autonomous unmanned aerial vehicles · an unmanned aerial vehicle (uav), also sometimes known as a...
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THE GEORGE WASHINGTON UNIVERISTY
Autonomous Unmanned Aerial Vehicles
A Technology Warning Assessment
Syed Azeem
2/29/2012
This report presents a technology warning assessment based on National Academies’ methodology. The particular technology area analyzed relates to fully autonomous unmanned aerial vehicles (AUAVs) from the perspective of the United States government with the objective to assess AUAV technology with the
goal of strongly enabling, promoting and increasing economic growth.
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Table of Contents
Focus ............................................................................................................................................... 4
Introduction ............................................................................................................................. 4
History ..................................................................................................................................... 5
UAVs Come to the Lime Light in Contemporary Times ....................................................... 5
Civilian Use of UAVs is Gaining Momentum ........................................................................ 6
The Road to Autonomy ............................................................................................................. 10
State of the Art ...................................................................................................................... 10
Alternative Energy and Extreme Endurance ......................................................................... 13
Micro UAVs .......................................................................................................................... 14
Identify: Evolving Technologies ................................................................................................... 15
Platform Technologies .............................................................................................................. 15
Alternative Energy, Lightweight and Efficient Power Supplies: .......................................... 15
Low-Observable or Stealth Technology: .............................................................................. 19
Sensor Technologies ................................................................................................................. 20
Synthetic Aperture Radar (SAR): ......................................................................................... 21
Light Detection and Ranging (LIDAR): ............................................................................... 22
On-board Intelligence ............................................................................................................... 23
Artificial intelligence: ........................................................................................................... 23
Communications bandwidth: ................................................................................................ 28
Identify: Observables .................................................................................................................... 29
Technology Warning Assessment ................................................................................................. 31
Assess: Accessibility ..................................................................................................................... 31
Assess: Maturity ............................................................................................................................ 32
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Assess: Consequence .................................................................................................................... 32
Prioritize & Task ........................................................................................................................... 33
Table of Figures ............................................................................................................................ 36
Bibliography ................................................................................................................................. 37
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Focus The scope of this research paper is focused on answering the following question: What is
the current state of autonomous unmanned aerial vehicles (AUAVs) and ongoing developments
in the R&D that is of interest in understanding the state of this particular technology?
Introduction
An unmanned aerial vehicle (UAV), also sometimes known as a unmanned aerial system
(UAS), refers specifically to an aircraft, or more generally a flying machine, being flown without
a human pilot on-board actively directing and piloting. Control functions are found either on-
board, in the form of sophisticated computer systems, or remotely controlled by human pilots on
the ground [6], or a combination of both. The closely related term, unmanned combat aerial
system (UCAS) refers to the variety of such unmanned aircraft with strike fighter size platform
and capabilities.
UAVs come in many different configurations akin to traditional aircraft. These
configurations may include: fixed-wing, rotary-wing or rotorcraft, helicopters, VTOL vehicles,
or short take-off and landing (STOL) [6]. However, UAV form factors are not necessarily
limited by the configurations offered by traditional aircraft. Smaller form factors UAVs are
called Miniature UAVs ─ some of which can be launched by catapault, or even by hand.
Similarly, advanced UAVs may also borrow their form and function from creatures such as birds
or flying insects. Another distinct category of unmanned systems is airships. They offer
unparalleled endurance over fixed wing or rotary configurations. Many of the models can stay
aloft for days or even months. Applications include surveillance, monitoring and
communications relay [6].
The focus of our assessment is to provide a thorough background on the history of
unmanned aircraft, current state-of-the-art of various UAVs, and discussing the trend towards
increased autonomy. The perspective of this report is that of the United States government with
the objective to assess autonomous UAV technology with the goal of strongly enabling,
promoting and increasing economic growth. For example, this technology has the promise to
create new and innovative business models and increased exports (in terms of both technology
goods and intellectual property).
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History
The first modern UAV, in its most rudimentary modern form, was the “Kettering Bug”. It
was developed during World War I and designed to be a “flying bomb” for the U.S. Army.
However, these “small, cheap, crudely built biplanes” were mired with crashes and were highly
unreliable [7].. The Kettering Bug never saw operational light of day. During World War II, the
Nazis developed a simple unmanned aircraft known as the V-1 “Buzzbomb” and used to it to
conduct 8892 one-way bombing missions in the UK [7]. The effects were devastating and
resulted in massive damages with 6,200 fatalities and 18,000 casualties [7]. Early-form UAVs,
such as the V-1 and the Kettering Bug, were essentially one-way bombing machines in the form
of an unmanned aircraft. They were similar in this most basic principle compared to modern
cruise missiles, with the exception of an aircraft configuration in terms of fixed wingspan.
Further substantial development of UAVs did not catch momentum until the Vietnam
War. During 1964 and 1972, the “Lightning Bug” and “Buffalo Hunter” UAVs flew more than
3,400 sorties conducting reconnaissance, surveillance and PSYOPs missions and suffered an
attrition rate of only 10% [7]. During the same period, more than 5,000 U.S. service members
lost their lives in downed aircraft and 90% of American POWs were pilots or crewmen who had
been captured [7]. “These UAVs returned from missions deep within enemy territory at a
fraction of the cost of manned reconnaissance aircraft, and without the threat to American
personnel” [7]. U.S. R&D efforts continued meagerly during the 1980’s and with increased
momentum during the 1990’s. However, it was not until after September 11, 2001 attacks on
U.S. soil that UAVs would become a key weapon in combating adversaries.
UAVs Come to the Lime Light in Contemporary Times
The benefits of using UAVs in military campaigns were never abundantly clearer than in
the past post-9/11 decade. Across theaters in Afghanistan and Iraq, the RQ-4 Global Hawk,
developed by Northrop Grumman, performed admirably and provided the U.S. and its allies a
tremendous advantage over its adversaries by conducting intelligence, surveillance and
reconnaissance (ISR) missions [7]. The UAS is considered a high-altitude, long-endurance
(HALE) aircraft. Flying at altitudes up to 65,000 feet (roughly twice as high as commercial
airliners and above inclement weather and prevailing winds) and being able to cruise for up to 35
hours, the Global Hawk provides joint war-fighting commanders near-real-time, high-resolution
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intelligence, surveillance and reconnaissance (ISR) images in terms of both wide-area and spot
imagery [7]. For example, in Iraq, it aided U.S. forces in accelerating defeat to Iraqi forces –
taking credit for identifying over half of all critical air defense targets and 38% of Iraqi armored
forces. The Global Hawk is able to autonomously take off, fly and surveil a region of interest
(pre-programmed by operators), and land [7]. It can image an area the size of the state of Illinois
in just one mission [8].
During these conflicts, General Atomics’ RQ-1 Predator UAV proved invaluable due to
its multi-faceted capabilities in conducting combat missions and real-time surveillance of the
battlefield. Flying at altitudes up to 25,000 feet and with an endurance of 40 hours, this UAV
features a sophisticated sensor package with the ability to survey 1,300 nautical miles, and, when
armed (MQ-1 configuration), carries Hellfire missiles for enemy targets [7]. Even when Predator
is not armed, it provides ground commanders a “eye in the sky” and is able to communicate
enemy target locations to pilots of conventional aircraft [7].
Aforementioned recent military conflicts in the post-9/11 era have garnered military
UAVs significant media coverage and public attention. However, UAV applications are not
limited to the military use and are vastly more diverse and broad than current overwhelmingly
military-specific usage would suggest.
