US Battlefield UAVs (3)

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Main article: History of unmanned aerial vehicles

This chapter completes the discussion of US battlefield UAVs by describing systems that have seen relatively limited service, or are currently highly experimental.

Contents

[edit] S-TEC SENTRY, SENTRY HP, NEPTUNE

S-TEC SENTRY
Payload Day / night imager or other payload.
Payload weight 27.2 kilograms 60 pounds
Length 2.24 meters 8 feet
Wingspan 3.35 meters 11 feet
Empty weight 59 kilograms 130 pounds
Launch weight 109 kilograms 240 pounds
Maximum speed 175 km/h 110 mph / 95 knot
Service ceiling 4,880 meters 16,000 feet
Endurance 8 hours
Launch scheme Wheeled dolly or pneumatic catapult.
Recovery scheme Parasail or skid landing.
Guidance system Programmable with radio control backup.
Unmanned aerial vehicle


S-TEC SENTRY HP
Payload Day / night imager or other payload.
Payload weight 34 kilograms 75 pounds
Length 2.57 meters 8 feet 5 inches
Wingspan 3.90 meters 12 feet 10 inches
Empty weight 81.6 kilograms 180 pounds
Launch weight 147 kilograms 325 pounds
Maximum speed 185 km/h 115 mph / 100 knot
Service ceiling 4,880 meters 16,000 feet
Endurance 8 hours
Launch scheme Pneumatic catapult or runway takeoff.
Recovery scheme Parasail, skid, or runway landing.
Guidance system Programmable with radio control backup.
Unmanned aerial vehicle


S-TEC SENTRY
Payload day / night imager or other payload.
Payload weight 9.1 kilograms 20 pounds
Length 1.83 meters 6 feet
Wingspan 2.13 meters 7 feet
Launch weight 36.3 kilograms 80 pounds
Maximum speed 155 km/h 100 mph / 85 knot
Service ceiling 4,880 meters 8,000 feet
Endurance 4 hours
Launch scheme water or pneumatic catapult.
Recovery scheme water or skid landing.
Guidance system programmable with radio control backup.
Unmanned aerial vehicle
  • S-TEC systems of Texas, now part of DRS Unmanned Technologies, builds a battlefield mini-UAV named the "Sentry" in roughly the same class as the BAI Dragon drone. In fact, the Sentry looks something like an Exdrone with a twin-boom raised tail. It is built of carbon composition and Kevlar, and powered by a 19.5 kW (26 hp) piston engine in a tractor configuration.

S-TEC's main business is building autopilots for civil aviation, and small UAVs were a logical extension of that business. S-TEC introduced the Sentry in 1986, and has sold over 130 since that time.

In an interesting experiment, the company has experimented with carriage of the BLU-108 Sensor Fuzed Weapon (SFW) anti-armor submunition on the Sentry. After release in a target area, the cylindrical SFW pops out a small parachute to orient itself and then fires out four "skeet" projectiles in four directions. The skeets have an infrared sensor to detect when they are flying over the top of an armored vehicle, and then fire a penetrator slug straight down to punch through the top armor.

S-TEC has now built a follow-on battlefield UAV, the "Sentry HP", which is a different design with a broad wing and a vee tail. The Sentry HP is larger, with greater payload capacity and an underwing stores capability. It is powered by a variant of the same engine as the Sentry. It can be ordered with an option for fixed landing gear to permit conventional takeoff and recovery.

S-TEC has also built another follow-on to the Sentry, a mini-UAV named the "Neptune", which has the interesting feature, as its name implies, that it can be operated off water -- think of it as a "flying boat" UAV. The 11.2 kW (15 hp) pusher engine is mounted high to keep it dry during takeoffs and landings. The Neptune can also be launched off a pneumatic catapult and land on a skid.

S-TEC has teamed with TRW Corporation in the US and IAI of Israel to sell UAVs on the international market.

