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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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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Deliberate Satellite Fragmentations and their Effects on the Long-Term Space Environment

Since 1964 at least 56 spacecraft and two launch vehicle upper stages have been deliberately fragmented while in Earth orbit. Many of these events have had no long-lasting effects on the near-Earth space environment, but one represents the most devastating satellite breakup in history that will pose hazards to operational spacecraft in low Earth orbit for decades to come. International space debris mitigation guidelines now call for avoiding the creation of long-lived debris from intentional satellite fragmentations. This paper summarizes the reasons for and environmental consequences of deliberate satellite fragmentations. Contrary to popular belief, only one in five deliberate fragmentations have been related to the testing of anti-satellite weapon systems, for which only one such test has occurred during the past 25 years. Other reasons for deliberate satellite fragmentations range from engineering tests to protecting national security information. Whereas the majority of deliberate satellite fragmentations have occurred in low Earth orbits, some have involved spacecraft in highly elliptical orbits. The former Soviet Union and the current Russian Federation have been responsible for 90% of all identified deliberate on-orbit satellite fragmentations.

Johnson, N. L.↗
NASA NTRSDate not supplied

Establishing Cleaning Methods for Cleanroom and Safety Suits at Remote Sites with Available Resources

"The James Webb Space Telescope (JWST) spent considerable time in multiple clean facilities during its launch campaign at the Centre Spatial Guyanais (CSG) in French Guiana. Throughout this time, it was imperative that personnel wear approved cleanroom or safety suits when working in proximity to the JWST observatory. This proved to be challenging for two reasons: 1) A large quantity of NASA cleanroom suits needed to be shipped to CSG to account for the heavy volume of NASA and ESA personnel requiring access to the clean facilities. It became evident that shipping clean suits from the US to CSG in a timely fashion during the launch campaign would be challenging. Consequently, a backup plan needed to be established to avoid running out. 2) For safety purposes, Self-Contained Atmospheric Protection Ensemble (SCAPE) and Splash suits were required for hazardous operations. Neither type of suit was cleanroom compatible; therefore, a viable cleaning process needed to be developed to ensure both types of suits met JWST’s approved cleanliness standards. The NASA Contamination Control (CC) team partnered with CSG’s S5E cleanroom and suit processing team. The teams were able to make modifications to the S5E facility to create a NASA approved makeshift clean environment where NASA cleanroom suits and CSG Splash suits were inspected, folded, and bagged for cleanroom use once they were washed and dried. Since SCAPE suits could not be cleaned using conventional methods, a procedure was developed to clean and inspect the suits by the CC team in a temporary clean environment prior to fueling. "

James Webb Space Telescope↗
NASA NTRSDate not supplied

Establishing Cleaning Methods For Cleanroom And Safety Suits At Remote Sites With Available Resources

The James Webb Space Telescope (JWST) spent considerable time in multiple clean facilities during its launch campaign at the Centre Spatial Guyanais (CSG) in French Guiana. Throughout this time, it was imperative that personnel wear approved cleanroom or safety suits when working in proximity to the JWST observatory. This proved to be challenging for two reasons: 1) A large quantity of NASA cleanroom suits needed to be shipped to CSG to account for the heavy volume of NASA and ESA personnel requiring access to the clean facilities. It became evident that shipping clean suits from the US to CSG in a timely fashion during the launch campaign would be challenging. Consequently, a backup plan needed to be established to avoid running out. 2) For safety purposes, Self-Contained Atmospheric Protection Ensemble (SCAPE) and Splash suits were required for hazardous operations. Neither type of suit was cleanroom compatible; therefore, a viable cleaning process needed to be developed to ensure both types of suits met JWST’s approved cleanliness standards. The NASA Contamination Control (CC) team partnered with CSG’s S5E cleanroom and suit processing team. The teams were able to make modifications to the S5E facility to create a NASA approved makeshift clean environment where NASA cleanroom suits and CSG Splash suits were inspected, folded, and bagged for cleanroom use once they were washed and dried. Since SCAPE suits could not be cleaned using conventional methods, a procedure was developed to clean and inspect the suits by the CC team in a temporary clean environment prior to fueling.