Civilian Use of UAVs is Gaining Momentum
The vast majority of UAVs in use in the U.S. are military craft. However, the civilian
fleet is growing fast. Civilian use of UAVs, is being planned or already underway, for missions
such as aiding in, border surveillance, maritime search-and-rescue missions, low cost
communications relay and aerial mapping, monitoring wild fires, hurricanes and icebergs [9].
Based on years of prior experience in developing UAVs designed for Japanese
agricultural use, in Yamaha introduced the RMAX in 1997, an industrial use unmanned
helicopter for agricultural use, with an increased payload capacity and ease of operations [10].
The RMAX has a range of approximately 1.25 miles and an endurance of 1.5 hours. It has been
primarily designed for agricultural crop dusting use. RMAX helicopters configured as the
“Autonomous-control Spec” and geared with GPS and gyro sensors, enable a high degree of
remote flight control and can be controlled from commands sent by a ground computer [10]. For
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example, in 2000 this configuration was successfully flown to observe the eruption of Mt. Usu in
Hokkaido, hence, becoming the first unmanned helicopter in history to be controlled out of sight
by means of GPS autonomous flight system [10]. Since then, expanded use of RMAX has grown
in research and observation of environmental, geographical, security and illegal dumping
prevention areas [10].
In 2008, NASA acquired Global Hawk UAS for first time use for environmental science
research. The agency has been using the UAS missions to support its Science Mission
Directorate and the Earth science community that require high-altitude, long-distance airborne
capability [11]. According to NASA, the Global Hawk provides superb new measurement
possibilities for climate science and applications programs. Twelve scientific instruments
integrated into the aircraft will collect atmospheric data while flying high through Earth's
atmosphere in the upper troposphere and lower stratosphere [11]. In 2010, the UAS successfully
completed the first science flight over the Pacific Ocean and flew a round trip of approximately
4,500 nautical miles along a flight path that took it from the Mojave Desert in California (Dryden
Flight Research Center) to just south of Alaska [12]. NASA is using the UAS to measure dust,
smoke and pollution that cross the Pacific from Asia and Siberia and affect U.S. air quality,
chemical composition of Earth’s two lowest atmospheric layers, to profile the dynamics and
meteorology of both, and to observe the distribution of clouds and aerosol particles [12]. The
Global Hawk UAS provides NASA “expanded access to the atmosphere beyond what NASA
[sic] has with piloted aircraft” and allowing it “go to regions they [sic] couldn't reach or go to
previously explored regions and study them for extended periods that are impossible with
conventional planes” [12]
Figure 1: Yamaha RMAX autonomous agricultural UAV (© Yamaha).
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The Global Hawk UAS has the potential for many applications beyond atmospheric and
climate change studies, such as for the advancement of science, improvement of hurricane
monitoring techniques, development of disaster support capabilities, and development of
advanced autonomous aircraft system technologies [11]. For example, in 2007 (again in and
2008), the Global Hawk was used to help monitor wildfires in Southern California. U.S. Air
Force few Global Hawks and the U-2 aircraft to provide still images and video to firefighting
commanders and civil authorities on the ground ─ marking the first time the Global Hawk was
flown in the U.S. as part of DOD’s “Defense Support to Civilian Authorities” mission [4].
Similarly, in 2010, the Global Hawk was used to survey earthquake-stricken Haiti and provide
real-time imagery to determine the extent of destruction and usability of surviving infrastructure
(such as airfields to land aircraft) [13]. High-quality images produced the by the Global Hawk
were sufficient to clearly identify usable airfields to land international relief crews. New aerial
imagery was compared with 2009 imagery to accurately analyze and determine the extent of
destruction [13].
Between 2005 and 2006, U.S. Customs and Border Protection (CBP) started the use of
General Atomics’ MQ-9 Predator B UAS (also known as the Reaper or Guardian) for monitoring
the Southwest border with Mexico and the Northern border with Canada [14]. By 2010, the
agency expanded its unmanned aerial operations to cover all the Southwest border States ─ from
Figure 2: (2007) Photo taken by USAF RQ-4A Global Hawk and analyzed for Southern California Firefighters. Infrared image depicts hot areas and objects as white on a darker background and shows the Horno Fire progressing [4]
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the El Centro Sector in California all the way to the Gulf of Mexico in Texas providing critical
aerial surveillance assistance to personnel on the ground [15].
In 2008, CBP and U.S. Coast Guard (USCG) established a Joint Program Office to
coordinate maritime land-based UAS policy and operations [16]. Currently, USCG is in the pre-
acquisition phase of developing mission needs (MNS) and concept of operations (CONOPS) for
land-based and cutter-based UAS [16]. In mid-2012, the CG plans to conduct a demonstration
with Insitu’s ScanEagle, a light-weight, small and low cost UAS, to assess its capabilities and
compatibility with USCG CONOPS [16]. The UAS uses a catapult launcher and unique
“SkyHook” wingtip recovery system,
performing launch and recovery operations
safely and autonomously on land and at
sea without the need of a net or runway
[17] .
During the late 1990s and early
2000s, a NASA program to develop cost-
effective, slow-flying and high-altitude
long-endurance (HALE) UAVs,
developed the Helios Prototype ─ an
ultra-lightweight and remotely piloted “flying wing” aircraft with a wingspan of 247 feet. The
Helios drew its power electrically from an array of 62,000 solar fuel cells on the upper surface of
the wing. In 2001, the Helios UAV achieved an altitude of 96,863 feet, a world record for
sustained horizontal flight by a winged aircraft [2]. The next and exciting step for this technology
demonstrator was to involve the use of fuel-cell technology to enable around the clock operations
due to the lack of solar energy during night time. Despite, the 2003 break up and crash of the
Helios prototype due to turbulence, the solar HALE concept proved viable and pioneered the
way for use of alternative energy in UAV designs, which had so far been beholden to typical
carbon-based fuel sources.
Figure 3: The ScanEagle launched from a ship (© Insitu).
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In 2006, NSF in collaboration with NASA and NOAA, funded a project that successfully
sent a fleet of miniature UAVs through the pollution-filled skies over the Indian Ocean and
achieved the goal of tracking of pollutants responsible for dimming Earth's atmosphere. The
lightweight and miniature instrument bearing autonomous unmanned aerial vehicles (AUAVs)
were flown in “swarms” of three in a vertical formation to observe conditions below, inside and
above clouds simultaneously [18].
The Road to Autonomy
State of the Art
Throughout aviation history introduction of varying levels of autonomy to both manned
and unmanned aircraft is a trend that has been gaining increased momentum recently. In the early
days of commercial aviation, the standard cockpit had a full cast of characters, including the
flight engineer, the navigator, and the radio operator [19]. Advances in automation of functions
through technology have replaced those people, one after the other and now all those remain are
the pilot and the copilot 19[ ]. Already, as soon as a commercial airliner is airborne,
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software
typically takes over the flight, handles the landing—and most of what happens in between [ ].
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The main job of the pilot is to just “babysit” and provide intelligent judgment and decision
making capability in regards to sense and avoid functionality [ ].
The Global Hawk is able to fly itself home and land on its own if it loses its satellite link
with its ground station. Upon losing its “heartbeat” signal from ground station, the aircraft being
“self-ware”, goes into self-repair mode, trying a second radio, checking circuit breakers, and so
Figure 4: At 10,000 feet in in skies northwest of Kauai, Hawaii in August 2001, the remotely piloted Helios is traveling at about 25 miles per hour (© NASA/AeroVironment).
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on. Finally, if nothing works, the it goes to its known profile, follows waypoints, and lands itself
with GPS and radar. Such levels of autonomy would be invaluable for a commercial airliner in
the event the pilot and copilot are either killed or incapacitated [19].
