* The Predator series of UAVs was intended mostly for the tactical role; work was performed in parallel on UAVs for the strategic role. The effort was initially focused on the Lockheed Martin "RQ-3A Darkstar" UAV, though that program proved "snakebitten" and was canceled. Further work on the Northrop Grumman "RQ-4 Global Hawk" proved more successful, with the Global Hawk now in extensive operational service. Following the Global Hawk, work is underway towards "ultra-long duration" UAVs for extended high-altitude surveillance missions.
* The Gnat 750 and Predator were the first in a series "Tier UAVs" considered by the US Air Force. In the USAF plan, the Gnat 750 was known as "Tier 1", while the Predator was known as "Tier 2". The original expectation was that the series would then move on to a very large and powerful long-range UAV known as "Tier 3", something along the lines of a B-2 Stealth bomber. This was not exactly a new idea, there having been work in the 1980s and on a comparable machine under the "Advanced Airborne Reconnaissance System (AARS)" program.
AARS remains mysterious, with the "super UAV" investigated under the program being known by various obscure codenames, one of the better-known being "Quartz". AARS involved a wide range of investigations, but it never produced operational hardware. It was a completely gold-plated program and was canceled in 1992 since the end of the Cold War had eliminated its expected mission. Although AARS designs were dusted off and tuned down for Tier 3, that program ran into budget cutting and was canned in turn in 1993. The entire AARS / Tier 3 fiasco soaked up a good deal of money and did much to inhibit development of UAVs in the USA during the 1980s.
In place of Tier 3, the USAF decided to develop a smaller "Tier 3-" UAV designated the "Darkstar", and a "Tier 2+" UAV, something like a "super Predator", the Teledyne-Ryan "Global Hawk". The Lockheed Martin / Boeing Tier 3- Darkstar was a stealthy design that resembled a big pumpkin seed with a long straight wing at the rear. It was to send real-time still images produced by either SAR or EO sensors, though it didn't have the capacity to carry both sensors at the same time. Data was to be returned using a satellite communications link with a bandwidth of 1.5 megabits per second (MBPS). The Darkstar was intended to penetrate protected airspace to observe high-value targets for a limited amount of time. Range and endurance were intended to be similar to that of the Predator, though the Darkstar's sensor suite could cover over twice the area, and of course it was harder to detect.
The Darkstar was powered by a Williams Research FJ-44-1A turbofan engine with 8.46 kN (862 kgp / 1,900 lbf) thrust, and could carry a 450 kilogram (1,000 pound) payload. The UAV was to cost about $10 million USD.
LOCKHEED MARTIN / BOEING RQ-3A DARKSTAR: _____________________ _________________ _______________________ spec metric english _____________________ _________________ _______________________ wingspan 21 meters 69 feet length 4.6 meters 15 feet height 1.5 meters 5 feet empty weight 1,980 kilograms 4,360 pounds max loaded weight 3,900 kilograms 8,600 pounds cruise speed 555 KPH 345 MPH / 300 KT service ceiling 15,200 meters 50,000 feet endurance 12 hours _____________________ _________________ _______________________
The Darkstar was unlucky. On its second takeoff in the spring of 1996, it stood up on one wing and slammed into the runway, bursting into fire and smoke. An analysis of the failure showed flight software and takeoff procedures to be faulty.
The Air Force and the contractors didn't give up right away, and a redesigned Darkstar, now formally designated "RQ-3A", flew in the early summer of 1998. However, the program was still unhealthy, and the Darkstar was canceled in early 1999. Although flight tests were generally satisfactory, the Darkstar was by no means close to being a useful operational system. Building an actual operational UAV based on the Darkstar would have required major redesign and improvement, and the costs were more than the Air Force was willing to spend.
* At least that was the official line. In the summer of 2003, confirming rumors that had been in circulation for some time, Air Force officials announced that Lockheed Martin's "Skunk Works" had developed several prototypes of a stealthy reconnaissance UAV similar to the Darkstar but larger, and that this machine had been used in an operational evaluation over Iraq during the American invasion of that country in the spring of 2003.
