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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
NASA NTRS2015

A Framework for Orbital Performance Evaluation in Distributed Space Missions for Earth Observation

Distributed Space Missions (DSMs) are gaining momentum in their application to earth science missions owing to their unique ability to increase observation sampling in spatial, spectral and temporal dimensions simultaneously. DSM architectures have a large number of design variables and since they are expected to increase mission flexibility, scalability, evolvability and robustness, their design is a complex problem with many variables and objectives affecting performance. There are very few open-access tools available to explore the tradespace of variables which allow performance assessment and are easy to plug into science goals, and therefore select the most optimal design. This paper presents a software tool developed on the MATLAB engine interfacing with STK, for DSM orbit design and selection. It is capable of generating thousands of homogeneous constellation or formation flight architectures based on pre-defined design variable ranges and sizing those architectures in terms of predefined performance metrics. The metrics can be input into observing system simulation experiments, as available from the science teams, allowing dynamic coupling of science and engineering designs. Design variables include but are not restricted to constellation type, formation flight type, FOV of instrument, altitude and inclination of chief orbits, differential orbital elements, leader satellites, latitudes or regions of interest, planes and satellite numbers. Intermediate performance metrics include angular coverage, number of accesses, revisit coverage, access deterioration over time at every point of the Earth's grid. The orbit design process can be streamlined and variables more bounded along the way, owing to the availability of low fidelity and low complexity models such as corrected HCW equations up to high precision STK models with J2 and drag. The tool can thus help any scientist or program manager select pre-Phase A, Pareto optimal DSM designs for a variety of science goals without having to delve into the details of the engineering design process.

Earth Science↗
NASA NTRS2018

Climates of Warm Earth-Like Planets. I. 3D Model Simulations

We present a large ensemble of simulations of an Earth-like world with increasing insolation and rotation rate. Unlike previous work utilizing idealized aquaplanet congurations we focus our simulations on modern Earth-like topography. The orbital period is the same as modern Earth, but with zero obliquity and eccentricity. The atmosphere is 1 bar N2-dominated with CO2=400 ppmv and CH4=1 ppmv. The simulations include two types of oceans; one without ocean heat transport (OHT) between grid cells as has been commonly used in the exoplanet literature, while the other is a fully coupled dynamic bathtub type ocean. The dynamical regime transitions that occur as day length increases induce climate feedbacks producing cooler temperatures, rst via the reduction of water vapor with increasing rotation period despite decreasing shortwave cooling by clouds, and then via decreasing water vapor and increasing shortwave cloud cooling, except at the highest insolations. Simulations without OHT are more sensitive to insolation changes for fast rotations while slower rotations are relatively insensitive to ocean choice. OHT runs with faster rotations tend to be similar with gyres transporting heat poleward making them warmer than those without OHT. For slower rotations OHT is directed equator-ward and no high latitude gyres are apparent. Uncertainties in cloud parameterization preclude a precise determination of habitability but do not a affect robust aspects of exoplanet climate sensitivity. This is the first paper in a series that will investigate aspects of habitability in the simulations presented herein. The datasets from this study are open source and publicly available.

Planetary systems↗
NASA NTRS2019

Summary and Highlights of the SPARC-Reanalysis Intercomparison Project

The climate research community uses global atmospheric reanalysis data sets to understand a wide range of processes and variability in the atmosphere; they are a particularly powerful tool for studying phenomena that cannot be directly observed. Different reanalyses may give very different results for the same diagnostics. The Stratosphere troposphere Processes And their Role in Climate (SPARC) Reanalysis Intercomparison Project (S-RIP) is a coordinated activity to compare key diagnostics that are important for stratospheric processes and their tropospheric connections among available reanalyses. S-RIP has been identifying differences among reanalyses and their underlying causes, providing guidance on appropriate usage of reanalysis products in scientific studies (particularly those of relevance to SPARC), and contributing to future improvements in the reanalysis products by establishing collaborative links between reanalysis centres and data users. S-RIP emphasizes diagnostics of the upper troposphere, stratosphere, and lower mesosphere. The draft S-RIP final report is expected to be completed in 2018. This poster gives a summary of the S-RIP project and presents highlights including results on the Brewer-Dobson circulation, stratosphere/troposphere dynamical coupling, the extra-tropical upper troposphere / lower stratosphere, the tropical tropopause layer, the quasi-biennial oscillation, lower stratospheric polar processing, and the upper stratosphere/lower mesosphere.

