High-altitude Flight Research Articles

High Altitude Micro gas turbine power plant investigation of Parametric Analysis using Quantum Chemistry techniques for Alternate fuel optimization.

Non-petroleum-based fuels help in mitigating climate change by reducing the emission. Many studies on the emission characteristics for the alternate fuel dimethyl ether (DME), resulted in a significant reduction in NOx, SOx, and particulate matter. Due to the potential impact of the use of DME, a need for an Alternate fuel powered Micro gas turbine power plant for high altitude flight was investigated. The potential energy of DME reacting with oxygen was calculated in the temperature range 800-1350 K at the total pressure exhibited on combustion chamber similar to that of high altitude flight. Multichannel ab-initio and RRKM calculation were performed on the DME combustion reaction in the presence of air C2H6O+O2+N2→CO2+H2O+N2. The computed energy value obtained at low pressure was used to study the thermodynamic cycle of a 6kW micro gas turbine power plant for the use of power generation at high altitude flight system. The resulting energy flow model obtained is significant to understand the system performance and efficiency optimization.

Parametric study and efficiency optimization of the solar coupled hybrid micro gas turbine power plant for high altitude flight.

The performance and feasibility study of a hybrid system designed by combining solar micro gas turbine for power generation process during high altitude flight were explored. The high altitude flight could be defined as long duration stratosphere balloon. Payloads in this high altitude balloon flight could be remote sensing satellites or communication satellites which require a continuous high-density power supply that cannot be provided by solar panels. To reduce greenhouse gas emission, the hybrid method was chosen and studied for its effectiveness in a gas turbine power plant. A thermodynamic cycle analysis for high altitude gas turbine power generator was analyzed along with various power conversion systems and recuperator placement configurations were investigated. The working parameters such as Overall Pressure Ratio and Turbine inlet temperature was investigated with the thermo gas dynamic calculation for designing an optimized power plant. Parametric optimization for determining the realistic and practical combination of recuperators for improving the specific fuel consumption and overall efficiency of the Micro gas turbine power plant was performed. The recuperators could be positioned either in the exhaust of a high-pressure turbine or at the exhaust of the free turbine. The recuperator position and heat extraction are explored and the resulting data depicts the recuperator surface area increases the effectiveness thus the fuel consumption decreases but the recuperator increases the overall mass and volume of the power plant size. A comprisable trade-off was made between the recuperator performance and its size and the results are optimized for high overall efficiency of the power plant. A short trade-off between the selected system and existing systems were made. The system performance, Efficiency optimization and the component size and weight characteristics were performed to deliver maximum payload capabilities.

Using drones and sirens to elicit avoidance behaviour in white rhinoceros as an anti-poaching tactic.

Poaching fuelled by international trade in horn caused the deaths of over 1000 African rhinoceros (Ceratotherium simum and Diceros bicornis) per year between 2013 and 2017. Deterrents, which act to establish avoidance behaviours in animals, have the potential to aid anti-poaching efforts by moving at-risk rhinos away from areas of danger (e.g. near perimeter fences). To evaluate the efficacy of deterrents, we exposed a population of southern white rhinos (C. simum simum) to acoustic- (honeybee, siren, turtle dove), olfactory- (chilli, sunflower), and drone-based stimuli on a game reserve in South Africa. We exposed rhinos to each stimulus up to four times. Stimuli were considered effective deterrents if they repeatedly elicited avoidance behaviour (locomotion away from the deterrent). Rhinos travelled significantly further in response to the siren than to the honeybee or turtle dove stimulus, and to low-altitude drone flights than to higher altitude flights. We found the drone to be superior at manipulating rhino movement than the siren owing to its longer transmission range and capability of pursuit. By contrast, the scent stimuli were ineffective at inciting avoidance behaviour. Our findings indicate that deterrents are a prospective low-cost and in situ method to manage rhino movement in game reserves.

Cumulative Cyclic Exposures to 8000-ft Pressurization Equivalence and Attention Network Responses.