The unnamed UAV's payload was described as less than that of a Lockheed U-2, featuring a "low probability of intercept (LPI)" SAR and electro-optic sensors, along with a satcom datalink. Range was less than that of the Global Hawk, described below, though cost is described as several times greater. The Air Force wanted to conduct the operational evaluation to see if putting the new machine into production was worthwhile. The most likely operational base for the UAV was Al Udeid Air Base in Qatar, which has extensive and well-developed facilities, is near to Iraq, and was off-limits to reporters during the invasion of Iraq.
In 2005, the Skunk Works did unveil a UAV named the "Polecat" that could, in development, be used as a high-altitude stealthy reconnaissance platform along the lines of the Darkstar, as well as for other missions such as strike. The Polecat was a flying wing, something like a "mini-B-2", powered by twin Williams Research FJ44-3E turbofans, with a 4,080 kilogram (9,000 pound) takeoff weight and a span of 27.4 meters (90 feet). It had a centerline payload bay for 450 kilograms (1,000 pounds) of sensors or munitions, and a ceiling of 18,300 meters (60,000 feet).
Lockheed Martin officials said the machine was strictly a demonstrator, intended to validate technologies for future military requirements, and was not designed in response to any specific current requirement. The Polecat crashed in December 2006 after only three flights and no more was heard about it as such. However, in late 2007 a UAV that had considerable similarity to the Polecat was observed at Kandahar Air Base in Afghanistan, with the mystery machine nicknamed the "Beast of Kandahar".
In late 2009 the USAF confirmed the existence of the Beast, identifying it as the Lockheed-Martin "RQ-170 Sentinel" but providing no details. The RQ-170 is judged to be an unarmed tactical surveillance platform with a degree of stealth, but for now saying much more is just guesswork. One was forced down in Iran in late 2011 due to a technical failure and captured.
BACK_TO_TOP* With the death of the Darkstar, the Ryan RQ-4A Global Hawk became the Air Force's great hope for a strategic UAV reconnaissance platform. With the purchase of Ryan by Northrop Grumman in July 1999, the aircraft became the Northrop Grumman Global Hawk.
The Global Hawk is not particularly stealthy, but it has sophisticated long-range sensors to allow it to operate outside of hostile air defenses, and can survey as much as 100,000 square kilometers (40,000 square miles) of terrain a day. In comparison to the Predator, if a Global Hawk were flown out of San Francisco, it would be able to fly to Maine, observe a 370 x 370 kilometer (230 x 230 mile) grid for 24 hours, and then fly back home.
A Global Hawk is powered by an Allison Rolls-Royce AE 3007H turbofan engine with 31.4 kN (3,200 kgp / 7,050 lbf) thrust, and carries a payload of 900 kilograms (2,000 pounds). The fuselage is mostly of conventional aluminum airframe construction, while the wings are made of carbon composite.
The Global Hawk initially carried the "Hughes Integrated Surveillance & Reconnaissance (HISAR)" sensor system. HISAR was a lower-cost derivative of the ASARS-2 package that Hughes developed for the Lockheed U-2. HISAR was also fitted in the US Army's RC-7B Airborne Reconnaissance Low Multifunction (ARLM) manned surveillance aircraft. HISAR integrated a SAR-MTI system, along with an optical and an infrared imager. All three sensors are controlled and their outputs filtered by a common processor. The digital sensor data could be transmitted at up to 50 MBPS to a ground station in real time, either directly or through a communications satellite link.
The SAR-MTI system operated in the X-band and provided a number of operational modes:
The visible and infrared imagers shared the same gimbaled sensor package, and use common optics, providing a telescopic close-up capability. The Global Hawk is also fitted with a countermeasures suite for self-defense.
NORTHROP GRUMMAN RQ-4A GLOBAL HAWK: _____________________ _________________ _______________________ spec metric english _____________________ _________________ _______________________ wingspan 35.4 meters 116 feet 2 inches length 13.5 meters 44 feet 5 inches height 4.6 meters 15 feet 2 inches empty weight 3,850 kilograms 8,490 pounds max loaded weight 10,400 kilograms 22,900 pounds cruise speed 650 KPH 404 MPH / 350 KT service ceiling 20,000 meters 65,000 feet endurance 34 hours _____________________ _________________ _______________________
First flight of the Global Hawk was on 28 February 1998. Five prototypes were built, and put through a thorough flight test program. Beginning in the spring of 1999, the Global Hawk performed a series of operational evaluation flights, some of which were remarkable demonstrations of the aircraft's capability. One of the prototypes flew from Eglin Air Force Base in the Florida panhandle to Alaska and back again, nonstop and unrefueled, in just under 25 hours.