Fujiwara, M.↗
NASA NTRS2015

An Integrated Physics-Based Risk Model for Assessing the Asteroid Threat

Although most asteroids and other near-Earth objects (NEOs) do not pose a threat to Earth’s inhabitants, impacts from objects that are just tens of meters in diameter can cause significant damage if they occur over a populated area. This paper forms the foundation of an effort at NASA Ames Research Center to quantify these risks and identify the greatest risk-driving parameters and uncertainties. An integrated risk model that couples dynamic probabilistic simulations of strike occurrences with physics-based models of NEO impact damage factors has been developed to generate casualty estimates for a range of NEO impact properties. Currently, the model focuses on the risk due to blast overpressure damage from airbursts and impacts on land. The model is first used to reproduce results from established sources, and then is extended to perform sensitivity studies that yield greater insights into risk driving parameters. Results show that meteor strength and entry angle play a role for small to mid-size NEOs, and that accounting for the specific target location significantly affects casualty estimates and dominates the risk. Future work will continue to refine and expand the models to better characterize key impact risk factors, include additional types of threats such as tsunamis and climate effects, and ultimately support assessments of potential asteroid mitigation strategies.

Asteroid Threat↗
NASA NTRS2015

TPSAS-NF1676L-21180-DND

Ablative materials are used as the Thermal Protection System (TPS) for space vehicles that enter a planetary atmosphere. During the entry phase, the vehicle experiences high rates of aerodynamic heating. These ablative materials, acting as a heat shield, protect the vehicle from the harsh environment and ensure a safe entry. Ablative materials reduce the incoming heat flux through various phenomena such as near-surface oxidation, pyrolysis chemical reaction, vaporization, and other erosive processes, collectively known as ablation. Spallation is one such ablative process, in which solid particles are ejected from the material into the flow field. The many conditions leading to spallation, however, are not well understood and cannot be described accurately by simple phenomenological models. However, the spallation phenomenon might impact the aerodynamic heating rates of re-entry vehicles using ablative heat shields. For example, the solid particles ejected from the surface can modify the near surface chemical processes and flow field. To investigate spallation effects, a code was developed to compute the dynamics of spalled particles. The code uses a finite-rate chemistry model to study the chemical interactions of the particles with the flow field. The spallation code is dynamically coupled to a CFD solver that models the time accurate hypersonic flow field around an ablative sample. An experimental investigation was also performed at the NASA Langley HYMETS facility. HYMETS is a 400 kW arcjet that can simulate hypersonic flight and Earth or Martian entry conditions. Using high speed cameras, an IR camera, NIR and UV-VIS spectrometers, and other diagnostic instruments, test data on various graphite, LI-900, FiberForm, and PICA test samples were obtained, using target heat flux conditions of 100, 200, and 400 W/cm 2 . From the test campaign, measurements of particle velocity, acceleration and trajectory are obtained.

A Martin↗
NASA NTRS2021

Core-Plasma Refilling and Erosion: Science Justification

Global magnetospheric models do not currently couple dynamic plasmaspheric plasma due to computational limitations that will be overcome by 2050. A true GGCM will need to include a dynamic plasmasphere for both physics and space weather prediction. Such inclusion requires that we answer longstanding, fundamental questions about the life cycle of core (<10 eV, plasmaspheric) plasma: how it gets into the inner magnetosphere, and how it is eroded. Erosion and refilling are processes controlling a fundamental space plasma population. During every geomagnetic disturbance, tens of metric tons of plasma are rapidly eroded away, then slowly and unevenly replenished. After several decades we still do not understand the cross-scale mechanisms proposed to be responsible for these 2 processes. Removal and replacement of this enormous plasma mass is as important to the dynamics of the magnetosphere as solar-wind driving. Our community must dedicate the resources and effort needed to solve this enduring puzzle. Other white papers submitted in response to the HP2050 call are discussing cold plasma and ionospheric outflow in more general contexts. This white paper deals specifically with the science justification for studying refilling and erosion.