[edit] RYAN MODEL 324 SCARAB, BQM-145A MEDIUM RANGE UAV

  • In the 1980s, Ryan followed up on its long history of robot aircraft development with two jet-propelled UAVs for tactical reconnaissance and other roles, named the "Model 324 Scarab" and the "BQM-145A".

The Scarab is a medium-range reconnaissance asset, similar in operational concept to the old Ryan FireFly UAVs, but implemented with improved technology. It was designed to Egyptian Air Force requirements, and was first flown in 1988. 56 were delivered and the type remains in service. It is a neat UAV with low-midbody-mounted swept wings, a twin-fin tail, and a rear-mounted Teledyne CAE 373-8C turbojet engine with the intake on the rear spine of the UAV.


RYAN MODEL 324 SCARAB
Payload Reconnaissance cameras.
Length 6.12 meters 20 feet 1 inch
Wingspan 3.35 meters 11 feet
Maximum loaded weight 1,130 kilograms 2,500 pounds
Maximum speed 970 km/h 600 mph / 520 knot
Service ceiling 13,100 meters 43,000 feet
Range 2,250 kilometers 1,400 MI / 1,220 NM
Launch scheme RATO launch.
Recovery scheme Parachute recovery.
Guidance system Programmable with radio control backup.
Unmanned aerial vehicle

The "Model 350 / BQM-145A" was developed in the early 1990s for a joint US Navy / Marine Corps and Air Force "Medium Range UAV" program, with the Navy developing the airframe and the Air Force providing the payload. The BQM-145A was designed to precede airstrike packages into a target area and relay reconnaissance information in real time.

Production BQM-145As were to have a metal airframes, but the initial two prototypes were built with plastic composites, with initial flight in May 1992. The program then collapsed in 1993 due to technical difficulties and funding cutbacks. However, six BQM-145As with plastic-composite airframes then under construction were completed, with first flight of a composite BQM-145A in 1997.

Apparently Northrop Grumman has continued to use them for other experiments. Some sources claim they have been evaluated for unmanned strike missions, and paintings have been circulated showing a BQM-145A fitted with an "high-power microwave (HPM)" generator in the nose to fry adversary electronic equipment. It has been confirmed that BQM-145As have been flown in the US on test flights carrying HPM payloads.

The BQM-145A has some broad similarities to the Scarab, with a similar configuration except that it has twin air intakes on either side of the fuselage, just forward of the wing roots. Like the Scarab, it has no landing gear. It is powered by a Teledyne CAE 382-10C (F408-CA-400) turbojet engine, with 4.4 kN (455 kgp / 1000 lbf) thrust. It can be air-launched from a standard fighter such as the F-16R Falcon or the F/A-18 Hornet.


RYAN BQM-145A
Payload Reconnaissance or other payload.
Payload weight 135 kilograms 300 pounds
Length 5.6 meters 18 feet 4 inches
Wingspan 3.2 meters 10 feet 6 inches
Launch weight 900 kilograms 2,000 pounds
Speed 1,115 km/h 690 mph / 600 knot
Ceiling 12,200 meters 40,000 feet
Range 1,300 kilometers 810 MI / 705 NMI
Launch scheme RATO or aircraft launch.
Recovery scheme Parachute or parafoil.
Guidance system Programmable with GPS-INS & radio control.
Unmanned aerial vehicle

[edit] AURORA GOLDENEYE / AEROVIRONMENT SKYTOTE

AURORA GOLDENEYE
Wingspan 3.0 meters 10 feet
Duct diameter 90 centimeters 3 feet
Height 1.7 meters 5 feet 6 inches
Empty weight 48 kilograms 105 pounds
Maximum loaded weight 68 kilograms 150 pounds
Maximum speed 295 km/h 185 mph / 160 knot
Hover endurance 1 hour
Cruise endurance 4 hours
Cruise range 1,000 kilometers 620 MI / 540 NMI
Unmanned aerial vehicle
  • In 2003, Aurora Flight Sciences, which has built a number of research UAVs for NASA that are discussed in a later chapter, unveiled the "Goldeneye", a ducted-fan UAV in roughly the same class as the Cypher II. This UAV was built under a DARPA contract and is apparently focused on covert or special forces operations.

