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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Battery Cell-to-Pack Scaling Trends for Electric Aircraft

Battery pack gravimetric energy density is one of the most important, yet often miss- estimated design parameters for sizing all-electric aircraft. Proper accounting for thermal, structural, and operational safety margins are frequently lost when extrapolating performance from the cell level to the aircraft level. This paper summarizes the relevant engineering and certification details needed to better account for the penalties associated when assembling battery packs. The relationship between the cell and pack energy density is not linear, as is often assumed. Furthermore, the relationship varies depending on pack requirements, cell chemistry, and architecture. Parametric, high-fidelity models are used to determine optimal battery pack sizes over a range of conditions to better quantify technology scaling effects.

Battery Electric Aircraft↗
NASA NTRS2005

Initial Experimental Airworthiness Certification Guidance for UAS. UAS Experimental Certification Process and Guidance

This paper addresses the regulatory processes and requirements already in place by which an applicant might obtain experimental airworthiness certification for a civil Unmanned Aircraft System (UAS). It is more extensive and subsequent to an earlier, similar deliverable, PD007, which was an interim study of the same topic. Since few regulatory airworthiness and operating standards exist for UAS like those for traditional manned aircraft and since most UAS have historically been developed and operated under military auspices, civil use of UAS in the NAS is a new and unfamiliar challenge requiring specific and unique considerations. Experimental certification is the most basic level of FAA approval toward routine UAS operation in the NAS. The paper reviews and explains existing FAA requirements for an applicant seeking experimental airworthiness approval and details the process for submission of necessary information. It summarizes the limited purposes for which experimental aircraft may be used and addresses pertinent aspects of UAS design, construction and operation in the NAS in harmony with traditional manned aircraft. Policy IPT position is that UAS, while different from manned aircraft, can use the same initial processes to gain civil operating experience under the experimental approval. Particular note is taken of those UAS-unique characteristics which require extra attention to assure equivalent safety of operation, such as the UAS control station and sense-and-avoid. The paper also provides "best practices" guidance for UAS manufacturers and FAA personnel in two appendices. The material in Appendix A is intended to provide guidance on assuring UAS safety to FAA, and provides FAA personnel with a suggested list of items to review, with a focus on UAS unique factors, prior to issuance of an experimental airworthiness certificate. Appendix B provides an outline for a program letter which a manufacturer could use in preparing the application for an UAS experimental airworthiness certificate.

Source record↗
NASA NTRS2017

Modelling the Risks Remotely Piloted Aircraft Pose to People on the Ground

Worldwide there is much e ort being directed towards the development of a framework of air- worthiness regulations for remotely piloted aircraft systems (RPAS). It is now broadly accepted that regulations should have a strong foundation in, and traceability to, the management of the safety risks. Existing risk models for RPAS operations do not provide a simple means for incorporating the wide range of technical and operational controls into the risk analysis and evaluation processes. This paper describes a new approach for modelling and evaluating the risks associated with RPAS operations near populous areas based on the barrier bow tie (BBT) model. A BBT model is used to structure the underlying risk management problem. The model focuses risk analysis, evaluation, and decision making activities on the devices, people, and processes that can be employed to reduce risk. The BBT model and a comprehensive set of example risk controls are presented. The general model can be applied to any RPAS operation. The foundations for quantitative and qualitative assessments using a BBT model are also presented. The modelling and evaluation framework is illustrated through its application to a case-study rotary wing RPAS for two operational scenarios. The model can be used as a basis for determining airworthiness certification requirements for RPAS.

Barrier bow tie model↗
NASA NTRS2023

Autonomy Verification & Validation Roadmap and Vision 2045

Advanced capabilities planned for the next generation of autonomous and increasingly autonomous air vehicles will include non-traditional components based on artificial intelligence, machine learning, and complex optimization and planning algorithms. These complex components will be used to provide enhanced safety and high-level decision-making functions. However, there are serious barriers to the deployment of autonomous aircraft in the National Airspace System (NAS). Current civil aviation certification processes are based on the concept that the correct behavior of a system or a component must be completely specified and verified prior to operation. This report from the Autonomy Verification and Validation (V&V) Roadmap and Vision 2045 project presents the most recent effort to build a comprehensive list of verification challenges and needs for autonomous aircraft, a roadmap to meet those autonomy V&V needs, the services they can enable, and point to the certification gaps they fill. To accomplish these goals, we assembled a team of world-class researchers from the aerospace industry (Boeing, Collins Aerospace, and GeneralElectric) and academia (University of Michigan, University of Texas, and Massachusetts Institute of Technology) with deep expertise in autonomy, aerospace systems, and assurance of Artificial Intelligence/machine learning systems.

