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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Spaceflight Safety on the North Coast of America

Spaceflight Safety (SFS) engineers at NASA Lewis Research Center (LeRC) are responsible for evaluating the microgravity fluids and combustion experiments, payloads and facilities developed at NASA LeRC which are manifested for spaceflight on the Space Shuttle, the Russian space station Mir, and/or the International Space Station (ISS). An ongoing activity at NASA LeRC is the comprehensive training of its SFS engineers through the creation and use of safety tools and processes. Teams of SFS engineers worked on the development of an Internet website (containing a spaceflight safety knowledge database and electronic templates of safety products) and the establishment of a technical peer review process (known as the Safety Assurance for Lewis Spaceflight Activities (SALSA) review).

Ciancone, Michael L.↗
NASA NTRS2021

Machine Learning Based Path Planning for Improved Rover Navigation

Enhanced AutoNav (ENav), the baseline surface navigation software for NASA’s Perseverance rover, sorts a list of candidate paths for the rover to traverse, then uses the Approximate Clearance Evaluation (ACE) algorithm to evaluate whether the most highly ranked paths are safe. ACE is crucial for maintaining the safety of the rover, but is computationally expensive. If the most promising candidates in the list of paths are all found to be infeasible, ENav must continue to search the list and run time-consuming ACE evaluations until a feasible path is found. In this paper, we present two heuristics that, given a terrain heightmap around the rover, produce cost estimates that more effectively rank the candidate paths before ACE evaluation. The first heuristic uses Sobel operators and convolution to incorporate the cost of traversing high-gradient terrain. The second heuristic uses a machine learning (ML) model to predict areas that will be deemed untraversable by ACE. We used physics simulations to collect training data for the ML model and to run Monte Carlo trials to quantify navigation performance across a variety of terrains with various slopes and rock distributions. Compared to ENav's baseline performance, integrating the heuristics can lead to a significant reduction in ACE evaluations and average computation time per planning cycle, increase path efficiency, and maintain or improve the rate of successful traverses. This strategy of targeting specific bottlenecks with ML while maintaining the original ACE safety checks provides an example of how ML can be infused into planetary science missions and other safety-critical software.

Yue, Yisong↗
NASA NTRS2012

Safety Risk Knowledge Elicitation in Support of Aeronautical R and D Portfolio Management: A Case Study

Aviation is a problem domain characterized by a high level of system complexity and uncertainty. Safety risk analysis in such a domain is especially challenging given the multitude of operations and diverse stakeholders. The Federal Aviation Administration (FAA) projects that by 2025 air traffic will increase by more than 50 percent with 1.1 billion passengers a year and more than 85,000 flights every 24 hours contributing to further delays and congestion in the sky (Circelli, 2011). This increased system complexity necessitates the application of structured safety risk analysis methods to understand and eliminate where possible, reduce, and/or mitigate risk factors. The use of expert judgments for probabilistic safety analysis in such a complex domain is necessary especially when evaluating the projected impact of future technologies, capabilities, and procedures for which current operational data may be scarce. Management of an R&D product portfolio in such a dynamic domain needs a systematic process to elicit these expert judgments, process modeling results, perform sensitivity analyses, and efficiently communicate the modeling results to decision makers. In this paper a case study focusing on the application of an R&D portfolio of aeronautical products intended to mitigate aircraft Loss of Control (LOC) accidents is presented. In particular, the knowledge elicitation process with three subject matter experts who contributed to the safety risk model is emphasized. The application and refinement of a verbal-numerical scale for conditional probability elicitation in a Bayesian Belief Network (BBN) is discussed. The preliminary findings from this initial step of a three-part elicitation are important to project management practitioners as they illustrate the vital contribution of systematic knowledge elicitation in complex domains.

