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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Predicting Spacecraft Trajectories

Calculations include drag, nonsphericity, and other perturbations. Artificial Satellite Analysis Program (ASAP) is general orbit-prediction program that incorporates sufficient orbit-modeling accuracy for mission design, maneuver analysis, and mission planning. Suitable for studying planetary orbit missions with spacecraft trajectories of exploratory (mapping) nature. Sample data included for study of drift cycle of geosynchronous station, strategy for mapping Venus by radar, frozen orbit about Mars, and repeat-ground-trace orbit. ASAP written in FORTRAN 77.

Kwok, J.↗
DOE OSTI2017

Lawrence Livermore National Laboratory FY 2016 Laboratory Directed Research and Development Annual Report

The LDRD annual report for FY2016 consists of two parts: The Overview. This section contains a broad description of the LDRD Program, highlights of recent accomplishments and awards, Program statistics, and the LDRD portfolio-management processes. Project Reports. Project reports are submitted by all principal investigators at the end of the fiscal year. The length and depth of the report depends on the project’s lifecycle. For projects that will be continuing the following year, the principal investigator submits a continuing project report, which is a brief update containing descriptions of the goals, scope, motivation, relevance (to DOE/NNSA and Livermore mission areas), and technical progress achieved in FY16, as well as a list of selected publications and presentations that resulted from the research. For projects that concluded in FY16, a more detailed final report is provided that is technical in nature and includes the background, objectives, scientific approach, accomplishments, and impacts on the Laboratory missions, as well as a list of publications and presentations that resulted from the research. Project reports are listed under their research topics and organized by year and type, such as exploratory research (ER), feasibility study (FS), laboratory-wide competition (LW), and strategic initiative (SI). Each project is assigned a unique tracking code, an identifier that consists of three elements. The first is the fiscal year in which the project began, the second represents the project type, and the third identifies the serial number of the project for that fiscal year. For example, 16-ERD-100 means the project is an exploratory research project that began in FY16. The three-digit number (100) represents the serial number for the project.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Optimal redesign study of the harm wing

The purpose of this project was to investigate the use of optimization techniques to improve the flutter margins of the HARM AGM-88A wing. The missile has four cruciform wings, located near mid-fuselage, that are actuated in pairs symmetrically and antisymmetrically to provide pitch, yaw, and roll control. The wings have a solid stainless steel forward section and a stainless steel crushed-honeycomb aft section. The wing restraint stiffness is dependent upon wing pitch amplitude and varies from a low value near neutral pitch attitude to a much higher value at off-neutral pitch attitudes, where aerodynamic loads lock out any free play in the control system. The most critical condition for flutter is the low-stiffness condition in which the wings are moved symmetrically. Although a tendency toward limit-cycle flutter is controlled in the current design by controller logic, wing redesign to improve this situation is attractive because it can be accomplished as a retrofit. In view of the exploratory nature of the study, it was decided to apply the optimization to a wing-only model, validated by comparison with results obtained by Texas Instruments (TI). Any wing designs that looked promising were to be evaluated at TI with more complicated models, including body modes. The optimization work was performed by McIntosh Structural Dynamics, Inc. (MSD) under a contract from TI.

Mcintosh, S. C., Jr.↗
NASA NTRS1992

LOP - Long-Term Orbit Predictor

Long-Term Orbit Preditor (LOP) trajectory-propagation computer program is useful tool in analysis of lifetime of orbiting spacecraft. Suitable for studying planetary-orbit missions with reconnaissance (flyby) and exploratory (mapping) trajectories. Includes sample data for study of drift cycle of geosynchronous station, strategy for radar mapping of Venus, frozen orbit about Mars, and orbit characterized by repeating ground trace. Executed faster than such programs based on Cowell's method. Written in FORTRAN 77.

Kwok, Johnny H.↗
DOE OSTI2023

Exploratory analysis of machine learning techniques in the Nevada geothermal play fairway analysis

Play fairway analysis (PFA) is commonly used to generate geothermal potential maps and guide exploration studies, with a particular focus on locating and characterizing blind geothermal systems. This study evaluates the application of machine learning techniques to PFA in the Great Basin region of Nevada. Following the evaluation of various techniques, we identified two approaches to PFA that produced promising results, 1) supervised Bayesian probabilistic neural networks to generate geothermal potential maps with confidence intervals, and 2) unsupervised principal component analysis paired with k-means clustering to generate both cluster maps to help identify spatial patterns, as well as new combined feature inputs. We applied these techniques to perform a comparative analysis between two principal sets of geological and geophysical features related to permeability and heat and a set of positive (known geothermal resources) and negative training sites (known drill sites with unsuitable geothermal conditions). We found that these methods constrain previously unrecognized feature controls on geothermal favorability, many of which are spatially organized within the extent of cluster groups and the major structural-hydrologic domains of the study area. Furthermore, we utilized exploratory unsupervised modeling to highlight spatial relationships between input data and predictive output results of our supervised modeling. As a result, we demonstrate how our models compare to the previous Nevada PFA and how the rapid insights these machine learning techniques offer may support future assessments of both known and undiscovered blind geothermal systems in the Great Basin region of Nevada and beyond.