INTRODUCTION: The literature is equivocal regarding the degree of cognitive impairment incurred at the 8000-ft (2438 m) maximal cabin pressure altitude equivalence for commercial aircraft. This study elaborates upon the investigation of the 8000-ft limit by introducing the cumulative effects of repeated daily exposures thereof.METHOD: Pilots completed four daily high-altitude chamber flights at both sea level and 8000 ft. During each chamber flight, attentional processing and executive function were assessed using the Attention Network Test and the antisaccade task.RESULTS: Antisaccade task performance likely reflected a learning effect at both altitudes. Attention Network Test results, however, exhibited sensitivity to the fatigue and altitude interaction. Orienting network scores were affected by fatigue differently depending on altitude, with superior efficiency at 8000 ft compared to sea level (M = 44.9, SD = 25.0 vs. M = 29.0, SD = 18.1) in the last flight of the exposure cycle. Conflict network performance, however, suggested that while fatigue increasingly compromised executive control at both altitudes, marginally worse overall executive efficiency was observed at 8000 ft compared to sea level, notably in the last flight of the exposure cycle (M = 98.3, SD = 19.8 vs. M = 87.8, SD = 21.7).DISCUSSION: Executive control function, as measured by inhibition of interference in reconciling conflicting stimuli, degraded as a function of cumulative exposures to mild hypobaric hypoxia, though adaptive measures possibly compensated to preserve performance to a degree. This study serves as a baseline against which longer 8000-ft exposures, including long-haul flight, can be measured.Thropp JE, Buza PW. Cumulative cyclic exposures to 8000-ft pressurization equivalence and attention network responses. Aerosp Med Hum Perform. 2019; 90(6):513-523.

Comparison of GNSS-, TLS- and Different Altitude UAV-Generated Datasets on the Basis of Spatial Differences

In this study, different in-situ and close-range sensing surveying techniques were compared based on the spatial differences of the resultant datasets. In this context, the DJI Phantom 3 Advanced and Trimble UX5 Unmanned Aerial Vehicle (UAV) platforms, Zoller + Fröhlich 5010C phase comparison for continuous wave-based Terrestrial Laser Scanning (TLS) system and Network Real Time Kinematic (NRTK) Global Navigation Satellite System (GNSS) receiver were used to obtain the horizontal and vertical information about the study area. All data were collected in a gently (mean slope angle 4%) inclined, flat vegetation-free, bare-earth valley bottom near Istanbul, Turkey (the size is approximately 0.7 ha). UAV data acquisitions were performed at 25-, 50-, 120-m (with DJI Phantom 3 Advanced) and 350-m (with Trimble UX5) flight altitudes (above ground level, AGL). The imagery was processed with the state-of-the-art SfM (Structure-from-Motion) photogrammetry software. The ortho-mosaics and digital elevation models were generated from UAV-based photogrammetric and TLS-based data. GNSS- and TLS-based data were used as reference to calculate the accuracy of the UAV-based geodata. The UAV-results were assessed in 1D (points), 2D (areas) and 3D (volumes) based on the horizontal (X- and Y-directions) and vertical (Z-direction) differences. Various error measures, including the RMSE (Root Mean Square Error), ME (Mean Error) or MAE (Mean Average Error), and simple descriptive statistics were used to calculate the residuals. The comparison of the results is simplified by applying a normalization procedure commonly used in multi-criteria-decision-making analysis or visualizing offset. According to the results, low-altitude (25 and 50 m AGL) flights feature higher accuracy in the horizontal dimension (e.g., mean errors of 0.085 and 0.064 m, respectively) but lower accuracy in the Z-dimension (e.g., false positive volumes of 2402 and 1160 m3, respectively) compared to the higher-altitude flights (i.e., 120 and 350 m AGL). The accuracy difference with regard to the observed terrain heights are particularly striking, depending on the compared error measure, up to a factor of 40 (i.e., false positive values for 120 vs. 50 m AGL). This error is attributed to the “doming-effect”—a broad-scale systematic deformation of the reconstructed terrain surface, which is commonly known in SfM photogrammetry and results from inaccuracies in modeling the radial distortion of the camera lens. Within the scope of the study, the “doming-effect” was modeled as a functional surface by using the spatial differences and the results were indicated that the “doming-effect” increases inversely proportional to the flight altitude.