Software Assurance↗
NASA NTRS1993

Illness/injury pattern complex 40 (Titan)

On July 31, 1991, EG&G Medical began providing medical support at the Titan Area Clinic (TAC). The hours of operation are 0700-2300, Monday through Friday, with Emergency Medical Services (EMS) provided 24-hours a day, seven days a week. The TAC consists of a 10 x 10 ft section of a trailer that also houses Bechtel Safety. Supplies consisted of an examining table, an eye wash chair, first aid equipment, over-the-counter medications, spine boards, a portable rescuscitator, etc. All of the nurses are Advanced Cardiac Life Support (ACLS) certified. Although the Titan Area Clinic is strictly a first-aid station with no ACLS facilities on-site, it is staffed with an Occupational Health Nurse with ACLS certification. If ACLS or additional help is needed, the nurse activates EMS by dialing 911. The nurse responds to any medical problems or emergencies on the complex, but activates EMS prior to leaving the TAC. A Bechtel Safety Representative accompanies the nurse to the site and assists as needed. Other aspects of the complex and its functions are presented.

Blasdell, Sharon↗
NASA NTRSDate not supplied

Development Strategies for Uncertainty Quantification to Enable Aircraft Certification by Analysis

Aircraft Certification by Analysis (CbA) is a broad term that describes the process by which engineering analysis tools are used to supplement flight testing to demonstrate compliance with regulatory requirements. For each requirement that is to be met through this process, the analysis tools must be sufficiently accurate to ensure that an equivalent level of safety is obtained as if the aircraft to be certified had been flight tested for the requirement. In recent decades, the ability of analysis tools to accurately predict aircraft performance has improved dramatically, leading to increasing interest and limited early adoption of Certification by Analysis across the aerospace industry. However, rigorously demonstrating the credibility of analysis tools remains a challenge for many types of certification requirements, yet is necessary for widespread adoption of CbA approaches in the future. The field of uncertainty quantification is well-suited to address this problem, but will require substantial advances in order to achieve the ambitious industry goals for Certification by Analysis. The objective of this position paper is to highlight gaps in the current technical and programmatic state of uncertainty quantification. Four main categories – Mindset & Awareness, Tools & Capabilities, Data and Benchmarks for V&V, and Applied Research & Established Processes – will be introduced. Each of these categories contains several shortcomings and impediments which, if overcome, will enable more widespread possibilities for Certification by Analysis in the 2040-2050 timeframe.

Uncertainty Quantification↗
NASA NTRS2001

Incorporation of EGPWS in the NASA Ames Research Center 747-400 Flight Simulator

The NASA Ames Research Center CAE Boeing 747300 flight simulator is used primarily for the study of human factors in aviation safety. The simulator is constantly upgraded to maintain a configuration match to a specific United Airlines aircraft and maintains the highest level of FAA certification to ensure credibility to the results of research programs. United's 747-400 fleet and hence the simulator are transitioning from the older Ground Proximity Warning System (GPWS) to the state-of-the-art Enhanced Ground Proximity Warning System (EGPWS). GPWS was an early attempt to reduce or eliminate Controlled Flight Into Terrain (CFIT). Basic GPWS alerting modes include: excessive descent rate, excessive terrain closure rate, altitude loss after takeoff, unsafe terrain clearance, excessive deviation below glideslope, advisory callouts and windshear alerting. However, since GPWS uses the radar altimeter which looks straight down, ample warning is not always provided. EGPWS retains all of the basic functions of GPWS but adds the ability to look ahead by comparing the aircraft position to an internal database and provide additional alerting and display capabilities. This paper evaluates three methods of incorporating EGPWS in the simulator and describes the implementation and architecture of the preferred option.