15 GEOTHERMAL ENERGY↗
DOE OSTI2019

Distributary Channel Networks as Moving Boundaries: Causes and Morphodynamic Effects

In this study, we propose an exploratory model to describe the morphodynamics of distributary channel network growth on river deltas. The interface between deep channels and the shallow, unchannelized delta front deposits is modeled as a moving boundary. Steady flow over the unchannelized delta front is friction dominated and modeled by Laplace's equation. Shear stress along the network boundary produces nonlinear erosion rates at the interface, causing the boundary to move and network elements (channels and branches) to form. The model was run for boundary conditions resembling the Wax Lake Delta in coastal Louisiana, 20 parameterizations of sediment transport, and 3 parameterizations of discharge. In each case, the model produced a complex channel network with channel number, width, bifurcation angle, and channel shape depending on the sediment transport formula. For reasonable sediment transport parameters and gradually increasing water discharge, the model produced network characteristics and progradation rates similar to theWax Lake Delta. Lastly, this suggests that the model contains the processes responsible for network growth, despite its abstract formulation.

58 GEOSCIENCES↗
DOE OSTI2025

Exploring Water System Vulnerabilities in California's Central Valley Under the Late Renaissance Megadrought and Climate Change

Abstract California faces cycles of drought and flooding that are projected to intensify, but these extremes may impact water users across the state differently due to the region's natural hydroclimate variability and complex institutional framework governing water deliveries. To assess these risks, this study introduces a novel exploratory modeling framework informed by paleo and climate‐change based scenarios to better understand how impacts propagate through the Central Valley's complex water system. A stochastic weather generator, conditioned on tree‐ring data, produces a large ensemble of daily weather sequences conditioned on drought and flood conditions under the Late Renaissance Megadrought period (1550–1580 CE). Regional climate changes are applied to this weather data and drive hydrologic projections for the Sacramento, San Joaquin, and Tulare Basins. The resulting streamflow ensembles are used in an exploratory stress test using the California Food‐Energy‐Water System model, a highly resolved, daily model of water storage and conveyance throughout California's Central Valley. Results show that megadrought conditions lead to unprecedented reductions in inflows and storage at major California reservoirs. Both junior and senior water rights holders experience multi‐year periods of curtailed water deliveries and complete drawdowns of groundwater assets. When megadrought dynamics are combined with climate change, risks for unprecedented depletion of reservoir storage and sustained curtailment of water deliveries across multiple years increase. Asymmetries in risk emerge depending on water source, rights, and access to groundwater banks.

Gupta, Rohini S. [School of Civil and Environmenta↗
DOE OSTI2017

Exploratory Modeling and Simulation of the Evolutionary Dynamics of Single-Stranded RNA Virus Populations

Infection, replication and mutation govern the population dynamics of viruses and are the key mechanisms driving their evolution. In particular, RNA viruses (such as the causative agents of Ebola, Dengue, Zika, West Nile, and SARS) have the highest mutation rates which enable them to form highly diverse populations within a single host, evade immune responses and develop resistances to drugs. Understanding the complexity of virus evolution is crucial for developing reliable countermeasures. We present an exploratory simulation model to study the evolution of heterogeneous virus populations in heterogeneous cell environments. This is a unique model that operates at three scales and captures the core mechanisms of the evolutionary process. To the best of our knowledge, this is the first HPC-based simulation of its kind.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1981

Transonic flutter and gust-response tests and analyses of a wind-tunnel model of a torsion-free-wing fighter airplane

The paper reports the results of analytical and exploratory wind-tunnel studies of the transonic flutter and gust response characteristics of a 1/5.5-size complete-airplane version of a torsion-free-wing (TFW) fighter aircraft. The critical flutter mode for the TFW-free configuration was found to occur at M = 0.95 and had the rigid-TFW pitch mode as its apparent aerodynamic driver. However, the minimum dynamic flutter for the TFW-free case was only about 20% lower than for the TFW-locked; therefore the present TFW is a viable design concept with respect to flutter. The present TFW was not effective as a gust alleviator.