Analysis of the IR Signature and Radiative Base Heating from a Supersonic Solid Rocket Exhaust Plume

The plume flow and radiative base heating of a solid rocket have been important factors for rocket survivability in the modern battlefield, in which the standard of technology determines the dominant position. To enhance rocket survivability and reduce base heating, infrared (IR) signatures emitted from an exhaust plume should be determined. In this work, therefore, IR signatures and radiative base heating characteristics in the plumes exhausted from a solid rocket operating at Mach number of 1.6 and altitudes of 5 km and 10 km, respectively, are numerically examined to find the physics related to the plume flow and radiative characteristics. The plume flow and radiative characteristics are obtained using a pre-conditioning method and weighted sum of gray gases model (WSGGM) coupled with finite volume method for radiation, respectively, and the IR signature at each location is post-processed with the narrow band-based WSGGM after plume fields are developed. After validating models adopted in this work by comparing with other solutions, the plume flow field, IR signature, and radiative base heating characteristics are investigated by changing such various parameters as altitude and particle concentrations in the exhaust plume. As a result, it is found that the particular wavelength IR signature level has high spectral characteristics because of $$ \text{CO}_{2} $$ and $$ \text{H}_{\text{2}} \text{O} $$ behaviors in the plume, and the radiative heat flux coming into the base plane decreases with higher flight altitude and longer distance from the nozzle exit.

Extraordinary Radiation Hardness of Atomically Thin MoS2.

We demonstrate that atomically thin layered two-dimensional (2D) semiconductors are promising candidates for space electronics owing to their inherent and extraordinary resilience to radiation damage from energetic heavy charged particles. In particular, we found that ultrathin MoS2 nanosheets can easily withstand proton and helium irradiation with fluences as high as ∼1016 and ∼1015 ions/cm2, respectively, corresponding to hundreds or thousands of years of unshielded exposure to radiation in space. While radiation effects on 2D material-based field effect transistors have been reported in the recent past, none of these studies could isolate the impact of irradiation on standalone ultrathin 2D layers. By adopting a unique experimental approach that exploits the van der Waals epitaxy of 2D materials, we were able to differentiate the effects of radiation on the 2D semiconducting channel from that of the underlying dielectric substrate, semiconductor/substrate interface, and metal/semiconductor contact interface, revealing the ultimate potential of these 2D materials. Furthermore, we used a statistical approach to evaluate the effect of radiation damage on critical device and material parameters, including threshold voltage, subthreshold slope, and carrier mobility. The statistical approach lends additional credence to the general conclusions drawn from this study, overcoming a common drawback of methods applied in this area of research. Our findings do not only offer exciting prospects for the operation of modern electronics in space, but may also benefit electronics applications in high-altitude flights, military aircraft, satellites, nuclear reactors, particle accelerators, and other high-radiation environments. Additionally, they highlight the importance of evaluating the impact of damage to the substrate and surrounding materials on electrical characteristics during future radiation studies of 2D materials.

Comparison of digital video surveys with visual aerial surveys for bird monitoring at sea

The increasing demand for robust marine bird abundance and distribution assessments coupled with technological advances has led to the development of digital survey techniques for birds. Although digital surveys for bird monitoring are becoming a standard method in some countries, their strengths and weaknesses and comparability with traditional visual surveys remain insufficiently documented and understood. Aiming to improve existing knowledge on digital video monitoring techniques, we conducted one parallel digital video survey with 2-cm ground resolution and a 544-m swath flown at 549 m and an aerial visual survey flown at 76 m over the southern Baltic Sea in March 2015. We assessed bird sighting rates, identification rates, observed densities, and model-based abundance estimates. The digital survey covered a larger area through direct registrations, provided higher numbers of bird sightings and identified species, and higher spatial accuracy than the visual survey. Overall species identification rates were similar between the survey methods; however, there were marked differences among bird taxonomic groups: more individuals were identified to species level in the digital survey dataset for the majority of taxonomic groups, except for grebes and auks. These advantages supplement other previously identified benefits of digital aerial surveys, such as the elimination of bird disturbance due to high flight altitude, reduced observer bias, and availability of raw data for quality assurance. Furthermore, higher numbers of direct bird sightings at a higher spatial resolution during digital surveys ensure better statistical analyses, including distribution modelling, of more species for the same survey effort.

