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

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

De Sitter decays to infinity

Bubbles of nothing are a class of vacuum decay processes present in some theories with compactified extra dimensions. We investigate the existence and properties of bubbles of nothing in models where the scalar pseudomoduli controlling the size of the extra dimensions are stabilized at positive vacuum energy, which is a necessary feature of any realistic model. We map the construction of bubbles of nothing to a four-dimensional Coleman-De Luccia problem and establish necessary conditions on the asymptotic behavior of the scalar potential for the existence of suitable solutions. We perform detailed analyses in the context of five-dimensional theories with metastable dS 4 x S 1 vacua, using analytic approximations and numerical methods to calculate the decay rate. We find that bubbles of nothing sometimes exist in potentials with no ordinary Coleman-De Luccia decay process, and that in the examples we study, when both processes exist, the bubble of nothing decay rate is typically faster. Our methods can be generalized to other stabilizing potentials and internal manifolds.

classical theories of gravity↗
DOE OSTI2018

Mass transport analysis for tritium removal in FHRs

Tritium control and mitigation is one of the most significant issues in Fluoride Salt-cooled Hightemperature Reactors (FHRs). To address this issue, a cross-flow tritium removal facility has been proposed to remove molecular tritium, T 2 , from the primary coolant. To model the performance of the design, a method is developed based on the logarithmic mean difference of the square root of the tritium partial pressures on the upstream side and the purging gas side. A computer code has been developed based on this global analysis method to study the effectiveness of tritium removal in such a cross-flow tritium removal facility. The code is benchmarked against experimental data from a hydrogen separation experiment in the literature and compared with the results from a code based on traditional finite volume method. Evaluation of the cross-flow tritium removal facility designed for FHR systems has also been performed. The results show how the key factors, i.e., the fluid flow rates and tritium inlet concentration affect the performance of the facility.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Comparison of the Effectiveness of Radiofrequency Ablation With Stereotactic Body Radiation Therapy in Inoperable Stage I Non-Small Cell Lung Cancer: A Systemic Review and Pooled Analysis

Purpose: To performed a systematic review and pooled analysis to compare clinical outcomes of stereotactic body radiation therapy (SBRT) and radiofrequency ablation (RFA) for the treatment of medically inoperable stage I non-small cell lung cancer. Methods and Materials: A comprehensive literature search for published trials from 2001 to 2012 was undertaken. Pooled analyses were performed to obtain overall survival (OS) and local tumor control rates (LCRs) and adverse events. Regression analysis was conducted considering each study's proportions of stage IA and age. Results: Thirty-one studies on SBRT (2767 patients) and 13 studies on RFA (328 patients) were eligible. The LCR (95% confidence interval) at 1, 2, 3, and 5 years for RFA was 77% (70%-85%), 48% (37%-58%), 55% (47%-62%), and 42% (30%-54%) respectively, which was significantly lower than that for SBRT: 97% (96%-98%), 92% (91%-94%), 88% (86%-90%), and 86% (85%-88%) (P<.001). These differences remained significant after correcting for stage IA and age (P<.001 at 1 year, 2 years, and 3 years; P=.04 at 5 years). The effect of RFA was not different from that of SBRT on OS (P>.05). The most frequent complication of RFA was pneumothorax, occurring in 31% of patients, whereas that for SBRT (grade ≥3) was radiation pneumonitis, occurring in 2% of patients. Conclusions: Compared with RFA, SBRT seems to have a higher LCR but similar OS. More studies with larger sample sizes are warranted to validate such findings.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

A new algorithm for estimating radioxenon concentrations

A new algorithm (Xcounts) is introduced for estimating the activity concentrations of the xenon isotopes 131m Xe, 133m Xe, 133 Xe, and 135 Xe using beta-gamma coincidence data. The algorithm simultaneously estimates the decay counts associated with the four xenon isotopes, background, and radon in contrast to the net-counts method that uses sequential residual removal to account for background and interreferences. Calibration data for background counts are determined from gas-background measurements and simulation. In Xcounts, the false positive count rates for 131m Xe and 133m Xe are lower than the false positive rates for 133 Xe and 135 Xe. This algorithm appears to reliably detect the metastable isotopes at lower activity levels than the net-counts method and have similar performance for the other isotopes.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Multi-modal Free-moving Data Fusion (MFDF) v1.0

Multi-modal Free-moving Data Fusion (MFDF) is a python package that implements low and high-level functionality for performing qualitative and quantitative gamma-ray imaging analyses. Such analyses enable the use of gamma-ray spectrometers and/or imagers to estimate the distribution and quantity of radiological materials in an environment. Free-moving 3D imaging requires additional information about the 3D trajectory and orientation of the system, however all of these methods can be applied to 2D static gamma-ray imaging as well. The package includes methods (MLEM and MAP) for distributed source reconstruction, methods (PSL) for point source reconstruction, the ability to ingest and utilize quantitative detector response functions (for absolute analyses), and the ability to perform 3D estimation of dose-rates from quantitative reconstructions.