Plasmasphere, core-plasma, erosion, refilling↗
NASA NTRS2022

Human Stability While Exercising on a VIS Device in Zero Gravity

BACKGROUND: A Vibration Isolation and Stabilization (VIS) system is being designed for use with the European Enhanced Exploration Exercise Device (E4D) [1]. The exercise bar is attached to cables that extend and retract through openings in the E4D platform, which the subject stands on while exercising. Since the E4D is mounted on a moving VIS device, the whole system moves under the subject’s feet. While tension in the cables does help stabilize a crew member in 0g by bracing him or her against the moving platform, flexible cables do not offer full support against falling. This raises the question of whether various exercises that are successfully performed in 1g on a stationary device can be performed without losing balance in 0g on a moving device. Quantifying stability conditions and establishing stability requirements for exercise countermeasure systems is a long-standing challenge and this work helped to inform this specific need for integrated E4D/VIS flight project development. METHODS AND RESULTS: A simplified stability analysis can be attempted based on platform accelerations generated by the VIS device simulation. In this type of analysis, the subject is conceived as standing on the platform in 0g while being held down to it by the tension in the cables. If the sideways acceleration of the platform is such that the cables cannot generate a sufficient moment relative to, e.g., the heels or the toes of the subject to overcome the tipping moment from the inertial forces on the accelerated subject’s body, the subject becomes unstable. This approach, which we refer to as the ‘static’ approximation, indicated failure of all the exercises that were considered in the comprehensive VIS analysis of the E4D. It was realized, however, that platform accelerations are not externally imposed but are themselves induced by the motion of the subject’s body during exercise, and a model calculation confirmed that this drastically altered the tipping moment on the subject, with the potential to even switch the direction in which the body would tip over. This made it imperative to consider in a coupled manner both the motion of the exercising subject’s body and the induced VIS platform motion while considering stability. The coupled dynamics requirement was met by the VIS simulation incorporating time-dependent human mass properties atop the platform and driven by the inertial forces from the prescribed subject motion relative to the platform based on motion-capture recorded human trajectories in 1g on a stationary E4D [2]. To analyze simulation results, a stability criterion was also needed. We do not know how to account for the human ‘control system’ that would take visual and vestibular cues as inputs as the platform moves in 0g. We thus chose to follow an approach we had previously used to analyze the dynamic feasibility of performing a task in lunar gravity along the human body trajectory recorded in 1g [3]. In this approach, one analyzes the center of pressure (COP) between the shoes and the ground (or platform) and checks if the COP remains within the convex hull of the footprints on the ground (or platform), commonly referred to as base of support (BOS). Since pressure is vertical and, in the absence of foot restraints, positive, the COP going outside the BOS indicates that the trajectory recorded in 1g is not dynamically feasible in microgravity and/or on the moving platform of the device. The outcome of the COP-based analysis was that some of the key exercises, especially the deadlift and the back squat exercises, were found to be dynamically feasible for at least some number of the exercise cycles, this number increasing with the cable tension. While this type of stability analysis does not account for the likely alteration of the exercise trajectory from its 1g form in space, it does show that there exist at least some realistic trajectories that pass the dynamic feasibility criterion. This adds confidence that, with further adjustment by the subject of the exercise form in 0g on a moving device, a number of exercises can be performed without losing balance.

D Frenkel↗
NASA NTRSDate not supplied

Timed Collections in the NASA Cosmic Dust Aircraft Collected Particle Collection Including Previous Collectors

The NASA Cosmic Dust Collections includes a collection of interplanetary particles gathered using high-altitude aircraft (the Aircraft Collected Particle collection, or ACP). These particles include cosmic-origin particles as well as particles of terrestrial origin such as volcanic ash, solid rocket motor effluent, and terrestrial dust. The cosmic-origin dust comes from two principal sources - material originating from the diffuse interplanetary background which are uncoupled from the orbits of larger bodies, and cometary-origin particles which are dynamically coupled with the orbits of their parent bodies to form dust streams. These dust stream particles generate short-lived, annual meteor showers and are important because, if they can be identified as originating from a given dust stream, they can be studied in the laboratory as samples of a specific comet. Collecting these particles requires dedicated ACP flights which are timed to coincide with a specific meteor shower. These “timed collections” hold the promise of providing samples from a suite of comets including those never visited by spacecraft [1-3]. This abstract describes a recent (Dec 2020) timed collection attempt, lists previous timed collections with collected particles available for request from the NASA Cosmic Dust Collections, as well as listing ACP collectors which were collected when no meteor showers were active for potential use as control samples.