Shih, Ann T.↗
NASA NTRS2017

Additive Manufacturing (AM) Activities and Non-Destructive Evaluation (NDE) at GSFC

NASA personnel will be meeting with a delegation from the Japan Aerospace Exploration Agency (JAXA) Office of Safety and Mission Assurance (OSMA) at Langley Research Center on 2217 through 3217. The purpose of the meeting is a technical interchange between NASA and JAXA to discuss Non-Destructive Evaluation (NDE) of Additive Manufacturing (AM) parts and the HALT process (relates to accelerated life testing). The visitors will be a small group of Japanese citizens. Goddard Space Flight Center (GSFC) has been asked to participate in the meeting, either in person or via teleconference. This presentation covers NDE efforts at GSFC and provides a cursory overview of AM and lab capabilities.

additive manufacturing↗
NASA NTRS1973

Directory of workers in the fire field

A directory was compiled to provide a list of workers engaged in fire research, their addresses and affiliations, and their principal fields of activity. The initial criteria for the selection of names for the directory are recent contributions to fire literature, teaching of subjects relevant to fire science, or participation in or support of fire research programs. With some exceptions, fire service personnel and fire protection engineers were excluded because directories already exist for these professionals. Also excluded are investigators engaged principally in studies of propulsion, combustion, and explosion phenomena, because these areas of study are somewhat aside from the main focus of fire research. For purposes of the directory, fire science is taken to be the body of knowledge, art, and skill related to the investigation, analysis, and interpretation of the phenomena of unwanted fires and the evaluation of materials methods, systems, and equipment related to fire safety, prevention, detection, and suppression.

Kuvshinoff, B. W.↗
NASA NTRS1987

Safety considerations in the design of manned spaceflight hardware

Some of the significant potential hazards affecting NASA's planned space-flight initiatives are discussed together with the safety design strategies they mandate. Attention is given to the role played by NASA's newly centralized safety organization during the design of manned space flight hardware and software. Prompt-effect/physical hazards include fire, explosions and depressurization, and natural and man-made space debris. Delayed-effect hazards include radiation and toxic contamination, microgravity effects, crew illness and injury, and isolation. Safety design considerations for software and hypersonic transatmospheric vehicles are evaluated.

Rodney, G. A.↗
NASA NTRS1995

Probabilistic risk assessment of the Space Shuttle. Phase 3: A study of the potential of losing the vehicle during nominal operation, volume 1

This document is the Executive Summary of a technical report on a probabilistic risk assessment (PRA) of the Space Shuttle vehicle performed under the sponsorship of the Office of Space Flight of the US National Aeronautics and Space Administration. It briefly summarizes the methodology and results of the Shuttle PRA. The primary objective of this project was to support management and engineering decision-making with respect to the Shuttle program by producing (1) a quantitative probabilistic risk model of the Space Shuttle during flight, (2) a quantitative assessment of in-flight safety risk, (3) an identification and prioritization of the design and operations that principally contribute to in-flight safety risk, and (4) a mechanism for risk-based evaluation proposed modifications to the Shuttle System. Secondary objectives were to provide a vehicle for introducing and transferring PRA technology to the NASA community, and to demonstrate the value of PRA by applying it beneficially to a real program of great international importance.

Fragola, Joseph R.↗
NASA NTRS2006

Dynamic Tunnel Usability Study: Format Recommendations for Synthetic Vision System Primary Flight Displays

A usability study evaluating dynamic tunnel concepts has been completed under the Aviation Safety and Security Program, Synthetic Vision Systems Project. The usability study was conducted in the Visual Imaging Simulator for Transport Aircraft Systems (VISTAS) III simulator in the form of questionnaires and pilot-in-the-loop simulation sessions. Twelve commercial pilots participated in the study to determine their preferences via paired comparisons and subjective rankings regarding the color, line thickness and sensitivity of the dynamic tunnel. The results of the study showed that color was not significant in pilot preference paired comparisons or in pilot rankings. Line thickness was significant for both pilot preference paired comparisons and in pilot rankings. The preferred line/halo thickness combination was a line width of 3 pixels and a halo of 4 pixels. Finally, pilots were asked their preference for the current dynamic tunnel compared to a less sensitive dynamic tunnel. The current dynamic tunnel constantly gives feedback to the pilot with regard to path error while the less sensitive tunnel only changes as the path error approaches the edges of the tunnel. The tunnel sensitivity comparison results were not statistically significant.

