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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Ultra-narrow-linewidth hybrid-integrated self-injection locked laser at 780 nm

Narrow-linewidth lasers are essential across a wide range of applications, including classical and quantum sensing, trapped ion systems, position/navigation/timing systems, optical clocks, and microwave frequency synthesizers. In the visible and near-visible spectrum, low-noise lasers are particularly important for laser trapping and cooling techniques, which are vital for trapped ion quantum computing, sensing, and atomic clocks. In this context, our work showcases a hybrid-integrated narrow-linewidth laser that operates at 780 nm, achieving a self-heterodyne linewidth of 105 Hz. To validate the experimental results, we performed a numerical analysis that combines insights from a many-body theory applied to the gain region with a travelling-wave model to capture the laser dynamics. Our investigation further delves into how the linewidth of the self-injection locked lasers is influenced by the parameters of micro-ring resonators, aiming to assess the potential for achieving Hz-level integrated laser linewidths at 780 nm. This work not only demonstrates the technical feasibility of Hz-level narrow-linewidth lasers but also lays the groundwork for future explorations in the field.

Prokoshin, Artem (ORCID:0009000699760238)↗
NASA NTRS2005

The Small Aircraft Transportation System (SATS), Higher Volume Operations (HVO) Concept and Research

The ability to conduct concurrent, multiple aircraft operations in poor weather at virtually any airport offers an important opportunity for a significant increase in the rate of flight operations, a major improvement in passenger convenience, and the potential to foster growth of operations at small airports. The Small Aircraft Transportation System, (SATS) Higher Volume Operations (HVO) concept is designed to increase capacity at the 3400 non-radar, non-towered airports in the United States where operations are currently restricted to one-in/one-out procedural separation during low visibility or ceilings. The concept s key feature is that pilots maintain their own separation from other aircraft using air-to-air datalink and on-board software within the Self-Controlled Area (SCA), an area of flight operations established during poor visibility and low ceilings around an airport without Air Traffic Control (ATC) services. While pilots self-separate within the SCA, an Airport Management Module (AMM) located at the airport assigns arriving pilots their sequence based on aircraft performance, position, winds, missed approach requirements, and ATC intent. The HVO design uses distributed decision-making, safe procedures, attempts to minimize pilot and controller workload, and integrates with today's ATC environment. The HVO procedures have pilots make their own flight path decisions when flying in Instrument Metrological Conditions (IMC) while meeting these requirements. This paper summarizes the HVO concept and procedures, presents a summary of the research conducted and results, and outlines areas where future HVO research is required. More information about SATS HVO can be found at http://ntrs.nasa.gov.

Baxley, B.↗
DOE OSTI2023

Deep neural operators can predict the real-time response of floating offshore structures under irregular waves

The use of neural operators in a digital twin model of an offshore floating structure holds the potential for a significant shift in the prediction of structural responses and health monitoring, offering valuable real-time control insights. In this work, we investigate the effectiveness of three neural operators, namely the deep operator network (DeepONet), the Fourier neural operator (FNO), and the Wavelet neural operator (WNO), to accurately capture the responses of a floating structure under six different sea state codes (3 − 8) based on the wave characteristics described by the World Meteorological Organization (WMO). To further enhance the accuracy of the vanilla architecture of the neural operators, novel extensions, such as wavelet-DeepONet and self-adaptive WNO, are proposed in this paper. The results demonstrate that these high-precision neural operators can deliver structural responses more efficiently, up to two orders of magnitude faster than a dynamic analysis using conventional numerical solvers. Additionally, compared to gated recurrent units (GRUs), a commonly used recurrent neural network for time-series estimation, neural operators are both more accurate and efficient, especially in situations with limited data availability. Taken together, our study shows that FNO outperforms all other operators for approximating the mapping of one input functional space to the output space as well as for responses that have small bandwidth of the frequency spectrum. Conversely, DeepONet, with historical states, proves most accurate in learning the mapping of multiple input functions to the output space and capturing responses within a broad frequency spectrum.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1974

Analysis of self-oscillating dc-to-dc converters

The basic operational characteristics of dc-to-dc converters are analyzed along with the basic physical characteristics of power converters. A simple class of dc-to-dc power converters are chosen which could satisfy any set of operating requirements, and three different controlling methods in this class are described in detail. Necessary conditions for the stability of these converters are measured through analog computer simulation whose curves are related to other operational characteristics, such as ripple and regulation. Further research is suggested for the solution of absolute stability and efficient physical design of this class of power converters.