Psychophysiological response of different aircrew in normobaric hypoxia training

Hypoxia remains the most important hazard in high altitude flights, but there is still a need for deeper analysis of the effect of hypoxia exposition in the psychophysiological and cognitive functions. The aim of this study was to study the effect of hypoxia training in cortical arousal, autonomic modulation, muscle strength and cognitive function. We analysed 23 male aircrew personnel of the Spanish Army and Air Force (10 Helicopter Pilots, 7 Transport Aircrew, 3 Transport Pilots and 3 F-18 Fighter Pilots) before, during and after a normobaric hypoxia exposition. Hypoxia produced an increase in perceived stress and effort, a higher Heart Rate and a decreased function of breath muscles. Working memory and pattern recognition were impaired after hypoxia exposition. Significant differences were found in cognitive tests performance among aircrew groups, suggesting differences on their previous training. These results can improve specific training for better preparation of pilots and aircrews for hypoxic threats.Practitioner summary: Distinct aircrew preparation produces a different hypoxia exposition effect on psychophysiological response and cognitive functions. Hypoxia produced an increase in Heart Rate, a decreased function of breath muscles, being more negatively affected in Transport Pilots. Cognition abilities were impaired after hypoxia exposition, independently of the aircrew group.

Limitations of Two-Stage Turbocharging at High Flight Altitudes

Limitations of Two-Stage Turbocharging at High Flight Altitudes

Toward a Quantitative Model for Simulation and Forecast of Solar Energetic Particle Production during Gradual Events. I. Magnetohydrodynamic Background Coupled to the SEP Model

Abstract Solar energetic particles (SEPs) are an important aspect of space weather. SEP events possess a high destructive potential, since they may cause disruptions of communication systems on Earth and be fatal to crew members on board spacecraft and, in extreme cases, harmful to people on board high-altitude flights. However, currently the research community lacks efficient tools to predict such a hazardous threat and its potential impacts. Such a tool is a first step for mankind to improve its preparedness for SEP events and ultimately to be able to mitigate their effects. The main goal of the presented research effort is to develop a computational tool that will have the forecasting capability and can serve as an operational system that will provide live information on the current potential threats posed by SEP based on the observations of the Sun. In the present paper we discuss the fundamentals of magnetohydrodynamical simulations to be employed as a critical part of the desired forecasting system.

Network Quality Measurements of LTE Drones

Cellular-connected drones can provide beyond line-of sight control (BVLOS), low latency, real time communication, robust security, and wide range coverage. Cellular-connected drones have several key potential applications in enhanced LTE and 5G networks. The objective of the study is to evaluate field measurement data collected during drone flights in the KT Long-Term Evolution (LTE) networks in Seoul and Jeju, Korea. The multicopter drones are developed with LTE modem and LTE test smart phone for field measurements. The radio network quality between drones and LTE base transceiver stations (BTS) is evaluated by measuring downlink metrics such as the serving cell RSRP, RSRQ, SINR, modulation types of downlink, the downlink and uplink throughputs, and LTE PUSCH Tx Power on reference signal. In the existing LTE networks, field measurements show that there is no problem in C&C of BVLOS operations in the flight height up to 150m but the data rate requirements for video transmission does not meet at high flight altitudes.