Sallant, Ghislain↗
NASA NTRS2010

The NASA Langley Research Center's Unmanned Aerial System Surrogate Research Aircraft

Research is needed to determine what procedures, aircraft sensors and other systems will be required to allow Unmanned Aerial Systems (UAS) to safely operate with manned aircraft in the National Airspace System (NAS). The NASA Langley Research Center has transformed a Cirrus Design SR22 general aviation (GA) aircraft into a UAS Surrogate research aircraft to serve as a platform for UAS systems research, development, flight testing and evaluation. The aircraft is manned with a Safety Pilot and systems operator that allows for flight operations almost anywhere in the NAS without the need for a Federal Aviation Administration (FAA) Certificate of Authorization (COA). The UAS Surrogate can be controlled from a modular, transportable ground station like a true UAS. The UAS Surrogate is able to file and fly in the NAS with normal traffic and is a better platform for real world UAS research and development than existing vehicles flying in restricted ranges or other sterilized airspace. The Cirrus Design SR22 aircraft is a small, singleengine, four-place, composite-construction aircraft that NASA Langley acquired to support NASA flight-research programs like the Small Aircraft Transportation System (SATS) Project. Systems were installed to support flight test research and data gathering. These systems include: separate research power; multi-function flat-panel displays; research computers; research air data and inertial state sensors; video recording; data acquisition; data-link; S-band video and data telemetry; Common Airborne Instrumentation System (CAIS); Automatic Dependent Surveillance-Broadcast (ADS-B); instrumented surfaces and controls; and a systems operator work station. The transformation of the SR22 to a UAS Surrogate was accomplished in phases. The first phase was to modify the existing autopilot to accept external commands from a research computer that was connected by redundant data-link radios to a ground control station. An electro-mechanical auto-throttle was added in the next phase to provide ground station control of airspeed. Additional phases are in progress to add waypoint navigation and long range satellite voice and data communications. Potential areas for UAS Surrogate research include the development, flight test and evaluation of sensors to aid in the process of air traffic detect-sense-and-avoid. These sensors could be evaluated in real-time and compared with onboard human evaluation pilots. This paper describes the systems and design considerations that were incorporated in the development of the UAS Surrogate along with details of development problems encountered and the corresponding solutions.

Howell, Charles T., III↗
NASA NTRS2011

The Proposed Use of Unmanned Aerial System Surrogate Research Aircraft for National Airspace System Integration Research

Research is needed to determine what procedures, aircraft sensors and other systems will be required to allow Unmanned Aerial Systems (UAS) to safely operate with manned aircraft in the National Airspace System (NAS). This paper explores the use of Unmanned Aerial System (UAS) Surrogate research aircraft to serve as platforms for UAS systems research, development, and flight testing. These aircraft would be manned with safety pilots and researchers that would allow for flight operations almost anywhere in the NAS without the need for a Federal Aviation Administration (FAA) Certificate of Authorization (COA). With pilot override capability, these UAS Surrogate aircraft would be controlled from ground stations like true UAS s. It would be possible to file and fly these UAS Surrogate aircraft in the NAS with normal traffic and they would be better platforms for real world UAS research and development over existing vehicles flying in restricted ranges or other sterilized airspace. These UAS surrogate aircraft could be outfitted with research systems as required such as computers, state sensors, video recording, data acquisition, data link, telemetry, instrumentation, and Automatic Dependent Surveillance-Broadcast (ADS-B). These surrogate aircraft could also be linked to onboard or ground based simulation facilities to further extend UAS research capabilities. Potential areas for UAS Surrogate research include the development, flight test and evaluation of sensors to aide in the process of air traffic "see-and-avoid". These and other sensors could be evaluated in real-time and compared with onboard human evaluation pilots. This paper examines the feasibility of using UAS Surrogate research aircraft as test platforms for a variety of UAS related research.