In May 2000, a prototype flew up the Atlantic coast of the US from Eglin AFB, transmitting radar images to a US Army ground station at Fort Bragg, North Carolina, and the aircraft carrier USS GEORGE WASHINGTON, at dock at Norfolk, Virginia. The RQ-4A then proceeded across the Atlantic, monitoring shipping movements, and reached its final target, an amphibious landing exercise near Setubal, Portugal. Once done, the Global Hawk retraced its steps and landing at Eglin, 28 hours after its departure.
The program suffered some setbacks in 1999, with one lost and another badly damaged in accidents. The Global Hawk was scheduled to reach operational service in late 2001, and this timeframe coincided with the US intervention in Afghanistan. Four Global Hawks were available at the time, though only three were regarded as suitable for operations. These three UAVs were operated in the war, though specific details of their missions are unclear. One crashed in December 2001 due to a malfunction.
Global Hawks also served in the invasion of Iraq in the spring of 2003. Although details of their service there are sketchy for the moment, apparently their SAR payload came in very handy for pinning down targets during intense sandstorms. Ironically, despite the service of the Global Hawks in these conflicts, none of them that flew these operations were actually regarded as production machines. The first production RQ-4A, the eighth Global Hawk built, was finally rolled out in the summer of 2003. A base for Global Hawks has been built in the United Arab Emirates to help keep a better eye on the region.
* The Global Hawk is a very high priority program for the Air Force. The initial version, the "Block 5", was more or less an evaluation machine, though as mentioned above, it was used operationally as well. It was followed by the "Block 10", which featured an improved sensor and self-protection suite, and more electrical power. The improved self-protection suite included a towed decoy plus improved radar warning receiver and jammer. The UAV autonomously acted on the information from the self-protection system, deciding whether to abort the mission, take evasive action, or continue with the towed jammer deployed. The remote operator could override whatever decision is taken.
BACK_TO_TOPNorthrop Grumman is now producing the "Block 20" or "RQ-4B" Global Hawk, with the first rolled out in August 2006. This variant features an uprated engine; a wingspan stretch from 35.4 meters (116 feet) to 39.9 meters (130 feet 10 inches); and a fuselage stretch from 13.5 meters (44 feet) to 14.5 meters (47 feet 7 inches). The RQ-4B provides 50% more electrical power than the RQ-4A and carry a larger payload, of up to 1,360 kilograms (3,000 pounds) as opposed to 910 kilograms (2,000 pounds), and also has an improved communications system and an "open architecture" that makes updates simpler. It also includes the Raytheon "Enhanced Integrated Sensor Suite (EISS)" to replace the early sensor system.
The "Block 30" Global Hawk, now going into service, carries a version of the ASIP SIGINT package.
* The Block 30 will be followed by the "Block 40", which will carry the "Multi-Platform Radar Technology Insertion Program (MP-RTIP)", providing an advanced "active electronically scanned array (AESA)" multifunction radar.
MP-RTIP originally started out as an upgrade program for the "E-8 Joint-STARS" manned battlefield reconnaissance aircraft, which is based on the Boeing 707-320 jetliner, but the scope of the program expanded to envision the development of an AESA that could be adapted for use on a range of platforms. An AESA can be thought of as a radio-frequency (RF) "array processor", composed of a grid of interconnected "transmit-receive" modules, each with its own RF, processing, and control electronics. The modules can work with each other to perform a wide variety of tasks. The AESA is scalable, allowing the fit of more or fewer modules as allowed by the size of the platform, with capability proportional to size. The AESA can perform communications, jamming, and sensing functions in parallel through juggling the use of its modules. The array will be carried in a 1.2 meter (4 foot) long fairing under the UAV.
Raytheon and Northrop Grumman were awarded a contract for the MP-RTIP system in late 2000, with Raytheon to build the AESA and Northrop Grumman to perform systems integration. The Global Hawk was selected as the initial target system for MP-RTIP, with initial flight tests in 2005. The Block 20 was in test by 2009, with the first flight of the initial Block 40 late that year. The Block 40 can be clearly recognized by the rectilinear canoe-style fairing on its belly for the MP-RTIP array.
