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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Certification of Safety-Critical Software Under DO-178C and DO-278A

The RTCA has recently released DO-178C and DO-278A as new certification guidance for the production of airborne and ground-based air traffic management software, respectively. Additionally, RTCA special committee SC-205 has also produced, at the same time, five other companion documents. These documents are RTCA DO-248C, DO-330, DO-331, DO- 332, and DO-333. These supplements address frequently asked questions about software certification, provide guidance on tool qualification requirements, and illustrate the modifications recommended to DO-178C when using model-based software design, object oriented programming, and formal methods. The objective of this paper is to first explain the relationship of DO-178C to the former DO-178B in order to give those familiar with DO- 178B an indication of what has been changed and what has not been changed. With this background, the relationship of DO-178C and DO-278 to the new DO-278A document for ground-based software development is shown. Last, an overview of the new guidance contained in the tool qualification document and the three new supplements to DO-178C and DO-278A is presented. For those unfamiliar with DO-178B, this paper serves to provide an entry point to this new certification guidance for airborne and ground-based CNS/ATM software certification.

Jacklin, Stephen A.↗
NASA NTRS2012

Using the VAHIRR Radar Algorithm to Investigate Lightning Cessation

Accurately determining the threat posed by lightning is a major area for improved operational forecasts. Most efforts have focused on the initiation of lightning within a storm, with far less effort spent investigating lightning cessation. Understanding both components, initiation and cessation, are vital to improving lightning safety. Few organizations actively forecast lightning onset or cessation. One such organization is the 45th Weather Squadron (45WS) for the Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). The 45WS has identified that charged anvil clouds remain a major threat of continued lightning and can greatly extend the window of a potential lightning strike. Furthermore, no discernable trend of total lightning activity has been observed consistently for all storms. This highlights the need for more research to find a robust method of knowing when a storm will cease producing lightning. Previous lightning cessation work has primarily focused on forecasting the cessation of cloud-to -ground lightning only. A more recent, statistical study involved total lightning (both cloud-to-ground and intracloud). Each of these previous works has helped the 45WS take steps forward in creating improved and ultimately safer lightning cessation forecasts. Each study has either relied on radar data or recommended increased use of radar data to improve cessation forecasts. The reasoning is that radar data is able to either directly or by proxy infer more about dynamical environment leading to cloud electrification and eventually lightning cessation. The authors of this project are focusing on a two ]step approach to better incorporate radar data and total lightning to improve cessation forecasts. This project will utilize the Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) algorithm originally developed during the Airborne Field Mill II (ABFM II) research project. During the project, the VAHIRR product showed a trend of increasing values with increases in the electric field magnitude above 3 kV/m. An extreme value analysis showed that VAHIRR values less than or equal to 10 dBZ-km showed that the probability of having an electric field magnitude larger than 3 kV/m was less than one in ten thousand. VAHIRR also was found to be sensitive at indicating anvil clouds that posed a threat of initiating a lightning flash. This project seeks to use VAHIRR to analyze its utility as a lightning cessation tool, particularly dealing with the threat posed by detached anvils. The results from this project will serve as a baseline effectiveness of radar ]based lightning cessation algorithms. This baseline will be used in the second, and concurrent work by the co ]author fs who are developing a lightning cessation algorithm based on dual ]polarimetric radar data. Ultimately, an accurate method for identifying lightning cessation can save money on lost manpower time as well as greatly improve lightning safety.

Stano, Geoffrey T.↗
DOE OSTI2023

Solid oxide metal-air redox batteries (SOMARB)

The solid oxide metal-air redox batteries (SOMARB), composed of reversible solid oxide fuel cell (RSOFC) and energy storage unit (ESU), is an emerging technology for large-scale energy storage owing to its advantages in high energy density, high rate capability, decoupled energy and power components, all solid state structure, high safety and scalability. Starting with introducing the working principle of this battery, thermodynamics and kinetics, and battery chemistries based on Fe, Mo, and Wo of SOMARB are illustrated. The strategies to improve the performance of Fe-based SOMARB via optimizing RSOFC and ESU are discussed in detail. Finally, several high temperature metal-air batteries derived from SOMARB are introduced. The comparison with other batteries shows that SOMARB is expected to play an important role in future grid and renewable energy storage with concurrent advances in SOFC stack and system design.

