
Three types of electrical propulsion systems are available for UAVs: batteries, fuel cells, and solar cells. Specific energy is the amount of energy a battery or fuel cell stores per unit mass, usually measured in watt-hours per kilogram (hp-hours per lb). Higher specific energies lead to batteries with increased lifespan, which would lead to battery-powered aircraft with increased range and endurance. Future growth in battery specific energy capability is expected with the introduction of the Lithium-polymer battery, which suffers from a rather short lifespan (the result of internal self-shorting when an electric current is passed over the metal in the polymer).
The solid oxide fuel cell (SOFC), together with the multi-carbonate fuel cell (MCFC), represents the current state-of-the-art in fuel cell technology. A jump in specific energy capability is anticipated with the advent of the hydrogen-air, or proton exchange membrane (PEM), fuel cell, which is at least 5 years from production. Further advances in fuel cell technology could occur with hybrid cells, which use the waste heat from the cell to generate additional power via an attached turbine engine. By 2004, the MSP of fuel cell powered engines should equal or exceed that of noisy internal combustion engines, enabling their use in fielding silent airborne sentries (Figure 4.1.2-2) (see section 4.1.3).
Solar energy is a viable option for other types of UAVs, including high-altitude, long endurance UAVs, either for reconnaissance or for airborne communications relays. The AeroEnvironment Pathfinder UAV set altitude records in 1998 and 1999 for propeller-driven aircraft by using solar cells to drive 8 electric motors, which together generated roughly 10 horsepower. While storage of solar energy for use during foul weather or night conditions is a possibility, the added weight of these storage systems probably make them prohibitive for use on micro air vehicles and combat UAVs.
The above numbers can be compared to the energy content of the most popular energy source, gasoline. The specific energy of gasoline is about 12 hp-hr/lb. The best batteries listed above remain less than 2 percent of gasoline in terms of their specific energy. Fuel cells, while an improvement over batteries, have specific energy values roughly 4 percent that of gasoline. However, by 2015, this disparity between fuel cells and gasoline will likely be reduced by over half.
Figure 4.1.2-3 Mass Specific Power Trends.
Emerging propulsion technologies include the following:
- Reciprocating Chemical Muscles (RCMs) are regenerative devices that use a chemically actuated mechanical muscle (ionomers) to convert chemical energy into motion through a direct, noncombustive chemical reaction. Power generated via an RCM can be used for both propulsion (via wing flapping) and powering of on-board flight systems. RCM technology could power future generations of micro-UAVs, providing vertical take-off and landing as well as hover capabilities.
- For dash or sustained high speed requirements, whether to enhance survivability or for access to space, propulsion options for future UAVs (and their level of maturity) include ramjets (mature), scramjets (developmental), integrated rocket-ramjet (developmental), air-turbo rocket (developmental), and pulse detonation engines (developmental), each with varying attributes depending on the mission.
Aircraft survivability is a balance of tactics, technology (for both active and passive measures), and cost for a given threat environment. For manned aircraft, aircraft survivability equates to crew survivability, on which a high premium is placed. For UAVs, this equation shifts, and the merits of making them highly survivable, vice somewhat survivable, for the same mission come into question. Insight into this tradeoff is provided by examining the Global Hawk and DarkStar programs. Both were built to the same mission (high altitude endurance reconnaissance) and cost objective ($10 million flyaway price); one (DarkStar) was to be more highly survivable by stealth, the other only moderately survivable. Performance could be traded to meet the cost objective. The resulting designs therefore traded only performance for survivability. The low observable DarkStar emerged as one third the size (8,600 versus 25,600 lbs) and had one third the performance (9 hrs at 500 nm versus 24 hrs at 1200 nm) of its conventional stablemate, Global Hawk. It was canceled for reasons that included its performance shortfall outweighing the perceived value of its enhanced survivability. Further, the active countermeasures planned for Global Hawk’s survivability suite were severely pared back as an early cost savings measure during its design phase.