The Goldeneye is a "tailsitter" or "pogo" machine that takes off and lands straight up. It is a stumpy-looking machine with four tailfins, each with landing gear on the fintip, and a wing that pivots, allowing it to be aligned with the aircraft centerline in cruise flight and at a right angle to the centerline in hover flight.

The Goldeneye is built of graphite and fiberglass composites, and has a low radar, infrared, and acoustic signature. It is powered by a 28 kW (38 hp) Wankel-rotary engine from UAV Engines LTD in the UK. It has an autonomous flight control system with GPS-INS navigation.

The Goldeneye can carry a small electo-optic sensor turret or other payload and features a radio datalink. Apparently the DARPA specification mysteriously required that it be able to carry "two coke-can size payloads" that were not described further. Aurora is working on a half-scale version of the Goldeneye for commercial sales.

  • Aerovironment INC of Monrovia, California, manufacturer of solar-powered endurance UAVs described in a later chapter, is also developing a pogo UAV named the "SkyTote" under an Air Force contract. It is described as a demonstrator for a vehicle intended for the precision delivery and pickup of "cargoes", a description that covers an extremely wide range of actual applications.

Details are unclear, but illustrations of the SkyTote show it to be another pogo-type tailsitter with a general configuration much like that of the Goldeneye. It is powered by a Wankel rotary engine. BAE Systems is working on yet another UAV similar to the GoldenEye, named the "AirWolf", to be used to deliver "Wolfpack" battlefield sensors and other payloads. No AirWolf prototype has been flown yet.

  • There seems to be quite a bit of interest in using small UAVs to deliver cargoes to front-line troops these days. In 2003, the US Special Operations Command (SOCOM) obtained five "SnowGoose" cargo-delivery UAVs from a Canadian firm named "Mist Mobility Integrated Systems Technology (MMIST)" for evaluation.

The SnowGoose, which was given the designation "CQ-10A", consists of a cargo / propulsion / control module with a pusher piston engine that flies using a parafoil and lands on skids. It can carry a payload of up 270 kilograms (600 pounds), including fuel, and can fly autonomously using a GPS-based navigation system. It can be launched from an aircraft or from a Hummer truck, and can drop its payload without landing and then return to its base.

[edit] FREEWING SCORPION

FREEWING SCORPION
Payload weight 23 kilograms 50 pounds
Length 3.60 meters 11 feet 10 inches
Wingspan 4.9 meters 16 feet
Maximum speed 235 km/h 146 mph / 130 knot
Service ceiling 4,570 meters 15,000 feet
Endurance 5 hours
Unmanned aerial vehicle
  • An interesting tactical UAV was developed by a company associated with the University of Maryland, Freewing Aerial Robotics Corporation. Working with well-known small-aircraft designer Burt Rutan, Freewing designed a series of piston-powered short-takeoff-and-landing UAVs, based on a design where the fuselage pivots relative to the wing surfaces. The "freewing" design also allows the UAV to operate as a stable observation platform during turbulent conditions.

The Scorpion will be offered for a US Army short-range UAV requirement, and is being proposed by Matra of France for use on French navy frigates and patrol boats. The Matra version is named "Marvel" and will carry a Matra-designed electro-optical day-night camera system initially, but the French navy has expressed interest in extending the payload to include communications relay, electronic warfare, and antisubmarine warfare equipment. Freewing is also offering the similar but smaller "Scorpiette", with a payload of up to 6.8 kilograms (15 pounds) for commercial, third-world military, and law enforcement organizations.

[edit] BOEING X-50 DRAGONFLY & A160 HUMMINGBIRD / UCAR

  • After failing to sell their BRAVE series of tactical UAVs, Boeing developed a twin-prop "tailsitter" or "pogo" UAV named the "Heliwing" that took off and landed standing on its tail, but this aircraft crashed on its sixth flight in 1995, and the project was abandoned.

