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NASA NTRS2013

Thermal Testing of a Stacked Core Mirror for UV Applications

The ASTRO2010 Decadal Survey stated that an advanced large-aperture ultraviolet, optical, near-infrared (UVOIR) telescope is required to enable the next generation of compelling astrophysics and exoplanet science; and, that present technology is not mature enough to affordably build and launch any potential UVOIR mission concept. Under Science and Technology funding, NASA's Marshall Space Flight Center and ITT Exelis have developed a more cost effective process to make 4m monolithic spaceflight UV quality, low areal density, thermally and dynamically stable primary mirrors. A proof of concept mirror was built and tested down to 250K which would allow imaging out to 2.5 microns. This mirror was thermally tested at the Marshall Spaceflight Center to understand the thermal changes between the processing temperature of 293K and the potential low end of the operational temperature of 250K. Isothermal testing results and front plate gradient results have been evaluated and compared to analysis predictions. Measurement of gravity effects on surface figure will be compared to analytical predictions. Future testing of a larger Pathfinder mirror will also be discussed.

Matthews, Gary↗

NASA NTRS2013

Thermal Testing of a Stacked Core Mirror for UV Applications

Matthews, Gary W.↗

DOE OSTI2024

Phonon modal analysis of thermal transport in ThO 2 with point defects using equilibrium molecular dynamics

Defects can significantly degrade the thermal conductivity of ThO 2 , an advanced nuclear fuel material as well as a surrogate for other fluorite-structured materials. Here, we investigate how point defects in ThO 2 impact phonon mode-resolved thermal transport. By incorporating phonon modes from lattice dynamics, we decompose the trajectory and heat flux to phonon normal mode space and extract key phonon properties, including phonon relaxation times and their contributions to thermal conductivity. We implement two methods. The first method is based on the Green Kubo formalism to resolve the contribution of each phonon mode to thermal conductivity. The second resolves the lifetime of individual phonon modes and the thermal conductivity is calculated using the Boltzmann transport equation within relaxation time approximation. Notably, a lower contribution of acoustic modes is revealed compared to perturbative approaches considering only three-phonon scattering processes. The effects of four types of point defects are evaluated. The strongest impact on a reduction in thermal conductivity is from Th interstitials, followed by Th vacancies. O interstitials/vacancies have a similar impact, albeit smaller than defects on the thorium sublattice. These observations are consistent with previous studies.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

NASA NTRS2001

Thermal Fault Tolerance Analysis of Carbon Fiber Rope Barrier Systems for Use in the Reusable Solid Rocket Motor ( RSRM) Nozzle Joints

Carbon Fiber Rope (CFR) thermal barrier systems are being considered for use in several RSRM (Reusable Solid Rocket Motor) nozzle joints as a replacement for the current assembly gap close-out process/design. This study provides for development and test verification of analysis methods used for flow-thermal modeling of a CFR thermal barrier subject to fault conditions such as rope combustion gas blow-by and CFR splice failure. Global model development is based on a 1-D (one dimensional) transient volume filling approach where the flow conditions are calculated as a function of internal 'pipe' and porous media 'Darcy' flow correlations. Combustion gas flow rates are calculated for the CFR on a per-linear inch basis and solved simultaneously with a detailed thermal-gas dynamic model of a local region of gas blow by (or splice fault). Effects of gas compressibility, friction and heat transfer are accounted for the model. Computational Fluid Dynamic (CFD) solutions of the fault regions are used to characterize the local flow field, quantify the amount of free jet spreading and assist in the determination of impingement film coefficients on the nozzle housings. Gas to wall heat transfer is simulated by a large thermal finite element grid of the local structure. The employed numerical technique loosely couples the FE (Finite Element) solution with the gas dynamics solution of the faulted region. All free constants that appear in the governing equations are calibrated by hot fire sub-scale test. The calibrated model is used to make flight predictions using motor aft end environments and timelines. Model results indicate that CFR barrier systems provide a near 'vented joint' style of pressurization. Hypothetical fault conditions considered in this study (blow by, splice defect) are relatively benign in terms of overall heating to nozzle metal housing structures.