Burger, P.↗
NASA NTRSDate not supplied

Promoting Crew Autonomy in a Human Spaceflight Earth Analog Mission through Self-Scheduling

Deep space exploration missions face the challenge of communication transmission latencies between ground stations and astronaut crews due to increasing distance between the Earth and spacecraft in transit. To address this, research at NASA has aimed toward supporting crew autonomy by enabling astronauts to schedule their own timelines with minimal oversight from Mission Control. While self-scheduling has been shown to be feasible, it is yet to be studied as an integral part of autonomous crew operations. The current paper reviews the operationalization of self-scheduling and a number of related objectives during Campaign 6 of HERA, a Human Exploration Research Analog. Research objectives include studying the effects of phasic autonomy over the course of a 45-day mission, evaluating differences in scheduling performance produced by software interface aids, and deploying a novel measure of crew attitudes toward self-scheduling and plan execution.

crew autonomy↗
NASA NTRSDate not supplied

Promoting Crew Autonomy in a Human Spaceflight Earth Analog Mission through Self-Scheduling

Deep space exploration missions face the challenge of communication transmission latencies between ground stations and astronaut crews due to increasing distance between the Earth and spacecraft in transit. To address this, research at NASA has aimed toward supporting crew autonomy by enabling astronauts to schedule their own timelines with minimal oversight from Mission Control. While self-scheduling has been shown to be feasible, it is yet to be studied as an integral part of autonomous crew operations. The current paper reviews the operationalization of self-scheduling and a number of related objectives during Campaign 6 of HERA, a Human Exploration Research Analog. Research objectives include studying the effects of phasic autonomy over the course of a 45-day mission, evaluating differences in scheduling performance produced by software interface aids, and deploying a novel measure of crew attitudes toward self-scheduling and plan execution.

crew autonomy↗
DOE OSTI2023

AI-ENABLED MONITORING OPTIONS TOWARDS SECURE MICROREACTOR DEPLOYMENT AND OPERATIONS

Global nuclear energy deployment scenarios suggest favorable economics for smaller, more versatile, and self-contained reactor technologies. Recognizing their key features as integrated, autonomous and either semi-remotely operated or fully remotely operated systems, microreactors are expected to be deployed in large numbers servicing off/micro-grids, many in geographically remote locations. Integrated nature of these systems as well as ease of their transportation as complete units, simplified installation and relocation/decommissioning challenge traditional continuity-of-knowledge practices used for conventional light water reactors where refueling is done onsite at designated times only replacing portions of their cores and only after their full commissioning for operations including completion of their containment building with security and safeguards measures in place. This effort is exploring AI (artificial intelligence)-enabled monitoring options that would be design agnostic and would assure secure unit deployment and operations. The principle is to maintain situational awareness via real-time evaluations of simultaneous and remotely transmitted monitoring data capturing key safeguards attributes including such characteristics as temperature, radiation, vibrational signals (inter alia), and others. The key principle is to provide reliable and resilient security options while maintaining simplified and economical deployment. The paper will review feasible options for AI-enabled solutions for such evaluations.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1994