Boeing has now developed a very interesting UAV demonstrator, the "X-50A Dragonfly", with funding from a three-year DARPA contract awarded in late 1998. DARPA provided $12 million USD of government money, while Boeing provided matching company funds.

The Dragonfly features a "canard-rotor wing (CRW)" configuration, with a slender fuselage, a wide twin-fin canard wing in back, canard fins up front, and a "rotor wing" on top. The CRW configuration provides true vertical take-off capability, with much better flight performance than a helicopter. On takeoff and landings, the rotor wing spins using jet exhausts in the wingtips, but once in flight the rotor wing is fixed in place to act as an auxiliary wing.

The DARPA contracts specified the construction of two prototypes. The initial flight of the first prototype was on 3 December 2003. The Dragonfly prototypes each weigh about 662 kilograms (1,460 pounds), have a length of 5.4 meters (17 feet 8 inches), with a rotor wing span of 3.66 meters (12 feet), a forward canard span of 2.71 meters (8 feet 11 inches), and a tail span of 2.47 meters (8 feet 1 inch). Boeing feels the design can be directly scaled up to as much as 2,500 kilograms (5,510 pounds).

The X-50s are powered by a Williams Research F-112 turbofan, as developed for the USAF Advanced Cruise Missile. The Dragonfly's engine exhaust is switched through a diverter through titanium pipes to the rotor wingtips for VTOL and hoverflight, or to provide rearward thrust through a tailpipe. Some of the engine output is directed through thrusters to assist in flight control in hovering flight.

The rotor uses a simple gimballed hub, which is locked in place after the aircraft transitions to forward flight. The CRW has no tail rotor, which is not required since the rotor jet-exhaust system does not transfer torque to the airframe, and the scheme also eliminates much of the complicated drive system of a conventional helicopter. However, the small rotor leads to high "disk loading", and the type is not expected to be very efficient in sustained hover. Top speed is expected to be about 700 km/h (430 mph).

The two X-50 prototypes are strictly demonstrators and will not have an operational payload capacity. If a production version follows, it will likely have an engine better optimized for its unique flight behavior. Boeing is also considering an 11 tonne (12.1 ton) piloted version for scout, light attack, or air escort operations, with considerable interest from the US Navy and Marine Corps. If the type enters production, it will be the first tip-jet rotary-wing craft to ever enter full operational service.

  • Another unusual UAV now in development is the A160 helicopter demonstrator, built by Abraham Karem and his team at Frontier Systems of Irvine, California, under contract to DARPA. Karem sold the company out to Boeing in the spring of 2004, and remains as a consultant on the project.

The A160 is intended to have range, endurance, and altitude capabilities unprecedented in the history of helicopter design. The A160 has a conventional main-tail-rotor helicopter configuration, but the conventional appearance is misleading. A contemporary helicopter features lightweight flexible rotors that are connected to the rotor hub through articulated joints. Such rotors are designed to provide smooth flight operation with little vibration and good control authority. However, they can only do so within a limited range of speeds, normally at as high an RPM as possible below that where the rotor tips break the sound barrier, and so the helicopter's rotor RPM is roughly constant while the aircraft is in flight. This is inefficient, particularly when the helicopter is flying below maximum speed or with a non-optimal load.

The A160's carbon-fiber composite rotor blades are tapered, and their cross-section varies from root to tip. They are light but stiff to avoid vibration, and their stiffness also varies from root to tip. The rotor system is rigid and hingeless, and features a larger diameter and lower disk loading than that of a conventional helicopter with the same lift capacity. The A160 rotor can be spun from 140 to 350 rpm. Coupled with a fuel-efficient piston engine results in a helicopter that not only has unbelievable fuel efficiency, but good speed, unprecedented altitude capability, and is very silent.