Clayton, J. Louie↗

DOE OSTI2020

A Privacy Preserving Model-Free Optimization and Control Framework for Demand Response from Residential Thermal Loads

We consider the problem of optimizing the cost of procuring electricity for a large collection of homes managed by a load serving entity, by pre-cooling or pre-heating the thermal inertial loads in the homes to avoid procuring power during periods of peak electricity pricing. We would like to accomplish this objective in a completely privacy-preserving and model-free manner, that is, without direct access to the state variables (temperatures or power consumption) or the dynamical models (thermal characteristics) of individual homes, while guaranteeing personal comfort constraints of the consumers. We propose a two-stage optimization and control framework to address this problem. In the first stage, we use a long short-term memory (LSTM) network to predict hourly electricity prices, based on historical pricing data and weather forecasts. Given the hourly price forecast and thermal models of the homes, the problem of designing an optimal power consumption trajectory that minimizes the total electricity procurement cost for the collection of thermal loads can be formulated as a large-scale integer program (with millions of variables) due to the on-off cyclical dynamics of such loads. We provide a simple heuristic relaxation to make this large-scale optimization problem model-free and computationally tractable. In the second stage, we translate the results of this optimization problem into distributed open-loop control laws that can be implemented at individual homes without measuring or estimating their state variables, while simultaneously ensuring consumer comfort constraints. We demonstrate the performance of this approach on a large-scale test case comprising of 500 homes in the Houston area and benchmark its performance against a direct model-based optimization and control solution.

Sivaranjani, S.↗

NASA NTRS1978

On the coupled nature of atmospheric phenomena

The interactions that take place in the stratosphere and the troposphere which are important to the maintenance of the chemical, dynamic, and thermal state and of the middle atmosphere, and which may be important in the determination of the state of the lower atmosphere are reviewed. Examples of these interactions due to either natural or anthropogenic processes are discussed, and promising areas for future research are indicated. Specific topics include: (1) coupling between temperature and chemistry via temperature dependent rate constants; (2) the effect of latitudinal temperature variations on zonal winds; (3) the effect of clouds, surface albedo, and the lower atmosphere on stratospheric chemistry due to the scattering and reflection of solar radiation; (4) the effect of trace constituents on thermal structure and thermal balance; (5) the effect of the stratosphere on tropospheric climate; (6) the effect of solar UV variability on stratospheric chemistry and temperature; and (7) the effect of trace constituents on stratospheric dynamics.

Callis, L. B.↗

NASA NTRSDate not supplied

Coupling a Computational Fluid Dynamics (CFD) Model to a Spacecraft Thermal System Model for the DraMS Instrument Thermal Analysis

The Dragonfly Mass Spectrometer (DraMS) is an instrument on the Dragonfly mission, which will spend 7 years in deep space cruise before landing and operating on the surface of Titan. Vacuum thermal analyses are required for deep space cruise, and convection analyses are required for the Titan surface operations. Model exchanges across multiple thermal teams are needed for all phases of the mission. For DraMS, Thermal Desktop (TD) has been the main thermal analytical tool of choice due to its capability in modeling complex thermal systems with relatively low computational power and for its availability across thermal teams. However, TD does not have computational fluid dynamics (CFD) capability and struggles to accurately capture complex convective behavior. DraMS has fans operating in tandem and gas flow behaviors are not easily predicted due to its complex flow paths. CFD software, such as Fluent, can model and predict such complex flow behaviors, but CFD models are computationally expensive, and its workflow processes are not tailored towards simulating large and complex systems. Therefore, a coupled modeling approach was chosen for DraMS: A TD model was used for simulating all the conductive, radiative, and source terms, while a Fluent CFD model was added on, as needed, to the TD model to provide the convective boundary conditions using the System Coupling software. The coupling software allows the TD and Fluent models to communicate data and arrive at a co-solved and co-converged solution. Furthermore, Thermal Iso-value Exchange (TIE) method was developed to facilitate and improve the TD-Fluent data exchange process. This paper will discuss the analytical studies that were done to verify the accuracy and usability of the coupled approach and the challenges associated, which lead to the development of the TIE approach. DraMS thermal design and co-solved analysis results will also be discussed.