Near-space operation of compact CsI, CLYC, and CeBr[formula omitted] sensors: Results from two high-altitude balloon flights

Three different types of gamma-ray sensors (CsI, CLYC, and CeBr3) were flown on balloon flights as hosted payloads. Two CsI sensors were flown from a September 2014 flight from Fort Sumner, New Mexico for 18 h; CLYC and CeBr3 sensors were flown from Antarctica in December 2016 for 22 days. The data from these flights were used to test and characterize the operation of these sensors in a near-space environment. All sensors returned excellent data. Gamma rays, neutrons, and energetic galactic cosmic rays (GCRs) were measured. Expected atmospheric features, such as the Regener–Pfotzer maximum, were observed, and gamma-ray line emission from materials near the sensors, as well as atmospheric oxygen and nitrogen, were detected. The measured data were compared to simulations of energetic protons, neutrons, and 0.511 MeV gamma rays produced by GCR interactions with the atmosphere. While the simulated protons and neutrons generally matched the data, there were fewer simulated 0.511 MeV gamma rays than measured with the data. This mismatch is likely due to additional 0.511 MeV gamma rays produced in material near the sensors that were not taken into account in the simulations. Discussion is provided for how these types of measurements in space-based missions can be used to characterize upper atmospheric densities at planets with dense atmospheres like the Earth.

High-altitude shorebird migration in the absence of topographical barriers: avoiding high air temperatures and searching for profitable winds.

Nearly 20% of all bird species migrate between breeding and nonbreeding sites annually. Their migrations include storied feats of endurance and physiology, from non-stop trans-Pacific crossings to flights at the cruising altitudes of jetliners. Despite intense interest in these performances, there remains great uncertainty about which factors most directly influence bird behaviour during migratory flights. We used GPS trackers that measure an individual's altitude and wingbeat frequency to track the migration of black-tailed godwits (Limosa limosa) and identify the abiotic factors influencing their in-flight migratory behaviour. We found that godwits flew at altitudes above 5000 m during 21% of all migratory flights, and reached maximum flight altitudes of nearly 6000 m. The partial pressure of oxygen at these altitudes is less than 50% of that at sea level, yet these extremely high flights occurred in the absence of topographical barriers. Instead, they were associated with high air temperatures at lower altitudes and increasing wind support at higher altitudes. Our results therefore suggest that wind, temperature and topography all play a role in determining migratory behaviour, but that their relative importance is context dependent. Extremely high-altitude flights may thus not be especially rare, but they may only occur in very specific environmental contexts.

Verification of a ground-based method for simulating high-altitude, supersonic flight conditions

Ground-based methods for accurately representing high-altitude, high-speed flight conditions have been an important research topic in the aerospace field. Based on an analysis of the requirements for high-altitude supersonic flight tests, a ground-based test bed was designed combining Laval nozzle, which is often found in wind tunnels, with a rocket sled system. Sled tests were used to verify the performance of the test bed. The test results indicated that the test bed produced a uniform-flow field with a static pressure and density equivalent to atmospheric conditions at an altitude of 13–15[Formula: see text]km and at a flow velocity of approximately M 2.4. This test method has the advantages of accuracy, fewer experimental limitations, and reusability.

The effect of crack wake roughness on the environmentally assisted fatigue behavior of an aerospace Al-alloy in low moisture environments

The effect of low PH2O environments (pertinent to high altitude flight conditions) on the fatigue crack growth behavior of 7075-T651 were quantified via linear elastic fracture mechanics (LEFM) testing. Real-time compliance based crack monitoring enabled K-shed and constant ΔK testing at various PH2O/f levels to elucidate the mechanical and chemical driving forces that govern the observed behavior. A breakdown in fracture mechanics similitude for constant ΔK, PH20/f, and crack length experiments is observed due to varying levels of crack wake roughness. This behavior is understood based on the rate limiting molecular transport step of the H-environment embrittlement process. Specifically, crack wake roughness will lead to impeded transport in the crack growth direction, this leads to the development of an irregular crack front due to environment enhanced crack extension occurring on the crack flanks where the transport distance is low and slow crack progression at the specimen center. The resulting through thickness gradients in the environmental and mechanical driving forces for crack extension provide the means to understand the breakdown of similitude and variation of the crack growth rates. It is necessary to incorporate this understanding into the data generation protocol for these environment specific da/dN vs. ΔK relationships in order to accurately incorporate environment into LEFM based damage tolerant approaches.

