July 10, 2009      

Summary: The ongoing conflicts in Iraq and Afghanistan have driven interest and investment in unmanned aerial vehicles. While a great deal of research into aspects of small UAV and M-UAV technology is going on at university-affiliated research centers and private labs, much of the money for the research, and potential demand for product, is coming from the Dept. of Defense.

  • Demand has been steady from the defense sector, but UAV technology is ready now for a whole range of other commercial applications.
  • Micro-UAVs are highly portable — they can be carried into an area of operations and can fly and navigate with minimal operator intervention.
  • Technical challenges such as the need to develop flight controls that are light and effective enough for tiny aircraft remain, but are being overcome by a range of design approaches that go beyond both fixed and rotary wing aircraft.
  • The economics of defense contracts — which fund research and development of complex products — make development of M-UAVs far more sustainable in the military market than in the civilian.
  • There is a wide range of potential civilian applications for current M-UAV designs, but the market demand for such applications is still undeveloped.
  • The best options for M-UAV investment are currently in hybrid fixed-wing and rotary-wing vehicles, whose aerodynamics are already well-understood. Designs that mimic birds, insects or other objects in shape to avoid detection show promise, but present higher risks to investors.
  • The ongoing conflicts in Iraq and Afghanistan have resulted in increased interest and investment in unmanned aerial vehicles. But while the larger unmanned systems such as General Atomic’s Predator have stolen all the headlines, another class of robotic flyers has been evolving quietly, while giving troops in the field an important set of eyes in the sky.

The concept of miniature robotic aircraft is hardly new. The Defense Advanced Research Projects Agency (DARPA) began inquiries into small robotic drones in the early 1990s. But developments over the last decade have rapidly accelerated advances in the development of small, portable UAVs — some the size of a radio-controlled models, some even smaller. Small UAVs such as Aerovironment’s Raven, which the U.S. Army has purchased in large numbers, are the forerunners of a new class of autonomous, small robotic flyers called Miniature UAVs ( M-UAV), or Micro Air Vehicles (MAVs) — semiautonomous flying vehicles with a wingspan under 24 inches. While a great deal of research into aspects of small UAV and MAVs. MAV technology is going on at university-affiliated research centers and private labs, much of the money for the research, and potential demand for product, is coming from the Dept. of Defense.

DARPA has seeded money into MAV and small UAV research for the past 20 years, and current operations in Iraq and Afghanistan have accelerated demand for small, lightweight flying sensors that can support troops involved in security and counterinsurgency operations. While the demand for small UAVs — most of which are scaled down, simplified versions of larger UAVs — has been steady from the defense sector, the technology is now ready for a whole range of other commercial applications. The DOD plans on spending $17 billion over the next 4 years for UAV systems, and a large portion of that spending will be allocated to small UAV designs in support of the DOD’s shifting focus to empowering small unit operations for what DOD now calls “Hybrid Warfare” — the blending of “irregular” warfare such as anti-terrorism, counterinsurgency or other security operations, with more organized threats. Small UAVs give units on the ground a dedicated source of local surveillance and intelligence.

A great deal of the money for M-UAV and MAV acquisition and R&D is being channeled through the large primary defense contractors — though some smaller competitors, like Aeroenvironment, based in Monrovia, Calif., are finding niches and making significant gains. The greatest investment opportunities — and the greatest risks — are at the leading edge of MAV development, where completely new technologies must be developed to make the units small, inexpensive, easy to control, and able to fulfill more than a single function. Unfortunately for investors interested in broader civilian business markets, most of the current M-UAV and MAV development opportunities are in defense.

There are plenty of pie-in-the-sky civilian applications — self-deploying wireless routers to relieve overutilized cell-phone networks during traffic jams or sporting events, for example, or monitoring of buildings or open areas for security, maintenance or pest control. The most immediate application and much of the current development, however, is focused on intelligence, surveillance and reconnaissance for military or, to a lesser extent, law-enforcement customers.

The U.S. military plans to spend hundreds of millions of dollars during each of the next five to ten years on independent research and development to make M-UAVs smaller, cheaper, and more reliable for those purposes. Investments now may pay off in commercial applications in 10 to 15 years, but the defense applications will pay off sooner. The defense applications for M-UAVs and MAVs are wide-ranging. Virtually self-flying, small UAVs like Raven can be given a set of Global Positioning System way-points to fly.

They can be carried, launched and controlled from the ground by a small team to offer troops an airborne view of the enemy, day or night. MAVs have the potential to perform a similar mission but be deployed by a single soldier, or en masse as a set of smart sensors. Some may be able to fly into tight quarters such as caves or buildings to search, or fly to a perch and sit on station for long periods, sending back surveillance data on a fixed target.

While the first generation of M-UAVS have mostly resembled their larger cousins, the aerodynamic challenges related to lightweight flight — especially in dynamic conditions like urban areas — has helped accelerate examination of alternative models for flight: from variations on more traditional fixed-wing and rotary craft, to more exotic alternatives including inflatables, dirigibles, and fliers modeled on the flight of birds and insects. All of these craft have several things in common.