The value of survivability in the UAV design equation will vary with the mission, but the DarkStar lesson will need to be reexamined for relevance to future UCAV designs. To the extent UAVs inherently possess low or reduced observable attributes, such as having seamless composite skins, fewer windows and hatches, and/or smaller sizes, they will be optimized for some level of survivability. Trading performance and/or cost for survivability beyond that level, however, runs counter to the prevailing perception that UAVs must be cheaper, more attritable versions of manned aircraft to justify their acquisition. As an illustration, both the the Air Force and the Navy UCAV demonstrators are being valued at one third the acquisition cost of their closest manned counterpart, the JSF.
Once these active and passive measures have failed to protect the aircraft, the focus of survivability shifts from completing the mission to saving the aircraft. Two emerging technologies hold significant promise in this area for UAVs, self repairing structures and fault tolerant flight control systems (FCSs). NASA research into ionomers shows they may be capable of sealing small holes or gaps inflight, such as those inflicted by small arms fire. Several on-going efforts are intent on developing FCS software that can "reconfigure" itself to use alternative combinations of remaining control surfaces when a primary control surface is damaged or lost. Fault tolerant FCSs will be key to enabling successful demonstration of the Services’ autonomous operation initiatives.
One low/reduced observable characteristic implicit in the CINC IPLs, specifically for the force protection and SEAD missions, is aircraft acoustic signature. These two missions can be better supported by using quieter vehicles that are less susceptible to detection, whether by base intruders (acoustic) in the force protection role or by a hostile integrated air defense system employing active and passive (radar and acoustic) detection systems for the SEAD mission. To meet local noise ordinances around airports, aircraft noise has been reduced by around 15 percent each decade since 1960, though not nearly to the point where sophisticated unattended ground sensors would have trouble picking it up. Electric power systems, such as fuel cells, offer lower noise and infrared signatures for smaller UAVs while providing comparable mass specific power to that of ICEs.
The requirements for various payload capabilities identified by the IPLs can be grouped into five functional areas: imagery intelligence (IMINT), signals intelligence (SIGINT), measurement and signatures intelligence (MASINT), communications, and munitions. Meteorological sensing stands outside this breakout, yet supports all of the others to some degree. Reporting of basic meteorological conditions can and should be made an integral part of all future sensor systems acquired for UAVs, providing the equivalent of pilot reports (PIREPS) from manned aircraft.
Figure 4.2-1: UAV Payload Requirements.
4.2.2 Imagery Intelligence (IMINT)
The ability to detect, recognize, classify, and identify targets is the key UAV payload requirement derived from the CINC IPLs. One solution translates to obtaining improved sensor resolution from technology advances. Another possible solution would require an architectural change to reconnaissance and surveillance by relying instead on micro air vehicles to obtain close-in imagery using modest sensors. Resolution in electro-optical/infrared (EO/IR) sensors is most commonly measured in terms of ground resolved distance (GRD), the minimum separation between two distinguishable objects. Whereas GRD is a function of range, instantaneous field of view (IFOV), the smallest angle a sensor can resolve, is not. Synthetic aperture radar (SAR) uses impulse response (IPR) as its measure of resolution. Finally, the interpretability of a given image, a subjective measure of its usefulness assigned by an image analyst, is rated on the National Imagery Interpretability Rating Scale (NIIRS) for visible and infrared (IR) (passive) imagery and on the National Radar Interpretability Scale (NRIS) for SAR (active) imagery.
Figure 4.2.2-1: EO/IR Sensor Ground Resolved Distance Trend.
Passive Imaging. Figure 4.2.2-1 depicts the trends in Ground Resolved Distance (GRD) at a slant range of 4 nm (maximum range of Man Portable Air Defense (MANPAD) systems) for large and small (i.e., gimbaled turrets) EO (visible), medium wavelength infrared (MWIR, 3 to 5 micron), and long wavelength infrared (LWIR, 8 to 12 micron) sensors over the past several decades. The relatively flat trends for the large systems represent the gradual, long term development of military systems, whereas the steep curves show the rapid impact of the commercial market (e.g., for police and media helicopters) for EO/IR sensors in smaller, gimbaled systems developed in the early 1990s.