A rose by any other name: Certification seen as process rather than content

Green (1990) believes that the two main factors safeguarding flying from human error are both related to certification and regulation. First is the increasingly proceduralized nature of flying whereby as much as possible is reduced to a rule-based activity. Second is the emphasis placed upon training and competency checking of aircrew in simulators and in the air, both generally and for all particular types of aircraft flown. This leaves, believes Green, other human factors that are relatively unaddressed as yet and which can give rise to human reliability problems. These include: hardware factors and especially pilot/co-pilot relationships; and system factors including fatigue and cost/safety trade-offs. He also, importantly, identifies problems with the integration of the 'electronic crew member' following increased automation. Human reliability failures with artificial intelligence and automation, due to over-reliance on the system fail-safe mechanisms, or to operator under- confidence in the integrity or self-regulating capacity of the system, or to out-of-loop effects, are widely accepted as being due to deficiencies in plant design, planning, management and maintenance more than to 'operator error' - Reason's (1990) latent error or organization pathogens argument. Reliability failures in complex systems are well enough documented to give cause for concern and at least promote a debate on the merits of a full certification program. The purpose of this short paper is to seek out and explore what is valuable in certification, at the least to show that the benefits outweigh the disadvantages and at best to identify positive outcomes perhaps not obtainable in other ways. On both sides of the debate on certification there is general agreement on the need for a better human factors perspective and effort in complex aviation systems design. What is at issue is how this is to be promoted. It is incumbent upon opponents of certification to say how else such promotion be enabled. This is an exploratory and philosophical review, not a focused and specific one, and it will draw upon much that is not firmly in the domain of complex aviation systems.

Wilson, John R.↗
NASA NTRSDate not supplied

Predicting Team Functioning in Long Term Space Missions Using Acoustic and Linguistic Measures

Maintaining optimal team functioning is critical for long-duration space exploration missions, yet traditional monitoring methods, such as self-reports and wearable sensors, often impose operational burdens or suffer from bias. This paper investigates a non-intrusive speech-based artificial intelligence (AI) framework to predict degradations in team functioning using data from the Human Exploration Research Analog (HERA) of the U.S. National Aeronautics and Space Administration (NASA). Using acoustic features, linguistic descriptors, and semantic embeddings, we evaluate static non-linear and temporal machine learning models to predict both objective (task accuracy) and subjective (self-reported efficacy and cohesion) team functioning outcomes. Results indicate that temporal models outperform static approaches, with prediction of objective task accuracy in Team Interaction Battery (TIB) improving from near chance to 71%. Self-reported outcomes, including team efficacy and cohesion, are predicted more reliably than task performance, achieving balanced accuracies of up to 85.56% and 78.12%, respectively, and are found to be most strongly associated with acoustic features. In a second interdependent task, the MMSEV–EVA, accuracies of up to 78% are achieved using temporal models with acoustic features. Furthermore, incorporating just 1–2 days of team-specific historical data systematically improved performance, and acoustic markers from informal pre-task interactions provided modest predictive gains. Finally, while automated preprocessing yielded viable accuracy, humancorrected data provided moderate performance gains, though transcription error rates did not significantly correlate with model performance. These findings highlight the potential of speech as a passive, high-fidelity monitoring tool for autonomous habitats.

Temporal modeling↗
NASA NTRS2014

Team Electronic Gameplay Combining Different Means of Control

Disclosed are methods and apparatuses provided for modifying the effect of an operator controlled input device on an interactive device to encourage the self-regulation of at least one physiological activity by a person different than the operator. The interactive device comprises a display area which depicts images and apparatus for receiving at least one input from the operator controlled input device to thus permit the operator to control and interact with at least some of the depicted images. One effect modification comprises measurement of the physiological activity of a person different from the operator, while modifying the ability of the operator to control and interact with at least some of the depicted images by modifying the input from the operator controlled input device in response to changes in the measured physiological signal.

