* Another growth field in UAVs are miniature UAVs, ranging from "micro-aerial vehicles (MAVs)" that can be carried by an infantryman to man-portable UAVs that can be carried and launched like an infantry anti-aircraft missile. This chapter outlines developments in miniature UAVs.
* The notion that small, even very small, UAVs might have practical uses arose in the early 1990s. In 1992, DARPA conducted a workshop titled "Future Technology-Driven Revolutions In Military Operations". One of the topics in the workshop was "mobile microrobots". The idea of using very small "microdrones" was discussed, and after initial skepticism the idea started to gain momentum. The RAND Corporation released a paper on the microdrone concept in 1994 that was widely circulated. DARPA conducted a series of "paper studies" and workshops on the concept in 1995 and 1996, leading to early engineering studies by the Lincoln Laboratories at the Massachusetts Institute of Technology (MIT), and the Naval Research Laboratory (NRL) in Washington DC.
The studies demonstrated that the concept was feasible. In 1997, DARPA then began a multi-year, $35 million USD development program to develop "micro aerial vehicles (MAVs)". The MAV project's goals was to develop a microdrone whose largest dimension was no more than 15 centimeters (6 inches); would carry a day-night imager; have an endurance of about two hours; and be very low cost. It would operate with a high degree of autonomy and was to be used in the squad-level combat environment. MAVs capable of hovering and vertical flight would be used to scout out buildings for urban combat and counter terrorist operations. A MAV could be included in a pilot's survival kit. A downed pilot could use it to keep a lookout for enemy search parties, or relay communications to search and rescue units.
This phase-one DARPA study ended in 2001, and was followed by a phase-two study that focused on particular vendors with an intent to develop MAVs closer to operational specification. A number of different MAVs were developed as part of these DARPA efforts, some of the more interesting being:
Along with the flight prototypes, the DARPA effort considered subsystems design, such as lightweight electric motors, small fuel cell systems, plus navigation, control, and sensor subsystems. The DARPA MAV effort ended in 2000 and the results of the effort were somewhat negative, demonstrating that a 15 centimeter UAV was simply too small to be useful for military applications, at least at the time.
* However, the effort did get a lot of people thinking about tiny aircraft, with considerable development work continuing in its wake. DARPA returned to the theme later, in particular with award of a contract to Aerovironment in 2008 for a "nano aerial vehicle (NAV)", to weigh no more than 10 grams and with a length of no more than 7.5 centimeters (3 inches). Aerovironment released videos of a flight prototype in 2011, the NAV being in the form of a hummingbird; the video showed it to have impressive agility and controllability.
Of course, the hummingbird configuration was strictly experimental, it making no sense to deploy a NAV that doesn't look like a local bird over much of the world. Aerovironment engineers say that while they have solved most of the flight control problems for their little ornithopter, due to the slow evolution of battery technology it only has an endurance of about ten minutes, inadequate for operational use, and similarly sluggish development of payload subsystems means the NAV isn't very capable.
Other ideas are being developed as well. In 2008, the AFRL and General Dynamics released a video on MAVS, providing animations of several types of MAVs. One was roughly pigeon-sized and in fact resembled a pigeon, with coloration added to enhance the illusion. It was not an ornithopter, however; it had a small video camera in a dome for a "head", with a folding prop around its "neck". It could perch on power lines to obtain observations and also pick up power through electromagnetic induction from the line. To move to another location, it would unfold the prop and its wings to take to the air.
The video focused primarily on an insect-sized ornithopter, resembling nothing more than a large black microchip package with an insectlike wing and three legs on each side. It could get around by flapping its wings or crawling on its six legs, and had a solar cell on the back to recharge its power supply. It was hard to know how seriously to take these concepts, since so far development of a practical insect-sized MAV has been stymied by the difficulty of developing useful miniaturized avionics and in particular with implementing a power supply that could provide adequate endurance.
MAVs have also attracted a hobbyist and amateur community, somewhat along the lines of the "robot war" competitions that make it onto TV, and yearly competitive events have been conducted. These home-built MAVs are of course relatively unsophisticated, but have demonstrated a great deal of ingenuity. Possibly one of these days somebody is going to come up with an idea that will catch on.BACK_TO_TOP
* While the early DARPA MAV effort did not lead to an operational system, there was still a general perception that UAVs for the infantry on a somewhat larger scale might be useful for military operations.