Even upcoming manned platforms, such as the F-35 Joint Strike Fighter Lightning II, are
increasingly using autonomous systems controls. The new multi-role, advanced stealthy fighter
has, for example, hover capability. The F-35B STOVL (short take off, vertical landing) variant is
controlled by the integrated propulsion system which precisely controls hover maneuvers. The
pilot simply decides on hover direction and altitude and the system does the rest. Unlike older
STOVL aircraft like the Sea Harrier, hovering does not require constant pilot attention and
simply not doing anything lets the JSF remain hovering [20].
For the last two decades Navy fighter jets have used automatic landing systems to land
and stop a jet on the small and fog-shrouded deck of a moving aircraft carrier [19]. Rotary-wing
VTOL aircraft such as helicopters are extremely vulnerable while operating in low-altitude
environments. The U.S. Army is currently funding R&D into robotic medical evacuation
vehicles based upon a system of sensors and software to launch and land a full-size helicopter on
cluttered, unmapped ground and also fly the vehicle at low altitudes [19]. As part of this effort, in
2010, Piasecki Aircraft and Carnegie Mellon University developed and demonstrated their flight
navigation and sensor system called “KlearPath”. During the demonstration, the system enabled
a full-sized helicopter to fly
autonomously at a low altitude,
avoid obstacles (even trees or
fences) in an unmapped and
obstacle-laden terrain, select a
suitable landing site (based on
provided coordinates for a casualty
or drop-off point for re-supply) and
guide the helicopter to a safe landing
[21]. This unprecedented feat of fully
autonomous operations of a VTOL
aerial vehicle was accomplished
Figure 5: KlearPath sensor/navigation system for autonomous helicopters keeps a running rank of possible landing sites and approach/abort paths in
order to allow rapid maneuvering to unexpected developments on the ground or in air (© Piasecki Aircraft/Carnegie Mellon University).
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without any human input or control. The KlearPath system uses an advanced laser radar
(LADAR) perception system to create a survey quality 3D map of the terrain while flying at a
safe altitude, even in low-light or low-visibility situations [21]. As the helicopter descends, the
sensor focuses on the terrain forward to create a real time threat map of obstacles such as
buildings, trees, fencing, power lines and even objects as small as a 4 inch high pallet on the
ground [21]. The sensors feed the onboard software to enable rapid decision making such as
calculating a new flight path, when an obstacle is ahead, and then resuming the strategic flight
path [21]. Currently, unmanned helicopters can only fly autonomously in mapped areas known to
be free of obstructions [21]. However, this new innovative approach has opened up promise of
widespread applications for autonomous VTOL aircraft.
The U.S. Navy’s X47-B is an upcoming stealth fighter-sized unmanned combat air
system (UCAS), able to fly up to 40,000 feet at high-subsonic speeds for up to six hours, will
take autonomous flight one-step further. It will be taking off from an aircraft carrier, using GPS
to fly a predetermined route, and landing on the carrier under light supervision—a minder,
somewhere onboard the ship, who stands ready to take control if necessary [19]. Once the X-47B
takes off, it flies a preprogrammed mission and finally returns to base in response to its mission
operator on ground. The operator monitors the X-47B air vehicle’s operation, but does not
actively “fly” it via remote control as is the case for other UAVs (such as the armed MQ-1
Predator configuration) currently in operation [22].
The X47-B is unique in being one of the first unmanned aircraft with autonomous aerial
refueling (AAR) capability including the Air Force’s preferred “boom/receptacle” approach and
the Navy’s “probe and drogue” method [22]. It will demonstrate this capability during flight tests
in 2014. Although, the capability is not just limited to the X-47B. In 2011, NASA Global Hawk
demonstrated that autonomous aerial refueling (AAR) interaction between two unmanned, high
altitude aircraft, an operation never before performed [23]. NASA Global Hawk flew as close as
40 feet apart from Proteus test aircraft at an altitude of 45,000 feet, an industry-setting record
[23]. The next step is for both UAVs to demonstrate AAR while flying autonomously, in other
words, not only they would be refueling autonomously, but also flying autonomously without
direct human control [23]. AAR capability for combat vehicles such as the X-47B is much more
critical than HALE vehicles like the Global Hawk. This is due to the differences in their
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respective designs, payload requirements, speed, size and mission roles. The X-47B has a
maximum un-fueled endurance of only 6 hours, whereas, as indicated earlier, the Global Hawk is
able to cruise at high-altitudes for up to 35 hours without any needing any refueling.
Alternative Energy and Extreme Endurance
An exciting trend in UAVs is the introduction of alternate energy and fuel sources. As
discussed earlier, NASA’s Helios prototype relied on a solar-electric power system to power
itself for around the clock operations. The premise behind this fuel cell-based system works by
combining oxygen and hydrogen to produce electric power, heat and water. As long as these
gases are supplied, the unit will continues to produce power. [2]. Further discussion of
alternative energy technologies is discussed in a later section.
AeroVironment’s Global Observer, a high-altitude long-endurance (HALE) UAV,
became the first aircraft in the world to have successfully completed first liquid hydrogen
powered, unmanned test flights. The prototype UAV uses fuel cells operating on liquid hydrogen
to power eight propellers [24]. A liquid hydrogen powered internal combustion engine drives a
generator that powers the four propellers as well as batteries and operational payloads. Similar to
the Global Hawk, the Global Observer flies above most weather and other air traffic, potentially
simplifying its use in a crowded Civilian airspace [25].
With a wingspan of 175 feet, the Global Observer is an extreme-endurance UAV and can
stay aloft up to a week (168 hours) at a time and is designed to serve as an observational and
telecommunications platform [25]. The aircraft would fly missions at 65,000 feet and would
serve as an observation platform and communications link over a very wide area of 600 miles in
diameter. By combining a pair of Global Observers, each of which could fly for up to a week,
Figure 6: Global Observer can fly up to altitudes of 65,000 feet, has an extreme endurance of 168 hours and is the first unmanned aircraft to use hydrogen fuel-cells (© AeroVironment).
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operators could provide continuous coverage over any part of the earth’s surface for as long as
dictated by mission requirements [25].
Similarly, while providing continuous coverage over a wide area, the Global Observer
can perform duties akin to a satellite, albeit at a much lower altitude and at a fraction of the cost.
The UAV has some of the persistence qualities of a satellite, along with the flexibility and higher
resolution of today’s unmanned aircraft. Civilian applications could include deploying it as a
communications relay over disaster areas, as a border patrol platform or for scientific remote
sensing. With the ability to quickly change payloads and capabilities, the Global Observer’s
mission could be changed or updated as needed [25]
Micro UAVs
The state-of-the-art in UAV technology is rapidly innovating in unique ways. While,
much of R&D efforts are being conducted in lightweight and aircraft-size platforms, micro
UAVs are emerging as an exciting development. In 2011, DARPA demonstrated a micro UAV
prototype that matches the appearance and functions of life size humming bird. The Nano
Hummingbird is capable of controlled precision hovering and fast-forward flight of a two-wing,
flapping wing aircraft that carries its own energy source, and uses only the flapping wings for
propulsion and control [26]. The prototype
demonstrated climbing and descending
vertically, flying sideways left and right, flying
forward and backward, as well as rotating
clockwise and counter-clockwise, under remote
control and carrying a full motion video (FMV)
camera payload. It flew in and out of a building
through a normal-size doorway [26]. The
current prototype demonstrated an endurance
flight time of only 5 minutes with body and
video payload. However, coupled with
advances in battery technology, the company Figure 7: Nano Hummingbird being piloted by remote
control (© AeroVironment).
