The Northrop Grumman RQ-4 Global Hawk

The Northrop Grumman (formerly Ryan Aeronautical) RQ-4 Global Hawk is an unmanned aerial vehicle (UAV) used by the United States Air Force and Navy and the German Air Force as a surveillance aircraft.

In role and operational design, the Global Hawk is similar to the Lockheed U-2, the venerable 1950s spy plane. It is a theater commander's asset to provide a broad overview and systematic target surveillance. For this purpose, the Global Hawk is able to provide high resolution synthetic aperture radar (SAR) – that can penetrate cloud-cover and sandstorms – and electro-optical/infrared (EO/IR) imagery at long range with long loiter times over target areas. It can survey as much as 40,000 square miles (103,600 square kilometers) of terrain a day.

It is used as a high-altitude platform for surveillance and security. Missions for the Global Hawk cover the spectrum of intelligence collection capability to support forces in worldwide military operations. According to the United States Air Force, the capabilities of the aircraft allow more precise targeting of weapons and better protection of forces through superior surveillance capabilities. The Global Hawk costs about US$35 million to procure each aircraft. With development costs included, the unit cost rises to US$218 million.

Design

The RQ-4 is powered by an Allison Rolls-Royce AE3007H turbofan engine with 7,050 lbf (31.4 kN) thrust, and carries a payload of 2,000 pounds (900 kilograms). The main fuselage is standard aluminum, semi-monocoque construction, while the wings are made of lightweight, high-strength composite materials.

Integrated system

The Global Hawk UAV system comprises an air vehicle segment consisting of air vehicles with sensor payloads, avionics, and data links; a ground segment consisting of a Launch and Recovery Element (LRE), and a Mission Control Element (MCE) with embedded ground communications equipment; a support element; and trained personnel.

The Integrated Sensor Suite (ISS) is provided by Raytheon and consists of a synthetic aperture radar (SAR), electro-optical (EO), and infrared (IR) sensors. Either the EO or the IR sensors can operate simultaneously with the SAR. Each of the sensors provides wide area search imagery and a high-resolution spot mode. The SAR has a ground moving target indicator (GMTI) mode, which can provide a text message providing the moving target's position and velocity. Both SAR and EO/IR imagery are processed on board the aircraft and transmitted to the MCE as individual frames. The MCE can mosaic these frames into images prior to further dissemination.

Navigation is via inertial navigation with integrated Global Positioning System updates. Global Hawk is intended to operate autonomously and "untethered" using a satellite data link (either Ku or UHF) for sending sensor data from the aircraft to the MCE. The common data link can also be used for direct down link of imagery when the UAV is operating within line-of-sight of users with compatible ground stations.

The ground segment consists of a Mission Control Element (MCE) and Launch and Recovery Element (LRE), provided by Raytheon. The MCE is used for mission planning, command and control, and image processing and dissemination; an LRE for controlling launch and recovery; and associated ground support equipment. (The LRE provides precision differential global positioning system corrections for navigational accuracy during takeoff and landings, while precision coded GPS supplemented with an inertial navigation system is used during mission execution.) By having separable elements in the ground segment, the MCE and the LRE can operate in geographically separate locations, and the MCE can be deployed with the supported command's primary exploitation site. Both ground segments are contained in military shelters with external antennas for line-of-sight and satellite communications with the air vehicles.

Sensor packages

The Global Hawk carries the Hughes Integrated Surveillance & Reconnaissance (HISAR) sensor system. HISAR is a lower-cost derivative of the ASARS-2 package that Hughes developed for the Lockheed U-2. HISAR is also fitted in the US Army's RC-7B Airborne Reconnaissance Low Multifunction (ARLM) manned surveillance aircraft, and is being sold on the international market. HISAR integrates 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 can be transmitted at up to 50 Mbit/s to a ground station in real time, either directly or through a communications satellite link.

The SAR-MTI system operates in the X-band and provides a number of operational modes:

The wide-area MTI mode can detect moving targets within a radius of 62 miles (100 kilometers).

The combined SAR-MTI strip mode provides 20 foot (6 meter) resolution over a swath 23 miles (37 kilometers) wide at ranges from 12.4 to 68 miles (20 to 110 kilometers).

The SAR spot mode can provide 6 foot (1.8 meter) resolution over 3.8 square miles (10 square kilometers), as well as provide a sea-surveillance function.

The visible and infrared imagers share the same gimballed sensor package, and use common optics, providing a telescopic close-up capability. It can be optionally fitted with an auxiliary SIGINT package. To improve survivability, the Global Hawk is fitted with a Raytheon developed AN/ALR-89 self-protection suite consisting of the AN/AVR-3 Laser Warning System, AN/APR-49 Radar Warning Receiver and a jamming system. An ALE-50 towed decoy also aids in the Global Hawk's deception of enemy air defenses.

In July 2006, the US Air Force began testing segments of the improved Global Hawk Block 30 upgrades in the Benefield Anechoic Facility at Edwards AFB. This version incorporates an extremely sensitive SIGINT processor known as the Advanced Signals Intelligence Payload.

In September 2006, testing began on a new specialty radar system, the Multi-Platform Radar Technology Insertion Program, or MP-RTIP, on board the Scaled Composites Proteus. Once validated, one Global Hawk will be modified to carry this radar set. Previously, the Air Force was considering a larger variant of the MP-RTIP (known as the Wide-Area Surveillance or WAS sensor) for the canceled E-10 MC2A testbed or E-8 Joint STARS aircraft.

In August 2010, Northrop announced that a new version, Block 40, was about to commence production; it would have a new sensor capabilities, including MP-RTIP radar, emphasising surveillance over reconnaissance. The Block 40 design also has a modified undercarriage.

Specifications

RQ-4A

General characteristics

Crew	0
Length	44 ft 5 in (13.54 m)
Wingspan	116 ft 2 in (35.41 m)
Height	15 ft 2 in (4.62 m)
Empty weight	8,490 lb (3,851 kg)
Gross weight	22,900 lb (10,387 kg)
Powerplant	1 × Allison Rolls-Royce AE3007H turbofan engine, 7,050 lbf (31.4 kN) thrust

Performance

Maximum speed	497.1 mph (800 km/h; 432 kn)
Cruise speed	404 mph (351 kn; 650 km/h)
Range	15,525 mi (13,491 nmi; 24,985 km)
Endurance	36 hours
Service ceiling	65,000 ft (19,812 m)

RQ-4B

General characteristics

Crew	0 onboard (3 remote: LRE pilot; MCE pilot and sensor operator)
Length	47.6 ft (14.5 m)
Wingspan	130.9 ft (39.9 m)
Height	15.3 ft (4.7 m)
Empty weight	14,950 lb (6,781 kg)
Gross weight	32,250 lb (14,628 kg)
Powerplant	1 × Allison Rolls-Royce F137-RR-100 turbofan engine, 7,600 lbf (34 kN) thrust

Performance

Cruise speed	357 mph (310 kn; 575 km/h)
Range	8,700 mi (7,560 nmi; 14,001 km)
Endurance	28 hours
Service ceiling	60,000 ft (18,288 m)

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