cosmic dust↗
NASA NTRS2022

Introduction to Special Collection ``The Exceptional Arctic Stratospheric Polar Vortex in 2019/2020: Causes and Consequences"

This paper introduces the special collection in Geophysical Research Letters and Journal of Geophysical Research: Atmospheres on the exceptional stratospheric polar vortex in 2019/2020. Papers in this collection show that the 2019/2020 stratospheric polar vortex was the strongest, most persistent, and coldest on record in the Arctic. The unprecedented Arctic chemical processing and ozone loss in spring 2020 have been studied using numerous satellite and ground-based data sets and chemistry-transport models. Quantitative estimates of chemical loss are broadly consistent among the studies and show profile loss of about the same magnitude as in the Arctic in 2011, but with most loss at lower altitudes; column loss was comparable to or larger than that in 2011. Several papers show evidence of dynamical coupling from the mesosphere down to the surface. Studies of tropospheric influence and impacts link the exceptionally strong vortex to reflection of upward propagating waves and show coupling to tropospheric anomalies, including extreme heat, precipitation, windstorms, and marine cold air outbreaks. Predictability of the exceptional stratospheric polar vortex in 2019/2020 and related predictability of surface conditions are explored. The exceptionally strong stratospheric polar vortex in 2019/2020 highlights the extreme interannual variability in the Arctic winter/spring stratosphere and the far-reaching consequences of such extremes.

Artic↗
NASA NTRSDate not supplied

Simulating the Martian Middle and Upper Atmosphere with the NASA Ames Mars GCM.

The NASA Ames Mars Global Climate Model (MGCM) continues to be utilized to examine the dynamical coupling between the lower atmosphere and middle/upper atmosphere. This coupling impacts the transport of water, dust, and chemistry which augments the thermal structure and circulation. The interactions and coupling within the atmosphere are important for understanding the present-day and past atmosphere and climate. MGCM simulations are compared with observations from recent Mars missions to provide model constraints, and in turn, the simulations can then provide context to the observations. This cycle is important to move us forward in our understanding of planetary atmospheres. We will present on one of the fundamental atmospheric features, the thermal structure, and how the physics in the MGCM can elucidate the observed diurnal and seasonal behavior. Additionally, we will focus on the distribution of chemical species which influences the thermal structure and provides additional information on the coupling between the lower and middle/upper atmosphere. Lastly, we will provide a summary of the model capabilities, as the MGCM continues to be improved upon to properly simulate Mars’ atmosphere from the ground to ~250 km.

Amanda Susanne Brecht↗
NASA NTRS2023

Connections Between Upper Tropospheric and Lower Stratospheric Circulation Responses to Increased Co 2

There are a myriad of ways atmospheric circulation responds to increased CO 2 . In the troposphere, the region of the tropical upwelling narrows, the Hadley Cells expand, and the upper level subtropical zonal winds that comprise the subtropical jet strengthen. In the stratosphere, the tropical upwelling narrows and strengthens, enhancing the Brewer-Dobson Circulation. Despite the robustness of these projections, dynamical coupling between the features remains unclear. In this study, we analyze output from the NASA Goddard Institute for Space Studies (GISS) ModelE coupled climate model to examine any connection between the upper tropospheric and lower stratospheric circulation by considering the features’ seasonality, hemispheric asymmetry, scaling, and transient response to a broad range of CO 2 forcings. We find that a narrowing and strengthening of upper tropospheric upwelling occurs with a strengthening of the subtropical jet. There is also a narrowing and strengthening of lower stratospheric upwelling that is related to an equatorward shift in critical latitude for wave breaking and the associated strengthening of the subtropical lower stratosphere’s zonal winds. However, the stratospheric responses display different seasonal, hemispheric, and transient patterns than those in the troposphere, indicating independent circulation changes between the two domains.

