v1.6.0 / chapter 17 of 19 / 01 mar 10 / greg goebel / public domain
* 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 has released artwork of a tiny ornithopter but there's no report the company has flown hardware yet.
Also 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.
* While the early DARPA MAV effort did not lead to an operational system, there was still a general perception that micro UAVs on a somewhat larger scale might be useful for military operations. In fact such systems now being acquired in quantity and some being used in combat.
In 1999, the US Army bought four Aerovironment Pointer small UAVs for testing in the service's "Military Operations In Urban Terrain" and was enthusiastic about the usefulness of the Pointer. The Pointer system is too large to be conveniently carried by soldiers and is normally hauled around in a Hummer vehicle or the like, and so the Army asked Aerovironment if the company could come up with a more portable solution. Aerovironment agreeably developed a half-sized control system and a cut-down version of the Pointer called the "Raven" (no relationship to the Flight Refueling 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.
* 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.
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 is now developing an "RQ-16B Block II" variant that replaces the current fixed visual / IR cameras with a sensor turret and provides improved flight control software, with service deliveries to begin in 2011. The company is also investigating a heavy-fuel / diesel version, with twice the endurance.
Troops in the field are extremely enthusiastic about MAVs. 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.
The proliferation of small UAVs is becoming something of a nuisance, and not surprisingly the US armed services are considering a common "Joint Small Unmanned Aircraft System (J-SUAS) that will be used by different services.
* Of course, man-portable UAVs are being developed or are being sold by other countries. The European EADS organization has designed a small UAV named the "DRAC / Tracker", which features a wide-span wing, twin booms for payload and so on, and a central pod with tractor and pusher propellers. It has a weight of 7.5 kilograms (16.5 pounds), a span of 1.4 meters (4 feet 7 inches), and an endurance of an hour. It is in service with the French Army.
In the spring of 2003 Elbit of Israel introduced two electrically-powered man-portable UAVs, the "Skylark" and the "Seagull". Both of these UAVs have a launch weight of about 5.5 kilograms (12 pounds), a speed of from 35 to 70 KPH (20 to 40 knots), and can carry either a color daylight imager or an infrared imager. The Skylark is of conventional configuration, resembling nothing so much as a large kid's rubber-band airplane with a pod under the fuselage. It has an endurance of two hours. The Skylark has been obtained by the Israeli Army, the Australian Army, Swedish Army, and by French special operations forces. An improved long-endurance "Skylark LE" variant has been introduced and also acquired by the Israeli Army.
The Seagull is much less conventional, in the form of a boomerang-shaped flying wing with wingtip fins and a pusher propeller. Size, performance, and payload details of the Seagull are similar to those of the Skylark, but the endurance is stretched to six hours.
* Rafael of Israel developed a man-portable UAV also named the "SkyLite", which is fired out of a tube like an antitank missile, and has an endurance of about an hour. It can be launched from a vehicle mount or shoulder-launched by a soldier.
The SkyLite is a tube a 110 centimeters (3 feet 7 inches) long with a glass sensor nose; a pusher propeller powered by an electric motor; pop-out straight wings with a span of 150 centimeters (4 feet 11 inches); and a cruciform pop-out tail. It has a launch weight of 6 kilograms (13.2 pounds). It was originally named "Skylark", but Rafael decided to change the name to avoid confusion with the Elbit Skylark. It has been adopted by the Israeli Defense Forces.
A "SkyLite B" was introduced in 2007, featuring endurance stretched to three hours; span increased to 240 centimeters (7 feet 11 inches); a vee tail replacing the original three-fin tail; weight increased to 8 kilograms 17.6 pounds); and a digital encrypted communications system. It is catapult launched over lightweight man-portable rail system. Rafael continues to sell the Skylite series, but the company found the competition in the field too intense and discontinued further development of UAVs in early 2010.
IAI Malat has introduced their own small UAV line, designated "BirdEye", intially offering the "BirdEye 400", with a weight of 5.6 kilograms (12.3 pounds), a span of 2.2 meters (7 feet 2 inches), and electric propulsion using lithium cells. It is launched by hand or bungee cord. Malat has promoted the BirdEye 400 for both military and civilian uses, with civilian uses including urban security, crime-fighting, and traffic observation. In 2010, the company introduced a larger variant with fuel-cell propulsion, the "BirdEye 650", with endurance doubled from 3 to 6 hours. It has a launch weight of 11 kilograms (24.2 pounds), a span of 3 meters (10 feet), and features a lightweight launch rail system. Malat also sells a micro-UAV, the "Mosquito".