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aims to refine the control system, developing the autonomous flight capabilities, possibly
outdoors and indoors, as well as improving the video payload system performance as next steps
[27].
Identify: Evolving Technologies Breakthroughs in UAV technology, with an emphasis on enhanced autonomy, are
continually occurring due to the emerging enabling technologies, broadly categorized as
following:
1. Advances in aircraft platform capabilities, supported by payload capabilities, low-
observable (or stealth) technology [7], alternative energy etc.
2. Advances in sensor technologies enable successful completion of mission objectives as
well as ensure safety, reliability and operational effectiveness.
3. Advances in on-board intelligence, such as sense and avoid technologies [7], which aid
in the guidance, control and navigations functions.
Technology Area Emerging Enabling Technologies
Platform Technologies Alternative energy, lightweight and efficient power supplies, low-
observable (stealth) technology
Sensor Technologies Synthetic Aperture Radar (SAR), multi-spectral imagery (MIS), Light
Detection and Ranging (LIDAR) imaging
On-board Intelligence Artificial intelligence, processors, mass-storage, communications
bandwidth Table 1: Identified technology areas with related enabling technologies. Adapted from [7].
Platform Technologies
Alternative Energy, Lightweight and Efficient Power Supplies: Advances in
alternative energy support autonomous UAV operations in ways previously unimaginable. Not
only alternative energy opens the possibilities of unparalleled flight endurance, it allows for
around the clock operations and persistent presence. Autonomous unmanned flights of the future
will require sufficient advances in these technologies for cost-effective applications. As
discussed earlier, successful demonstration of solar-electric fuel cells in the Helios Prototype and
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liquid-hydrogen fuel cells in the Global Observer, have proved the viability of the concept of
UAVs powered by alternative energy.
Most importantly, the future of aviation may not rely on fossil fuels. Today, most
aviation fuels are jet fuels originating from crude oil ─ a limited natural resource subject to
depletion as several reports indicate that the world's crude oil production is close to the
maximum level and that it will start to decrease after reaching this maximum [28] − a
phenomenon known as “peak oil”. The aviation industry predicts that aviation traffic will keep
on increasing. The industry has put ambitious goals on increases in fuel efficiency for the
aviation fleet [28]. Traffic is predicted to grow by 5% per year to 2026, fuel demand by about
3% per year. At the same time, aviation fuel production is predicted to decrease by several
percent each year after the crude oil production peak is reached resulting in a substantial shortage
of jet fuel by 2026 [28]. The aviation industry will have a hard time replacing this with fuel from
other sources, even if air traffic remains at current levels. [28].
Recently, the Pentagon has been implementing a plan to source 50 percent of domestic
aviation fuel for Air Force use from an alternative fuel blend by 2016 [29]. The synthetic
paraffinic kerosene (SPK) is the latest fuel to be tested [29]. In 2010, the Global Hawk
successfully started using a blend of synthetic fuel. JP-8 jet fuel (the kind typically used in the
Air Force) was combined with SPK (derived from liqufied coal), and another derived from
natural gas, to make up the blend [29]. In the past military aircraft have used other non-
traditional jet fuels, but this is both the first for an unmanned aircraft, and the first time any type
of aircraft has flown with this type of fuel [29]. Although, this transitory move is most
welcomed, the eventual demise of jet-fuel and synthetic fuels, due eventual depletion of natural
resources in the coming decades, demands finding new sources. Therefore, R&D efforts in
harnessing alternative energy sources for UAVs based on fuel-cell designs cannot be over
emphasized. As peak oil is reached, the future of UAVs, like other forms of aviation, will be
dependent upon harnessing alternative, possibly renewable, non-carbon based fuel sources.
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Fortunately, technological advances in alternative energy technologies developed for
prior UAVs continue to aid the way in development of more advanced designs. For example, as
illustrated in Figure 7, fuel-cell systems developed for prior UAVs have paved the way for
Global Observer’s extreme-endurance. Without these contributions, the technological
breakthroughs and milestones achieved by the Global Observer would not have been possible. In
particular, advances made by the earlier NASA Pathfinder and Helios prototypes, in terms of
lightweight hydrogen tanks, high efficiency electric motors, regenerative storage systems and
hydrogen power plants.
Fuel-cells work on the principle of converting chemical energy within a fuel, such as
hydrogen, through electro-chemical processes, directly into electricity. In the case of the Helios
Prototype, fuel cell-based system works by combining oxygen and hydrogen to produce electric
power, heat and water [2].To enable around the clock operations, the Helios Prototype needed a
mechanism to store the solar energy captured during the day to stay in operation during the night
when no sun light is available [2]. Using traditional NiCad or lithium batteries would have
proved to be impractical due to their heavy payload [2]. Instead, it was determined that using
proton-exchange membrane fuel cell technology would be the best option to have full day-and-
night flight capability [2]. Proton-exchange membrane—also known as polymer electrolyte—
Figure 8: Global Observer UAS technologies were developed and tested across several platforms [3].
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technology has advanced significantly in recent
years due to the large interest and investment in
alternative energy research, primarily by the
automotive industry [2].
The importance of lightweight and efficient
power supplies as a key supporting technology for
alternative energy systems for UAV flight and
operations is illustrated by the case of the Global
Observer. Based on customer requirements, it was
determined that the HALE UAS would have to use
a liquid hydrogen fuel propulsion system due to the
high specific energy content of liquid hydrogen [3]. Developmental efforts were focused on the
additional key technologies, primarily a lightweight liquid hydrogen tank and ultrahigh-
efficiency electric generation and motor drive systems, required to deploy a practical HALE
UAS, such as the Global Observer, into the stratosphere [3].
As discussed earlier, the Global Observer uses a hydrogen powered fuel-cell energy
system. It has a liquid hydrogen powered internal combustion engine driving a generator that
powers the four propellers as well as batteries and operational payloads [25]. One of the key
benefits of using liquid hydrogen as fuel is reduced fuel requirement in tons of fuel per year
when compared to fossil fuels. Similarly, since HALE UAS such as the Global Observer can
remain in flight for extended periods of time (in this case an entire week), less take offs and
landings are required [3]. Figure 9 illustrates flights and tons of fuel necessary for a scenario
requiring a 24-hours-per-day, 365-days-per-year persistence in the stratosphere with 1500
nautical miles distance from take-off to the area of interest [3].
Figure 9: Helios Prototype fuel-cell energy system [2].
Figure 10: Use of liquid hydrogen fuel in UAV platforms has obvious logistical benefits [3].
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The extreme endurance of the Global Observer carries the benefit of a very low pace of
operations and low operational costs with minimum required logistics. This ensures an
affordable system in the operations phase. Conventional airborne (manned and unmanned)
systems with relatively low endurance (one to two days) have a high pace of operations that
require significantly more manpower and sustainment costs due to many more takeoff/flight
operations/landing cycles [3].
Another key benefit of using fuel-based energy systems for UAV results in increased
system reliability. These energy systems are not only attractive from an environmental
standpoint and flight times not possible with manned aircraft, but since they have very few
moving parts, they have the potential of very high sub-system reliability [2] and contribute to the
overall system reliability.
