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At least 181 records · Page 10

Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

A coordinated aircraft - radar project that investigated the electric fields, cloud microphysics and radar reflectivity of thunderstorm anvils near Kennedy Space Center is described. Measurements from two cases illustrate the extensive nature of the microphysics and electric field observations. As the aircraft flew from the edges of anvils into the interior, electric fields very frequently increased abruptly from approximately 1 to more than 10 kV m(exp -1) even though the particle concentration and radar reflectivity increased smoothly. The abrupt increase in field usually occurred when the aircraft entered regions with a reflectivity of 10 to 15 dBZ. It is suggested that the abrupt increase in electric field may be because the charge advection from the storm core did not occur across the entire breadth of the anvil and was not constant in time. Screening layers were not detected near the edges of the anvils. Some long-lived anvils showed subsequent enhancement of electric field and reflectivity and growth of particles, which if localized, might be a factor in explaining the abrupt change of field in some cases. Comparisons of electric field magnitude with particle concentration or reflectivity for a combined data set that included all anvil measurements showed a threshold behavior. When the average reflectivity, such as in a 3-km cube, was less than approximately 5 dBZ, the electric field magnitude was les than kV m(exp -1). Based on these findings, the Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) is now being used by NASA, the Air Force and Federal Aviation Administration in new Lightning Launch Commit Criteria as a diagnostic for high electric fields in anvils.

Dye, J. E.↗

Design and Performance of a Hybrid-Electric Fuel Cell Flight Demonstration Concept

As electric powertrain and propulsion-airframe integration technologies advance, airborne electric propulsion concepts appear to be on the cusp of disrupting or transforming aviation markets. One of the many challenges to this transformation lies within the onboard energy storage and generation technologies. State-of-the-art battery technology is heavy and lacks support infrastructure; purely combustion-based solutions to electrical power generation suffer from increased inefficiency as compared to a traditional combustion powertrain. This paper explores another alternative: a hybrid-electric, solid oxide fuel cell power system. This power system reforms traditional fuels to feed fuel cells that generate electrical power for the aircraft electric powertrain. A representative power system is designed based on the requirements for NASA’s X-57 Mod II electric flight demonstrator platform, and is shown to exceed system feasibility goals of 300 W/kg and 60% efficiency in at least one configuration. The hybrid-electric fuel cell power system is shown to be competitive with the range performance of a combustion-based power architecture and comparable in mission energy cost to a battery-electric power system.

Borer, Nicholas K.↗

Cybersecurity Considerations for Hydrogen Infrastructure in Airport Environments

This report explores key cybersecurity concerns and best practices within environments that serve as reference points for the development of hydrogen fueling infrastructure for aviation. This cybersecurity analysis leverages prior NREL studies: 1) hydrogen fueling station component validation to identify vulnerabilities and failure events documented in physical equipment, and 2) electric aircraft charging infrastructure analysis to explore primary cybersecurity vulnerabilities. It reviews the criticality of digitized technologies in sustaining hydrogen fuel production, storage, and fueling systems, noting cybersecurity concerns that are universal to power systems and industrial control systems in general. In considering cybersecurity vulnerabilities within a future landscape of hydrogen energy for aviation applications, a reference architecture was intended to reveal the points of connection between assets and the potential sensors that are vulnerable to manipulation in the event of compromised access or communication within a SCADA system. A generalized reference architecture can help stakeholders, engineers, or strategists understand connections, criticalities, and standard practices when it comes to designing and planning for new systems. There are several gaps to account for in assessing the future of hydrogen production, storage, and fueling for aviation. Engaging stakeholders, including aircraft manufacturers, electric utilities, site property owners, and local communities, will inform decision-making around site structure, operations, and resources for future hydrogen fueling infrastructure to understand operational needs and cybersecurity awareness. Cybersecurity mitigation strategy must consider physical attack vectors that emerge with the integration of hydrogen systems into existing airport security requirements. The cybersecurity risk assessment contained in this report is an entry point into potential future granular-level analyses to be conducted as part of hazard and risk assessments for safe aviation hydrogen infrastructure, determining how the scale of hydrogen fuel infrastructure for aviation impacts the volume of cyber attack vectors, and what, if any, are the vulnerabilities associated with different types of on-board hydrogen systems. In this nascent development phase, assessing how best to integrate cybersecurity practices into an evolving U.S. aviation landscape provides critical insights into building increased awareness and stakeholder engagement to support a cyber-resilient infrastructure.

