Global Hawk Unmanned Aerial Vehicle Research Articles

Wing Optimization Design Based on Composite Global Hawk Unmanned Aerial Vehicle

Composite materials have become the approach to solve the high stiffness and light weight of unmanned aerial vehicle structures. The wing had an extremely important influence on the flight of the unmanned aerial vehicle. The optimal composite wing design aroused widespread attention since it enhanced the aerodynamic performance of unmanned aerial vehicles. This article was intended to optimize and design the unmanned aerial vehicle with advantages in aerodynamic performance. According to the parameters of the military-civilian integrated unmanned aerial vehicle, a three-dimensional model of the overall structure of the composite Global Hawk unmanned aerial vehicle was designed. The effect of composite materials on the wing and the optimization of the laminate layup structure were studied. XFLR5 software was utilized to analyze the aerodynamic performance of the wing. The original NACA0012 airfoil and the optimized NACA3412 airfoil of the composite Global Hawk unmanned aerial vehicle were analyzed respectively for structure and performance. XFLR5 software was utilized to conduct flight simulation under the set parameters, and the effect of changing the angle of attack on the wing performance was analyzed. The results demonstrated that the optimized wing outperformed the original wing in terms of the lift, drag, torque, and lift-drag ratio.

Validation of the High-Altitude Wind and Rain Airborne Profiler during the Tampa Bay Rain Experiment

This paper deals with the validation of rain rate and wind speed measurements from the High-Altitude Wind and Rain Airborne Profiler (HIWRAP), which occurred in September 2013 when the NASA Global Hawk unmanned aerial vehicle passed over an ocean rain squall line in the Gulf of Mexico near the North Florida coast. The three-dimensional atmospheric rain distribution and the associated ocean surface wind vector field were simultaneously measured by two independent remote sensing and two in situ systems, namely the ground-based National Weather Service Next-Generation Weather Radar (NEXRAD); the European Space Agency satellite Advanced Scatterometer (ASCAT), and two instrumented weather buoys. These independent measurements provided the necessary data to calibrate the HIWRAP radar using the measured ocean radar backscatter and to validate the HIWRAP rain and wind vector retrievals against NEXRAD, ASCAT and ocean buoys observations. In addition, this paper presents data processing procedures for the HIWRAP instrument, including the development of a geometric model to collocate time-morphed rain rates from the NEXRAD radar with HIWRAP atmospheric rain profiles. Results of the rain rate intercomparison are presented, and they demonstrate excellent agreement with the NEXRAD time-interpolated rain volume scans. In our analysis, we find that HIWRAP produces wind and rain rates that are consistent with the supporting ground and satellite estimates, thereby providing validation of the geolocation, the calibration, and the geophysical retrieval algorithms for the HIWRAP instrument.

GreenHouse gas Observations of the Stratosphere and Troposphere (GHOST): an airborne shortwave-infrared spectrometer for remote sensing of greenhouse gases

Abstract. GHOST is a novel, compact shortwave-infrared grating spectrometer, designed for remote sensing of tropospheric columns of greenhouse gases (GHGs) from an airborne platform. It observes solar radiation at medium to high spectral resolution (better than 0.3 nm), which has been reflected by the Earth's surface using similar methods to those used by polar-orbiting satellites such as the JAXA GOSAT mission, NASA's OCO-2, and the Copernicus Sentinel-5 Precursor. By using an original design comprising optical fibre inputs along with a single diffraction grating and detector array, GHOST is able to observe CO2 absorption bands centred around 1.61 and 2.06 µm (the same wavelength regions used by OCO-2 and GOSAT) whilst simultaneously measuring CH4 absorption at 1.65 µm (also observed by GOSAT) and CH4 and CO at 2.30 µm (observed by Sentinel-5P). With emissions expected to become more concentrated towards city sources as the global population residing in urban areas increases, there emerges a clear requirement to bridge the spatial scale gap between small-scale urban emission sources and global-scale GHG variations. In addition to the benefits achieved in spatial coverage through being able to remotely sense GHG tropospheric columns from an aircraft, the overlapping spectral ranges and comparable spectral resolutions mean that GHOST has unique potential for providing validation opportunities for these platforms, particularly over the ocean, where ground-based validation measurements are not available. In this paper we provide an overview of the GHOST instrument, calibration, and data processing, demonstrating the instrument's performance and suitability for GHG remote sensing. We also report on the first GHG observations made by GHOST during its maiden science flights on board the NASA Global Hawk unmanned aerial vehicle, which took place over the eastern Pacific Ocean in March 2015 as part of the CAST/ATTREX joint Global Hawk flight campaign.

SCAT-1 and Omnistar: a performance comparison

The Global Hawk Unmanned Aerial Vehicle (VA V) was developed by Northrop Grumman's Ryan Aeronautical Center to perform high altitude reconnaissance. The initial design of the Global Hawk navigation system utilized a RTCA DO-217 compliant special category 1 (SCAT -1) differential GPS (DGPS) system to provide sufficient navigation accuracy for taxi, takeoff, and landing operations. The SCAT -1 DGPS system consists of a ground station that produces the differential corrections, a data link transmitter to uplink the corrections to the aircraft, a data link receiver in the aircraft, and a GPS receiver able to utilize differential GPS corrections. The SCAT-1 DGPS system has been shown, both during flight-tests of the navigation system in a company owned King Air, and during actual flights of the UAV to provide more than sufficient accuracy for takeoff and landing operations. At the point in time that the Global Hawk was to fly outside Edwards Air Force Base restricted airspace, discussions were held relative to oft' field landings. The problem raised relative to getting in and out of an emergency landing field was how to provide differential corrections to the aircraft in such a situation. It was undesirable to have to install a SCA T -1 DGPS ground station at each of the anticipated emergency landing fields. It was at this juncture that the use of commercially available world-wide DGPS services was investigated. The system chosen for providing DGPS corrections to the aircraft in the event of an emergency landing is Omnistar. This paper describes the system implementation of the Omnistar on-board Global Hawk, and provides data comparing the accuracy of this system against the accuracy of the SCAT -1 DGPS system initially designed into the UAV.