The A160 project began in early 1998, with Frontier Systems modifying a light commercial Robinson R22 helicopter to a UAV configuration, named the "Maverick", to test flight-control systems. The R22 was lost in an accident in early 2000, but not before it had flown for 215 hours under autonomous control. Program officials believe the A160's advanced flight control system will allow it to operate in weather that would ground most other helicopters.

The A160 demonstrator, named the "Hummingbird", performed its first flight on 29 January 2002. The machine weighed about 1,800 kilograms (4,000 pounds), had three rotor blades 5.2 meters (17 feet) long, and featured retractable landing gear. The demonstrator was powered by a commercial automobile engine providing over 225 kW (300 hp), and had a payload capacity of more than 135 kilograms (300 pounds). Two more demonstrators were built, with these machines featuring four-blade rotors of the same diameter as the original rotor. The third crashed in October 2003, forcing a flight halt for a year. The program is now going full speed ahead, with Boeing's Phantom Works building five more demonstrators. The new demonstrators will have more powerful engines and other improvements.

The objective of the program is to build a long-endurance helicopter with a top speed of 260 km/h (160 mph), more than 24 hours endurance, 4,625 kilometer (2,875 mile) range, and a flight ceiling of 9,150 meters (30,000 feet). These specifications are well beyond the capability of the current demonstrators, which are simply intended for technology evaluation and which are not suitable for operational use. The general design concept envisions a UAV that could deploy itself from the US to a combat area, or perform deep penetrations into hostile territory. Possible payloads for a production machine, if any is built, include EO/IR imaging and SAR sensors. Apparently there is work being done on integrating SAR receiving antennas into the rotors themselves, though the transmit antenna will be mounted on the fuselage.

The US Army and SOCOM are interested in the project, with the SOCOM considering uses such as extracting troops trapped behind enemy lines. Other uses under consideration are typical UAV applications such as reconnaissance, targeting, and communications relay. The DARPA program will run into 2007, and at that time it may be picked up by the Army, leading to service introduction as early as 2009.

  • DARPA conducted a program with the Army on development of prototypes for an "Uninhabited Combat Armed Rotorcraft (UCAR)", originally given the snappy name of "Robotic Rotary Wingman". A requirement was issued in the spring of 2002, specifying a robot rotorcraft to be armed with missiles, unguided rockets, guns, and nonlethal directed energy weapons, and with the capability of attacking masked targets. The UCAR was to cost $4 million to $8 million USD, and have operating costs 10% to 40% of those of an AH-64 Apache. Operational cost reductions were expected to be achieved at least in part by reducing the number of personnel required to maintain and operate the machine.

Two finalists, Northrop Grumman and Lockheed Martin were selected in the summer of 2003 to come up with a detailed design; ironically, neither company had ever built a full-production rotorcraft. The Northrop Grumman design used the twin-two-blade-rotor "eggbeater" scheme usually associated with Kaman helicopters -- in fact Kaman has teamed with Northop Grumman on the project -- while the Lockheed Martin design used a four-blade rotor with a "no-tail-rotor (NOTAR)" jet exhaust in the tail to cancel torque.

Both were "stealthy" designs with weapon stores in internal bays; both eliminated the tail rotor, which is the noisiest element on a conventional helicopter. The Northrop Grumman eggbeater was to be able to fly at more than 295 km/h (160 knots) and at an altitude of up to 6,100 meters (20,000 feet), with an endurance with auxiliary fuel tanks of 10 hours and a range of up to 2,000 kilometers (1,250 miles). Northrop Grumman envisioned two variants: an attack variant, the baseline version, optimized for low-altitude operation and carrying a nav-attack sensor suite; and a scout variant, optimized for high-altitude operation and carrying a SAR payload and communications relay. The Lockheed Martin proposal provided similar performance but less endurance; the baseline payload configuration included a SAR.

A single contractor was to be chosen to develop two X-vehicle prototypes. It was to lead to a "B-model", closer to an operational machine, with a warload of from 225 to 450 kilograms (500 to 1,000 pounds), including nonlethal directed-energy weapons.