08 HYDROGEN↗

Low-Noise Operating Mode for Propeller-Driven Electric Airplanes

Mechanical shaft power and shaft speed of reciprocating internal combustion engines are closely coupled. Maximum rated shaft power is typically produced at or near peak shaft speed. If a general aviation airplane equipped with a reciprocating engine and a variable-pitch propeller attempts a low-noise takeoff by reducing propeller tip speed, propeller power and thrust are reduced. Such takeoffs are not tolerated due to punishing performance effects, such as increased field lengths and poor climb rates. Certain electric motors, however, are able to deliver maximum shaft power over a wide range of shaft speed. Electric or hybrid-electric propeller-driven airplanes should be able to exploit this behavior. At low shaft speeds, high shaft power levels and high blade pitch angles could be combined to recover much of the thrust that would otherwise be lost. This could enable a low-noise operating mode for propellers normally designed for performance rather than for noise. The subject of this paper is an analytical investigation into low-noise takeoffs and steady overflights of a notional general aviation airplane equipped with a propeller driven by an electric motor.

Berton, Jeffrey J.↗

The Next Challenge: High Power Electric Aircraft Propulsion

Introduction of the Aeronautic Research Mission Directorate Technical Challenge 10.2 “High Power Electric Aircraft Propulsion” to the power electronics community. The presentation was given as part of a panel discussion “Challenges of Power Electronics Systems for Sustainable Aviation” during the 2024 Sustainable Aviation Workshop held at The Ohio State University.

power electroics↗

Environmental Analysis

Burns & McDonnell Engineering's environmental control study is assisted by NASA's Computer Software Management and Information Center's programs in environmental analyses. Company is engaged primarily in design of such facilities as electrical utilities, industrial plants, wastewater treatment systems, dams and reservoirs and aviation installations. Company also conducts environmental engineering analyses and advises clients as to the environmental considerations of a particular construction project. Company makes use of many COSMIC computer programs which have allowed substantial savings.

Source record↗

Accessibility Design and Operational Considerations in the Development of Urban Aerial Mobility Vehicles and Networks

Urban aerial mobility vehicles and networks have recently gained considerable interest in the aviation community. These small, short-range vehicles with all-electric or hybrid-electric propulsion systems, tailored to metropolitan aerial transportation needs, promise to radically change passenger mobility and cargo distribution in cities. Accessibility issues have not been a major consideration in UAM vehicle and network discussions to date. This paper seeks to help change that.

Young, Larry A.↗

Hybrid Electric Propulsion Technologies for Commercial Transports

NASA Aeronautics Research Mission Directorate has set strategic research thrusts to address the major drivers of aviation such as growth in demand for high-speed mobility, addressing global climate and capitalizing in the convergence of technological advances. Transitioning aviation to low carbon propulsion is one of the key strategic research thrust and drives the search for alternative and greener propulsion system for advanced aircraft configurations. This work requires multidisciplinary skills coming from multiple entities. The Hybrid Gas-Electric Subproject in the Advanced Air Transportation Project is energizing the transport class landscape by accepting the technical challenge of identifying and validating a transport class aircraft with net benefit from hybrid propulsion. This highly integrated aircraft of the future will only happen if airframe expertise from NASA Langley, modeling and simulation expertise from NASA Ames, propulsion expertise from NASA Glenn, and the flight research capabilities from NASA Armstrong are brought together to leverage the rich capabilities of U.S. Industry and Academia.

electric motor vehicles↗

Enabling Electric Propulsion for Flight - Hybrid Electric Aircraft Research at AFRC