By way of comparison, an unarmed individual can be distinguished from an armed one with a 4-8 inch GRD (NIIRS 8), corresponding to an IFOV of 7-14 microradians (mrad). Facial features on an individual can be identified (or at least partially discriminated) with a <4 inch GRD (NIIRS 9), corresponding to an IFOV of less than 7 mrad. Both cases assume a slant range of 4 nm, equivalent to the maximum range of most currently fielded MANPAD threats. Examples illustrating the ability of current EO/IR systems to meet these capabilities are shown in Table 4.2.2-1.
Table 4.2.2-1: Operational Performance of Current EO/IR sensors.
|
Calculated IFOV ( mrad) |
Pixel Pitch/Array Size ( mm / pixels) |
Distinguish Armed v. Unarmed? @ NIIRS 8 (7.1 < IFOV < 14.3 mrad) |
Distinguish Facial Features? @ NIIRS 9 (IFOV < 7.1 mrad) |
|||
|
Needed Pitch ( mm) |
Needed Array Size |
Needed Pitch ( mm) |
Needed Array Size |
|||
|
Visible Wavelength Raytheon Integrated Sensor Suite, planned for Global Hawk UAV Wescam Model 14TS/QS, employed on Predator UAV IAI Tamam MOSP, employed on Hunter UAV |
10
9
30 |
9 / 307,200
8.3 / 379,392
9 / 393,216 |
YES
YES
NO 6.2 |
YES
YES
NO 825,564 |
NO 7.6
NO 7.4 NO 4.4 |
NO 430,071
NO 478,024 NO 1,651,474 |
|
MWIR Wescam Model 14TS/QS, employed on Predator UAV ROI CA-295 |
55
20 |
30 / 65,536
30 / 4,000,000 |
NO 15.3 NO 25.4 |
NO 252,256 NO 5,598,712 |
NO 10.8 NO 17.9 |
NO 504,617 NO 11,199,776 |
|
LWIR Indigo Alpha, uncooled |
1576 |
51 / 20,480 |
NO 4.9 |
NO 2,258,834 |
NO 3.4 |
NO 4,518,617 |
As EO sensors are nearing the theoretical limits in achievable array size and pixel pitch, they will rely increasingly on evolutionary advancements in other areas of technology to increase resolution. Examples of emerging technologies for imaging systems include uncooled IR sensors, microelectro-mechanical systems (MEMS), new detector materials and better fabrication techniques, and multiple aperture optical systems. In the next few years, it is predicted that uncooled sensors will approximate the performance of their cooled counterparts while at the same time lowering costs, increasing reliability, reducing power requirements, and allowing for more compact packaging. The commercial sector is pushing applications in rifle sights and driver’s viewers, while the military is focusing on applications in threat warning, long-range targeting, and unattended ground sensors. MEMS will enable the next generation of lithography for manufacturing focal plane arrays characterized by reduced pixel sizes, high fill-factors, and analog-to-digital converters on a single wafer chip, while offering increased reliability by replacing mechanical parts. A better understanding of the material characteristics of detectors, specifically Vanadium Oxide (VOx), amorphous silicon, and Barium Strontium Titanium (BST) used in uncooled LWIR detectors, and fabrication techniques of thin pixels will enable improved thermal responsivity and lower read-out noise. One of the most promising areas of optics technology development is multiple aperture optical systems. The potential increase in resolution offered by such systems would be revolutionary. The benefits of multiple apertures have been demonstrated in the RF bands and in astronomical telescopes, but it is a long-term concept in tactical optical systems using visible and IR bands.
Figure 4.2.2-2: SAR Weight and Coverage/Resolution Trends.