The Army seemed very enthusiastic about the program, but then pulled out abruptly late in 2004, citing more immediate demands on aviation funding. DARPA searched around for another service sponsor, was unable to find one, and axed the procurement of the demonstrators at the end of the year. However, the idea of a UCAR is so attractive that it seems likely it will be revived, possibly with Lockheed Martin or Northrop Grumman continuing some degree of development using company funding.

[edit] INSITU AEROSONDE & SCANEAGLE MINI-UAVS

INSITU AEROSONDE
Payload Meteorological and other sensors.
Payload weight 2 kilograms 4.4 pounds
Length 1.74 meters 5 feet 8 inches
Wingspan 2.9 meters 9 feet 6 inches
Empty weight 15 kilograms 33 pounds
Maximum speed 103 km/h 64 mph / 56 knot
Service ceiling 4,880 meters 16,000 feet
Range 2,500 kilometers 1,550 MI / 1,350 NMI
Launch scheme Launched from cartop.
Recovery scheme Belly landing.
Guidance system Programmed with GPS & radio command backup
Unmanned aerial vehicle
  • In July 1998, a small long-range piston-powered UAV, named the "Aerosonde", made history by crossing the Atlantic non-stop, and they have made a number of research flights into the deep Arctic.

The Aerosonde was designed to provide a low-cost weather observation platform. It was designed by the Aerosonde Group of Australia, now part of Sweden's SAAB company, with design consulting by the Insitu Group of Bingen, Washington, in collaboration with the University of Washington. It has a high-mounted wing, twin tailbooms with a standup inverted vee tail, is powered by a 0.75 kW (1 hp) engine, and is built from wood and composite materials.

Four Aerosondes were sent on the flight from Nova Scotia to Scotland, but only one completed the trip. It was named "Laima", after the Latvian goddess of good luck, in tribute to University of Washington aeronautics professor Juris Vagners, who was heavily involved with the project and is from Latvia. These four Aerosondes appear to have been configured for extra fuel, since the total trip distance was 3,270 kilometers (2,044 miles). The flight time for the aircraft that made the crossing was almost 27 hours.

  • The Aerosonde is not really a tactical UAV -- it is discussed in this chapter partly because it's hard to find any other appropriate place -- but the Insitu group has worked with Boeing on a more sophisticated follow-on UAV, the "ScanEagle", which is the centerpieces of the "SeaScan" surveillance system. Boeing and Insitu are promoting the ScanEagle for both military and civilian operators.

The ScanEagle is a tailless machine, with long, slightly swept wings ending in fins and attached to a tubular fuselage. It is driven by a pusher propeller and has a sensor dome in front, containing visible or infrared cameras. It has a wingspan of 3.05 meters (10 feet), a length of 1.22 meters (4 feet), a weight of 18.1 kilograms (40 pounds), a maximum speed of 125 km/h (68 knots), and up to 15 hours endurance. Boeing will provide advanced sensors and avionics.

Initial flight of the ScanEagle was in June 2002. The ScanEagle can be carried on small vessels, such as coastal patrol cutters. It is launched by catapult and recovered by a Skyhook snag scheme. A SeaScan system includes two ScanEagles, as well as launch, control, and recovery gear. In 2004, the US Marines ordered two "mobile deployment units" based on the ScanEagle, with each unit including a number of the UAVs and associated control and support gear, with Marine ScanEagles quickly seeing service in Iraq. In late 2004, the British Royal Navy also ordered the ScanEagle as part of an experimental investigation, with Thales of France fronting the deal and providing systems integration.

Boeing and Insitu are now working on a larger ScanEagle, with a more powerful engine, a weight of 45 kilograms (100 pounds), an endurance of up to 24 hours, and two payload bays for larger and more diverse payloads. An even larger version, with an endurance of more than 48 hours, is also being planned.

[edit] References

This article contains material that originally came from the web article Unmanned Aerial Vehicles by Greg Goebel, which exists in the Public Domain.

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