It is to be noted that our discussion of alternate energy, fuel-cell systems and light-weight
and efficient power supplies is limited to technology demonstrations discussed in the context of
two HALE UAS, namely, the Global Observer and Helios Prototype. Since HALE UAS tend to
be lightweight and require extreme endurance, therefore, reduced numbers of flights, increased
reliability, increased energy efficiency and renewable energy technologies support their potential
in an enormous way. However, the implications of these energy systems would be much
different in the context of heavier unmanned systems with much heavier payload requirements,
such as the Global Hawk, or those with combat capabilities, such as the X-47B. Still, as
discussed earlier, due to reduced availability of jet-fuel in the coming decades, even UAVs with
heavier payload or combat requirements will benefit significantly from alternative energy.
Low-Observable or Stealth Technology: Low-observable or stealth technology
enables aircraft evade detection by radar. The reduced Radar Cross Section (RCS) ensures
improved combat survivability [30]. The technology uses special production techniques and only
certain materials in the applications (i.e., aircraft, ships, etc.) where it is used [30]. The correct
combination of these techniques and materials significantly reduces aircraft detection by enemy
radar [30]. Some of the design features used in stealth technology are the use of non-metallic,
radar-opaque composites, and a low profile that does not reflect radar directly back to the sender
[30]. It may also use an overall coating of a radar absorbing material and shield engine exhaust
[30].
20
Although, stealth capability has been available for military aircraft for at least two
decades, stealth features have only been recently developed for UAVs. In 2009, USAF
acknowledged the existence of the RQ-170 Sentinel, a reconnaissance and surveillance
31
UAS
built by Lockheed Martin, developed and deployed secretly with stealth capabilities [ ]. The
existence of the RQ-170 Sentinel was classified until a series of pictures emerged from Kandahar
airfield in Afghanistan [32].
As discussed earlier, the X-47B UCAS features stealth capability. The X-47B focus on
low-observability at sea potentially puts the Navy on a fast track to catch up with the U.S. Air
Force in stealth design. However, to be a viable option for the Navy's emerging F/A-XX
requirement for a 2025-timeframe strike aircraft, the UCAS must show that it can replace a
manned aircraft on carrier flight decks [33].
Recently, another Navy UCAS demonstrator with stealthy features, Boeing’s Phantom
Ray successfully completed its first flight [34]. Phantom Ray is considered one of the "starting
points" for a U.S. Navy Unmanned Carrier-Launched Airborne Surveillance and Strike Systems
(UCLASS) stealthy aircraft. It is one of four known low-observable, unmanned reconnaissance
or combat aircraft being readied for various U.S. military programs [35]. Two of them of which
are the RQ-170 Sentinel and X-47B.
The fourth stealth UAV in development is the next generation Predator unmanned
aircraft, the Predator C Avenger. It incorporates a pure jet engine and is faster than its
predecessors. It will be capable of flying at over 400 KTAS and can operate up to 60,000 feet. It
will come equipped with a sensor package consisting of Synthetic Aperture Radar (SAR) and
various Electro-optical/Infrareds (EO/IR) camera systems [36].
Sensor Technologies Sensors act as the “eyes and ears” of UAVs. Sophisticated sensor packages enable
operators to not only control and guide UAVs, but most importantly fulfill key mission
requirements such as Intelligence, Surveillance and Reconnaissance (ISR). Civilian UAVs have
remote sensing capabilities such as scientific measurements, aerial mapping and environmental
monitoring. Most importantly, advanced sensor systems are one of the key enablers of
21
autonomous operations. A brief description of various emerging sensor technologies for UAVs
follows.
Synthetic Aperture Radar (SAR): Environmental monitoring, earth-resource
mapping, and military systems require broad-area imaging at high resolutions. Many times the
imagery must be acquired in inclement weather or during night as well as day. Synthetic
Aperture Radar (SAR) provides such a capability. SAR systems take advantage of the long-range
propagation characteristics of radar signals and the complex information processing capability of
modern digital electronics to provide high resolution imagery. Synthetic aperture radar
complements photographic and other optical imaging capabilities because of the minimum
constraints on time-of-day and atmospheric conditions and because of the unique responses of
terrain and cultural targets to radar frequencies [37].
Synthetic aperture radar technology has provided terrain structural information to
geologists for mineral exploration, oil spill boundaries on water to environmentalists, sea state
and ice hazard maps to navigators, and reconnaissance and targeting information to military
operations. There are many other applications or potential applications. Some of these,
particularly civilian, have not yet been adequately explored because lower cost electronics are
just beginning to make SAR technology economical for smaller scale uses [37].
Current evolutionary SAR technologies include, ultra-high resolution imaging [38] and
low-observable bistatic SAR [39].
Of particular interest is a three
dimensional SAR imaging system proposed
by [5]. The 3D imaging radar, called
ARTINO (Airborne Radar for Three-
dimensional Imaging and Nadir Observation)
is being designed t operate on a low-flying
UAV and will able to map a directly
overflown scene into a high resolution 3D
image by looking downwards [5]. This
downward looking approach is ideal for Figure 11: Artist’s impression of ARTINO operational concept [5]
22
imaging of street canyons and deep terrain in mountainous areas [5]. The 3D imaging capability
combined with a small and mobile UAV platform is an ideal way to capture timely data on fast
changing terrains, like snow slopes (danger of avalanches) and active volcanoes [5]. Other
applications include Digital Elevation Model (DEM), generation, surveying, city planning,
environmental monitoring, disaster relief and ISR [5]. Current commercially available imaging
radar systems, do not provide a capability which avoids the shadowing problems and supplies
high resolution three-dimensional maps in a single flight [5].
Multi-spectral imagery (MIS): is a method of remote sensing that obtains optical
representations in two or more ranges of frequencies or wavelengths [40]. It is able to
discriminate between blue, green, red and near IR regions of the electromagnetic spectrum [41].
Remote sensing and the MIS sensors offer other advantages besides being able to image in
specific spectral regions, such as, the ability to “capture” images digitally, transmit the imagery
electronically, store the information and process the digital information using computers [41]. As
illustrated by Figure 11, different materials can be differentiated based on their distinct
reflectivity across a portion of the electromagnetic spectrum.
Figure 12: Spectral responses and band positions [41].
Light Detection and Ranging (LIDAR): All ranging systems, such as RADAR,
LIDAR, or LADAR, function by transmitting and receiving electromagnetic energy, but differ in
the operating frequency band.
23
LIDAR is an airborne laser-ranging technique commonly used for acquiring high-
resolution topographic data [40]. LIDAR data can be further incorporated into 3D models to
enhance modeling and simulation activities.
In the past, LIDAR imaging was primarily achieved through satellites. UAVs as
alternative platforms for laser scanning provide a good choice to overcome the economic
unfeasibility of satellites. The current challenge is to make LIDAR systems (particularly the
power supplies) small enough to be flown by miniature UAVs. Mini-UAVs seem to be a natural
choice as the supplementary solution. Installed with IMU and GPS, mini-UAV-borne LIDAR
systems can act further as a promising mapping plan, which can deploy efficient, accurate, and
flexible surveying projects [42].
Similarly, we discussed earlier the use of LADAR technology in example of
Piasecki/CMU sensor/navigation system for autonomous helicopter operations. The
demonstration used a LADAR perception system to create a real-time survey quality 3D map of
the terrain while flying at a safe altitude, even in low-light or low-visibility situations [21].
Advances in LIDAR and LADAR technology, integrated with sophisticated navigation systems,
will enable increasingly autonomous aerial operations.
On-board Intelligence On-board intelligence refers capabilities that allow unmanned aircraft to autonomously
take off, fly, navigate, and accomplish the mission and land safely. These include, but are not
limited to, artificial intelligence (enabled by advanced algorithms) and incredible amounts of
processing power within low-power and miniature platforms. Currently, autonomous UAV
operations are conducted primarily by employing pre-programmed flight flights, however,
emerging sense and avoid, navigation and guidance systems are being demonstrated along with
robust R&D effort.