Joshi, Tenzing↗
DOE OSTI2023

Los Angeles Air Force Base Vehicle-to-Grid Demonstration (Final Project Report)

Electrification of non-tactical vehicle fleets represents a key efficiency and energy security objective for the United States Department of Defense. To achieve electrification, the department targeted vehicle-to-grid services as a way to decrease the overall cost of operating the vehicle fleet and achieve rough parity with traditional internal combustion engine vehicle fleets. This report describes efforts to aggregate a fleet of bi-directional electric vehicles and charging stations to provide regulation up and regulation down in the California Independent System Operator ancillary services market. A 29-vehicle electric vehicle demonstration fleet, consisting of mixed purpose and duty vehicles such as sedans, pickups, vans, and medium-duty trucks, was deployed at the Los Angeles Air Force base. The fleet provided frequency regulation to the California Independent System Operator’s wholesale electricity market to determine the capability of recouping some of the additional costs of procuring electric vehicles and their supporting infrastructure. Lawrence Berkeley National Laboratory, with its partner Kisensum, LLC, developed the fleet scheduling, optimization, and control software to allow the vehicle fleet at the air force base to participate in the ancillary services markets. This report focuses on the control software and market interactions, the significant challenges faced and solutions devised to address them, and examines the potential of using the electric vehicle fleet as an energy storage resource for the base buildings, an application known as vehicle-tobuilding, in providing demand response and emergency backup power. The report discusses key findings related to providing frequency regulation to the California Independent System Operator market, electric vehicle fleet performance, compatibility of varying resource parameters of vehicle fleet aggregation, the need for automated methods for communicating hour-ahead energy bidding, challenges related to battery capacity and charge/discharge rates, and monthly settlement revenue.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2024

Assessment of Envelope- and Machine Learning-Based Electrical Fault Type Detection Algorithms for Electrical Distribution Grids

This study introduces envelope- and machine learning (ML)-based electrical fault type detection algorithms for electrical distribution grids, advancing beyond traditional logic-based methods. The proposed detection model involves three stages: anomaly area detection, ML-based fault presence detection, and ML-based fault type detection. Initially, an envelope-based detector identifying the anomaly region was improved to handle noisier power grid signals from meters. The second stage acts as a switch, detecting the presence of a fault among four classes: normal, motor, switching, and fault. Finally, if a fault is detected, the third stage identifies specific fault types. This study explored various feature extraction methods and evaluated different ML algorithms to maximize prediction accuracy. The performance of the proposed algorithms is tested in an emulated software–hardware electrical grid testbed using different sample rate meters/relays, such as SEL735, SEL421, SEL734, SEL700GT, and SEL351S near and far from an inverter-based photovoltaic array farm. The performance outcomes demonstrate the proposed model’s robustness and accuracy under realistic conditions.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

Herding Cats: Firm Non-Compliance in China’s Industrial Energy Efficiency Program

Here we study firm responses to a large-scale energy efficiency program in China, focusing on the quality of reporting and compliance outcomes. Using statistical methods to detect data manipulation in compliance reports, we find evidence that firms deliberately exaggerated performance during the first phase of the program (2006-2010), suggesting the high compliance rate was overstated. In its second phase (2011-2015), the number of firms in the program expanded by an order of magnitude, and the compliance rate decreased. We develop a simple model to show how the observed increase in non-compliance is consistent with reduced misreporting. Statistical tests find no evidence of manipulation in the second phase. Larger firms, especially those not controlled by the state, and firms in cities with relatively low growth were more likely to report non-compliance, which suggests a role for state control and local protectionism in shaping compliance decisions. Based on our findings, we offer several lessons for future program design.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
NASA NTRS1972

Determination of the effects of graphite material properties on ablation performance.

Application of statistical methods to the problem of identifying those material properties of artificial graphite having the strongest effect on ablation performance. Ablation performance, as determined by total length change during test, recession rate, surface temperature, surface texture, and degree of gouging, was measured on 40 different, commercially available, artificial graphites in a Mach 2 airstream having a nominal enthalpy of 2.2 MJ/kg and a stagnation pressure of 5.6 atm. Eighteen material properties were measured on these same graphites, and correlations between pairs of these material properties were developed where possible, reducing the original 18 properties to ten mutually independent properties. Multiple regression equations were formulated relating ablation performance to the reduced set of ten independent material properties, thereby identifying those material properties having the most pronounced effect on ablation performance. These regression equations reveal that for optimum ablation performance in the present environment, grain size should be small, ash content low, density and thermal conductivity high, and mean pore radius large.