Howell, Charles T., III↗
NASA NTRS2012

An Assessment of Civil Tiltrotor Concept of Operations in the Next Generation Air Transportation System

Based on a previous Civil Tiltrotor (CTR) National Airspace System (NAS) performance analysis study, CTR operations were evaluated over selected routes and terminal airspace configurations assuming noninterference operations (NIO) and runway-independent operations (RIO). This assessment aims to further identify issues associated with these concepts of operations (ConOps), and their dependency on the airspace configuration and interaction with conventional fixed-wing traffic. Safety analysis following a traditional Safety Management System (SMS) methodology was applied to CTR-unique departure and arrival failures in the selected airspace to identify any operational and certification issues. Additional CTR operational cases were then developed to get a broader understanding of issues and gaps that will need to be addressed in future CTR operational studies. Finally, needed enhancements to National Airspace System performance analysis tools were reviewed, and recommendations were made on improvements in these tools that are likely to be required to support future progress toward CTR fleet operations in the Next Generation Air Transportation System (NextGen).

Chung, William W.↗
NASA NTRS2017

Insights into the Behavior of Potential Structural Failures Originating from Localized High Stress Regions in Configurations Relevant to Solid Rocket Motor Nozzles

During the structural certification effort for the Space Launch System solid rocket booster nozzle, it was identified that no consistent method for addressing local negative margins of safety in non-metallic materials had been developed. Relevant areas included bond-line terminations and geometric features in the composite nozzle liners. In order to gain understanding, analog test specimens were designed that very closely mimic the conditions in the actual full scale hardware. Different locations in the nozzle were represented by different analog specimen designs. This paper describes those tests and corresponding results. Finite element analysis results for the tests are presented. Strain gage correlation of the analysis to the test results is addressed. Furthermore, finite fracture mechanics (a coupled stress and energy failure criterion) is utilized to predict the observed crack pop-in loads for the different configurations. The finite fracture mechanics predictions are found to be within a 10% error relative to the average measured pop-in load for each of four configurations. Initiation locations, arrest behaviors, and resistances to further post-arrest crack propagation are also discussed.

McCutcheon, David Matthew↗
NASA NTRS2019

Urine Removal from Suited Crew in Orion Vehicle Depressurization Scenario

Humankind wants to continually venture deeper into space, but there are many hazards of deep space exploration. NASA’s Orion Program seeks to incrementally identify these hazards and begin addressing the difficulties of such long-duration missions. One of the largest risks and areas of program focus is crew survival in a vehicle cabin depressurization scenario. As part of proactive mitigation efforts, contingency operations and associated hardware are being developed to sustain crew members for up to 6 days. While the Orion launch and entry suit would provide the crew a pressurized safe haven for that duration, additional systems are needed to handle crew waste while within the suit. NASA’s Orion Crew Survival Systems (OCSS) and Collins Aerospace are working together to develop and test an external suit system to aid in the evacuation of urine from pressurized suits to ensure crew health and safety. This paper describes the recent and on-going design and testing that is driving evolution of hardware and requirements towards eventual flight certification.

OCSS↗
NASA NTRS2015

Towards Real-Time, On-Board, Hardware-Supported Sensor and Software Health Management for Unmanned Aerial Systems

For unmanned aerial systems (UAS) to be successfully deployed and integrated within the national airspace, it is imperative that they possess the capability to effectively complete their missions without compromising the safety of other aircraft, as well as persons and property on the ground. This necessity creates a natural requirement for UAS that can respond to uncertain environmental conditions and emergent failures in real-time, with robustness and resilience close enough to those of manned systems. We introduce a system that meets this requirement with the design of a real-time onboard system health management (SHM) capability to continuously monitor sensors, software, and hardware components. This system can detect and diagnose failures and violations of safety or performance rules during the flight of a UAS. Our approach to SHM is three-pronged, providing: (1) real-time monitoring of sensor and software signals; (2) signal analysis, preprocessing, and advanced on-the-fly temporal and Bayesian probabilistic fault diagnosis; and (3) an unobtrusive, lightweight, read-only, low-power realization using Field Programmable Gate Arrays (FPGAs) that avoids overburdening limited computing resources or costly re-certification of flight software. We call this approach rt-R2U2, a name derived from its requirements. Our implementation provides a novel approach of combining modular building blocks, integrating responsive runtime monitoring of temporal logic system safety requirements with model-based diagnosis and Bayesian network-based probabilistic analysis. We demonstrate this approach using actual flight data from the NASA Swift UAS.