That wasn't a completely new idea. A small UAV was tested operationally during the First Gulf War. The "FQM-151A Pointer", was designed by AeroVironment Incorporated, which is run by Paul McCready, famous for such pioneering aircraft as the human-powered Gossamer Condor and a robotic flying pterodactyl replica. The Pointer was developed with company funds, with the US Army and Marine Corps obtaining a total of about 50, essentially for evaluation, beginning in 1990.
The radio-controlled Pointer was built mostly of high-impact Kevlar. It resembled a hobbyist's RC sailplane with a small engine added, with the wing standing up above the fuselage on a pylon and a pusher propeller on the wing behind the pylon. A lithium battery pack powered the UAV's compact electric motor to drive the propeller. The little Pointer was hand-launched. It was recovered simply by putting it into a flat spin, allowing it to flutter down to the ground.
AEROVIRONMENT POINTER: _____________________ _________________ _______________________ spec metric english _____________________ _________________ _______________________ wingspan 2.74 meters 9 feet length 1.83 meters 6 feet max loaded weight 4.1 kilograms 9 pounds maximum speed 73 KPH 46 MPH / 40 KT service ceiling 300 meters 1,000 feet endurance 1 hour _____________________ _________________ _______________________
The Pointer carried a CCD camera fixed in its nose, meaning it had to be directly pointed at its target to see it, which is how the machine got its name. Video could be fed back to the ground station by radio or fiber-optic link. The ground station recorded flight imagery on an eight-millimeter video cassette recorder. Digital compass headings were superimposed on the imagery and the controller could add verbal comments. The imagery could be inspected with normal, freeze-frame, fast, or slow-motion replay. The aircraft system and the ground control station were carried in separate backpacks. It required a pilot and an observer. Pointers in US military service were later upgraded with a GPS-INS capability.
* The Pointer was seen as very attractive but it still left something to be desired in terms of endurance and control, and was seen as still too big for the infantry role. However, Aerovironment had continued research on the concept, and when the Army asked the company for a more portable solution, Aerovironment agreeably developed a half-sized control system and a downsized version of the Pointer called the "Raven".
The Raven has the same configuration and central pod of the Pointer, but a shorter tail and a wing reduced to a 52% span of 1.34 meters (4 feet 5 inches). The Raven has an endurance of 80 minutes. The entire system can be carried by two soldiers. Following the Afghanistan campaign in 2001:2002, the US SOCOM ordered 80 Ravens from Aerovironment, which was more than the total number of Pointers that had been sold to that time. The US Army also placed orders for up to 105 Ravens in the late summer of 2003 after the US occupation of Iraq led to persistent insurgent attacks on US forces. The UAV was given the designation of "RQ-11A" and proved an outstanding success.
An upgraded version of the Raven, the "RQ-11B", went into production in 2006; improvements included more endurance, a lighter ground-control system, better sensors, and a laser target designator. By early 2008, the Army had obtained over a thousand Ravens, and the Marines had expressed interest in buying the machine as well. It is now being obtained by Norwegian forces.
The Pointer remains in use, having seen action during the intervention in Afghanistan in 2001:2002 and the invasion of Iraq in 2003. AeroVironment has introduced a second-generation Pointer, the "Pointer Upgraded Mission Ability (PUMA)", generally similar in configuration to the original but with twice the endurance, as well as a more sophisticated daylight camera / infrared imager system. It leveraged off the avionics developed for the smaller AeroVironment Raven UAV, discussed later. AeroVironment also developed an "PUMA AE" for "all environment", which is basically a watertight Puma that can set down on the water for recovery.
* US forces are using other mini-UAVs in combat. The Lockheed Martin "Desert Hawk" weighs 3.2 kilograms (7 pounds), has a wingspan of 1.32 meters (52 inches) and a length of 86.4 centimeters (34 inches). It is made mostly of plastic foam, suggesting something like a Nerf toy, and uses an electric motor driving a pusher propeller as a powerplant, making it very quiet. It is launched with a bungee cord, carries three small CCD cameras, and has an endurance of about an hour. It flies mostly under autonomous control, with the "pilot" keeping track of what's going on with a laptop computer.