They are highly portable — they can be carried into an area of operations and they can fly and navigate with minimal operator intervention. But the evolutionary paths they are taking lead to a widely varying set of applications, and immense opportunities that range far beyond those the U.S. Dept. of Defense has in mind. Small and micro-UAVs are already filling a major gap in the military’s air power requirements. They give soldiers immediate access to “ISR” — intelligence, surveillance and reconnaissance — that would normally have to be passed through multiple organizational levels before it got to the troops, and would arrive too late to be useful.

They can be deployed nearly anywhere. They are hard to detect, almost impossible to defend against from an adversary’s standpoint, and are increasingly easy to deploy. As M-UAVs evolve, they will take on more and more of the dull, dirty and dangerous tasks of warfare, providing eyes, ears and sensors in places that it would be impossible to put a human.

Technological Challenges

The challenges facing M-UAV and MAV developers are significant. There are simple issues of aerodynamics to be conquered—the handling characteristics of aircraft that weigh as little as a few ounces are significantly different from those aircraft designers have coped with in the past:

  • Aerodynamics
    • Watch a plastic bag flying in a light breeze, or an insect react to a small gust of wind, and you understand the vulnerability of a “micro-flyer” to the dynamics of the atmosphere, especially in urban areas where rounding a corner can mean hitting a gust of “canyon wind.” Designers have to take those factors into account to make the vehicles stable fliers, but they can’t do it by adding weight, wingspan, expansive control surfaces or many options that work well for larger aircraft but not for micros.
  • Autonomy
    • New control and navigation systems need to be perfected to make it possible for MAVs to carry out missions. The differing flight characteristics and frequent need to navigate indoors or in other tight quarters — as well as the assumption that operators will not be qualified pilots as is the case with Predator and other full-size UAVs — make human and GPS-based control impractical for some small MAV applications. GPS may not be accurate enough, or even available, indoors or under cover. Both MAVs and small M-UAVs need to be more autonomous. Even if a human operator is looking through a small MAV’s-eye-view camera, human reflexes in themselves are not designed for dealing with the “skittishness” of flying a bird or bug-sized aircraft. That means more of the flight intelligence of the M-UAV must be on-board, and less must depend upon a control station or operator. The contradiction between the need to pack more autonomy in such a small package and the requirement that small MAVs be extremely small and light is another of the ongoing design challenges. While current M-UAVs can operate largely by a set of waypoints, additional capabilities to reduce the workload of the operator are still required. Being able to maintain mission disconnected when communications are not available, storing and forwarding video (using technology such as disruption-tolerant networking) and automatic target identification and tracking are essential for large-scale M-UAV “perch and stare” surveillance operations.
  • Maneuvering
    • On-board flight controls for smaller UAVs must take a different approach than other UAVs. The actuator-based systems that move the control surfaces of many full-size UAVs may be too heavy for extremely-low-weight fliers. With the change in aerodynamics and weight involved, conventional controls might not even be effective — particularly at low speed. Depending on the propulsion type used, ducted fans or directed engine exhaust may be more feasible ways to maneuver MAVs than more typical controls that are based on the speed and volume of wind crossing the control surfaces.
  • Power
    • Batteries are heavy. Chemical fuels have more potential energy relative to weight, and a faster turnaround time for relaunch. Some researchers are investigating the use of micro pulse jet engines, which are simple and offer a superior weight-to-thrust ratio over propellers and fans, but these might not be practical for some mission types.
  • Swarming
    • Interaction among small MAVs may be required to carry out some missions — that means that they need to communicate with each other and behave in tandem. For example, while operating indoors or out of line of sight, Inter-MAV communications would be necessary to pass off targeting information and relay communications back to the control station. As the range of M-UAVs increases, the need to stretch the communications line further — especially in urban environments where a “perch and stare” M-UAV may not have a clear line of sight back to a control station — the ability to network multiple M-UAVs together and relay sensor data will become more important.
    • This is particularly true in environments where standard radio frequency communications might not be possible or desirable because of the need for stealth or because of the saturation of radio frequency usage in urban and battlefield environments. Low-power radios, or even laser communications relays are a potential capability requirement for the next generation of M-UAVs.

Design Options — Fixed-Wing, Rotary, Other

  • The current and near-term generations of small UAVs and M-UAVs are based largely on the two primary aircraft metaphors of modern flight — fixed-wing and rotary wing. Hybrid small UAV systems have also been demonstrated that use a combination of fixed wing lift with ducted-fan propulsion for vertical takeoff and landing and on-station hover.
  • The predominant small UAV design is fixed-wing. Most designs leverage lightweight, tube-transportable components that can be assembled in the field, using folding or semi-rigid wings. UAVs like Raven, Cyber Defense Systems’ Cyber Bug (though the current status of Cyber Defense Systems is somewhat in doubt) have begun to move into the public safety sector as well, with purchases by local and regional law enforcement. They have simplified operator controls, can fly without a human pilot’s intervention, and their robotic systems can fly flight plans based on Global Positioning System “waypoints.” Fixed-wing small UAVs offer reasonable flight endurance, simple operation and recovery, and are relatively quiet, making them ideal for surveillance and reconnaissance tasks.