Maahs, H. G.↗
NASA NTRS1985

Applications of high pressure differential scanning calorimetry to aviation fuel thermal stability research

High pressure differential scanning calorimetry (DSC) was studied as an alternate method for performing high temperature fuel thermal stability research. The DSC was used to measure the heat of reaction versus temperature of a fuel sample heated at a programmed rate in an oxygen pressurized cell. Pure hydrocarbons and model fuels were studied using typical DSC operating conditions of 600 psig of oxygen and a temperature range from ambient to 500 C. The DSC oxidation onset temperature was determined and was used to rate the fuels on thermal stability. Kinetic rate constants were determined for the global initial oxidation reaction. Fuel deposit formation is measured, and the high temperature volatility of some tetralin deposits is studied by thermogravimetric analysis. Gas chromatography and mass spectrometry are used to study the chemical composition of some DSC stressed fuels.

Neveu, M. C.↗
NASA NTRS1995

A flying qualities study of longitudinal long-term dynamics of hypersonic planes

The NASA Dryden Flight Research Center and the Technical University of Munich are cooperating in a research program to assess the impact of unstable long-term dynamics on the flying qualities of planes in hypersonic flight. These flying qualities issues are being investigated with a dedicated flight simulator for hypersonic vehicles located at NASA Dryden. Several NASA research pilots have flown the simulator through well-defined steady-level turns with varying phugoid and height mode instabilities. Th data collected include pilot ratings and comments, performance measurements, and pilot workload measurements. The results presented in this paper include design guidelines for height and phugoid mode instabilities, an evaluation of the tapping method used to measure pilot workload, a discussion of techniques developed by the pilots to control large instabilities, and a discussion of how flying qualities of unstable long-term dynamics influence control power design requirements.

Cox, T.↗
NASA NTRS1995

A Flying Qualities Study of Longitudinal Long-Term Dynamics of Hypersonic Planes

The NASA Dryden Flight Research Center and the Technical University of Munich are cooperating in a research program to assess the impact of unstable long-term dynamics on the flying qualities of planes in hypersonic flight. These flying qualities issues are being investigated with a dedicated flight simulator for hypersonic vehicles located at NASA Dryden. Several NASA research pilots have flown the simulator through well defined steady-level turns with varying phugoid and height mode instabilities. The data collected include Pilot ratings and comments, performance measurements, and Pilot workload measurements. The results presented in this paper include design guidelines for height and Phugoid mode instabilities, an evaluation of the tapping method used to measure pilot workload, a discussion of techniques developed by the pilots to control large instabilities, and a discussion of how flying qualities of unstable long-term dynamics influence control Power design requirements.

Cox, Timothy H.↗
NASA NTRS1999

Salivary Pharmacodynamics and Bioavailability of Promethazine in Human Subjects

The acute effects of exposure to microgravity include the development of space motion sickness which usually requires therapeutic intervention. The current drug of choice, promethazine (PMZ), has side effects which include nausea, drowsiness, dizziness, sedation and impaired psychomotor performance. In a ground-based study with commercial airline pilots and shuttle simulator trainers, we measured sleep and psychomotor performance variables, and physiological variables such as blood pressure and heart rate, as a function of circulating drug concentrations in the body. We evaluated a non-invasive sampling method (saliva) as a means of assessing pharmacodynamics following a single intramuscular (IM) dose of PMZ.

Putcha, Lakshmi↗
DOE OSTI2017

Autonomous Unmanned Aerial Vehicles for Examining Current and Evolving Distribution of Contamination from the FDNPP Accident - 17020

Estimates as well as subsequent measurements of the radiation released following the events at the Fukushima Daiichi Nuclear Power Plant in March 2011 place the incident as the second greatest nuclear event to have ever occurred - duly rated at the maximum of Level 7 on the INES Event Scale. The releases of radioactivity from the plant were detected worldwide, however the multi-reactor nature of the events at the FDNPP has complicated the understanding of the radionuclide release inventory and the subsequent distribution of the material. As a result of this highly-complex release scenario, it is important to understand the current and evolving state of contamination within the rapidly evolving, topographically extreme and frequently typhoon impacted environment on Japan's eastern coast. Existing systems rely either on high-altitude manned aircraft to perform such contamination surveys, correcting results to ground-level, or, on humans manually measuring the dose-rate on foot. In order to overcome the shortcomings of both methods, a low-altitude unmanned aerial vehicle (UAV) has been developed at the University of Bristol and successfully deployed to the affected areas surrounding the FDNPP. In contrast to these other methods; the use of low-altitude UAVs provides a spatial resolution previously achievable only through the deployment of humans on the ground, with the potential for significant radiation exposure. This high-resolution monitoring allows for subsequent modelling to inform our understanding of the behaviour and long-term stability of the fallout material. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Performance Analysis, Design Considerations, and Applications of Extreme-Scale In Situ Infrastructures