Ruhlin, C. L.↗
DOE OSTI2025

Robust Solution Verification Experiments on Nonuniform Meshes

The activities of verification, validation, and uncertainty quantification (VVUQ) provide a comprehensive means to assess the credibility of computational models. Within VVUQ, solution verification assesses numerical errors and evaluates whether the simulation is sufficiently accurate for its intended applications. As computational modeling gains traction in the development of complex, high-consequence systems, the need for robust solution verification intensifies, particularly because experimental data for these systems are often limited. This work examines improvements in the robustness of Richardson extrapolation (RE), a method commonly used in solution verification to study the discretization error of computational models using a power law. Nonuniform mesh refinement is discussed alongside other pollutants that affect the robustness of the power law model. Maximum likelihood estimation (MLE) is proposed as a robust strategy to address the uncertainty generated by nonuniform mesh refinement. An exploratory computational fluid dynamics (CFD) study of a 2D planar Poiseuille flow is conducted to determine if nonuniform mesh noise can be modeled with this MLE approach for more robust RE.

Weinmeister, Justin [ORNL] (ORCID:0000000160090237↗
DOE OSTI2014

Profitability of Cellulosic Biomass Production in the Northern Great Lakes Region

Producing bioenergy feedstocks on non‐crop land can largely avoid the food price feedbacks of energy biomass production on cropland. The U.S. northern tier grassland‐to‐forest ecotone offers large areas of marginal land that is not currently cropped. In this ecological transition zone, the relative profitability of grassy vs. woody sources of energy biomass is little studied. This paper reports an exploratory investment analysis of cellulosic biomass production in the northern Great Lakes region. It compares two short‐rotation tree crops, willow ( Salix sachalinensis F. Schmidt)and hybrid poplar ( Populus nigra L. X P. maximowiczii A. Henry), and switchgrass ( Panicum virgatum L.) (a native prairie grass) to conventional mixed hay. Because biomass markets are not yet well developed, this study calculates threshold prices and yields at which biomass crops become at least as profitable as mixed grass hay. At 2010–2012 prices and available production technologies, none of the cellulosic crops is competitive with the hay baseline system. The breakeven price of energy biomass ranges from $90–100 per oven‐dry Mg −1 for all three energy crops. Breakeven yields are much more variable, due to the high cost of harvesting woody biomass. At 2010–2012 prices, necessary biomass yield increases range from 3.5‐fold for switchgrass and willow to over 25‐fold for poplar. While the ratio of input costs to revenue remains relatively constant between the northern and southern Great Lakes regions, the opportunity cost of active cropland in the southern zone is much higher, implying an economic comparative advantage for marginal land of the northern tier of the Great Lakes region.

Kells, Bradley J.↗
DOE OSTI2025

Using feature importance as an exploratory data analysis tool on Earth system models

Abstract. Machine learning (ML) models are commonly used to generate predictions, but these models can also support the discovery of new science. Generating accurate predictions necessitates that a model captures the structure of the underlying data. If the structure is properly extracted, ML could be a useful exploratory and evidential tool. In this paper, we present a case study that demonstrates the use of ML for exploratory data analysis (EDA) in the climate space. We apply the ML explainability method of spatiotemporal zeroed feature importance (stZFI) to understand how climate-variable associations evolve over space and time. Our analyses focus on data from ensembles of Earth system models (ESMs) which provide data on different climate states and conditions. We elect to work with ESM ensembles since they allow us to compare feature importance across alternative scenarios not available with observed data. The ensembles also account for natural variability so that we can distinguish between signal and noise due to natural climate variability when computing feature importance. The use of perturbed initial condition ensembles introduces variability mimicking the natural variability in the atmosphere; thus the signals emerging using feature importance (FI) can be evaluated against the natural variability in the climate system. For our analyses, we consider the 1991 volcanic eruption of Mount Pinatubo, which was a large stratospheric aerosol injection. We explore the climate pathway associated with the eruption from aerosols to radiation to temperature at both the near-surface and stratospheric levels. In addition to applying the method to data generated from two different ESMs, we apply stZFI to reanalysis data to compare the associations identified by stZFI. We show how stZFI tracks the importance of aerosol optical depth over time on forecasting temperatures. This case study illustrates usefulness of an ML tool (stZFI) for EDA on a well-studied climate exemplar.

Ries, Daniel (ORCID:0000000250294647)↗
NASA NTRS1993

Prospects for future solar-wind missions

Possible activities and future goals for solar wind research in the post Soho era are discussed. Two major enterprises which will open up important fields in the future study of the Sun are addressed. The first deals with in situ study of the solar corona, a region that has not been accessible for direct study in the past. This exploratory work will include the coronal heating and the acceleration of the solar wind much closer to its origin and the determination of the charge states of a large number of ions as a diagnostic tool for fractionation processes in these regions. The second major goal will be the setting up of a baseline for the isotopic composition in the solar system by studying a sample from the Sun in detail. These studies will be complemented by a direct comparison with extra solar samples of interstellar pick up ions, which become accessible with the same instrumentation as is necessary for the detailed investigation of the solar wind's isotopic composition. In order to achieve these goals, advanced composition experiments are developed to investigate the solar wind with enhanced mass resolution, considerably increased geometrical factor, and improved time resolution. The placing of sophisticated mass/charge spectrometers, with the ability to investigate both charge and velocity distributions with enhanced time resolution, in the solar wind acceleration region, is also proposed.