Zhang, Cuijuan↗
NASA NTRS2024

Communications System Concept of Operations (ConOp) for Supporting Second Shift (SS) Operations

Wildland fires take place most often in remote areas without access to communications infrastructure. Communication during wildfire operations is crucial for safe and effective command and control of air assets, ground-based firefighters, and fire management. Without connectivity, Incident Command (IC) cannot exchange information, receive alerts or work with all parties involved in the wildfire suppression operation. Current policy directs IC to use voice radio communications, which require no prior infrastructure, to provide information needed for the command, control and safety of personnel and resources. Cellular communications are used only for logistical purposes unless no other method is available. To address some of the shortcomings of the current state of communications, the Advanced Capabilities for Emergency Response Operations (ACERO) Second Shift (SS) technical team is developing characteristics of an air-to-ground Mesh Radio System (MRS) and preparing for a future demonstration. The MRS will allow air and ground assets to automatically join a radio network without relying on existing infrastructure and exchange information critical to maintaining situation awareness and air traffic management by the onsite IC. The MRS will also give users more options for communications in addition to voice communications.

David Fuller↗
DOE OSTI2022

Multi-modular capacitive wireless power transfer circuit and related techniques

A high performance kilowatt-scale large air-gap multi-modular capacitive wireless power transfer (WPT) system is provided for electric vehicle (EV) charging. In one particular implementation, the multi-modular system achieves high power transfer while maintaining fringing electric fields within prescribed safety limits. The fringing fields are reduced using near-field phased-array field-focusing techniques, wherein the adjacent modules of the multi-modular system are out-phased with respect to one another. The inter-module interactions in this multi-modular system can be modeled, and an approach to eliminate these interactions in a practical EV charging environment is provided. To illustrate one example implementation, a prototype 1.2-kW 6.78-MHz 12-cm air-gap multi-modular capacitive WPT system comprising two 600-W modules is provided. This prototype system achieves 21.2 kW/m2 power transfer density and a peak efficiency of 89.8%. This multi-modular system also achieves a fringing field reduction of 50% compared to its individual modules.

Afridi, Khurram K.↗
NASA NTRS2011

Evaluation of High Density Air Traffic Operations with Automation for Separation Assurance, Weather Avoidance and Schedule Conformance

In this paper we discuss the development and evaluation of our prototype technologies and procedures for far-term air traffic control operations with automation for separation assurance, weather avoidance and schedule conformance. Controller-in-the-loop simulations in the Airspace Operations Laboratory at the NASA Ames Research Center in 2010 have shown very promising results. We found the operations to provide high airspace throughput, excellent efficiency and schedule conformance. The simulation also highlighted areas for improvements: Short-term conflict situations sometimes resulted in separation violations, particularly for transitioning aircraft in complex traffic flows. The combination of heavy metering and growing weather resulted in an increased number of aircraft penetrating convective weather cells. To address these shortcomings technologies and procedures have been improved and the operations are being re-evaluated with the same scenarios. In this paper we will first describe the concept and technologies for automating separation assurance, weather avoidance, and schedule conformance. Second, the results from the 2010 simulation will be reviewed. We report human-systems integration aspects, safety and efficiency results as well as airspace throughput, workload, and operational acceptability. Next, improvements will be discussed that were made to address identified shortcomings. We conclude that, with further refinements, air traffic control operations with ground-based automated separation assurance can routinely provide currently unachievable levels of traffic throughput in the en route airspace.

Prevot, Thomas↗
NASA NTRS2011

An overview of the V&V of Flight-Critical Systems effort at NASA

As the US is getting ready for the Next Generation (NextGen) of Air Traffic System, there is a growing concern that the current techniques for verification and validation will not be adequate for the changes to come. The JPDO (in charge of implementing NextGen) has given NASA a mandate to address the problem and it resulted in the formulation of the V&V of Flight-Critical Systems effort. This research effort is divided into four themes: argument-based safety assurance, distributed systems, authority and autonomy, and, software intensive systems. This paper presents an overview of the technologies that will address the problem.

validation↗
DOE OSTI2025

Cool rooms for indoor heat resilience: Evaluating affordable cooling strategies in heat-stressed California homes