James Webb Space Telescope↗
NASA NTRSDate not supplied

Curating AI-Ready Datasets for Equity and Environmental Justice: A Data-Centric AI Case Study

An equitable and environmentally just community is essentialin order to avoid disproportionate burden borne by vulnerablecommunities. This need becomes pressing in the aftermathof an extreme event such as disaster or hazard when it is diffi-cult for the governing bodies to implement resource allocationas per the need. Artificial Intelligence (AI) algorithms canhelp surface Equity and Environmental Justice (EEJ) issueswhen trained on EEJ datasets. However, curating AI-readyEEJ training datasets is challenging due to differences in fac-tors such as heterogeneity, resolution, modality, and level ofexpertise in labeling. Additionally, EEJ issues involve sensi-tive information where uncertainties and errors could degradethe performance of AI algorithms. For eg. Error in seasonalcrop yield information can highly affect the prediction of an-nual crop yield. To address these challenges, Data-centricAI (DCAI) methods are employed, which enhance AI algo-rithm performance even with limited training samples. DCAIprioritizes data quality, thereby reducing the adverse effectsof uncertainties and errors during the model training process.This research proposes a novel dataset and benchmark for an-alyzing the effect of the Maui Wildfire of 2023 for Equityand Environmental Justice (EEJ) issues. The proposed datasetaligns with the concepts of DCAI such as annotation quality,data preprocessing, privacy, feature engineering, governanceand provenance. We firmly believe that the proposed datasetwould lay a foundation to implement robust and reliable mod-ern AI algorithms for addressing EEJ issues.

Paridhi Parajuli↗
NASA NTRS2011

Integration of Weather Avoidance and Traffic Separation

This paper describes a dynamic convective weather avoidance concept that compensates for weather motion uncertainties; the integration of this weather avoidance concept into a prototype 4-D trajectory-based Airborne Separation Assurance System (ASAS) application; and test results from a batch (non-piloted) simulation of the integrated application with high traffic densities and a dynamic convective weather model. The weather model can simulate a number of pseudo-random hazardous weather patterns, such as slow- or fast-moving cells and opening or closing weather gaps, and also allows for modeling of onboard weather radar limitations in range and azimuth. The weather avoidance concept employs nested "core" and "avoid" polygons around convective weather cells, and the simulations assess the effectiveness of various avoid polygon sizes in the presence of different weather patterns, using traffic scenarios representing approximately two times the current traffic density in en-route airspace. Results from the simulation experiment show that the weather avoidance concept is effective over a wide range of weather patterns and cell speeds. Avoid polygons that are only 2-3 miles larger than their core polygons are sufficient to account for weather uncertainties in almost all cases, and traffic separation performance does not appear to degrade with the addition of weather polygon avoidance. Additional "lessons learned" from the batch simulation study are discussed in the paper, along with insights for improving the weather avoidance concept. Introduction

Consiglio, Maria C.↗
NASA NTRS1997

Cockpit Displays to Support Hazard Awareness in Free Flight

Three experiments are described which each examine different aspects of the formatting and integration of cockpit displays of traffic information to support pilots in traffic avoidance planning. The first two experiments compared two-dimensional (coplanar) with three-dimensional (perspective) versions of a cockpit display of traffic information. In Experiment 1, 30 certified flight instructors flew a series of traffic conflict detection and avoidance maneuvers around an intruder aircraft, sometimes in the presence of a second intruder. The results revealed an advantage for the coplanar display, particularly when there was vertical intruder behavior. In Experiment 2, 17 instructors flew with the coplanar and perspective formats when weather information was either overlaid or displayed separately. Again performance was best with the coplanar display, particularly when the weather data were overlaid. The results of both experiments are also discussed in ten-ns of the traffic maneuver stereotypes exhibited by the pilots. Experiment 3 examined the benefits of the two different predictor elements used in the coplanar displays of Experiments 1 and 2. The study was carried out in a multitask context. These elements were both found to improve safety (reduce actual and predicted conflicts) and to reduce workload, although the different elements affected workload in different ways. Neither predictor element imposed a cost to concurrent task performance.

Wickens, Christopher D.↗
NASA NTRS2004

Characterizing the Preturbulence Environment for Sensor Development, New Hazard Algorithms and NASA Experimental Flight Planning