Artificial intelligence: Sophisticated artificial intelligence functionality enabled by
software-based on-board systems is required in order to achieve fully autonomous unmanned
aerial flights.
Commercial use of UAVs in civilian airspace is currently limited by their inability to
detect, sense and avoid airborne hazards [43]. The transition from remote control to truly
24
autonomous flight, requires onboard software to interpret the data from the aircraft's cameras,
radars, and other sensors and then use artificial intelligence to make good decisions [19]. It must
also be compatible with manned aircraft, making sure to keep distance in the air, responding to
air-traffic controllers' directives, as well as collision avoidance on the ground [19].
A brief discussion of various case studies in research, development and testing and
evaluation in the area of achieving fully autonomous flight using a combination of artificial
intelligence and sensor autonomy follows. Although, these autonomous aerial flights were
demonstrated using smaller than aircraft-sized UAVs, their approach and results are potentially
transferrable to larger sized unmanned systems.
Obstacle and Terrain Avoidance
44
: In 2006, Brigham Young University (BYU), funded by
the U.S. Air Force, demonstrated results of R&D efforts toward an approach to enable a fixed-
wing MAV with obstacle and terrain avoidance capability using a combination of utilizing map
and sensory information [ ]. While map information may be useful in planning nominal paths
through city or mountain terrain, it is often imperfect (limited in resolution, out of date, or offset
in location) [44]. Therefore, sensory information must be utilized to detect and avoid obstacles
unknown to the path planner [44]. A laser range finder and three optic flow sensors were used for
this purpose [44].
A heuristic algorithm was developed to utilize the laser range finder in detecting and
avoiding obstacles [44]. A Random Tree (RRT) algorithm was used to find nominal paths
through different types of terrain (urban or canyon) [44]. A vector field path following approach
was developed to ensure that the MAV remains on the path (despite of wind disturbances,
imprecise sensors and controls and dynamic limitations) [44].
During the urban flight test, the MAV was flown at 40 m altitude on waypoint path that
passed through a BYU campus building 50m high and 35m square without providing
information on the size and location of the building [44]. As it approached the building, the laser
ranger detected the building and its location. The reactive planner generated a new path and the
MAV passed the building and turned back to the original waypoint path [44]. During the second
test flight, the MAV was flown through a canyon with steeping walls reaching over 75 m [44].
The flight path was set to go through one of the walls, in order to verify that the navigation
25
algorithms will correct the planned path and avoid collision [44]. Results showed that the MAV
biased its desired path up to 10m to successfully avoid the canyon walls [44].
Vision Based Navigation and Target Tracking
45
: The addition of a camera enables UAVs
to perform variety of tasks autonomously on the GTMax unmanned research helicopter − a
modified configuration of the Yamaha RMAX industrial helicopter [ ]. Georgia Institute of
Technology developed and tested a vision-based navigation system, an automated search routine
for stationary ground targets and a target architecture for moving ground targets [45].
UAVs, such as the GTMax, typically use a combination of GPS and inertial sensors to
navigate [45]. However, in urban or low altitude environments, GPS receivers are prone to losing
line-of-sight (LOS) with the satellite, hence, visual data can be used as an alternative to GPS
measurements to aid in navigation [45]. The authors suggest that the system described could be
extended to allow multiple targets to be tracked and acquired allowing vehicles to perform a
variety of missions without GPS [45]. This approach assumes that the target (such as a landing
site) is within camera view and its shape, background, position, orientation, and area are known
[45].
During the second experiment, an urban reconnaissance mission was conducted by means
of an automated search for an identification symbol placed on buildings, as well as identifying
the building and collecting information about it [45]. Algorithms aided in the symbol detection
and classification process and also in matching contours of the building windows with known
buildings [45]. In a village of 15 buildings, three tests were conducted and the correct building
was selected each time based on the identification symbol, appearing for approximately 5
seconds over a total search flight time of over 15 minutes [45].
The third system utilized a particle filter algorithm to successfully track a moving ground
target [45]. By estimating the performance of the tracking filter, the system was able to function
in real-time. The system was able to track a moving target autonomously by integrating the
particle filter with a camera controller and generated image [45].
Vision-based Autonomous Landing: Landing rotary-wing aircraft, such as a helicopter, is
difficult due to the inherent instability faced by such aircraft near ground. The design and
implementation of a real-time, vision-based landing algorithm for an autonomous model
26
helicopter in unstructured terrains is presented by [46]. Their results demonstrate that the
algorithm was able to ensure that the helicopter landed on the helipad repeatedly and accurately.
The algorithm provides a fast and inexpensive method of autonomously landing unmanned
helicopters. However, it assumes that the helipad is a known geometric shape and aligns
perpendicularly with the camera [46] and would have serious limitations in harsher
environments.
Multi UAV Relative Position Estimation
47
: Active cooperation amongst several UAVs has
important advantages, such as, exploiting sensor synergies and cooperative visual perception
[ ]. Cooperative perception refers to a consistent view of the world containing dynamic objects
by a group of agents (in this case cooperating UAVs) using one or more sensors [47]. GPS
estimates are subject to errors and inaccuracies and cannot be used for relative positioning of a
UAV with respect to another objects, for example, landmarks or moving platforms [47]. Using
this approach, different UAVs identify common objects in a scene (using blob features) and,
consequently, the relative displacement between them is calculated [47]. In experiments, two
MAVs were launched. Algorithms matched blobs between images from different MAVs and the
relative displacement between the MAVs was calculated in real-time [47]. The limitation of this
method, as with most vision-based approaches, is the presence of a scene with sufficient
structure [47].
Evolutionary Algorithm Based Path Planning:
48
Under a scenario where multiple UAVs
are launched from a known single location or multiple locations, a proposed approach is to
enable collision free planning by generating three dimensional trajectories [ ]. In this method,
on-board UAV sensors exchange information to maximize their situational awareness of the
surrounding environment [48]. The path planner algorithm enables navigation for a group of
cooperating UAVs while avoiding collisions with obstacles [48]. Further research and
development in this area would enable cooperating UAVs to autonomously coordinate flight
paths amongst themselves and ensure airspace safety and efficiency.
As evidenced by our brief discussion, various methods and approaches of using artificial
intelligence, in the form of algorithms, sensors, processing and analysis techniques, are enabling
demonstration of promising concepts and contributes results towards increasingly autonomous
UAV operations. Figure 12 illustrates the DOD perspective on trends in military UAV autonomy
27
based on autonomous control levels. Our limited analysis supports that autonomous control
levels are currently in R&D phases up until levels 5 and 6.
Processors and mass-storage: Advances in processors have the potential to enable
on-board intelligence, sensor data processing and generally contribute towards greater autonomy.
Faster CPU’s with multiple cores, reduced heat emission and reduced energy requirements are
suitable for UAVs. Larger UAVs are able to carry payloads in hundreds, and sometimes even
thousands, of pounds. This includes electrical power generators, large sensor suites, multiple
high power computers and multiple redundant components [49].
However, the challenge with small UAVs, due to their very limited payload capabilities,
remains to carry sufficient computing power on-board without sacrificing performance,
reliability and cost-effectiveness [49]. With increasing autonomy enabled sophisticated
algorithms and data processing, processing power on-board small UAVs is just as critical as
larger UAVs. The low payload limits are also a limiting factor in carrying on-board hardware
with high power requirements because not only the weight of adding the new hardware must be
considered, but also the weight of extra power required to operate the hardware [49].