Bochsler, P.↗
DOE OSTI2020

Exploratory Efforts to Constrain Geologic Material Properties from Remote Sensing Data: Joint Study (FY2020 Final Report)

Identification and characterization of underground events from surface or remote data requires a thorough understanding of the rock material properties. However, material properties usually come from borehole data, which is expensive and not always available. A potential alternative is to use topographic characteristics to approximate the strength, but this has never been done before quantitatively. Here we present the results from the first steps towards this goal. We have found that there are strong correlations between compressive and tensile strengths and slopes, but these correlations vary depending on data analysis details. Rugosity may be better correlated to strength than slope values. More comprehensive analyses are needed to fully understand the best method of predicting strength from topography for this area. We also found that misalignment of multiple GIS datasets can have a large influence on the ability to make interpretations. Lastly, these results will require further study in a variety of climatic conditions before being applicable to other sites.

58 GEOSCIENCES↗
DOE OSTI2026

From microbial diversity to functional potential using dimensionality reduction

The high dimensionality of microbial diversity data from ‘omics observations can be reduced using Machine Learning, with many recent studies showcasing ML utility for exploratory ecological feature finding and process prediction. Here, we compare the Self Organizing Map (SOM) dimensionality reduction method to the well-documented sample-based Principal Coordinate Analysis (PCoA) and taxa-based Weighted Gene Correlation Network Analysis (WGCNA) using near daily 16S rRNA gene amplicon sequencing data from the 2019 to 2020 MOSAiC International Arctic Drift Expedition. We then map k-means clustering outputs from each method to available metagenomes, extracting functionally distinct seasonal microbial ecotypes in the surface Arctic Ocean. Our results indicate the SOM method better represented expected seasonal transitions and identified a greater number of metabolically distinct functional groups than the more traditional PCoA ordination. Ultimately, we identified four community ecotypes with distinct taxonomic and functional cut-offs driven by seasonality, water mass, and substrate turnover, highlighting the importance of succession in functional diversity for the central Arctic Ocean. These results reinforce ML dimensionality reduction as a meaningful translator in the mining of historical amplicon datasets to address modern mechanistic questions and potentially provide ’omics informed ecotype diversity to leverage in mechanistic biogeochemical models.

Arctic Ocean↗
NASA NTRS1973

Space science plans for the shuttle era.

Three separate and distinct modes of using the space shuttle system have been identified. These modes include the boost of a spacecraft plus one or more propulsion stages into earth orbit or parking orbit, the establishment and maintenance of automated observatories in space, and the support of exploratory research and instrument development. Studies show that approximately 60% of all planned NASA missions require a shuttle third stage. Illustrations are presented to show how the largest spacecraft, Viking, and its propulsion system, Centaur, and a communications satellite, with an Agena stage to place it into a geostationary orbit, would fit into the shuttle. Results of the NASA Shuttle Sortie Workshop studies are discussed together with prospects of European cooperation in future workshop experiments.

Naugle, J. E.↗
NASA NTRSDate not supplied

Common Habitat Architecture

The Common Habitat is a human habitation element for inner solar system long duration (assessed up to 1200 days) space missions, inclusive of both orbital and surface missions. Exploration Science is supported by both internal laboratories and external science platforms (e.g., telescopes and other remote sensing systems). The Common Habitat is integrated with other elements needed (e.g., propulsion, heat rejection, airlock, etc.) to make the total system a spacecraft, space station, base, or other facility. The Common Habitat Architecture is an exploratory, primarily volunteer, NASA conceptual study and is NOT the current Artemis architecture. Common Habitat elements do show a similarity to some elements under development for Artemis but do not imply any relationship to, influence on, or influence by Artemis requirements, objectives, or acquisitions.

Common Habitat↗
DOE OSTI2021

Exploratory Efforts to Constrain Geologic Material Properties from Remote Sensing Data: A Joint Study

Identification and characterization of underground events from surface or remote data requires a thorough understanding of the rock material properties. However, material properties usually come from borehole data, which is expensive and not always available. A potential alternative is to use topographic characteristics to approximate the strength, but this has never been done before quantitatively. Here we present the results from the first steps towards this goal. We have found that there are strong correlations between compressive and tensile strengths and slopes, but these correlations vary depending on data analysis details. Rugosity may be better correlated to strength than slope values. More comprehensive analyses are needed to fully understand the best method of predicting strength from topography for this area. We also found that misalignment of multiple GIS datasets can have a large influence on the ability to make interpretations. Lastly, these results will require further study in a variety of climatic conditions before being applicable to other sites.

42 ENGINEERING↗