Extreme heat conditions pose significant indoor survivability challenges for resource-constrained communities, which often lack access to cooling, have poorly insulated homes, and face compounding socioeconomic vulnerabilities. Moreover, concurrent power outages worsen health risks and heat-related illnesses. It is therefore crucial to develop innovative and affordable cooling approaches to protect vulnerable populations. This study assesses the efficacy of “cool rooms”– a designated space within a home equipped with passive and low-power active cooling measures to maintain safe indoor temperatures during extreme heat events and power disruptions. Using a physics-based building energy modeling approach, we evaluate the efficacy of various retrofit packages in maintaining thermal safety within the cool room under recent extreme heat conditions. The results indicate that passive measures can reduce 64% of hours with unmet standard effective temperatures, while the combination of passive and low-power active measures with built-in batteries further cuts this to 86%. Nevertheless, these strategies remain insufficient to maintain indoor thermal safety during extended outages. In contrast, integrating a solar-powered mini-split heat pump, whose technical potential was evaluated in this study, reduces indoor air temperatures below the 28 °C overheating threshold and significantly improves indoor habitability. The localized cool room strategy also offers potential for grid resilience by reducing peak electricity demand by up to 70% compared to whole house cooling during heat waves. The findings can inform the development of actionable heat mitigation plans and retrofit policies for residential communities with relatively low adoption of air conditioning such as warm marine climates.

Cool room↗
DOE OSTI2024

Regulations, Codes, and Standards Review for Underground Hydrogen Storage

Hydrogen continues to show promise as a viable contributor to achieving energy storage goals such as energy security and decarbonization in the United States. However, many new and expanded hydrogen use applications will require identifying methods of larger-scale storage than the solutions that currently exist for smaller storage applications. One possibility is to store large quantities of gaseous hydrogen below ground level. Underground storage of other fuels such as natural gas is already currently utilized, so much of the infrastructure and basic technologies can be used as a basis for underground hydrogen storage (UHS). A few commercial UHS facilities currently exist in the United States, including salt caverns owned and operated by Air Liquide, Linde, and Conoco Philips, but UHS is still a relatively new concept that has not been widely deployed. It is necessary to understand the safety risks and hazards associated with UHS before its use can be expanded and accepted more broadly. Many of these risks are addressed through regulations, codes, and standards (RCS) issued by governing bodies and organizations with expertise in certain hazards. This report is a review of RCS documents relevant to UHS, with a particular lens on potential technical gaps in existing guidance. These gaps may be specific to the physical properties of hydrogen or due to the different technologies relevant for hydrogen vs. natural gas storage. This is meant to be a high-level review to identify relevant documents and potential gaps. Formally addressing the individual gaps identified here within the codes and standards themselves would involve a more intensive analysis and differ based on the code or standard revision processes of the various publishing organizations. Therefore, presenting specific recommendations for revising the verbiage of the documents for UHS applications is left for future work and other publications.

08 HYDROGEN↗
NASA NTRS1977

Alternate aircraft fuels prospects and operational implications

The paper discusses NASA studies of the potentials of coal-derived aviation fuels, specifically synthetic aviation kerosene, liquid methane, and liquid hydrogen. Topics include areas of fuel production, air terminal requirements for aircraft fueling (for liquid hydrogen only), and the performance characteristics of aircraft designed to utilize alternate fuels. Energy requirements associated with the production of each of the three selected fuels are determined, and fuel prices are estimated. Subsonic commercial air transports using liquid hydrogen fuel have been analyzed, and their performance and the performance of aircraft which use commercial aviation kerosene are compared. Environmental and safety issues are considered.

Witcofski, R. D.↗
NASA NTRS1984

Power Sources Symposium, 31st, Atlantic City, NJ, June 11-14, 1984, Proceedings

The present conference on electrochemical power sources encompasses systems of such types as the thermoelectric, advanced rechargeable, lithium reserve, rechargeable, and nonrechargeable, nickel-cadmium and nickel-hydrogen rechargeable, lead-acid, nickel-zinc and nickel-iron rechargeable, nickel-cadmium and nickel-hydrogen rechargeable, and fuel cells. Attention is given to Si-Ge alloy multicouple technology, sodium-sulfur battery development status, the safety aspects of a rechargeable lithium C cell, fiber-structure electrodes for nickel-cadmium batteries, energy density improvements in Li/carbon monofluoride cells, zinc-air button cell technology, catalyzed cathodes for Li/SOCl2 cells, the effect of polymer structure on the rate capability of the lithium-iodine cell, and a methanol fuel cell powerplant.

Source record↗
NASA NTRS1987

Full-scale Transport Controlled Impact Demonstration Program

The Federal Aviation Administration (FAA) and NASA conducted a full-scale air-to-surface impact-survivable impact demonstration with a remotely piloted transport aircraft on 1 December 1984, at Edwards Air Force Base, California. The test article consisted of experiments, special equipment, and supporting systems, such as antimisting kerosene (AMK), crashworthiness structural/restraint, analytical modeling, cabin fire safety, flight data recorders, post-impact investigation, instrumentation/data acquisition systems, remotely piloted vehicle/flight control systems, range and flight safety provisions, etc. This report describes the aircraft, experiments, systems, activities, and events which lead up to the Controlled Impact Demonstration (CID). An overview of the final unmanned remote control flight and sequence of impact events are delineated. Preliminary post CID observations are presented.