Active Imaging. Since airborne radars first appeared during World War II, they have been adapted to a wide variety of applications, from fire control and early warning to reconnaissance weather monitoring. Their key military value has been their ability to see farther than optical means and through conditions (night, clouds) which would otherwise deny their use. Conversely, their resolution is poorer, their use revealing to hostile forces, and their size, weight, and power (SWAP) a burden to their host aircraft, particularly to the smaller UAVs. Resolution has been significantly improved in the past two decades by the introduction of synthetic aperture radars (SARs), in which onboard processing uses the aircraft’s forward motion to simulate a physically larger, fixed antenna, thereby increasing system gain and thus resolution.
As can be seen from Figure 4.2.2-2, in the short history of SAR advancement, the ratio of swath width covered to resolution achieved for SAR area search modes has increased about 1 nautical mile in width per foot of resolution every 6 years. This equates to resolution halving, or area of coverage doubling, (or a combination thereof) every 6 years compared to the previous 6 years. Concurrently the SWAP of these sensors is on a downward trend, with examples now available that are compatible with tactical UAV payload limits (100-lb class). Transmit/receive modules (a.k.a. "tiles" or "bricks") have also shown substantial decreases in weight and cost over the past decade, while providing expanded modes of operation.
One specific mode of SARs, moving target indicator (MTI), detects the presence of moving vehicles on the ground through Doppler processing of the radar return. This can be done with a single scan of the radar through a wide area search (WAS) mode. In addition to having the resolution needed to detect the moving targets, the system must be able to surveil a large ground area per scan to be operationally useful. The amount of time required to scan a given area (revisit rate) is driven by the square of the radar’s power, so to halve the revisit rate requires quadrupling the output power with current technologies.
One of the more promising near term radar development efforts is Interferometric SAR. IFSAR provides precision terrain elevations over large areas by employing a SAR transmitter with two receivers located some distance from it, in the case of airborne IFSAR, in the wingtips. The difference in the two received returns can be processed to generate Digital Terrain Elevation Data (DTED), critical for precision targeting applications such as cruise missile guidance. A preliminary evaluation of airborne IFSAR is being conducted in the Rapid Terrain Visualization ACTD. The potential value of IFSAR to theater commanders justifies its demonstration on a large wingspan UAV (i.e., Global Hawk) in the near future.
In the far term, range-gated laser imaging radars (LIDARs) will complement traditional radars by providing the capability to build three-dimensional images in real time of suspected targets found by the latter. Such LIDARs will enable imaging through obscurants, improve target identification by capitalizing on the higher resolution offered by using optical frequencies, and better assess target damage with 3-D images. In addition, the same light returns will be processed to extract polarization and vibration information, allowing foliage penetration and aimpoint refinement, respectively (see section 4.2.4). Future airborne imaging sensors will become multi-dimensional in nature, gathering and correlating data in real time from multiple phenomena to build a more complete target picture than that available from any one of them.
4.2.3 Signals Intelligence (SIGINT)
Although endurance-class UAVs, with their ability to be present throughout the entire development of a radio conversation, seem tailor-made for the SIGINT mission, little has been done to exploit UAVs in this role. Funding for exploring this mission on Global Hawk was deleted in 1997 but reinstated in the FY02-07 FYDP. Besides a handful of demonstrations flown on Pioneer and Hunter UAVs in 1995-97 and an extensive characterization of Predator’s EMI environment in 1996-98, few current programs exist to operationalize SIGINT UAVs. An integrated program to demonstrate continuous 24-hour airborne SIGINT collection capability at the national/theater, operational/joint task force, and tactical/unit level would address SIGINT concerns expressed by most CINCs. Current technology would support the following feasibility demonstrations and timeframes:
Table 4.2.3-1. Proposed UAV SIGINT Demonstration Program.
Level Supported Candidate UAV Capabilities Payload Available Endurance Demo By
National/Theater RQ-4/Global Hawk ELINT and COMINT up to 1200 lbs 30+ hrs 2005-10*
Operational/JTF RQ-1/Predator ELINT or COMINT up to 200 lbs 24+ hrs 2003-05
Tactical/Unit Aerosonde COMINT up to 4 lbs 24+ hrs 2003-05
* Currently planned for by Air Force in the FYDP.