During the grant period, several tasks were performed in support of the NASA Turbulence Prediction and Warning Systems (TPAWS) program. The primary focus of the research was on characterizing the preturbulence environment by developing predictive tools and simulating atmospheric conditions that preceded severe turbulence. The goal of the research being to provide both dynamical understanding of conditions that preceded turbulence as well as providing predictive tools in support of operational NASA B-757 turbulence research flights. The advancements in characterizing the preturbulence environment will be applied by NASA to sensor development for predicting turbulence onboard commercial aircraft. Numerical simulations with atmospheric models as well as multi-scale observational analyses provided insights into the environment organizing turbulence in a total of forty-eight specific case studies of severe accident producing turbulence on commercial aircraft. These accidents exclusively affected commercial aircraft. A paradigm was developed which diagnosed specific atmospheric circulation systems from the synoptic scale down to the meso-y scale that preceded turbulence in both clear air and in proximity to convection. The emphasis was primarily on convective turbulence as that is what the TPAWS program is most focused on in terms of developing improved sensors for turbulence warning and avoidance. However, the dynamical paradigm also has applicability to clear air and mountain turbulence. This dynamical sequence of events was then employed to formulate and test new hazard prediction indices that were first tested in research simulation studies and then ultimately were further tested in support of the NASA B-757 turbulence research flights. The new hazard characterization algorithms were utilized in a Real Time Turbulence Model (RTTM) that was operationally employed to support the NASA B-757 turbulence research flights. Improvements in the RTTM were implemented in an effort to increase the accuracy of the operational characterization of the preturbulence environment. Additionally, the initial research necessary to create a statistical evaluation scheme for the characterization indices utilized in the RTTM was undertaken. Results of all components of this research were then published in NASA contractor reports and scientific journal papers.

Kaplan, Michael L.↗
DOE OSTI2024

Using a 1D Radially Symmetric Coda Envelope Model for Robust Moment Magnitude ( M w ) Estimation in Iraq’s Tectonically Diverse Zones

Robust estimation of moment magnitude (M w ) can be challenging for Iraq due to the strong lateral heterogeneity across diverse tectonic zones. We aim to improve moment magnitude estimation by investigating the reliability of using a 1D coda envelope model in diverse tectonic zones of different lateral effects and offer a way forward for reliable estimates of M w for small events that are difficult to waveform model. Iraq comprises two main tectonic zones: (1) the Outer platform, consisting of the northwestern Zagros fold-thrust belt and the Mesopotamian foredeep, and (2) the Inner Arabian platform which is overlain by the Iraqi desert. A simple 1D coda envelope model was used because coda waves have a low sensitivity to the source and path heterogeneity. Three separate coda calibrations were conducted to investigate the robustness of a single 1D calibration to fit the country: Whole-region calibration, Zagros calibration, and Mesopotamia calibration. In the whole-region calibration, we used stations from both the Zagros and Mesopotamia zones. In the two other calibration models, we used only stations that were in those particular zones. Ground-truth reference spectra derived from the coda spectral ratio method were used to constrain high-frequency site terms. There was no drastic difference when comparing the moment magnitudes calculated from the waveform modeling and the three calibration models. The results show that the 1D coda envelope model is a reliable method even for a region with diverse tectonic zones. Therefore, we recommend using the whole-region calibration model for moment magnitude estimation that provides more complete path coverage and avoids biases introduced by path correction failures. The proposed calibration is a fundamental step in updating the comprehensive earthquake catalog and probabilistic seismic hazard assessments for Iraq.

58 GEOSCIENCES↗
NASA NTRS1987

Application of radar for automotive collision avoidance. Volume 1: Technical report

The purpose of this project was research and development of an automobile collision avoidance radar system. The major finding was that the application of radar to the automobile collision avoidance problem deserves continued research even though the specific approach investigated in this effort did not perform adequately in its angle measurement capability. Additional findings were that: (1) preliminary performance requirements of a candidate radar system are not unreasonable; (2) the number and severity of traffic accidents could be reduced by using a collision avoidance radar system which observes a fairly wide (at least + or - 10 deg) field of view ahead of the vehicle; (3) the health radiation hazards of a probable radar design are not significant even when a large number of radar-equipped vehicles are considered; (4) effects of inclement weather on radar operation can be accommodated in most cases; (5) the phase monopulse radar technique as implemented demonstrated inferior angle measurement performance which warrants the recommendation of investigating alternative radar techniques; and (6) extended target and multipath effects, which presumably distort the amplitude and phase distribution across the antenna aperture, are responsible for the observed inadequate phase monopulse radar performance.