heat transfer↗

NASA NTRS2001

Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the Polar satellite is studied by using a three-dimensional particle-in-cell (PIC) code. When the satellite passes through the region of low-density plasma, the satellite charges to positive potentials as high as 40-50 V, owing to the photoelectron emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, ion-rich xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at approximately 2 V. Accordingly, in our three-dimensional PIC simulation we considered that the potential of the satellite is 2 V as a fixed bias. Considering the relatively high density of the xenon plasma in the sheath (10-10(exp 3)/cc), the ambient plasma of low density (<1/cc) is neglected. In the simulations the electric fields and plasma dynamics are calculated self-consistently. We found that an 'apple'-shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission a high positive potential hill develops. Near the Thermal Ion Dynamics Experiment detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations it takes only about a couple of tens of electron gyroperiods for the sheath to reach a quasi steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. After this time the expansion of the sheath in directions transverse to the ambient magnetic field slows down because the electrons are magnetized. Using the quasi steady sheath, we performed trajectory calculations to characterize the detector response to a highly supersonic polar wind flow. The detected ions' velocity distribution shows significant deviations from a shifted Maxwellian in the ambient polar wind population. The deviations are caused by the effects of electric fields on the ions' motion as they traverse the sheath.

Singh, N.↗

NASA NTRSDate not supplied

The Influence of Material Characterization on Thermal Loads Development and Flight Vehicle Design

The thermal management team faces a significant challenge to meet the aggressive thermal loading associated with hypersonic flight. Design strategies require the involvement of many engineering disciplines, as each must design their respective subsystem and then interface with all remaining subsystems to successfully close the vehicle design space. High fidelity thermal solid models will capture the variation in material properties and the effects of chemical reactions associated with hypersonic flight. Selection of the best materials for the mission will be based upon computational fluid dynamics and thermal modeling results. To enhance the probability for success, it is recommended that frequent communication occur between the thermal modeler and the materials scientist regarding design strategies and modeling assumptions. Early in the design process, lower fidelity modeling will be used to narrow the trade space. As promising designs are found, greater fidelity in the modeling process will be required to address more of the flowfield challenges and the material performance under the prescribed flight profile. The end goal is to select the most technically sound and physically advantageous material for the mission while avoiding overdesigning the vehicle due to modeling or material uncertainties. This presentation seeks to give an overview of the key thermal parameters that are affected through materials engineering, the interactions between a thermal engineer and other disciplines, and an example of the thermal design process, the X-43.

hypersonic↗

DOE OSTI2021

Asymptotic reversibility of thermal operations for interacting quantum spin systems via generalized quantum Stein’s lemma

Abstract For quantum spin systems in any spatial dimension with a local, translation-invariant Hamiltonian, we prove that asymptotic state convertibility from a quantum state to another one by a thermodynamically feasible class of quantum dynamics, called thermal operations, is completely characterized by the Kullback–Leibler (KL) divergence rate, if the state is translation-invariant and spatially ergodic. Our proof consists of two parts and is phrased in terms of a branch of the quantum information theory called the resource theory. First, we prove that any states, for which the min and max Rényi divergences collapse approximately to a single value, can be approximately reversibly converted into one another by thermal operations with the aid of a small source of quantum coherence. Second, we prove that these divergences collapse asymptotically to the KL divergence rate for any translation-invariant ergodic state. We show this via a generalization of the quantum Stein’s lemma for quantum hypothesis testing beyond independent and identically distributed situations. Our result implies that the KL divergence rate serves as a thermodynamic potential that provides a complete characterization of thermodynamic convertibility of ergodic states of quantum many-body systems in the thermodynamic limit, including out-of-equilibrium and fully quantum situations.

Physics↗

DOE OSTI2022

A fast dynamic model for a large scale heat pipe embedded latent heat thermal energy storage system for optimal sizing and control

Not Available

Pan, Chunjian↗

NASA NTRS1991

Numerical simulations of thermal instabilities in stratified gases. II - Exploration of the parameter space

The temporal evolution of density perturbations in an initially hydrostatic isothermal atmosphere consisting of an optically thin radiating compressible plasma is studied. Numerical techniques are used to describe the nonlinear evolution of the perturbations, and the relative equilibrium between dynamic and thermal instabilities as governed by three independent control parameters are examined, namely, the initial density contrast of the perturbation, the ratio of the local buoyancy oscillation period to the local radiative cooling time, and the ratio of the perturbation radius to the local scaleheight. Four orders of magnitude of initial density contrasts and ratios of buoyancy and cooling times, and one order of magnitude of the bubble dimensions are explored. Well-defined oscillations were found to occur in a limited parameter range, and thermal instability to occur even within secondary condensations deriving from the bubble fragmentation.