Currently in development
Figure 13: Advancing trends in military UAV autonomy [1].
28
Off-line data processing at a local ground station provides the benefit nearly unlimited
computing and electrical power [49]. High-speed mass storage media with higher data transfer
and increased reliability, such as solid-state drives (SSD) enable efficient and abundant data
storage capability on-board for late processing on the ground.
On-board processing systems that are modular, flexible and easily integrated with several
platforms appear promising in enabling autonomous navigation [49]. The plug in and out, or
modular, concept along with light-weight and cost-effective components within the on-board
processing systems, are virtually requirements for autonomous aerial operations for small UAVs
[49].
Communications bandwidth: Satellite communications (SATCOM) is the key
communications link for most UAVs [50]. This bandwidth is as vital for UAV operations just as
the fuel that powers their engines, however, up until recently, these links were slow, and carried
FM links for standard definition video [50]. Currently the DOD, and parts of the Intelligence
Community, are in the process of a multi-year and multi-billion dollar SATCOM modernization
effort, consisting of array of new satellite spacecraft being launched and brought online [50]. As
a result UAV operations will enjoy, higher throughput, better security, improved range, efficient
use of spectrum, and support for a variety of complex sensors such as high definition video, laser
designators, imaging radar and ground moving target indicators, and multi-spectral imagers [50].
For example, each new Wideband Global SATCOM (WGS), is ten times faster than its
predecessor DSCS III ─ each WGS can downlink 2.4Gbps to tactical users on the ground such as
UAV operators [50].
29
Identify: Observables A decade’s long trend towards automation in the commercial airliner industry has been
ongoing. In the early days of commercial aviation, the standard cockpit had the flight engineer,
the navigator, and the radio operator [19]. Advances in automation have replaced those people,
one after the other and now all those remain are the pilot and the copilot 19[ ]. Already, as soon
as a commercial airliner is airborne,
19
software typically takes over the flight, handles the
landing—and most of what happens in-flight [ ].
19
The pilot is there to provide intelligent
judgment and decision making capability in regards to sense and avoid functionality [ ].
As discussed earlier,
43
commercial use of UAVs in civilian airspace is currently limited by
their inability to detect, sense and avoid airborne hazards [ ]. However, once advances in on-
board intelligence are able to provide full detect, sense and avoid (SAA) capabilities. However,
R&D efforts are underway to develop demonstration systems capable of SAA.
Current UAVs are able to fly entire missions with little or no human intervention [7]
assuming objectives are pre-programmed and operating in unrestricted airspace. The ultimate
goal is to be able replace a pilot with a machine of equal or superior thinking speed, memory
capacity, and responses gained from training and experience (Cook, 2007. Even though super
computers are likely to achieve human parity by the 2015 timeframe, they will continue to
remain uncompetitive with a trained human in terms of cost [1]. However, by 2030, DOD
forecasts that the cost of a 100 million MIP processor should approach $10,000 [1].
According to some experts, before autonomous unmanned commercial airliners become a
reality certain milestones must come to fruition first [19]. They point out that we are likely to see
autonomous freighters carrying cargo to the shore first. Then eventually, autonomous UAVs will
serve as cargo transports. Finally, they will serve as commercial airliners carrying people [19].
Autonomous automobiles also have the potential to accelerate the pace of advances towards
autonomous UAVs and lead to greater public acceptance if and when autonomous commercial
carriers do take flight.
Besides technical and business problems, regulatory hurdles of integrating autonomous
unmanned flight into the civilian airspace remains a key challenge. In 2008, the Federal Aviation
Administration (FAA) stated that preliminary proposals detailing how UAVs can be widely
30
integrated into the U.S. airspace are at least seven years away and final regulatory approval
unlikely before end of 2020 [51].
Due to privacy and safety concerns, the FAA currently limits commercial and
recreational opportunities for UAVs and requires special permits for flight in the National
Airspace System (NAS)— a complex network of more than 19,000 airports with 100,000 daily
flights directed by thousands of air traffic controllers [52] . As of May 2011, the agency had
issued only 240 permits for unmanned flight in NAS — including permission for DHS to patrol
the border and NASA to spot wildfires across the West [52]. However, the FAA is currently
considering releasing more lenient rules towards commercial and recreational UAV use.
Observables Potential Source
Advances in computer processor design, performance, capabilities and cost
Gartner Research http://www.gartner.com/
Forrester Research http://www.forrester.com
Trends and breakthroughs in trade journals, magazines and publications
Unmanned Systems http://www.auvsi.org/publications/unmannedsystemsmagazine/
Airforce Technology http://www.airforce-technology.com
Popular Science http://www.popsci.com
IEEE Spectrum http://spectrum.ieee.org/aerospace
Overall rate of robust research in academic and scientific publications
IEEE Explore Digital Library http://ieeexplore.ieee.org
Academic Databases (EBSCO Host, ProQuest, WorldCat, LexisNexis Academic, ABI/Inform, JSTOR, Academic Search Premier, ArticlesPlus)
Industry/academic conferences AUVSI's Unmanned Systems North America Conference http://www.auvsi.org/AUVSI/Events/AUVSIEvents/
International Conference on Unmanned Aircraft Systems http://uasconferences.com
Unmanned Aircraft Systems West Conference http://www.uaswest.com/
The UAS Global Exhibition and Conference http://www.dk-export.dk/UAS-Global/Mainpage
Advances in UAV technology (both foreign and domestic)
Intelligence community, NSF, DOD, NASA, DARPA
Table 2: Potential Observables and Sources of Information on Autonomous UAVs.
31
Technology Warning Assessment
Technology Observables
Unmanned aerial vehicles (UAVs) capable autonomous flight ─ ability to take off, navigate, coordinate, sense and avoid, and land in a safe, efficient and reliable manner without requiring any human control, in the U.S. National Airspace System (NAS).
Human parity is achieved by processors (100 million MIPs) for $10,000 or less [1].
Full-fledged Sense and Avoid (SAA) on-board UAVs able to operate and coordinate with manned and unmanned aircraft in NAS [43].
Autonomous freighters, autonomous cargo transport UAVs [19] and autonomous automobiles gain mass adoption and proven commercially viable.
Final regulatory approval to allow autonomous UAVs to be widely integrated into the NAS [52].
Accessibility Maturity Consequence
Level III Watch
Autonomous commercial airliners, local air service, robotic medevacs [19]
Fully autonomous swarms of UAVs and UCASs [1]
De-skilling paradox affecting human operators [53]
Table 3: Technology Warning Assessment Chart for Autonomous UAVs
Assess: Accessibility Currently, the U.S. Government, and particularly the DOD, remains the largest funder in
terms of R&D and procurement for UAV technology [6]. According to a 2011 market study by
the Teal Group, over the next decade United States will spend 77% of the worldwide RDT&E
funding on UAV technology and do 69% of the procurement [54]. As of 2007, US companies
held about 63%-64% of the market share, while European companies accounted for less than 7%
[6]. The Teal Group study also forecasts that annual worldwide UAV spending will almost
double from $5.9 billion to $11.3 billion. Similarly, annual worldwide spending on UAV
payload technologies, particularly sensors, will almost double from $2.6 billion to $5.6 billion
[54]. According to FAA estimates, there are approximately 50 companies, universities and
government organizations working on at least 155 UAV designs in the United States alone [52].