Unmanned Aerial System↗
DOE OSTI2022

An Introduction to Los Alamos National Laboratory [Slides]

The Weapon Systems Engineering Division (W) provides the system engineering and program management necessary to sustain the safety, reliability, and security of the Los Alamos National Laboratory’s assets in the active United States nuclear stockpile - the B61, W76, W78 and W88. The Division generates key certification data for Annual Assessment supporting the Laboratory Director's letter to the President on the health of those warheads. This role demands ongoing surveillance of the active stockpile and evaluation of the potential impact of any issues through design, engineering, fabrication, testing using state-of-the-art computational simulation tools and engineering test facilities. The Division works in close liaison with the several production facilities across the nuclear security complex as well as with the customers in the US Navy and Air Force.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
NASA NTRS2015

Certification Considerations for Adaptive Systems

Advanced capabilities planned for the next generation of aircraft, including those that will operate within the Next Generation Air Transportation System (NextGen), will necessarily include complex new algorithms and non-traditional software elements. These aircraft will likely incorporate adaptive control algorithms that will provide enhanced safety, autonomy, and robustness during adverse conditions. Unmanned aircraft will operate alongside manned aircraft in the National Airspace (NAS), with intelligent software performing the high-level decision-making functions normally performed by human pilots. Even human-piloted aircraft will necessarily include more autonomy. However, there are serious barriers to the deployment of new capabilities, especially for those based upon software including adaptive control (AC) and artificial intelligence (AI) algorithms. Current civil aviation certification processes are based on the idea that the correct behavior of a system must be completely specified and verified prior to operation. This report by Rockwell Collins and SIFT documents our comprehensive study of the state of the art in intelligent and adaptive algorithms for the civil aviation domain, categorizing the approaches used and identifying gaps and challenges associated with certification of each approach.

Bhattacharyya, Siddhartha↗
NASA NTRS2017

Formal Methods Tool Qualification

Formal methods tools have been shown to be effective at finding defects in safety-critical digital systems including avionics systems. The publication of DO-178C and the accompanying formal methods supplement DO-333 allows applicants to obtain certification credit for the use of formal methods without providing justification for them as an alternative method. This project conducted an extensive study of existing formal methods tools, identifying obstacles to their qualification and proposing mitigations for those obstacles. Further, it interprets the qualification guidance for existing formal methods tools and provides case study examples for open source tools. This project also investigates the feasibility of verifying formal methods tools by generating proof certificates which capture proof of the formal methods tool's claim, which can be checked by an independent, proof certificate checking tool. Finally, the project investigates the feasibility of qualifying this proof certificate checker, in the DO-330 framework, in lieu of qualifying the model checker itself.

Wagner, Lucas G.↗
NASA NTRSDate not supplied

Machine-Learning for Safety Critical Airborne Applications Part II: Case Study

The exceptional progress in the field of Artificial Intelligence (AI) systems, enabled by Machine Learning (ML) technology in recent years provides historic opportunities for the aviation industry. Current certification standards for avionics were developed prior to the ML renaissance and have several fundamental incompatibilities with the ML technology. WG-114 is working hard to release a new standard as soon as possible but for now there is no recognized means of compliance for ML based systems even of low criticality. In this talk, we present the custom ML workflow that can be used comply with all objectives of the current certification standards for a low-criticality (DAL D and C) ML-based system. To illustrate the practical application of the custom ML workflow we present a case study of a system based on a Deep Neural Network (DNN) intended to detect and identify airport runway signs. We present the system design, data generation, training, and verification in detail and describe how the design assurance objectives can be met for a DAL D and DAL C systems.

Johann Schumann↗
NASA NTRS1972

Training and certification program of the operating staff for a 90-day test of a regenerative life support system

Prior to beginning a 90-day test of a regenerative life support system, a need was identified for a training and certification program to qualify an operating staff for conducting the test. The staff was responsible for operating and maintaining the test facility, monitoring and ensuring crew safety, and implementing procedures to ensure effective mission performance with good data collection and analysis. The training program was designed to ensure that each operating staff member was capable of performing his assigned function and was sufficiently cross-trained to serve at certain other positions on a contingency basis. Complicating the training program were budget and schedule limitations, and the high level of sophistication of test systems.

Source record↗