Reale, F.↗

NASA NTRS1998

The Anatomy of the Perseus Spiral Arm: 12 CO and IRAS Imaging Observations of the W3-W4-W5 Cloud Complex

Panoramic images of 12CO J = 1-0 and thermal dust emissions from the W3-W4-W5 region of the outer Galaxy are presented. These data and recently published H I 21 cm line emission images provide an approximate 1' resolution perspective to the dynamics and thermal energy content of the interstellar gas and dust components contained within a 9 deg. arc of the Perseus spiral arm. We tabulate the molecular properties of 1560 clouds identified as closed surfaces within the l-b-v CO data cube at a threshold of 0.9 K T* (sub R). Relative surface densities of the molecular (28:1) and atomic (2.5:1) gas components determined within the arm and interarm velocity intervals demonstrate that the gas component that enters the spiral arm is predominantly atomic. Molecular clouds must necessarily condense from the compressed atomic material that enters the spiral arm and are likely short lived within the interarm regions. From the distribution of centroid velocities of clouds, we determine a random cloud-to-cloud velocity dispersion of 4 km s (exp. -1) over the width of the spiral arm but find no clear evidence within the molecular gas for streaming motions induced by the spiral potential. The far-infrared images are analyzed with the CO J = 1-0 and H I 21 cm line emission. The enhanced UV (Ultraviolet) radiation field from members of the Cas OB6 association and embedded newborn stars provide a significant source of heating to the extended dust component within the Perseus arm relative to the quiescent cirrus regions. Much of the measured far-infrared flux (69% at 60 micrometers and 47% at 100 micrometers) originates from regions associated with star formation rather than the extended, infrared cirrus component.

Heyer, Mark H.↗

NASA NTRS1998

The Anatomy of the Perseus Spiral ARM: (sup 12)CO and IRAS Imaging Observations of the W3-W4-W5 Cloud Complex

Panoramic images of (sup l2)CO J = 1-0 and thermal dust emissions from the W3-W4-W5 region of the outer Galaxy are presented. These data and recently published H (sub I) 21 cm line emission images provide an approx. 1 min resolution perspective to the dynamics and thermal energy content of the interstellar gas and dust components contained within a 9 deg arc of the Perseus spiral arm. We tabulate the molecular properties of 1560 clouds identified as closed surfaces within the l-b-v CO data cube at a threshold of 0.9 K T(sup *)(sub R). Relative surface densities of the molecular (28:1) and atomic (2.5: 1) gas components determined within the arm and interarm velocity intervals demonstrate that the gas component that enters the spiral arm is predominantly atomic. Molecular clouds must necessarily condense from the compressed atomic material that enters the spiral arm and are likely short lived within the interarm regions. From the distribution of centroid velocities of clouds, we determine a random cloud-to-cloud velocity dispersion of 4 km/s over the width of the spiral arm but find no clear evidence within the molecular gas for streaming motions induced by the spiral potential. The far-infrared images are analyzed with the CO J = 1-0 and H (sub I) 21 cm line emission. The enhanced UV radiation field from members of the Cas OB6 association and embedded newborn stars provide a significant source of heating to the extended dust component within the Perseus arm relative to the quiescent cirrus regions. Much of the measured far-infrared flux (69% at 60 microns and 47% at 100 microns) originates from regions associated with star formation rather than the extended, infrared cirrus component.