Yet another Israeli firm, Aeronautics Defense Systems, has introduced a lightweight UAV named the "Orbiter". It is in the form of a flying wing with winglets, a pusher prop with electric drive, and an imager in the nose. Span is 2.2 meters (7 feet 2 inches) and takeoff weight is 6.5 kilograms (14.3 pounds), including a 1.5 kilogram (3.3 pound) payload. It is launched by bungee catapult and recovered by parachute and airbag. Endurance is up to three hours, with navigation by a preprogrammed guidance system and GPS-INS. The system can be hauled by truck or by backpack.
* Italian special forces have adopted a man-portable UAV named "Strix", developed by Alpi Aviation of Italy. The Strix is a "boomerang"-style flying wing with winglets, featuring a span of 3.2 meters (10 feet 6 inches) and a weight of 6 kilograms (13.2 pounds), a tenth of that being a video camera payload. It is launched by a bungee catapult and is prop driven, using an electric motor. Initial endurance is 90 minutes, with plans to enhance that by 50%. The entire UAV system can be broken down and stuffed into a backpack carrier with a loaded weight of 25 kilograms (55 pounds).
* The US Army has 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.
The MIT group modified a standard illumination flare round to serve as the external case. After firing, the shell popped out six fins to keep it from tumbling. Once the shell was 20 kilometers (12.4 miles) downrange, a parachute popped out the tail to extract the drone. The parachute slowed the drone, which then unfolded into flight configuration. The WASP had a folding vee tail, a folding two-blade propeller up front, and two straight folding wings. The wings were folded into six sections and unfolded into a total span of 94.5 centimeters (3.1 feet). Once unfolded, the right wing was higher on the fuselage than the left, a result of the packaging scheme.
The WASP drone had a flight endurance of fifteen minutes, including ten minutes of powered flight and five minutes of glide. It had a tiny camera in its lower fuselage, and relayed both imagery and its own current GPS coordinates back to the warship or artillery battery that fired it. At least two WASP prototypes were built and tested.
The WASP appears to have been a one-shot demonstration program, but in 2006 ILC Dover, a company that manufactures a range of interesting and unusual items such as space suits, gas masks, protective suits, and various inflatable technologies, announced an inflatable wing system that could be used for gun-launched or air-dropped projectiles. Although the company has flown demonstrators, it is unclear if any production UAV using the technology is in the works.
* The Army has worked on a UAV that can be launched out of a 70 millimeter (2.75 inch) unguided rocket pod mounted on a helicopter and could also be carried by larger UAVs. 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 may also be airdropped by various kinds of aircraft; it can carry a small warhead for direct attacks on targets.
Raytheon has worked on an airdrop UAV named "SilentEyes". SilentEyes looks like a simple metal cylinder with a rounded nose, straight folding wings mounted in the middle of the UAV and with a noticeable dihedral, and a folding inverted-vee tail. The UAV is 46 centimeters (18 inches) long and less than 7 centimeters (2.75 inches) in diameter. It can carry an infrared or color TV camera, as well as a jammer payload or a warhead.
* The US Navy has been conducting a parasite UAV effort of their own, involving 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.
* Galileo Avionica of Italy is currently working on their own "parasite" UAV, called simply the "Miniature Air Launched Payload (MALP)", to be carried on a Falco or similar UAV. The MALP has large cruciform tailfins, small cruciform nosefins, and "switchblade" wings stowed back along the fuselage that pop out straight when the UAV is released. It is intended to carry imaging or other sensors to probe dangerous targets.
The Russian Tula organization, which makes the "Smerch (Tornado)" multiple-launch rocket system, has introduce the "R-90" tactical UAV, which is launched as a payload on a Smerch 30 centimeter (1 foot) diameter rocket. The rocket can deliver the UAV to a target area up to 90 kilometers (55 miles) away, with the UAV operating for up to 30 minutes to relay TV images along with target coordinates back to a control station. The R-90 has a weight of 42 kilograms (92 pounds), and can also be launched from a pod on a helicopter or fixed-wing aircraft.