Molly E. Menzel↗
NASA NTRS2025

HabSim: A Modular Coupled Virtual Testbed for Simulating ExtraTerrestrial Habitat Systems

Extraterrestrial habitats involve a tightly coupled combination of hardware, software, and humans while operating in an unforgiving environment that poses many risks, both anticipated and unanticipated. Traditional approaches with such systems of systems focus on reliability, robustness, and redundancy. These approaches seek to avoid failure rather than reduce overall risk. However, faults are inevitable, and understanding and managing the complex and emergent behavior and cascading events of such a complex system is critical. This study describes the development of HabSim, a computational simulation environment intended to support research to establish the know-how to design and operate resilient and autonomous SmartHabs. HabSim is a modular virtual testbed composed of many of the coupled dynamic systems expected in a typical SmartHab. A heterogeneous set of interconnected physics-based and phenomenological models is used to represent the essential functions of a SmartHab. HabSim further considers disruptions and models damage and repair of certain components. This paper discusses a) system and subsystem requirements of the deep space habitat included in the HabSim platform; b) architectural choices made in response to the requirements; c) technical considerations for developing, verifying, configuring, and executing HabSim; and d) illustrative sample results from a simulation of a representative disruption scenario.

Mohsen Azimi↗
DOE OSTI2025

Quasinormal Coupled-Mode Analysis of Dynamic Gain in Exceptional-Point Lasers

One of the key features of lasers operating near exceptional points (EPs) is that the gain medium can support an oscillating population inversion above a pump threshold, leading to self-modulated laser dynamics. This unusual behavior opens up new possibilities for frequency comb generation and temporal modulation. However, the dynamic population inversion couples signals with different frequencies and is difficult to capture using conventional temporal coupled-mode theory (TCMT) based on stationary saturable gain. In this paper, we develop a perturbative coupled-mode analysis framework to capture the spatial-temporal dynamics of near-EP lasers. By decomposing discrete frequency generation into multiple excitations of resonant modes, our analysis establishes a minimal physical model that translates the local distribution of dynamic population-inversion into a resonant modal interpretation of laser gain. Furthermore, this work enables the exploration of unique properties in this self-time-modulated systems, such as time-varying scattering and nonreciprocal transmission.

Absorption↗
NASA NTRS1980

Wind tunnel determination of dynamic cross-coupling derivatives - A new approach

The latest developments in the NAE ongoing dynamic stability research program are briefly summarized. Emphasis is placed on the recently developed wind-tunnel data reduction procedures used to obtain cross and cross-coupling derivatives due to an oscillatory motion. These procedures, which account for the dynamic behaviour of the model-balance subsystem, are described for the balance configurations currently in use. The principles on which they are based, however, are quite general and can therefore be applied to other balance configurations. Two full-model dynamic stability apparatuses are described and typical results, obtained from dynamic calibrations as well as from wind-tunnel experiments, are presented.

Hanff, E. S.↗
DOE OSTI2024

Generalized gluon distribution for quarkonium dynamics in strongly coupled N = 4 Yang-Mills theory

We study the generalized gluon distribution that governs the dynamics of quarkonium inside a non-Abelian thermal plasma characterizing its dissociation and recombination rates. This gluon distribution can be written in terms of a correlation function of two chromoelectric fields connected by an adjoint Wilson line. We formulate and calculate this object in N = 4 supersymmetric Yang-Mills theory at strong coupling using the AdS/CFT correspondence, allowing for a nonzero center-of-mass velocity v of the heavy quark pair relative to the medium. The effect of a moving medium on the dynamics of the heavy quark pair is described by the simple substitution T → γ T in agreement with previous calculations of other observables at strong coupling, where T is the temperature of the plasma in its rest frame, and γ = ( 1 − v 2 ) − 1 / 2 is the Lorentz boost factor. Such a velocity dependence can be important when the quarkonium momentum is larger than its mass. Contrary to general expectations for open quantum systems weakly coupled with large thermal environments, the contributions to the transition rates that are usually thought of as the leading ones in Markovian descriptions vanish in this strongly coupled plasma. This calls for new theoretical developments to assess the effects of strongly coupled non-Abelian plasmas on in-medium quarkonium dynamics. Finally, we compare our results with those from weakly coupled QCD, and find that the QCD result moves toward the N = 4 strongly coupled result as the coupling constant is increased within the regime of applicability of perturbation theory. This behavior makes it even more pressing to develop a non-Markovian description of quarkonium in-medium dynamics. Published by the American Physical Society 2024

