Introduction
The RQ-4 Global Hawk is a high altitude, long endurance (HALE) and fully autonomous unmanned aircraft system (UAS) that is optimized to support intelligence, surveillance and reconnaissance (ISR) missions. Equipped with multi-intelligence payload, it is commonly used by the military to collect essential imagery and intelligence data for war theatre commanders in order to support ground units (USAF, 2014). At the same time, it incorporates capabilities that are ideal for meteorological applications. The prime contractor for this UAS is Northrop Grumman Corporation and various developments of Global Hawk systems have evolved over the years that feed a block build approach (Kinzig & Brown, 2010).
System Infrastructure and Sensors
The Global Hawk UAS comprises the unmanned aircraft, sensor payloads, communications data links, launch and recovery element (LRE), mission control element (MCE), support element and trained personnel to operate the UAS. The MCE includes a shelter measuring 8ftx8ftx24ft and provides the management of aircraft and its sensors. The element has personnel that provide command and control, mission planning, imagery quality control, and communication functions with data up-and-down links to the UA directly and via Ku satellite and UHF satellite systems. The LRE is housed in an 8ftx8ftx10ft shelter and handles the loading of the autonomous flight mission plan into the UA and monitoring the operation of the aircraft during its take-offs and landings (Northrop Grumman, n.d.). By having separable elements, the MCE and LRE can be operated in different geographical locations, with the MCE deployable with the supported command’s primary exploitation site (Gatlin, 2003). The UAS is able to utilize direct line of sight (LOS) communications with the ground station via a common data link as well as a beyond line of sight (BLOS) communication channel using Ku band satellite communication (SATCOM). The integrated sensor suite on board the Global Hawk includes an X-band synthetic aperture radar, electro-optical and infrared sensor system that is able to provide wide area search coverage of 40,000 square nautical miles a day (Airforce-technology, n.d.).
Benefits and Challenges
According to Northrop Grumman (2012), the deployed crew for the Global Hawk is significantly smaller than other UASs due to its unmanned capabilities, mission and flight management system and technical sophistication of the system. Once the mission parameters are entered into the Global Hawk, it has the ability to taxi, take off, fly the mission, and land autonomously. As the name of the UAS implies, Global Hawks, with its LOS and BLOS control capabilities, are well suited to be deployed anywhere globally due to its high endurance capability. At the same time, its ability to operate at altitudes above 60,000 feet ensures its survivability in hostile airspace (Airforce-technology, n.d.).
Naftel (2011) highlighted that mission planning for unmanned aircraft is more laborious compared to mission planning for manned aircraft. In the case of Global Hawk, it is required for the whole team to develop procedures covering pre-flight, flight, and post-flight, along with mission rehearsals and simulations prior to actual flight (Naftel, 2011). As reported by Rogoway (2014), Global Hawk struggles to keep up with the 55-year old Lockheed U2 in that it cannot fly through bad weather. Global Hawk lacks deicing and lightning protection and the on-board weather and optics equipment cannot see a storm ahead of its flight path. Therefore, certain adverse weather missions are restricted. At the same time, the Global Hawk lacks the ability to operate in dense airspace without prior intensive preparation since there is no pilot on board to integrate civilian traffic with its own.
There are also challenges that need to be addressed when using communication links over long distances. The transmission of radio signals and its associated processing will introduce latencies such as time delays between pilot control inputs, aircraft response execution, and the display of the responses to ground operators. Such latencies will be more obvious when the link is via a geostationary satellite. At the same time, there can also be voice latencies when Global Hawks are used to relay voice communications between UA and ATC. Therefore, operators have to be aware of these limitations and ensure that communications do not reach a level that is disruptive to safe operations.
The system must also cater for any lost links and if such event occurs, the UA must be capable enough to continue flight in accordance with any expected contingencies programmed in the Global Hawk such as link reacquisition and flight terminations. With the highly automated Global Hawk, there is also a challenge for operators to remain vigilant during its operation. Even though Global Hawks can be operated with full autonomy, operators are still able to inject any command to the UA in case of any need for diversion due to weather or other unforeseen circumstances. As such, good situational awareness of operators during the prolonged hours of Global Hawk flights is important.
Applications
There are many uses of the Global Hawk UAS today. They have been used to support humanitarian efforts including California wildfires, hurricane Ike, Haiti earthquakes and the tsunami in Japan (NAGSMA, 2011). NASA had previously used Global Hawks for hurricane research, examining greenhouse effects and conducting autonomous aerial refueling trials. The most recent application by NASA was to use it to study severe El Nino weather over the Pacific Ocean (Northrop Grumman, 2016). With the ability to fly at ceilings of 65,000 feet for 30 hours, the NASA Global Hawk enables meteorological entities to study intense and remote weather conditions and major floods that were previously unreachable.
Conclusion
Global Hawk is a valuable asset to any organization that utilizes it for both LOS and BLOS operations. Similar to other HALE UASs, there will be continued challenges for its BLOS usage due to inherent issues of communication latencies and sustained crew situational awareness during highly automated phases of operations. However, while many of the world’s aviation authorities are resolving the numerous issues regarding the integration of UAS into the national airspace system, Global Hawks in the meantime can be regarded as an ongoing research and development investment rather than just an operational aircraft. It still remains the most advanced known HALE unmanned aircraft system capable of BLOS operation anywhere in the world (Rogoway, 2014).
References
Airforce-technology (n.d.). RQ-4A/B Global Hawk HALE reconnaissance UAV, United States of America. Retrieved from http://www.airforce-technology.com/projects/rq4-global-hawk-uav/
Gatlin, A. (2003). The Global Hawk. Retrieved from http://www.456fis.org/GLOBAL_HAWK.htm
Kinzig, B., & MacAulay-Brown (2010). Global Hawk systems engineering case study. Retrieved from http://www.lboro.ac.uk/media/wwwlboroacuk/content/systems-net/downloads/pdfs/GLOBAL%20HAWK%20SYSTEMS%20ENGINEERING%20CASE%20STUDY.pdf
Naftel, J. C. (2011). NASA global hawk: Project overview and future plans. Retrieved from http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110011985.pdf
NAGSMA (2011, March 28). Press release from external sources, Northrop Grumman submits final proposal for NATO alliance ground surveillance. Retrieved from http://www.nagsma.nato.int/news/Lists/Press%20Releases/DispForm.aspx?ID=7
Northrop Grumman (n.d.). RQ-4 Global Hawk maritime demonstration system. Retrieved from http://www.northropgrumman.com /Capabilities/RQ4Block10GlobalHawk/Documents/GHMD-New-Brochure.pdf
Northrop Grumman (2016, February 5). NASA Global Hawk studies severe El Nino weather over the Pacific Ocean. Globe NewsWire. Retrieved from https://globenewswire.com/news-release/2016/02/05/808255/10159833/en/NASA-Global-Hawk-Studies-Severe-El-Nino-Weather-over-the-Pacific-Ocean.html
Q4 HALE enterprise. (2012). Northrop Grumman Systems Corporation. Retrieved from http://www.northropgrumman.com/Capabilities/GlobalHawk/Documents/Brochure_Q4_HALE_Enterprise.pdf
Rogoway, T. (2014). Why the USAF’s massive $10 billion Global Hawk UAV is worth the money. Foxtrot Alpha. Retrieved from http://foxtrotalpha.jalopnik.com/why-the-usafs-massive-10-billion-global-hawk-uav-was-w-1629932000
USAF (2014, October 27). RQ-4 Global hawk. Retrieved from http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104516/rq-4-global-hawk.aspx
No comments:
Post a Comment