The Desert Hawk was designed by Lockheed Martin for the Air Force on a quick-reaction contract issued late in the winter of 2002, with the first system delivered in the early summer. It was designed quickly because it leveraged heavily off of technology and design studies developed for the MicroSTAR MAVs; the DARPA effort paid off even in the short run. The Desert Hawk has been continuously improved since its introduction to service, with refinements such as a 360-degree infrared imager introduced in 2009. The latest iteration, the "Desert Hawk III", is in service with both US and British Army forces.
In addition, Honeywell research on ducted-fan UAVs for DARPA led to the introduction of a ducted-fan MAV with a loaded weight of 8.4 kilograms (18.5 pounds) that was introduced to the Iraq theater in 2007, primarily to help troops find "improvised explosive devices (IEDs)". The machine is known as the "RQ-16A T-Hawk", originally known as the "G-MAV", the "G" indicating that it was gasoline-powered, using a high-end RC aircraft piston engine manufactured by 3W of Germany. Honeywell developed a prototype in 2005, coming up with a new design based on the company's previous work with DARPA, with the US Army performing evaluations in the summer of that year.
After modifications as indicated by the trials, an initial batch of T-Hawks were sent to Iraq to see how they fared in a war theater, being used by US Navy mine-hunters. Honeywell then introduced "RQ-16B Block 2" variant that replaced the initial fixed visual / IR camera with a sensor turret, provided improved flight control software, and updated to a fuel-injected engine that made getting the machine off the ground a quicker procedure. The Block 2 was followed in 2010 by a "Block 3" configuration that added an encrypted command-control "digital datalink (DDL)".
The T-Hawk has a length of about 60 centimeters (2 feet), a dry weight of 7.7 kilograms (17 pounds), and an endurance of about 45 minutes. Troops found it useful for scouting out roadside bombs, thanks to its ability to "hover and stare", a trick fixed-wing UAVs can't pull off. However, in 2010 the Army suddenly became unenthusiastic about the T-Hawk and decided not to pursue it any further, the most prominent complaint being that it was simply too noisy to be useful in a tactical environment: everyone could hear it coming. However, it is getting some use in civil applications, so it may not be dead yet.
Troops in the field are extremely enthusiastic about MAVs in general. One of the first officers to make use of the Raven in Iraq spotted a team of insurgents planting a bomb the first time he flew the UAV operationally, and the good word spread like wildfire. So many little UAVs are flying there that they became something of an air collision hazard. After a few close calls, operational procedures were tightened up.
* The Naval Research Laboratory and US Marines Warfighting Laboratory have developed a man-portable UAV of roughly the same size as the Aerovironment Raven, the "RQ-14 Dragon Eye" -- not the same machine as the BAI Aerosystems Dragon. The Dragon Eye is a tailless design with a rectangular wing and twin props. It is designed to fit into a backpack, with a weight of 2.25 kilograms (5 pounds) and a span of 1.14 meters (3 feet 9 inches). It can be launched by hand or bungee slingshot and has a GPS-INS-based waypoint navigation system.
One of the interesting features is that the operator monitors Dragon Eye operation through "video goggles" connected to a laptop computer. The control system weighs about 5.4 kilograms (12 pounds). The Dragon Eye's endurance is an hour. It was quickly put into service with the US Marine Corps, and the Marines were so enthusiastic about it that they ordered over a thousand of them, with Aerovironment performing production. An "RQ-14B" was introduced that used the same control system as fitted to Aerovironment mini-UAVs.
Work is underway to improve on the Dragon Eye. Marines like to launch the UAV off of rooftops in Iraq, and they want a longer span to make it easier to land on the same rooftop it was launched from; the longer span will also improve flight endurance. A better imager is being considered, as well as a payload to allow a Dragon Eye to act as a communications relay for another, permitting a wider radius of action. Yet another improvement is a control system with eight instead of four channels, doubling the number of Dragon Eyes that could be flown in the same area; and a wearable control system. This control system will not only be compatible with the Dragon Eye, but also the "Dragon Runner" ground robot, said to be a four-wheel vehicle about the size of a breadbox, and the "Small Unit Remote Sensing System", which is based on a static module with EO/IR imagers and an acoustic sensor.