Arthur, Jarvis J., III↗
NASA NTRS2004

High Altitude Long Endurance Remotely Operated Aircraft - National Airspace System Integration - Simulation IPT: Detailed Airspace Operations Simulation Plan. Version 1.0

The primary goal of Access 5 is to allow safe, reliable and routine operations of High Altitude-Long Endurance Remotely Operated Aircraft (HALE ROAs) within the National Airspace System (NAS). Step 1 of Access 5 addresses the policies, procedures, technologies and implementation issues of introducing such operations into the NAS above pressure altitude 40,000 ft (Flight Level 400 or FL400). Routine HALE ROA activity within the NAS represents a potentially significant change to the tasks and concerns of NAS users, service providers and other stakeholders. Due to the complexity of the NAS, and the importance of maintaining current high levels of safety in the NAS, any significant changes must be thoroughly evaluated prior to implementation. The Access 5 community has been tasked with performing this detailed evaluation of routine HALE-ROA activities in the NAS, and providing to key NAS stakeholders a set of recommended policies and procedures to achieve this goal. Extensive simulation, in concert with a directed flight demonstration program are intended to provide the required supporting evidence that these recommendations are based on sound methods and offer a clear roadmap to achieving safe, reliable and routine HALE ROA operations in the NAS. Through coordination with NAS service providers and policy makers, and with significant input from HALE-ROA manufacturers, operators and pilots, this document presents the detailed simulation plan for Step 1 of Access 5. A brief background of the Access 5 project will be presented with focus on Steps 1 and 2, concerning HALE-ROA operations above FL400 and FL180 respectively. An overview of project management structure follows with particular emphasis on the role of the Simulation IPT and its relationships to other project entities. This discussion will include a description of work packages assigned to the Simulation IPT, and present the specific goals to be achieved for each simulation work package, along with the associated deliverables necessary to achieve these goals and the needs of other Access 5 IPTs. The simulation environment chosen for this task is then outlined. This section includes a description of the system architecture, a list of the necessary assumptions made by the Simulation IPT, and the roles, responsibilities and interactions of simulation participants. The method of simulation conduct is presented in the next section with particular emphasis on scenario development and applicability to evaluation of Step 1 HALE-ROA operations. Following, data collection and analysis methods are discussed for air traffic specialists and air vehicle control station operators. Lastly, a schedule of Step 1 simulation activities is presented for reference.

Source record↗
NASA NTRS2008

Deflection Analysis of the Space Shuttle External Tank Door Drive Mechanism

Upon observing an abnormal closure of the Space Shuttle s External Tank Doors (ETD), a dynamic model was created in MSC/ADAMS to conduct deflection analyses of the Door Drive Mechanism (DDM). For a similar analysis, the traditional approach would be to construct a full finite element model of the mechanism. The purpose of this paper is to describe an alternative approach that models the flexibility of the DDM using a lumped parameter approximation to capture the compliance of individual parts within the drive linkage. This approach allows for rapid construction of a dynamic model in a time-critical setting, while still retaining the appropriate equivalent stiffness of each linkage component. As a validation of these equivalent stiffnesses, finite element analysis (FEA) was used to iteratively update the model towards convergence. Following this analysis, deflections recovered from the dynamic model can be used to calculate stress and classify each component s deformation as either elastic or plastic. Based on the modeling assumptions used in this analysis and the maximum input forcing condition, two components in the DDM show a factor of safety less than or equal to 0.5. However, to accurately evaluate the induced stresses, additional mechanism rigging information would be necessary to characterize the input forcing conditions. This information would also allow for the classification of stresses as either elastic or plastic.