Advances in electric machine efficiency and energy storage capability are enabling a new alternative to traditional propulsion systems for aircraft. This has already begun with several small concept and demonstration vehicles, and NASA projects this technology will be essential to meet energy and emissions goals for commercial aviation in the next 30 years. In order to raise the Technology Readiness Level of electric propulsion systems, practical integration and performance challenges will need to be identified and studied in the near-term so that larger, more advanced electric propulsion system testbeds can be designed and built. Researchers at NASA Armstrong Flight Research Center are building up a suite of test articles for the development, integration, and validation of these systems in a real world environment.

electric propulsion↗

FUELEAP Model-Based System Safety Analysis

NASA researchers, in a partnership with Boeing, are investigating a fuel-cell powered variant of the X-57 “Maxwell” Mod-II electric propulsion aircraft, which is itself derived from a stock Tecnam P2006T. The “Fostering Ultra-Efficient Low-Emitting Aviation Power” (FUELEAP) project will replace the X-57 power subsystem with a hybrid Solid-Oxide Fuel Cell (SOFC) system to increase the potential range of the electric-propulsion aircraft while dramatically improving efficiency and emissions over stock internal-combustion engines. Our FUELEAP safety analysis faces two primary challenges. First, the Part 23 certificated Tecnam P2006T is undergoing significant modifications to host the hybrid electric-propulsion system, and the challenge is to assure that the safety inherent in the stock aircraft (and subsequently in X-57 Mod-II) is not compromised by changes in avionics, aircraft structural loading, weight and balance, or other considerations. Secondly, because the SOFC power system has little (if any) relevant in-service precedent, our challenge is to assure that we identify and mitigate all reasonably plausible hazards introduced by unique FUELEAP equipage. We are investigating and utilizing Model-Based Safety Analysis (MBSA) methods to help us address these FUELEAP safety challenges. We captured aircraft-level system hazard conditions using instances of a SysML hazard block via aircraft-level Functional Hazard Analysis (FHA). Then, using SysML models of the FUELEAP architecture, we related the hazard conditions to initiating system events and possible mitigations, such as design architecture modifications or operational constraints. We are continuing to define our approach to MBSA by developing a component-by-component inventory of local failure modes and tracing their possible contribution to hazard conditions. Finally, we are applying an argument-based approach to FUELEAP assurance. Through a FUELEAP “safety case,” we are providing an explicit argument for FUELEAP safety by associating assurance evidence with overarching safety claims through a structured argument.

Woodham, Kurt P.↗

Spark Plug Defects and Tests

The successful operation of the spark plug depends to a large extent on the gas tightness of the plug. Part 1 of this report describes the method used for measuring the gas tightness of aviation spark plugs. Part 2 describes the methods used in testing the electrical conductivity of the insulation material when hot. Part 3 describes the testing of the cold dielectric strength of the insulation material, the resistance to mechanical shock, and the final engine test.

Silsbee, F B↗

Novel Processing, Testing and Characterization of Copper/Carbon Nanotube (Cu/CNT) Yarn Composite Conductor

Sustainable electrified aircraft propulsion (EAP) is likely to lead to an increase in the electrical wiring contained within a single aircraft. Since the electrical resistance and mass of copper (Cu) conductors are associated with power losses, it is desirable to design high-conductivity lightweight conductor materials, thus reducing the mass of components like motor windings, low-voltage signal cables, and transmission cables for data and power to improve the overall energy efficiency. This paper describes a unique framework for manufacturing metalized carbon nanotube (CNT) composite conductors, measuring their electrical conductivity and strength, and modeling the overall conductivity and current sharing within such composites. Tensile testing was conducted on the processed composite conductor cables with the use of acoustic emission and electrical resistivity to determine stress-dependent-failure mechanisms while monitoring the electrical conductivity. The average of measured electrical conductivities of annealed Cu/CNT samples from batch 5 was greater than theoretical predictions by 9.8 percent and was also greater than the conductivity of pure annealed Cu by 4.8 percent and had comparable ultimate tensile strengths. Additionally, those Cu/CNT samples provide a 13.5% weight saving over current state of the art copper wires. Theories explaining improved intrinsic conductivity are discussed.