Source record↗
NASA NTRS1989

Digital, Satellite-Based Aeronautical Communication

Satellite system relays communication between aircraft and stations on ground. System offers better coverage with direct communication between air and ground, costs less and makes possible new communication services. Carries both voice and data. Because many data exchanged between aircraft and ground contain safety-related information, probability of bit errors essential.

Davarian, F.↗
NASA NTRS1990

Development of the Space Station Freedom Environmental Health System

The Environmental Health System (EHS), a subsystem of the Space Station Freedom (SSF) Crew Health Care System, was established to ensure that crewmembers will have a safe and healthy environment in which to live and work. EHS is comprised of six subsystems: Microbiology, Toxicology, Water Quality, Radiological Health, Vibroacoustics, and Barothermal Physiology. Each subsystem contributes to the overall functions of the EHS including environmental planning, environmental monitoring, environmental monitoring, environmental health assessments, and operations support. The EHS will provide hardware for monitoring the air, water, and internal surfaces of Freedom, including capabilities for inflight sample collection, processing, and analysis. The closed environment of SSF, and its dependence on recycled air and water, will necessitate a reliable monitoring system to alert crewmembers if contamination levels exceed the maximum allowable limits established to ensure crew health and safety. This paper describes the functions and hardware design status of the EHS.

Richard, Elizabeth E.↗
NASA NTRS1992

Analysis of debris from Spacelab Space Life Sciences-1

Airborne microbiological and particulate contamination generated aboard Spacelab modules is a potential safety hazard. In order to shed light on the characteristics of these contaminants, microbial and chemical/particulate analyses were performed on debris vacuumed from cabin and avionics air filters in the Space Life Sciences-1 (SLS-1) module of the Space Transportation System 40 (STS-40) mission 1 month after landing. The debris was sorted into categories (e.g., metal, nonmetal, hair/fur, synthetic fibers, food particles, insect fragments, etc.). Elemental analysis of particles was done by energy dispersive analysis of x rays (metals) and Fourier transform infrared spectroscopy (nonmetals). Scanning electron micrographs were done of most particles. Microbiological samples were grown on R2A culture medium and identified. Clothing fibers dominated the debris by volume. Other particles, all attributed to the crew, resulted from abrasions and impacts during missions operations (e.g., paint chips, plastic, electronic scraps and clothing fibers). All bacterial species identified are commonly found in the atmosphere or on the human body. Bacillus sp. was the most frequently seen bacterium. One of the bacterial species, Enterobacter agglomerans, could cause illness in crew members with depressed immune systems.

Caruso, S. V.↗
NASA NTRS1993

Electric-Field Instrument With Ac-Biased Corona Point

Measurements indicative of incipient lightning yield additional information. New instrument gives reliable readings. High-voltage ac bias applied to needle point through high-resistance capacitance network provides corona discharge at all times, enabling more-slowly-varying component of electrostatic potential of needle to come to equilibrium with surrounding air. High resistance of high-voltage coupling makes instrument insensitive to wind. Improved corona-point instrument expected to yield additional information assisting in safety-oriented forecasting of lighting.

Markson, R.↗
NASA NTRS1992

First entry operations for spacecraft

First entry procedures implemented in the industrial setting are considered to identify those applicable to the situation on the SSF. Particular attention is given to consequences when these procedures are not followed. Operational scenarios for nominal first entry procedures intended to verify air quality before the crew enters the module are outlined. Components of the Environmental Health System will provide necessary monitoring capability to protect crew health and safety during the planned first entry procedures of the man-tended capability phase of the SSF program. It is apparent that first-entry scenarios have drawn heavily upon industry experience, tempered with the specific characteristics of the space flight environment.

Wilson, Steven↗
NASA NTRS1924

Testing airplane fabrics

The following considerations determine the strength of airplane fabrics: 1. maximum air forces acting on the surfaces (including local stresses); 2. tensions produced in the fabrics, in the directions of both warp and filling; 3. factor of safety required. The question of the permissible depression of the fabric as affecting the aerodynamic requirements in regard to the maintenance of shape of the section, the tenacity and extensibility of the layer of dope, its strength and its permeability to water is almost as important.

Proll, A↗