Tosto, Michael A.↗
NASA NTRS2011

Pilot/Controller Coordinated Decision Making in the Next Generation Air Transportation System

Introduction: NextGen technologies promise to provide considerable benefits in terms of enhancing operations and improving safety. However, there needs to be a thorough human factors evaluation of the way these systems will change the way in which pilot and controllers share information. The likely impact of these new technologies on pilot/controller coordinated decision making is considered in this paper using the "operational, informational and evaluative disconnect" framework. Method: Five participant focus groups were held. Participants were four experts in human factors, between x and x research students and a technical expert. The participant focus group evaluated five key NextGen technologies to identify issues that made different disconnects more or less likely. Results: Issues that were identified were: Decision Making will not necessarily improve because pilots and controllers possess the same information; Having a common information source does not mean pilots and controllers are looking at the same information; High levels of automation may lead to disconnects between the technology and pilots/controllers; Common information sources may become the definitive source for information; Overconfidence in the automation may lead to situations where appropriate breakdowns are not initiated. Discussion: The issues that were identified lead to recommendations that need to be considered in the development of NextGen technologies. The current state of development of these technologies provides a good opportunity to utilize recommendations at an early stage so that NextGen technologies do not lead to difficulties in resolving breakdowns in coordinated decision making.

Bearman, Chris↗
NASA NTRS2015

NASA Manufacturing and Test Requirements for Normally Closed Pyrovalves for Hazardous Flight Systems Applications

Pyrovalves (figure 1, Basic Pyrovalve Design and Features,) are typically lighter, more reliable, and in most cases less expensive than other types of valves. They also consume less electrical power. They are single-use devices that are used in propulsion systems to isolate propellants or pressurant gases. These fluids may be hazardous because of their toxicity, reactivity, temperature, or high pressure. Note that in the simplified block diagram below not all detail features are shown so that those of major interest are more prominent. The diagram is provided to point out the various features that are discussed in this Specification. Features of some NC parent metal valve designs may differ. In 2013, the NESC concluded an extensive study of the reliability and safety of NC parent metal valves used in payloads carried aboard ELVs. The assessment successfully evaluated technical data to determine the risk of NC parent metal valve leakage or inadvertent activation in ELV payloads. The study resulted in numerous recommendations to ensure personnel and hardware/facility safety during ground processing of ELV payloads. One of those recommendations was to establish a NASA specification for NC parent metal valves. This Specification is a result of that recommendation, which is documented in NESC-RP-10-00614.

McDougle, Stephen H.↗
NASA NTRS2019

Effects of Topography on Tropical Forest Structure Depend on Climate Context

Topography affects abiotic conditions which can influence the structure, function, and dynamics of ecological communities. An increasing number of studies have demonstrated biological consequences of fine-scale topographic heterogeneity but we have a limited understanding of how We merged high-resolution (1 sq. meter) data on topography and canopy height derived from airborne lidar with ground-based data from 15 forest plots in Puerto Rico distributed along a precipitation gradient spanning ca. 800 to 3,500 mm yr(exp -1). Ground-based data included species composition, estimated above-ground biomass (AGB), and two key functional traits (wood density and leaf mass per area, LMA) that reflect resource-use strategies and a trade-off between hydraulic safety and hydraulic efficiency. We used hierarchical Bayesian models to evaluate how the interaction between topography climate is related to metrics of forest structure (i.e., canopy height and AGB), as well as taxonomic and functional alpha- and beta-diversity. Fine-scale topography (characterized with the topographic wetness index, TWI) significantly affected forest structure and the strength (and in some cases direction) of these effects varied across the precipitation gradient. In all plots, canopy height increased with topographic wetness but the effect was much stronger in dry compared to wet forest plots. In dry forest plots, topographically wetter microsites also had higher levels of AGB but in wet forest plots, topographically drier microsites had higher AGB. Fine-scale topography influenced functional composition but had only weak or non-significant effects on taxonomic and functional alpha- and beta-diversity. For instance, community-weighted wood density followed a similar pattern to AGB across plots. We also found a marginally significant association between variation of wood density and topographic heterogeneity that depended on climate context. Synthesis: The effects of fine-scale topographic heterogeneity on tropical forest structure and composition depend on the climate context. Our study demonstrates how a stronger integration of topographic heterogeneity across precipitation gradients could improve estimates of forest structure and biomass, and may provide insight to the ways that topography might mediate species responses to drought and climate change.