32
Our analysis suggests that sophisticated UAV technology with autonomy is a Level III
investment, requiring hundreds of millions of dollars of sustained R&DTE investments,
specialized expertise and facilities, potentially afforded only afforded by governments. Simply,
possessing the financial means would not be enough. Like in the case of the Global Observer,
enabling technologies necessary for a successful autonomous UAV, will be first tested, refined
and improved based on experiences in developing less sophisticated UAV designs.
Assess: Maturity The Joint Strike Fighter Lighting II is currently the only manned fighter aircraft planned
by the Department of Defense [6]. As mentioned in the previous section, the Pentagon is the
largest acquirer of UAV technology. Our analysis supports the notion that the Pentagon is
making an enormous bet on the enormous potential of autonomous UAVs due to its current focus
on developing AUAVs for ISR and combat missions ─ case in point, the X-47B.
Based on our initial analysis, UAVs originated in the World War I era and have come a
long way since then. Advances in platform design, sensor technologies, lightweight design,
communications and alternative energy have enabled contemporary UAVs to become an
operationally mature and reliable technology for intended missions. However, AUAVs, as
discussed earlier, pose significant challenges in terms of increased safety requirements.
Therefore, we conclude that the technology maturity for autonomous unmanned aircrafts is still
in the very early innovation stages. Early adapters are developing operational prototypes, but we
are still likely decades away from the days of hoping into a pilotless commercial airliner.
Assess: Consequence Once autonomous UAV flights become an operational reality, many exciting
opportunities await in the civilian and commercial arena with positive potential to contribute
towards U.S. economic growth, including but not limited to:
•
• Robotic medevacs rescuing people stranded by flood or fire
Pilotless commercial airliners [19].
[19].
33
• An air-taxi service. “In many places just getting to the airport or to the main airport hub
is the hardest leg of the trip. If small robo-planes could get you there, air travel would
become vastly more attractive” [19].
• FedEx-style air cargo transport [19].
However, with all technological breakthroughs there are can be drawbacks and unintended
consequences. One such problem is the “de-skilling” phenomenon experienced by skilled human
workers when they are no longer able to stay current on their skills due excessive autonomy of
operations [19]. The problem is an argument for using humans alone, or machines alone, but not
putting them together [19]. Automation of routine tasks can atrophy skills of pilots, who would
be less likely to be able to handle unexpected situations in the air [19].
The more advanced the automated system, the more crucial the contribution of the human
operator (in this case, the pilot, whether on board or on the ground) becomes to the successful
operation of the system. However, one of the main paradoxes of automation is that “the more
reliable the automation, the less the human operator may be able to contribute to that success”
[53]. Unless autonomous UAVs reach 100% reliability, the paradox of de-skilling will persist. It
would be extremely difficult for operators to flawlessly detect and recover from unexpected
“errors” when they are not even able to detect them due to atrophied on-the-job skills [53].
Prioritize & Task Although, the focus of our assessment is to gain a better understanding of AUAV
technology in ways that it may promote U.S. economic growth, we must still pay close attention
to the state-of-the-art of AUAV R&D happenings occurring in the defense sector due to its
dominant role in this area. As discussed earlier, the U.S. Government is the largest acquirer and
R&D funding source for UAV technology at the moment and Europe stands at distant second
[6], [54]. However, this trend may change in the future. Potential countries with interest in this
technology may include, China, Brazil and India. With this in mind, resources must be
prioritized towards monitoring observables from state entities with the most interest as well as
willingness to commit large amounts of funds in acquiring this capability. Close monitoring of
observables from interested states will allow the U.S. to ensure technological superiority in this
area.
34
Due to globalized nature of the commercial marketplace, large and sophisticated aviation
projects, such as the Boeing 777, have the potential to become off-shored partially (or globally
distributed) amongst integrators, suppliers, manufactures, labs and sub-contractors working on
the project from many different countries and regions. However, in order to maintain its
competitive advantage as the leading and first innovator in practical, safe and cost-effective
autonomous unmanned aerial flights, the U.S. must not only commit resources to sustain, but
increase funding in relation to the competition, towards R&D efforts. Furthermore, resources and
attention must be committed towards preventing espionage and loss of valuable intellectual
property by U.S Government or commercial entities engaged in highly advanced and specialized
R&D in this area.
A team of 10 dedicated analysts, from scientific, military and academic backgrounds,
with expertise in UAV technology will be committed to perform the ongoing task of monitoring
trends and new developments in this arena. Their objective will be to execute against capturing,
monitoring and assessing observables and assessing the consequences on U.S. competitive stance
in this field. However, efforts must be balanced between developments occurring within the
defense and civilian (commercial, academic, scientific and government) space.
It is expected that our team of analysts will form close and recurring relationships with
the academic, government and industry community within the U.S.. They must have access to
classified information and work closely with the intelligence community in order to have an
information sharing mechanism regarding foreign interest and developments in this area.
Furthermore, since much of advance UAV technology is being used by the IC, it will also be an
ideal method to stay informed on ISR applications enabled by AUAVs. Working closely with
industry will be crucial in order to ensure a viable and growing private sector dedicated to R&D
in this area. Information on efforts in exciting basic research, concepts, technology
demonstrators and prototypes developed by the scientific and academic community will allow
our team to stay current on the cutting edge of this technology.
This must be a persistent and on-going assessment and monitoring effort and is expected
to stay in sustainment until the technology is commercially viable to the point of profitable
business models being developed, regulatory hurdles being overcome and technical obstacles
towards fully autonomous flight being overcome. Funding for initial year operations and
35
continuing awards will be obtained from U.S. Government grant programs with potential sources
as the NSF, FAA and DARPA.
36
Table of Figures Table 1: Identified technology areas with related enabling technologies. Adapted from [7]. ...... 15
Table 3: Potential Observables and Sources of Information on Autonomous UAVs. .................. 30
Table 2: Technology Warning Assessment Chart for Autonomous UAVs .................................. 31
Figure 1: Yamaha RMAX autonomous agricultural UAV (© Yamaha). ....................................... 7
Figure 2: (2007) Photo taken by USAF RQ-4A Global Hawk and analyzed for Southern
California Firefighters. Infrared image depicts hot areas and objects as white on a darker
background and shows the Horno Fire progressing [4] .................................................................. 8
Figure 3: The ScanEagle launched from a ship (© Insitu). ............................................................ 9
Figure 4: At 10,000 feet in in skies northwest of Kauai, Hawaii in August 2001, the remotely
piloted Helios is traveling at about 25 miles per hour (© NASA/AeroVironment). .................... 10
Figure 5: KlearPath sensor/navigation system for autonomous helicopters keeps a running rank
of possible landing sites and approach/abort paths in order to allow rapid maneuvering to
unexpected developments on the ground or in air (© Piasecki Aircraft/Carnegie Mellon
University). ................................................................................................................................... 11
Figure 6: Global Observer can fly up to altitudes of 65,000 feet, has an extreme endurance of 168
hours and is the first unmanned aircraft to use hydrogen fuel-cells (© AeroVironment). ........... 13
Figure 7: Nano Hummingbird being piloted by remote control (© AeroVironment). ................. 14
Figure 8: Global Observer UAS technologies were developed and tested across several platforms
[3]. ................................................................................................................................................. 17
Figure 9: Helios Prototype fuel-cell energy system [2]. ............................................................... 18
Figure 10: Use of liquid hydrogen fuel in UAV platforms has obvious logistical benefits [3]. ... 18
Figure 11: Artist’s impression of ARTINO operational concept [5] ............................................ 21
Figure 12: Spectral responses and band positions [41]. ................................................................ 22
Figure 13: Advancing trends in military UAV autonomy [1]. ...................................................... 27
37
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