Recording animal vocalizations from a UAV: bat echolocation during roost re-entry

Unmanned aerial vehicles (UAVs) are rising in popularity for wildlife monitoring, but direct recordings of animal vocalizations have not yet been accomplished, likely due to the noise generated by the UAV. Echolocating bats, especially Tadarida brasiliensis, are good candidates for UAV recording due to their high-speed, high-altitude flight. Here, we use a UAV to record the signals of bats during morning roost re-entry. We designed a UAV to block the noise of the propellers from the receiving microphone, and report on the characteristics of bioacoustic recordings from a UAV. We report the first published characteristics of echolocation signals from bats during group flight and cave re-entry. We found changes in inter-individual time-frequency shape, suggesting that bats may use differences in call design when sensing in complex groups. Furthermore, our first documented successful recordings of animals in their natural habitat demonstrate that UAVs can be important tools for bioacoustic monitoring, and we discuss the ethical considerations for such monitoring.

Improved structural properties, morphological and optical behaviors of sprayed Cu2ZnSnS4 thin films induced by high gamma radiations for solar cells

Cu2ZnSnS4 (CZTS) thin films have been synthesized by spray pyrolysis technique, deposited on glass substrates and then irradiated by high gamma radiations. Six gamma radiation doses have been applied: 10, 20, 30, 40, 50 and 100 kGy. The main objective of this work was to study the physical properties behavior of CZTS thin films under high gamma irradiation. Structural, optical and morphological properties of CZTS thin films were explored by X-ray diffraction, spectrophotometer and Scanning Electron Microscope, respectively. Structural analysis has shown that no noticeable changes have been occurred in the preferred orientation (112) or diffraction angles after gamma irradiation. Nevertheless, a significant increase in crystallite size from 52 to 79 nm has been observed after irradiation with 100 kGy gamma dose, which indicates a clear enhancement in crystalline structure. Certain optical parameters such as absorption and extinction coefficients (α(λ),K(λ)) have been only slightly affected, which indicate a radiation hardness of the CZTS thin films within the ionizing radiation range studied in this paper. Band gap energy of the irradiated thin films have been increased with the irradiation and reached 1.6 eV at 100 kGy gamma dose. Other optical parameters such as refractive index n(λ) and lattice dielectric constant (ε) have been determined and analyzed. All these experimental results clearly showed that structural properties of CZTS films have been improved by gamma irradiation while the optical properties have been slightly changed, which is favorable for optoelectronic applications working near nuclear environments or even for outer space solar cells and instrumentation for high-altitude flight, where gamma radiations are abundant.

Hazardous Gas Detection Sensor Using Broadband Light-Emitting Diode-Based Absorption Spectroscopy for Space Applications

As space travel matures and extended duration voyages become increasingly common, it will be necessary to include arrays of early fire detection systems aboard spacefaring vessels, space habitats, and in spacesuits. As gasses that are relevant to combustion and pyrolysis have absorption features in the mid-infrared range, it is possible to utilize absorption spectroscopy as a means of detecting and quantifying the concentration of these hazardous compounds. Within this work, a sensor for detecting carbon dioxide has been designed and tested autonomously on a high-altitude balloon flight. The sensor utilizes a 4.2-μm light-emitting diode source, amplitude modulation to characterize species concentrations, and frequency modulation to characterize ambient temperature. Future work will include expanding the sensor design to detect other gases, and demonstrating suborbital flight capability.

Mission Analysis of Solar UAV for High-Altitude Long-Endurance Flight

AbstractThis study presents the analysis of a hybrid solar high-altitude, long-endurance unmanned aerial vehicle (HALE UAV) designed to perform meteorological observation and surveillance-related m...