* Yet another high-priority update that is being considered for the Global Hawk is to fit it with a SIGINT payload. This option was being considered as a long-term program until the spring of 2001, when a Chinese F-8 fighter trying to "spook" a US Navy EP-3 Aries SIGINT aircraft cruising off the Chinese coast collided with it instead. The F-8 and its pilot were lost, and the EP-3 was forced to make an emergency landing on Tainan Island. The result was a protracted, nasty-tempered diplomatic quarrel, with the Chinese holding the aircraft and the crew while demanding that the US end surveillance of Chinese territory. The crew was returned unharmed, but the Chinese refused to let the EP-3 fly out, forcing the Americans to retrieve it with a leased Antonov Condor transport.
The 1969 shootdown of an EC-121 SIGINT aircraft by the North Koreans led to the development of the COMBAT DAWN Lightning Bug variant, and the 2001 incident led to widespread discussion of adopting a similar strategy to ensure that the problem wouldn't arise again. While the Global Hawk does not have the payload capability to replace a large SIGINT aircraft like the EP-3, it would provide an interim solution if nothing else were available. The Global Hawk SIGINT payload is now a high priority.
Other upgrades are also being considered, such as a fast-track effort to add stores pylons for external payloads, including improved electro-optic / infrared and multispectral sensors; or jamming pods. While a Global Hawk configuration carrying two 225 kilogram (500 pound) or four 112 kilogram (250 pound) GPS-guided bombs has been considered, senior Air Force brass are not enthusiastic about arming the type, since that would make it politically more difficult to use in peacekeeping operations or to obtain overflight permission from friendly nations.
Another possible role is for "Information Warfare (IW)", picking up and penetrating enemy voice, video, and data communications, but currently no miniaturized IW payload suitable for the Global Hawk is available. Northrop Grumman is promoting schemes where several Global Hawks with different but complementary payloads could be used to perform a single mission. Current USAF plans project 78 Global Hawks in service by 2020, with 40 carrying EO payloads and the other 38 carrying SIGINT payloads.
* NASA has obtained three Global Hawks for research purposes, fitting them with an environmental sensor suite, and following the conflict in Afghanistan, the US Navy also became interested in the Global Hawk, ordering two Block 10 machines. The two UAVs were used to evaluate concepts for a naval endurance UAV under the "Broad Area Maritime Surveillance (BAMS)" program, which would complement manned maritime patrol aircraft.
The Navy conducted a competition for BAMS whose contenders included UAV version of the Gulfstream 550 business jet, offered by Boeing; a derivative of the Predator B called the "Mariner", offered by a Lockheed Martin / General Atomics team; and the Global Hawk, offered by Northrop Grumman. In the spring of 2008, the Navy selected the Global Hawk for BAMS. A prototype "RQ-4N" BAMS air vehicle, based on the enlarged RQ-4B Block 20 Global Hawk configuration, is expected to fly by 2011, with operational introduction in 2019. The total buy may run to 68 machines.
The RQ-4N will fly out of land bases, but it could be controlled by airborne and maritime platforms. It will feature some airframe reinforcement and a deicing system since the Navy wants to be able to operate at low altitudes for "close-ups" when necessary. It will feature a high-resolution EO/IR imager in a nose turret and a "Multi-Function Active Sensor (MFAS)" AESA radar in a belly radome. Improved datalinks will be added in a second revision, with a SIGINT capability added in a third. The Navy has flatly said there is no interest in weapons carriage.
Northrop Grumman has been trying to sell the Global Hawk internationally. Germany is now planning to buy a fleet of five "Eurohawks", which will be Block 20 Global Hawks fitted with an EADS-built SIGINT suite. The first was rolled out in the fall of 2009 and went into service in 2010. NATO is planning to acquire a fleet of eight Global Hawks as well for the "Airborne Ground Surveillance (AGS) program, carrying MP-RTIP radar. The Germans are offering to host the NATO Global Hawks, saying the NATO machines would be able to leverage off the support infrastructure the Germans have in place for their Eurohawks.