Lichtenberg, C. L.↗
NASA NTRS1994

Characterizing the wake vortex signature for an active line of sight remote sensor

A recurring phenomenon, described as a wake vortex, develops as an aircraft approaches the runway to land. As the aircraft moves along the runway, each of the wing tips generates a spiraling and expanding cone of air. During the lifetime of this turbulent event, conditions exist over the runway which can be hazardous to following aircraft, particularly when a small aircraft is following a large aircraft. Left to themselves, these twin vortex patterns will converge toward each other near the center of the runway, harmlessly dissipating through interaction with each other or by contact with the ground. Unfortunately, the time necessary to disperse the vortex is often not predictable, and at busy airports can severely impact terminal area productivity. Rudimentary methods of avoidance are in place. Generally, time delays between landing aircraft are based on what is required to protect a small aircraft. Existing ambient wind conditions can complicate the situation. Reliable detection and tracking of a wake vortex hazard is a major technical problem which can significantly impact runway productivity. Landing minimums could be determined on the basis of the actual hazard rather than imposed on the basis of a worst case scenario. This work focuses on using a windfield description of a wake vortex to generate line-of-sight Doppler velocity truth data appropriate to an arbitrarily located active sensor such as a high resolution radar or lidar. The goal is to isolate a range Doppler signature of the vortex phenomenon that can be used to improve detection. Results are presented based on use of a simplified model of a wake vortex pattern. However, it is important to note that the method of analysis can easily be applied to any vortex model used to generate a windfield snapshot. Results involving several scan strategies are shown for a point sensor with a range resolution of 1 to 4 meters. Vortex signatures presented appear to offer potential for detection and tracking.

Heil, Robert Milton↗
NASA NTRS2018

Utility of Visual and Auditory Warning Alerting for Traffic Avoidance During UAS Operations

This presentation covers the results of a human-in-the-loop simulation that examined the effect of caution versus warning-level alerting in the context of Unmanned Aircraft System (UAS) operations in civil airspace. Minimum Operational Performance Standards (MOPS) are currently being developed by RTCA Special Committee 228 for UAS Detect-and-Avoid (DAA) systems. Input from subject matter experts and multiple research studies have informed display requirements for DAA systems aimed at supporting timely and appropriate pilot responses to collision hazards. DAA alerting is designed to inform pilots of potential threats to DAA "well clear"; the two highest alert levels - caution and warning - indicate how soon pilot action is required and whether there is adequate time to coordinate with the air traffic controller (ATC). Additional empirical support is needed to clarify the extent to which warning-level alerting impacts DAA task performance. The present study explores the differential effects of the auditory and visual cues provided by the DAA Warning alert, and performance implications compared to caution-only alerting are discussed.

detect and avoid↗
NASA NTRS1993

Mapping the distribution of vesicular textures on silicic lavas using the Thermal Infrared Multispectral Scanner

To investigate the effect of vesicularity on TIMS (Thermal Infrared Multispectral Scanner) imagery independent of chemical variations, we studied a large rhyolitic flow of uniform composition but textural heterogeneity. The imagery was recalibrated so that the digital number values for a lake in the scene matched a calculated ideal spectrum for water. TIMS spectra for the lava show useful differences in coarsely and finely vesicular pumice data, particularly in TIMS bands 3 and 4. Images generated by ratioing these bands accurately map out those areas known from field studies to be coarsely vesicular pumice. These texture-related emissivity variations are probably due to the larger vesicles being relatively deeper and separated by smaller septa leaving less smooth glass available to give the characteristic emission of the lava. In studies of inaccessible lava flows (as on Mars) areas of coarsely vesicular pumice must be identified and avoided before chemical variations can be interpreted. Remotely determined distributions of vesicular and glassy textures can also be related to the volatile contents and potential hazards associated with the emplacement of silicic lava flows on Earth.

Ondrusek, Jaime↗
NASA NTRS1990

Cockpit display of hazardous wind shear information

Information on cockpit display of wind shear information is given in viewgraph form. Based on the current status of windshear sensors and candidate data dissemination systems, the near-term capabilities for windshear avoidance will most likely include: (1) Ground-based detection: TDWR (Terminal Doppler Weather Radar), LLWAS (Low-Level Windshear Alert System), Automated PIREPS; (2) Ground-Air datalinks: Air traffic control voice channels, Mode-S digital datalink, ACARS alphanumeric datalink. The possible datapaths for integration of these systems are illustrated in a diagram. In the future, airborne windshear detection systems such as lidars, passive IR detectors, or airborne Doppler radars may also become available. Possible future datalinks include satellite downlink and specialized en route weather channels.