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Chemo‐Mechanical Coupling in Hydrogels: Dynamics in the Diffusion‐Limited Regime

Hydrogels are characterized by substantial volume changes in response to external stimuli, making them promising candidates for developing smart materials with enhanced adaptability and responsiveness. By integrating chemical reactions, hydrogels acquire dynamic and tunable responsiveness to external stimuli through chemo‐mechanical coupling, expanding their potential in emerging applications. However, capturing their transient behavior remains challenging due to the complex interplay of chemical reactions, solvent transport, and polymer network deformation. Classical theories capture equilibrium swelling but fail to describe time‐dependent phenomena. To address this, a time‐dependent continuum model is developed that explicitly couples these processes. Volume phase transition in hydrogels with homogeneous chemical reactions is investigated, then the effects of reaction kinetics on these transitions are analyzed. The coupling of these mechanisms is further explored through a study of transient mechanical instabilities. To illustrate the impact of distinct reaction and diffusion timescales, a photo‐active gripper is studied for robotic applications. Finally, a photo‐active microswimmer that exhibits non‐reciprocal motion is proposed to highlight the solvent diffusion for locomotion at the micro‐ and nano‐ scales. The work establishes that transient dynamics of chemo‐mechanical hydrogels generate functions not accessible by steady state models and provides a predictive platform for designing adaptive materials in emerging applications.

chemo-mechanical coupling↗
NASA NTRS1999

Inlet-Compressor Analysis Performed Using Coupled Computational Fluid Dynamics Codes

A thorough understanding of dynamic interactions between inlets and compressors is extremely important to the design and development of propulsion control systems, particularly for supersonic aircraft such as the High-Speed Civil Transport (HSCT). Computational fluid dynamics (CFD) codes are routinely used to analyze individual propulsion components. By coupling the appropriate CFD component codes, it is possible to investigate inlet-compressor interactions. The objectives of this work were to gain a better understanding of inlet-compressor interaction physics, formulate a more realistic compressor-face boundary condition for time-accurate CFD simulations of inlets, and to take a first step toward the CFD simulation of an entire engine by coupling multidimensional component codes. This work was conducted at the NASA Lewis Research Center by a team of civil servants and support service contractors as part of the High Performance Computing and Communications Program (HPCCP).

Cole, Gary L.↗
DOE OSTI2025

The Water Table Model (WTM) (v2.0.1): coupled groundwater and dynamic lake modelling

Abstract. Ice-free land comprises 26 % of the Earth's surface and holds liquid water that delineates ecosystems, affects global geochemical cycling, and modulates sea levels. However, we currently lack the capacity to simulate and predict these terrestrial water changes across the full range of relevant spatial (watershed to global) and temporal (monthly to millennial) scales. To address this knowledge gap, we present the Water Table Model (WTM), which integrates coupled components to compute dynamic lake and groundwater levels. The groundwater component solves the 2D horizontal groundwater flow equation using non-linear equation solvers from the C++ PETSc (Portable, Extensible Toolkit for Scientific Computation) library. The dynamic lake component makes use of the Fill–Spill–Merge (FSM) algorithm to move surface water into lakes, where it may evaporate or affect groundwater flow. In a proof-of-concept application, we demonstrate the continental-scale capabilities of the WTM by simulating the steady-state climate-driven water table for the present day and the Last Glacial Maximum (LGM; 21 000 calendar years before present) across the North American continent. During the LGM, North America stored an additional 14.98 cm of sea-level equivalent (SLE) in lakes and groundwater compared to the climate-driven present-day scenario. We compare the present-day result to other simulations and real-world data. Open-source code for the WTM is available on GitHub and Zenodo.

Callaghan, Kerry L. (ORCID:0000000226740838)↗