Tropical dry forest↗
NASA NTRSDate not supplied

NASA HRP Food and Nutrition Risk Strategy

The Human Health Countermeasures (HHC) Element of NASA’s Human Research Program (HRP), along with other organizations within NASA, conduct research and capability developments to buy down the risk of performance decrement and crew illness due to inadequate food and nutrition. Food and nutrition are critical for health and performance both in low Earth orbit and on exploration missions. On the International Space Station (ISS), crewmembers share a defined set of pantry foods, and have limited preference and shelf-life foods (e.g. fruits and vegetables) from resupply missions. Exploration design reference missions (DRMs) will likely be more constrained than missions to ISS, where those crewmembers would be subject to a more restricted food system due to resource limitations. HRP food and nutrition research consists of studies to close the following research gaps: determination of the nutritional requirements to maintain health and performance for the defined DRMs, determining the nutrient content, safety, and acceptability of the spaceflight food system specific to DRM and vehicle constraints, development of countermeasures either within or in addition to the food system to mitigate decrements to health and performance by DRM, and the validation and integration of food system countermeasures in analogs and in flight. The current spaceflight food system is shelf-stable, consisting of freeze-dried foods, thermostabilized foods, natural form foods, and powdered beverages. Crops represent a food system countermeasure that has the potential to supplement the pre-packaged food system. As an applied research program, HRP goals for crop research are centered around three main themes: nutrition, safety, and acceptability. As crops advance through Crop Readiness Level evaluations, HHC partners with the sponsoring organization to ensure that HRP goals are met for crops to be consumed in spaceflight.

food↗
NASA NTRS1999

Development, Analysis and Testing of the High Speed Research Flexible Semispan Model

This report presents the work performed by Lockheed Martin Engineering and Sciences (LMES) in support of the High Speed Research (HSR) Flexible Semispan Model (FSM) wind-tunnel test. The test was conducted in order to assess the aerodynamic and aeroelastic character of a flexible high speed civil transport wing. Data was acquired for the purpose of code validation and trend evaluation for this type of wing. The report describes a number of activities in preparing for and conducting the wind-tunnel test. These included coordination of the design and fabrication, development of analytical models, analysis/hardware correlation, performance of laboratory tests, monitoring of model safety issues, and wind-tunnel data acquisition and reduction. Descriptions and relevant evaluations associated with the pretest data are given in sections 1 through 6, followed by pre- and post-test flutter analysis in section 7, and the results of the aerodynamics/loads test in section 8. Finally, section 9 provides some recommendations based on lessons learned throughout the FSM program.

Schuster, David M.↗
NASA NTRS2017

Automated Analysis of Stateflow Models

Stateflow is a widely used modeling framework for embedded and cyber physical systems where control software interacts with physical processes. In this work, we present a framework a fully automated safety verification technique for Stateflow models. Our approach is two-folded: (i) we faithfully compile Stateflow models into hierarchical state machines, and (ii) we use automated logic-based verification engine to decide the validity of safety properties. The starting point of our approach is a denotational semantics of State flow. We propose a compilation process using continuation-passing style (CPS) denotational semantics. Our compilation technique preserves the structural and modal behavior of the system. The overall approach is implemented as an open source toolbox that can be integrated into the existing Mathworks Simulink Stateflow modeling framework. We present preliminary experimental evaluations that illustrate the effectiveness of our approach in code generation and safety verification of industrial scale Stateflow models.

Stateflow↗