There has also been Middle Eastern interest in a "GulfHawk". Spain, Australia, and Japan are considering the type; the Japanese wanted to build their own endurance UAV to keep an eye on the North Koreans, but common sense prevailed and the decision was made to obtain an available solution.
BACK_TO_TOP* The Global Hawk has been followed by efforts to develop very long endurance UAVs, conceptually along the lines of HALSOL, capable of staying aloft for a week or more.
There has been some difference of opinion over the use of solar power for very long endurance. In June 2005, Aerovironment began flying a demonstrator for the "Global Observer", a HALE UAV powered strictly by hydrogen. The demonstrator, the "GO-0", had a wingspan of 15.25 meters (50 feet) and obtained power from the hydrogen fuel using a fuel cell.
Three "GO-1" machines were ordered by a group of six US government organizations with SOCOM in the lead, with the first performing its initial flight on 5 August 2010. The GO-1 is of more conventional configuration than the Helios and its brethren, featuring a conventional arrangement along the lines of a fat, oversized sailplane with fixed tricycle landing gear and four props on the wings. It has a wingspan of 53.4 meters (175 feet), a payload of 180 kilograms (400 pounds), and an endurance of five to seven days. A fuel cell is not used in the GO-1; instead, the liquid hydrogen fuel is burned in an internal combustion engine to generate power for the electric motors driving the four props. Initial test flights were on battery power only, with the engine system installed for later test flights.
The program suffered a setback on 1 April 2011, when the first GO-1 crashed at Edwards AFB in California. The program is still moving ahead, and Aeroviroment is prepared to put the GO-1 into production if customer interest is there. Farther down the road, the company envisions a "GO-2" that would have an 80 meter (262 foot) wingspan, eight props, a payload of 450 kilograms (990 pounds), and an endurance of eight days. The company is still interested in a fuel cell powerplant, though right now an appropriate fuel cell isn't available.
Boeing is working using company funds on a somewhat comparable UAV known as the "Phantom Eye", which will use hydrogen fuel to directly drive twin four-cylinder automotive-type engines built by Ford, each fitted with a three-stage turbocharger for high-altitude operation. Boeing is working towards construction of a demonstrator with a wingspan of 46 meters (150 feet) and an endurance of four days, with first flight expected in 2011. The production machine would be about 50% bigger and have an endurance of a week.
* If AeroVironment has moved away from the solar-powered UAV, at least for the time being, AC Propulsion (ACP), a startup company based in San Dimas, California, is trying to move into the vacuum. During the summer of 2005, ACP began test flights of their own solar-powered UAV, the "SoLong", with an early flight lasting two days.
The SoLong is a small UAV, with a weight of 12.8 kilograms (28.2 pounds), a span of 4.76 meters (15 feet 7 inches), and a 1 horsepower electric motor. It has a conventional sailplane appearance, with an upright vee tail; the wings are covered by solar sails, with night power provided by a bank of lithium batteries. The SoLong is strictly a technology demonstrator, with no real operational payload, and is intended to lead to larger operational machines.
UK defense research organization Qinetiq (pronounced "kinetic") has also flown a comparable small solar-powered demonstrator named the "Zephyr", with a wingspan of 12 meters (39 feet 4 inches) and a weight of 27 kilograms (57.5 pounds). It uses twin props, one on each wing, and carries lithium batteries for backup power. Trials were performed at White Sands, New Mexico, beginning in late 2005 -- the UK not being noted for an excess of sunshine, particularly in the winter months. Launches were performed with the UAV carried by three people, one hanging on to the fuselage and one on each wingtip, with the carriers releasing when the UAV flew up out of their hands as they ran.
By 2007, the demonstrator had achieved an endurance of 54 hours during a flight that reached a maximum altitude of 17,800 meters (58,350 feet). The flight would have been longer but for a systems failure. A refined version performed an endurance flight of over 84 hours in the summer of 2008. An enlarged version of the Zephyr was then built, with a wingspan of 22.5 meters (73 feet 10 inches) and a weight of 50 kilograms (110 pounds). The wing was reprofiled to provide more area and also featured downward-turned winglets; lithium-sulfur batteries with improved current density and reliability were also incorporated, being powered by lightweight amorphous solar cells on the airframe. Payload is 2.7 kilograms (6 pounds), with Qinetiq having developed (separate) communications relay, SIGINT, and imager payloads.