A SIGINT system is expected to perform three functions: emitter mapping (geolocation of emitters), exploitation (signal content), and technical analysis of new signals. Taking a long view, the primary factor that will drive RF SIGINT system design will be the reduction in received power due largely to power management, spread spectrum techniques, and use of higher frequencies with higher atmospheric absorption. Also decreasing the effective power level will be the increase in spectrum utilization, resulting in increased noise in the environment. Three choices exist to improve this situation: moving closer to the emitter, improving the antenna gain, and using coherent processing techniques.
Moving closer to the emitter would allow lower-powered signals to be collected using readily available equipment, but also increases the threat to the collector aircraft—an argument for UAV use. Improving antenna gain can be achieved through concepts like AFRL’s Sensorcraft, in which the antenna becomes the wing and largely determines the flight characteristics of the aircraft.
Coherent processing techniques use additional information about the signal to wring the most energy out of the signal. One technique, matched filter processing, attempts to match the signal’s size, phase and shape as exactly as possible. Another technique, cross-ambiguity function (CAF) processing, uses mathematical techniques and intensive processing to find signals even if the average noise level is 10 times that of the signal. Using conventional algorithms, the processing load increases by the fourth power of the bandwidth, i.e., to double the width of the spectrum the processing load increases by a factor of 16. If CAF and algorithm improvements can reduce the bandwidth scaling factor from a fourth to a third- or second- power function, processing time can be dramatically decreased (see Figure 4.2.3-2).
Figure 4.2.3-2: Forecast of Amount of Bandwidth Continuously Processable.
4.2.4 Measurement & Signatures Intelligence (MASINT)
Increases in resolution are nearing a leveling point where new technologies will not produce leaps in resolution. Near and mid-term increases in the operational capability to detect, identify, and recognize targets will be based on increased target signature information, not just pixel resolution. For example, normal two-dimensional spatial imaging of an obscure object of interest may be insufficient for detection unless and until it is combined with vibration or polarization data on the same object. A target may hide in a few dimensions but not in all, and once it is detected in one dimension, additional resources can be focused for recognition and identification. The capability to increase target information content is enabled by emerging multi-dimensional sensing technology.
Sensing across multiple phenomena will be most effective when used in combination, applying their additive information to culminate in target identification. One logical result could be the combination of such sensing phenomena as 2-D range gating and vibration on the same FPA used for imaging.
Characteristics of multi-phenomena sensing under development are described in Table 4.2.4-1, which describes them as either passive or active in their sensing nature, categorizes their timeframes for fielding on UAVs into near-term (0-5 years), mid-term (5-15 years), or long-term (15+ years) windows, and describes their potential military applications.
Table 4.2.4-1. Potential UAV MASINT Sensing Applications.
Phenomenology Sensor(s) Used Sensing Timeframe Military Applications
Polarimetry IR, Ladar Passive/ Mid Term Foliage penetration
Active Ground penetration
Terrain assessment
Multi-Spectral Imaging Spectrometer Passive Near Term Camouflage detection
Minefield detection
Crop maturity/health
Hyper-Spectral Imaging Spectrometer Passive Mid Term Foliage penetration
Chem/bio agent detection
Subsurface damage assessment
Vibration Laser Active Long Term Target recognition
Aimpoint refinement
Target operating condition
Fluorescence Laser Active Long Term Chem/bio agent identification
Fuel loading/leakage detection
Drug manufacturing detection
Surface Acoustic Wave Piezoelectric Passive Near Term Chemical agent identification
Bacteriological agent detectors employ a number of techniques that key on a variety of properties produced by the suspect agent; the relation of techniques to these properties is summarized in the matrix below. All current bio-agent detection systems are point detectors, i.e., there is no standoff technique at present for detecting and identifying bacteriological agents. The Naval Research Laboratory (NRL) integrated an immunoassay-based bio-agent detector on a Telemaster UAV and tested its effectiveness in detecting and identifying an agent surrogate in January 1996. In addition, the Air Force Researc