Wanke, Craig↗
NASA NTRS2004

The NASA Aircraft VOrtex Spacing System (AVOSS): Concept Demonstration Results and Future Direction

Since the late 1990s the national airspace system has been recognized as approaching a capacity crisis. In the light of this condition, industry, government, user organizations, and educational institutions have been working on procedural and technological solutions to the problem. One aspect of system operations that holds potential for improvement is the separation criteria applied to aircraft for wake vortex avoidance. These criteria, applied when operations are conducted under instrument flight rules (IFR), were designed to represent safe spacing under weather conditions conducive to the longest wake hazards. It is well understood that wake behavior is dependent on meteorological conditions as well as the physical parameters of the generating aircraft. Under many ambient conditions, such as moderate crosswinds or turbulence, wake hazard durations are substantially reduced. To realize this reduction NASA has developed a proof-of-concept Aircraft VOrtex Spacing System (AVOSS). Successfully demonstrated in a realtime field demonstration during July 2000 at the Dallas Ft. Worth International Airport (DFW), AVOSS is a novel integration of weather sensors, wake sensors, and analytical wake prediction algorithms. AVOSS provides dynamic wake separation criteria that are a function of the ambient weather conditions for a particular airport, and the predicted wake behavior under those conditions. Wake sensing subsystems provide safety checks and validation for the predictions. The AVOSS was demonstrated in shadow mode; no actual spacing changes were applied to aircraft. This paper briefly reviews the system architecture and operation, reports the latest performance results from the DFW deployment, and describes the future direction of the project.

Rutishauser, David K.↗
NASA NTRSDate not supplied

A Provably Correct Floating-Point Implementation of Well Clear Avionics Concepts

The NASA DAIDALUS library provides formal definitions for Detect-and-Avoid avionics concepts such as when an aircraft is well-clear with respect to the surrounding air traffic, i.e., it does not operate in such proximity to create a collision hazard. While several properties are proven correct for DAIDALUS assuming ideal real number arithmetic, an actual implementation that uses floating-point numbers may behave unexpectedly because of round-off errors and run-time exceptions. This paper presents an experience report on the application of a formal methods toolchain to extract and verify floating-point C code from a real-valued specification of the well-clear module of DAIDALUS. This toolchain comprises the PVS theorem prover, the PRECiSA floating-point analyzer and code generator, and the Frama-C analysis suite. The generated code is automatically instrumented to detect when the control flow of the floating-point program may diverge from the ideal real number specification, and it is annotated with contracts that state the maximum accumulated round-off error. The absence of overflows is also formally verified for the generated code. In order to apply the toolchain to an industrial case study such as DAIDALUS, a formally verified pre-processing of the input specification is performed, which includes a program slicing and several semantic-preserving simplifications.

Program verification↗
NASA NTRS1988

Final results of the NASA storm hazards program

Lightning swept-flash attachment patterns and the associated flight conditions were recorded from 1980-1986 during 1496 thunderstorm penetrations and 714 direct strikes with a NASA F-1068 research airplane. These data were studied with an emphasis on lightning avoidance by aircraft and on aircraft protection design. The individual lightning attachment spots, along with crew comments and on-board photographic data were used to identify lightning swept-flash attachment patterns and the orientations of the lightning channels with respect to the airplane. The full-scale in-flight data were compared to results from scale-model arc-attachment tests. The airborne and scale-model data showed that any exterior surface of this airplane may be susceptible to direct lightning attachment. In addition, the altitudes, ambient temperatures, and the relative turbulence and precipitation levels at which the strikes occurred in thunderstorms are summarized and discussed. It was found that the peak strike rate occurred at pressure altitudes betwen 38,000 ft and 40,000 ft, corresponding to ambient temperatures colder than -40 C.

Fisher, Bruce D.↗
DOE OSTI2024

Logical Approach to Tritium Vacuum Pump Selection

Introduction Vacuum pumps are essential to the operation of tritium purification and recovery processes. However, not all vacuum pumps sold meet the requirements for tritium service. Manufacturers routinely do not fully appreciate the hazards associated with tritium, or the complex materials interactions. Therefore, a decision tree was established detailing which pump types, and certain manufacturers, are either fully compatible, limited use, or to avoid at all costs to establish a more structured and uniform approach to tritium vacuum pumps.

ANGELETTE, LUCAS↗
NASA NTRS1986

The Galileo single-event upset solution and risk assessment

The Galileo probe will be subject to radiation fields and energetic particle bombardment during its outward bound journey and in orbit around Jupiter and its moons. To avoid the occurrence and propagation of effects of single event upset (SEU) bit state changes induced by the bombardments attempts were made to harden the Galileo electronics against SEUs. The hazards are especially acute for Schottky diode and low-power Schottky TTL parts. The preventive action options which were scheduled are reviewed, noting the selection of CMOS chips as replacements for SEU-susceptible devices. The simulation and risk assessment that were performed to evaluate the potential success of the replacements are summarized, with emphasis on the data employed to ensure the accuracy of the assessments and the predicted effects of SEUs in the various Galileo subsystems.

Burdick, Garry M.↗