Pope, Alan T.↗
DOE OSTI2017

Symptoms and the use of wireless communication devices: A prospective cohort study in Swiss adolescents

Background: We investigated whether radiofrequency electromagnetic fields (RF-EMF) from mobile phones and other wireless devices or by the wireless device use itself due to non-radiation related factors in that context are associated with an increase in health symptom reports of adolescents in Central Switzerland. Methods: In a prospective cohort study, 439 study participants (participation rate: 36.8%) aged 12–17 years, completed questionnaires about their mobile and cordless phone use, their self-reported symptoms and possible confounding factors at baseline (2012/2013) and one year later (2013/2014). Operator recorded mobile phone data was obtained for a subgroup of 234 adolescents. RF-EMF dose measures considering various factors affecting RF-EMF exposure were computed for the brain and the whole body. Data were analysed using a mixed-logistic cross-sectional model and a cohort approach, where we investigated whether cumulative dose over one year was related to a new onset of a symptom between baseline and follow-up. All analyses were adjusted for relevant confounders. Results: Participation rate in the follow-up was 97% (425 participants). In both analyses, cross-sectional and cohort, various symptoms tended to be mostly associated with usage measures that are only marginally related to RF-EMF exposure such as the number of text messages sent per day (e.g. tiredness: OR:1.81; 95%CI:1.20–2.74 for cross-sectional analyses and OR:1.87; 95%CI:1.04–3.38 for cohort analyses). Outcomes were generally less strongly or not associated with mobile phone call duration and RF-EMF dose measures. Conclusions: Stronger associations between symptoms of ill health and wireless communication device use than for RF-EMF dose measures were observed. Such a result pattern does not support a causal association between RF-EMF exposure and health symptoms of adolescents but rather suggests that other aspects of extensive media use are related to symptoms. - Highlights: • This is a prospective cohort study with approximately one year of follow-up. • Self-reported and operator recorded mobile phone use data were collected. • The cumulative RF-EMF dose for the brain and for the whole body was calculated. • Associations were stronger for the use of wireless devices than for RF-EMF dose. • This suggests that rather aspects of extensive media use than RF-EMF are related to symptoms.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Development of Temperature Compensation Tools for SPNDs Operating in High Temperature Environments

Two rhodium-based self-powered neutron detectors (Rh-SPNDs) were irradiated at the Massachusetts Institute of Technology Reactor as a follow-on experiment to the heated irradiation previously conducted at the Neutron Radiography facility at Idaho National Laboratory. The experiment was conducted over the temperature ranges of 600-850°C to further examine the effects of temperature on the Rh-SPNDs. Four tests of varying temperature and power were performed. The tests identified two types of temperature effects consistent with historical evaluations. One effect is a prompt proportionality to temperature at steady-state reactor power due to the decrease in Rh-SPND insulation resistance. The other effect is a delayed effect generated from displacement currents generated by changing the space charge within the insulator as a function of temperature. The result of this experiment demonstrates a characterizable responses to temperature that is feasible for developing a temperature compensation tool for SPND operating in high temperatures. The characteristics identified in this experiment will be integrated within the delayed-response compensation techniques for FY23 evaluation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Radiation transport in kinetic simulations and the influence of photoemission on electron current in self-sustaining discharges

A kinetic description for electronic excitation of helium for principal quantum number n $\leqslant $ 4 has been included into a particle-in-cell (PIC) simulation utilizing direct simulation Monte Carlo (DSMC) for electron-neutral interactions. The excited electronic levels radiate state-dependent photons with wavelengths from the extreme ultraviolet (EUV) to visible regimes. Photon wavelengths are chosen according to a Voigt distribution accounting for the natural, pressure, and Doppler broadened linewidths. This method allows for reconstruction of the emission spectrum for a non-thermalized electron energy distribution function (EEDF) and investigation of high energy photon effects on surfaces, specifically photoemission. A parallel plate discharge with a fixed field (i.e. space charge neglected) is used to investigate the effects of including photoemission for a Townsend discharge. When operating at a voltage near the self-sustaining discharge threshold, it is observed that the electron current into the anode is higher when including photoemission from the cathode than without even when accounting for self-absorption from ground state atoms. As a result, the photocurrent has been observed to account for as much as 20% of the total current from the cathode under steady-state conditions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1978

Manned maneuvering unit: User's guide

The space shuttle will provide an opportunity to extend and enhance the crew's inherent capabilities in orbit by allowing them to operate effectively outside of their spacecraft by means of extravehicular activity. For this role, the shuttle crew will have a new, easier to don and operate space suit with integral life support system, and a self-contained propulsive backpack. The backpack, called the manned maneuvering unit, will allow the crew to operate beyond the confines of the Shuttle cargo bay and fly to any part of their own spacecraft or to nearby free-flying payloads or structure. This independent mobility will be used to support a wide variety of activities including free-space transfer of cargo and personnel, inspection and monitoring of orbital operations, and construction and assembly of large structures in orbit.