A key trend facing extreme-scale computational science is the widening gap between computational and I/O rates, and the challenge that follows is how to best gain insight from simulation data when it is increasingly impractical to save it to persistent storage for subsequent visual exploration and analysis. One approach to this challenge is centered around the idea of in situ processing, where visualization and analysis processing is performed while data is still resident in memory. This paper examines several key design and performance issues related to the idea of in situ processing at extreme scale on modern platforms: Scalability, overhead, performance measurement and analysis, comparison and contrast with a traditional post hoc approach, and interfacing with simulation codes. We illustrate these principles in practice with studies, conducted on large-scale HPC platforms, that include a miniapplication and multiple science application codes, one of which demonstrates in situ methods in use at greater than 1M-way concurrency.

Ayachit, Utkarsh↗
NASA NTRSDate not supplied

Onboard Doppler Compensation for Low-Rate Communications over Commercial Relay Satellites

NASA spacecraft performing scientific and exploration missions may increasingly communicate over commercial relay satellites, including those that operate at Ka-band. Ideally these spacecraft could use the same Ka-band terminal for low-rate telemetry/commanding. However, this use case presents an issue since most commercial relay systems were designed with terrestrial users in mind and cannot easily handle the Doppler effects of orbiting spacecraft. In this work we propose onboard Doppler compensation allowing spacecraft to use existing relay satellite infrastructure without modification. Specifically, we present a method for digital compensation based on a series of piecewise linear sweeps which minimizes resources used on the spacecraft’s radio. We perform orbital mechanics simulations to estimate the worst-case Doppler profiles experienced by spacecraft in several low-Earth orbits. We emulate these effects in a laboratory experiment and demonstrate the proposed technique will reduce Doppler effects by more than two orders of magnitude. The residual Doppler is small enough that modems used at commercial relay sites are able to receive error-free data even when operating at their lowest supported symbol rate.

Adam Gannon↗
NASA NTRS2003

SpaceDock: A Performance Task Platform for Spaceflight Operations

Preliminary evidence during both short- and long-duration spaceflight indicates that perceptual-motor coordination changes occur and persist in-flight. However, there is presently no in-flight method for evaluating astronaut performance on mission-critical tasks such as docking. We present a portable platform we have developed for attempting and evaluating docking, and describe the results of a pilot study wherein flight novices learned the docking task. Methods: A dual-joystick, six degrees of freedom platform-called SpaceDock-was developed to enable portable, adaptable performance testing in a spaceflight operations setting. Upon this platform, a simplified docking task was created, involving a constant rate of approach towards a docking target and requiring the user to correct translation in two dimensions and attitude orientation along one dimension (either pitch or roll). Ten flight naive subjects performed the task over a 45 min period and all joystick inputs and timings were collected, from which we could successfully reconstruct travel paths, input profiles and relative target displacements. Results: Subjects exhibited significant improvements in docking over the course of the experiment. Learning to compensate for roll-alterations was robust, whereas compensation for pitch-alterations was not in evidence in this population and relatively short training period. Conclusion: The SpaceDock platform can provide a novel method for training and testing subjects, on a spaceflight-relevant task, and can be used to examine behavioral learning, strategy use, and has been adapted for use in brain imaging experiments.

Marshburn, Thomas H.↗
NASA NTRS2007

A Simplified Approach for the Rapid Generation of Transient Heat-Shield Environments

A simplified approach has been developed whereby transient entry heating environments are reliably predicted based upon a limited set of benchmark radiative and convective solutions. Heating, pressure and shear-stress levels, non-dimensionalized by an appropriate parameter at each benchmark condition are applied throughout the entry profile. This approach was shown to be valid based on the observation that the fully catalytic, laminar distributions examined were relatively insensitive to altitude as well as velocity throughout the regime of significant heating. In order to establish a best prediction by which to judge the results that can be obtained using a very limited benchmark set, predictions based on a series of benchmark cases along a trajectory are used. Solutions which rely only on the limited benchmark set, ideally in the neighborhood of peak heating, are compared against the resultant transient heating rates and total heat loads from the best prediction. Predictions based on using two or fewer benchmark cases at or near the trajectory peak heating condition, yielded results to within 5-10 percent of the best predictions. Thus, the method provides transient heating environments over the heat-shield face with sufficient resolution and accuracy for thermal protection system design and also offers a significant capability to perform rapid trade studies such as the effect of different trajectories, atmospheres, or trim angle of attack, on convective and radiative heating rates and loads, pressure, and shear-stress levels.

Wurster, Kathryn E.↗