* The USAF has also obtained a small UAV, the Aerovironment "Wasp III". Aerovironment had developed a MAV named the "Black Widow" for the original DARPA MAV investigation, and developed into a "Wasp I". This machine was in the form of a rectangular flying wing with a swept leading edge, a prop in front, and a fin under each wing. It was about big enough to fit into a shoe box, with a span of 33 centimeters (13 inches); it was followed by the "Wasp II", which was along the same lines but scaled up, about big enough to fit into a boot box, with a span of 41 centimeters (16 inches).
In 2006, the Air Force began a "Battlefield Air Targeting MAV (BATMAV)" competition, with Aerovironment winning the award with the Wasp III. The Wasp III was a clear evolution of its predecessor, but scaled up to a span of 72 centimeters (28.5 inches), with a weight of 430 grams (less than a pound). It carries a small imaging system and is battery operated, with a flight endurance of about 45 minutes. The intended operators appear to be Air Force SOCOM and forward air controller teams.
In 2010, Aurora Flight Sciences introduced a MAV named the "Skate", in the configuration of a rectangular flying wing with a central payload pod, twin tailfins, and twin electrically-driven props. It was capable of vertical takeoff and landing, using the tailfins as legs, and could be folded up for carriage in a briefcase-sized case. The proliferation of small UAVs is becoming something of a nuisance, and not surprisingly the US armed services have been talking about a common "Joint Small Unmanned Aircraft System (J-SUAS) that will be used by different services.
Boeing's Insitu organization has also got into the MAV act with a small helicopter, the "Inceptor", actually developed by Adaptive Flight INC of Marietta, Georgia. The Inceptor is of conventional main-tail-rotor configuration, flies on battery power, weighs about 1.6 kilograms (3.5 pounds), and has an endurance of about half an hour. It carries a daylight or infrared imager and has a smart waypoint flight control system, with an autonomous landing capability; control is provided by a tablet module. It is intended for law enforcement use.BACK_TO_TOP
* The US military is interested in developing MAVs that can be deployed as munitions, typically being fired from a rocket launch tube and then popping out wings. Aerovironment has developed such a "wing-store UAV" named the "Switchblade" that features a forward-mounted prop driven by an electric motor, twin pop-out tailfins, and a set of pop-out wings fore and aft. It can also be carried by fixed-wing aircraft, while ground forces can launch it with the launch tube set up on legs like a mortar. It can carry a small warhead for direct attacks on targets.
The US Navy is developing a "submerged launch vehicle (SLV)" scheme to permit launch of a Switchblade from a submarine. The SLV module will be dispensed through a sub's trash-disposal unit; the module will sink to clear the submarine, then discard a weight to float to the surface and launch the UAV. It appears to be a demonstration effort. The US Navy is also working on UAVs that could be launched from the sonar buoy tubes of an ocean patrol aircraft. Dropping a small expendable UAV to inspect a target would allow the aircraft to remain at cruising altitude, instead of having to descend to low altitude to get a good look. Descent and climb is expensive in terms of fuel and stresses the aircraft; expending a cheap UAV would actually save money.
BAE Systems has developed one such sonobuoy-launched UAV, named the "Coyote", in the form of a fuselage with pop-out straight wings fore and aft, twin pop-up tailfins, and a folding pusher prop driven by an electric motor. It carries an EO or IR imager in the rounded nose, plus a datalink, and has a cruise speed of 110 KPH (70 MPH) along with an endurance of 90 minutes. It is dropped in a standard sonobuoy container to drop to low altitude, where the UAV is then braked by a parachute while it deploys its flight surfaces and prop to go into operation. Length is 79 centimeters (2 feet 7 inches), span is 1.47 meters (5 feet 10 inches), and weight is 5.9 kilograms (13 pounds). The first test flight was in early 2010.
The US Army has even been interested in developing MAVs that could be deployed as munitions, fired from artillery or unguided rocket launcher pods. A research team at the Massachusetts Institute of Technology (MIT) developed a prototype artillery-launched UAV. The UAV, named the "Wide Area Surveillance Projectile (WASP)", was fired out of a 127 millimeter (5 inch) naval gun in a "cargo shell" that popped open when it reached the target area, with the MAV then deploying flight surfaces. It didn't go beyond a demonstration program, but the idea is likely to come up again.BACK_TO_TOP