The scaled-up Zephyr set an unprecedented endurance record at Yuma Proving Grounds in Airzona in the summer of 2010, staying aloft for 336 hours and 24 minutes, a little over two weeks -- the limit of the charge-discharge lifetime of the batteries. During the day it cruised at 18,300 meters (60,000 feet), dropping down to as low as two-thirds that altitude at night. The current version is seen as a preproduction prototype; it breaks down for air transport, requiring a few hours for reassembly. Production machines are expected to be available by 2012. The US SOCOM has expressed interest in obtaining a production version for operational use in Iraq and Afghanistan, the primary role being envisioned as a SIGINT platform.
Aurora Flight Sciences has got into the solar airplane game as well, flying the "Sunlight Eagle" in 2009. It was actually a prototype for a man-powered airplane named the "Light Eagle" that was built by the Massachusetts Institute of Technology in 1987. The aircraft was hauled out of storage, fitted with an array of solar cells on top of its wing plus an electric motor and a control system.
In late 2010 Aurora Flight Sciences rolled out the first of three "Orion" long-endurance UAV demonstrators for the US Air Force. It was somewhat reminiscent of the Boeing Condor, a large UAV with twin piston engines and a flight endurance of 120 hours. The project started in 2006, when Aurora began studies for the US Army for a long-endurance UAV; the effort then began to shift organizationally, becoming a joint capability technology demonstration (JCTD) effort run by the Air Force Research Lab as the "Medium Altitude Global Intelligence, Surveillance, Reconnaissance & Communications (MAGIC)" program.
Orion has a length of 15.25 meters (50 feet) and a wingspan of 40.25 meters (132 feet). Empty weight is 2,345 kilograms (5,170 pounds) and MTO is 5,065 kilograms (11,170 pounds), including 450 kilograms (1,000 pounds) of payload and a whopping 2,270 kilograms (5,000 pounds) of fuel. Fuel can be traded off for stores loads up to a total of kilograms (2,500 pounds), with gear in forward and rear fuselage bays and on a pylon under each wing, each pylon being capable of hauling 545 kilograms (1,200 pounds) of stores -- including fuel tanks, munitions, or equipment pods. It typically has an E/O turret under the nose, though other reconnaissance kit such as a SAR or wide-area imager can be carried, and it has a satcom antenna in a bulbous nose. The UAV has tricycle landing gear -- with main gear being fixed in spats and the nose gear retracting backward to clear the field of view of the turret -- and a cruciform tail arrangement.
Powerplants are twin turbocharged Austro Engines AE300 diesels, the same as used on the well-known Diamond DA42 Twinstar, rated at 125 kW (170 HP) each and driving three-bladed variable props. The engines provide excellent fuel economy, permitting an operational range of 17,575 kilometers (10,925 miles / 9,500 NMI) and a ferry range of 24,050 kilometers (14,950 miles / 13,000 NMI). Not too surprisingly, the Orion is slow, with a speed of only about 165 KPH (105 MPH / 90 KT). The UAV's wing is single-piece so it has to self-deploy, but given its range it can reach anywhere in the world, if in no great hurry. The long range and endurance also means the Orion doesn't have to be stationed in forward areas where providing fuel and support is expensive, and that it doesn't have to land or take off as often, reducing its accident rate. It features an autonomous control system and can take off or land without supervision.
* DARPA has now initiated a program codenamed "Vulture" for development of a high-altitude UAV with a mission endurance of five years. The goal is for the UAV to carry a payload of 450 kilograms (1,000 pounds) to high altitude and maintain station even in the face of strong winds. The program is willing to consider innovative designs, for example an aircraft that could dock with resupply aircraft, or composed of multiple elements, each of which could detach and fly back to earth for repair or update.
Aurora Flight Sciences, Boeing, and Lockheed Martin all submitted concepts. Boeing won the award in late 2010 with the company's "Solar Eagle" design. A "near full scale" demonstrator is being built, based on technologies validated on the Zephyr, but the production Solar Eagle will be much bigger, with a wingspan of about 130 meters (400 feet). Boeing expects the demonstrator to be performing month-long flights in 2014.
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