Metalized CNT↗

The mechanical stability of polyimide films at high pH

Polyimide insulated electrical wire has been widely used in the aerospace industry in commercial, military, and to a lesser degree, general aviation aircraft since the early 1970s. Wiring failures linked to insulation damage have drawn much attention in the media and concerns have developed regarding the long term stability and safety of polyimide insulated electrical wire. The mechanical durability and chemical stability of polyimide insulated wire are affected by hydrolysis, notch propagation, wet and dry arc tracking, topcoat flaking, and degradation due to high pH fluids. Several polyimides were selected for evaluation for resistance to degradation by various aqueous alkaline solutions. The polyimides under evaluation include commercially available films such as KAPTON (tradename), APICAL (tradename), LARC-TPI, and UPILEX (tradename) R and S, as well as a number of experimental films prepared at NASA-Langley. Material properties investigated include viscosity, solubility, moisture absorption, glass transition temperature, dielectric constant, and mechanical properties before and after exposure to various conditions.

Croall, Catharine I.↗

Colorado Alternatively Powered Aircraft Airport Infrastructure Study

Advanced Air Mobility encompasses emerging technologies in propulsion of general aviation and commuter aircraft for the purpose of moving passengers and goods. The State of Colorado has a strong aerospace and aviation legacy, and this research explores the potential energy implications of a transition from traditional aircraft propulsion systems to more-electric, full electric and hydrogen powered aircraft in flight schools, and small community air service utilizing NASA's Regional Air Mobility Model. Effort includes identifying potential energy needs and cost-effective solutions to support those emerging needs analyzing potential benefits on on-site generation and storage to optimize energy systems.Advanced Air Mobility encompasses emerging technologies in propulsion of general aviation and commuter aircraft for the purpose of moving passengers and goods. The State of Colorado has a strong aerospace and aviation legacy, and this research explores the potential energy implications of a transition from traditional aircraft propulsion systems to more-electric, full electric and hydrogen powered aircraft in flight schools, and small community air service utilizing NASA's Regional Air Mobility Model. Effort includes identifying potential energy needs and cost-effective solutions to support those emerging needs analyzing potential benefits on on-site generation and storage to optimize energy systems.