Lenda, J. A.↗
NASA NTRS2002

Aeroelastic Calculations of Quiet High- Speed Fan Performed

An advanced high-speed fan was recently designed under a cooperative effort between the NASA Glenn Research Center and Honeywell Engines & Systems. The principal design goals were to improve performance and to reduce fan noise at takeoff. Scale models of the Quiet High-Speed Fan were tested for operability, performance, and acoustics. During testing, the fan showed significantly improved noise characteristics, but a self-excited aeroelastic vibration known as flutter was encountered in the operating range. Flutter calculations were carried out for the Quiet High-Speed Fan using a three-dimensional, unsteady aerodynamic, Reynolds-averaged Navier-Stokes turbomachinery code named "TURBO." The TURBO code can accurately model the viscous flow effects that can play an important role in various aeroelastic problems such as flutter with flow separation, flutter at high loading conditions near the stall line (stall flutter), and flutter in the presence of shock and boundary-layer interaction. Initially, calculations were performed with no blade vibrations. These calculations were at a constant rotational speed and a varying mass flow rate. The mass flow rate was varied by changing the backpressure at the exit boundary of the computational domain. These initial steady calculations were followed by aeroelastic calculations in which the blades were prescribed to vibrate harmonically in a natural mode, at a natural frequency, and with a fixed interblade phase angle between adjacent blades. The AE-prep preprocessor was used to interpolate the in-vacuum mode shapes from the structural dynamics mesh onto the computational fluid dynamics mesh and to smoothly propagate the grid deformations from the blade surface to the interior points of the grid. The aeroelastic calculations provided the unsteady aerodynamic forces on the blade surface due to blade vibrations. These forces were vector multiplied with the structural dynamic mode shape to calculate the work done on the blade during one vibration period, then this result was converted to an aerodynamic damping. Flutter occurs when the aerodynamic damping becomes negative, if structural damping is ignored. The results of these aeroelastic calculations are summarized in this plot of aerodynamic damping versus mass flow rate at a constant rotational speed. As the backpressure is increased, the mass flow rate through the fan decreases and the fan operating point moves towards the stall line. The aeroelastic calculations showed that the aerodynamic damping decreases as the stall line is approached, as observed during testing. In addition, the aeroelastic calculations with the TURBO code correctly predicted the aeroelastic parameters: the most unstable vibration mode and interblade phase angle, as observed during testing. The Quiet High-Speed Fan demonstrated significant noise reductions during testing, but flutter imposed limits on its operating range. The accurate calculation of the aeroelastic characteristics using the TURBO code is a significant step toward eliminating flutter from the operating range and toward realizing the benefits of reduced fan noise. The aeroelastic calculations described here were performed under a grant by University of Toledo researchers in collaboration with Glenn's researchers.

Bakhle, Milind A.↗
NASA NTRS1991

Simulation of extra-vehicular activity (EVA) self-rescue

Self-rescue during EVA is examined in terms of the use of a hand-held thruster that is similar to the hand-held maneuvering units HHMU developed for earlier programs. The problem of assessing velocity-increment requirements is addressed by means of examples of simulation technologies for studying EVA. The technologies evaluated include virtual reality systems such as the Virtual Interactive Environment Workstation (VIEW) and the Space Operations Simulator, and standard approaches like the air-bearing floor and the space shuttle. The VIEW is employed for a study of five trained NASA subjects that conduct a simulated return to a spacecraft with an HMMU under variable conditions. The study demonstrates the efficacy of VIEW for obtaining fuel-consumption values, and separation velocity is identified as the most significant determinant of the fuel and time requirements for a self-rescue operation.

Brody, Adam R.↗