Heyer, Mark H.↗

NASA NTRSDate not supplied

12.5kW Advanced Electric Propulsion System Thruster Development Testing

Since 2012, NASA has been developing the12.5kW Hall Effect Rocket with Magnetic Shielding (HERMeS)thruster to serve the need for deep space propulsion. Aerojet Rocketdyne (AR)is developing the HERMeS Hall Current Thruster (HCT)into a flight capable design through the Advanced Electric Propulsion System (AEPS) program. In execution of this program, Aerojet Rocketdyne has designed, built and begun test of two Engineering Test Unit (ETU)HCTs, designated ETU-1 and ETU-2. This paper presents some of the preliminary results from theETU-1 thruster and draws comparisons to previous HERMeS Technology Demonstration Units (TDUs)and theETU-2 characterization unit. The ETU-1 thruster serves to evaluate the ETU design against dynamic and thermal environments while ETU-2 undergoes operational characterization and wear testing. The thruster has been exposed to acceptance and qualification-level vibration and shock testing and has undergone acceptance and characterization hot-firing to evaluate thruster performance after exposure to dynamic environments. The results have demonstrated that the dynamic environments have not had an adverse effect on performance and demonstrated that stability and operating characteristics remain unaffected. Together, ETU-1 and ETU-2 HCTs have demonstrated operating performance and characteristics in-family with each other and with the NASA HERMeS Technology Demonstration Units.

AEPS↗

NASA NTRS2004

Design and Performance of the Terrestrial Planet Finder Coronagraph

Terrestrial Planet Finder Coronagraph, one of two potential architectures, is described. The telescope is designed to make a visible wavelength survey of the habitable zones of at least thirty stars in search of earth-like planets. The preliminary system requirements, optical parameters, mechanical and thermal design, operations scenario and predicted performance is presented. The 6-meter aperture telescope has a monolithic primary mirror, which along with the secondary tower, are being designed to meet the stringent optical tolerances of the planet-finding mission. Performance predictions include dynamic and thermal finite element analysis of the telescope optics and structure, which are used to make predictions of the optical performance of the system.

designs↗

DOE OSTI2025

Advancing simulations of coupled electron and phonon nonequilibrium dynamics using adaptive and multirate time integration

Electronic structure calculations in the time domain provide a deeper understanding of nonequilibrium dynamics in materials. The real-time Boltzmann equation (rt-BTE), used in conjunction with accurate interactions computed from first principles, has enabled reliable predictions of coupled electron and lattice dynamics. However, the timescales and system sizes accessible with this approach are still limited, with two main challenges being the different timescales of electron and phonon interactions and the cost of computing collision integrals. As a result, only a few examples of these calculations exist, mainly for two-dimensional (2D) materials. Here we leverage adaptive and multirate time integration methods to achieve a major step forward in solving the coupled rt-BTEs for electrons and phonons. Relative to conventional (non-adaptive) time-stepping, our approach achieves a 10x speedup for a target accuracy, or greater accuracy by 3–6 orders of magnitude for the same computational cost, enabling efficient calculations in both 2D and bulk materials. This efficiency is showcased by computing the coupled electron and lattice dynamics in graphene up to ~100 ps, as well as modeling ultrafast lattice dynamics and thermal diffuse scattering maps in bulk materials (silicon and gallium arsenide). In addition to improved efficiency, our adaptive method can resolve the characteristic rates of different physical processes, thus naturally bridging different timescales. This enables simulations of longer timescales and provides a framework for modeling multiscale dynamics of coupled degrees of freedom in matter. Our work opens new opportunities for quantitative studies of nonequilibrium physics in materials, including driven lattice dynamics with phonons coupled to electrons, spin, and other degrees of freedom.

Yao, Jia [California Institute of Technology (CalT↗

DOE OSTI2025

Predictions of Cell-to-Cell Propagation and Vent Gas Production in the Thermal Runaway of Lithium-Ion Battery Stacks

This work presents the thermal runaway propagation model LIM1TR (Lithium-ion Modeling with 1-D Thermal Runaway) as an efficient tool to predict different cell-to-cell thermal runaway propagation scenarios. Here, we explored the vent gas volume production and reaction duration highlighting the relationship between these parameters and thermal runaway propagation due to convection by the vented gases. Two metrics based on gas production rate and heating rate are utilized as good indicators of the start and end of thermal runaway. LIM1TR results are compared with and validated by experiments from the literature for single-cell and multicell array experiments of 5 Ah and 10 Ah cells. By accounting for intraparticle diffusion of reacting species in the electrodes, we were able to capture the general dynamics of thermal runaway propagation and estimate acceptable reaction durations compared with the experimental values. Simulation results further demonstrated that varying heating modes lead to distinct reaction durations, consistent with experimental observations. Vent gas volume predictions indicate the need to consider both full and partial oxidation of the electrolyte. The outcomes of this work are building blocks for further investigations of module-to-module propagation by vented gases through convective heat transfer.

25 ENERGY STORAGE↗