33 ADVANCED PROPULSION SYSTEMS↗

Urban Air Mobility Noise: Current Practice, Gaps, and Recommendations

AN Air Mobility (UAM) is an opportunity for aviation to improve transportation systems across the world. Representative UAM vehicle attributes include electrical vertical takeoff and landing (eVTOL) vehicles that can accommodate up to 6 passengers (or equivalent cargo), are possibly autonomous, perform missions of up to 100 nautical miles at altitudes up to 3000 ft. above ground level, have flight speeds up to 200 knots, and weigh between 800 and 8000 pounds. Along with the many anticipated benefits, there will be noise issues that need to be addressed. In 2018, NASA formed an Urban Air Mobility Noise Working Group (UNWG) to assemble noise experts from industry, universities and government agencies to identify, discuss, and address UAM noise issues. This oral presentation summarizes technology gaps and goals associated with four areas of interest: Tools & Technologies, Ground & Flight Testing, Human Response & Metrics, and Regulation & Policy, and is drawn from a draft white paper [1] by the same title. Tools & Technologies include noise prediction tools and noise reduction technologies that have been developed for conventional rotorcraft and fixed-wing vehicles that may be applicable or need to be modified for UAM. Prediction tools need to be able to account for variable speed rotors and other temporal variation effects that impact community noise. A reprioritization of noise sources needs to be done since UAM vehicles include multiple rotors/propellers, often in proximity to one another and/or the airframe, with dynamic transition, and new noise sources such as electric motors or hybrid-electric propulsion. Scattering and propagation methods need to be developed that include the vehicle components and surfaces near a receiver such as buildings and vertiports. Validation databases are needed to quantify prediction uncertainties. Prediction tools used to evaluate community noise will need source models appropriate for a wide range of UAM vehicles. Existing noise reduction technologies need to be evaluated and new noise reduction technologies should be developed in anticipation of future noise requirements. Although the prediction and treatment of interior cabin noise is a secondary goal, it is recognized that new tools and methods may be needed due to the uniqueness of the vehicle design and the presence of both acoustic and structure-borne loads. Ground & Flight Testing has been a critical part of validating noise reduction technologies and verifying that an air vehicle is ready for certification. UAM vehicles introduce new challenges for test procedures such as different source noise directivity, unsteady sources due to maneuvers, and a variety of takeoff and approach trajectories. The operating environment will be more complex than current aircraft with the introduction of vertiports in populated areas with “urban canyons” making reflections an important part of noise prediction and annoyance. It is expected that new test procedures and measurement methods will be necessary. Consideration will need to be given for both piloted and autonomous operations. Human Response & Metrics may be very different for UAM noise compared to current experience with airport noise. Current metrics used to certify rotorcraft and fixed-wing aircraft may not be as useful for evaluating UAM noise. Operations at lower altitudes may influence annoyance. Psychoacoustic and community testing will be needed to quantify annoyance and assess appropriate metrics. In addition to conventional noise level metrics, considerations such as audibility and temporal variation of the sound may be required. Differences between indoor or outdoor exposure will have an impact with dependence on urban and residential flight paths. Aircraft noise is currently regulated at a national level and typically involves partnerships with the industry to establish regulations. Regulators realize that current policies and procedures may not be appropriate for some of the emerging air vehicles and new procedures may be needed to address UAM noise. Development of new policies and procedures are needed so that local communities do not hastily attempt to establish their own restrictions that will both limit growth of the market and create an inconsistent and confusing regulatory environment. To expedite this development, it is crucial early measurement data are shared through partnership arrangements to support both noise certification and noise modeling/noise assessment. At the same time, an effective engagement strategy should be developed to address local community noise issues associated with UAM vehicles and flight operations as they arise.

urban air mobility↗

Design of an Open Rotor, Braced-Wing Electric Transport

A notional, 19-passenger, battery-powered, fully electric airplane is investigated in this study. It is designed to serve the regional aviation market of the near future. Three strategies are used to reduce energy demands placed on its batteries: 1) a high aspect ratio, braced wing, 2) two efficient open rotor propellers, and 3) flying at comparatively low cruise speeds. It has an otherwise conventional airframe architecture. Parametric system weight, aerodynamic, propeller, and mission performance models are developed. Single-rotation and contra-rotation propellers are studied. Implementation of a novel selective noise reduction system is also investigated. During sizing and optimization of its design variables, battery cell specific energy is treated as a technology parameter that is varied to determine its influence on mission range. To achieve a minimum range success criterion of 250 nmi with reserves, it is found that battery cell specific energy must be at least 600 W-h/kg, more than twice the capability of today’s lithium-ion cells.

Electric Aircraft↗

SUbsonic Single Aft eNgine (SUSAN) Power/Propulsion System Control Architecture Updates

The development of hybrid-electric propulsion technology for transport aircraft presents opportunities for new designs that can reduce fuel consumption and greenhouse gas emissions from commercial aviation and improve on safety and reliability when compared to modern aircraft. The SUbsonic Single Aft eNgine (SUSAN) Electrofan is a conceptual design for a transport aircraft with a series/parallel partial hybrid-electric propulsion system that is being developed by NASA as a reference design for a regional transport aircraft with a high degree of electrification. The SUSAN concept incorporates multiple tightly coupled power, propulsion, and flight control systems that introduce new challenges to the control design process, requiring a hierarchical and more coordinated control architecture. This paper summarizes updates to the SUSAN Power/Propulsion System (PPS) model and control architecture made in preparation for planned flight simulator and hardware-in-the-loop testing at NASA Glenn Research Center (GRC). These updates include a new electrical power system (EPS) model based on the NASA-developed Electrical Modeling and Thermal Analysis Toolbox (EMTAT), and a new PPS control architecture that improves the operational flexibility and responsiveness of the propulsion system. The performance of the upgraded control system is also demonstrated and discussed.

SUSAN↗