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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

A computer tool to perform entry vehicle ablative thermal protection systems sizing has been developed. Two options for calculating the thermal response are incorporated into the tool. One, an industry-standard, high-fidelity ablation and thermal response program was integrated into the tool, making use of simulated trajectory data to calculate its boundary conditions at the ablating surface. Second, an approximate method that uses heat of ablation data to estimate heat shield recession during entry has been coupled to a one-dimensional finite-difference calculation that calculates the in-depth thermal response. The in-depth solution accounts for material decomposition, but does not account for pyrolysis gas energy absorption through the material. Engineering correlations are used to estimate stagnation point convective and radiative heating as a function of time. The sizing tool calculates recovery enthalpy, wall enthalpy, surface pressure, and heat transfer coefficient. Verification of this tool is performed by comparison to past thermal protection system sizings for the Mars Pathfinder and Stardust entry systems and calculations are performed for an Apollo capsule entering the atmosphere at lunar and Mars return speeds.

Dec, John A.↗
NASA NTRS2006

An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

A computer tool to perform entry vehicle ablative thermal protection systems sizing has been developed. Two options for calculating the thermal response are incorporated into the tool. One, an industry-standard, high-fidelity ablation and thermal response program was integrated into the tool, making use of simulated trajectory data to calculate its boundary conditions at the ablating surface. Second, an approximate method that uses heat of ablation data to estimate heat shield recession during entry has been coupled to a one-dimensional finite-difference calculation that calculates the in-depth thermal response. The in-depth solution accounts for material decomposition, but does not account for pyrolysis gas energy absorption through the material. Engineering correlations are used to estimate stagnation point convective and radiative heating as a function of time. The sizing tool calculates recovery enthalpy, wall enthalpy, surface pressure, and heat transfer coefficient. Verification of this tool is performed by comparison to past thermal protection system sizings for the Mars Pathfinder and Stardust entry systems and calculations are performed for an Apollo capsule entering the atmosphere at lunar and Mars return speeds.

Dec, John A.↗
DOE OSTI2021

Distinguishing localization from chaos: Challenges in finite-size systems

Highlights: • Provides an overview of the current understanding of the many-body localization phase transition. • Discusses the subtleties of finite-size scaling near this transition • Assesses the implications of these subtleties for numerical studies of spin chains. • Explores scaling of diagnostics in models with known localization transitions. • Presents suggestions for future numerical work. We re-examine attempts to study the many-body localization transition using measures that are physically natural on the ergodic/quantum chaotic regime of the phase diagram. Using simple scaling arguments and an analysis of various models for which rigorous results are available, we find that these measures can be particularly adversely affected by the strong finite-size effects observed in nearly all numerical studies of many-body localization. This severely impacts their utility in probing the transition and the localized phase. In light of this analysis, we discuss a recent study (Šuntajs et al., 2020) of the behaviour of the Thouless energy and level repulsion in disordered spin chains, and its implications for the question of whether MBL is a true phase of matter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2011

Spacesuit Soft Upper Torso Sizing Systems

The passive sizing system consists of a series of low-profile pulleys attached to the front and back of the shoulder bearings on a spacesuit soft upper torso (SUT), textile cord or stainless steel cable, and a modified commercial ratchet mechanism. The cord/cable is routed through the pulleys and attached to the ratchet mechanism mounted on the front of the spacesuit within reach of the suited subject. Upon actuating the ratchet mechanism, the shoulder bearing breadth is changed, providing variable upper torso sizing. The active system consists of a series of pressurizable nastic cells embedded into the fabric layers of a spacesuit SUT. These cells are integrated to the front and back of the SUT and are connected to an air source with a variable regulator. When inflated, the nastic cells provide a change in the overall shoulder bearing breadth of the spacesuit and thus, torso sizing. The research focused on the development of a high-performance sizing and actuation system. This technology has application as a suit-sizing mechanism to allow easier suit entry and more accurate suit fit with fewer torso sizes than the existing EMU (Extravehicular Mobility Unit) suit system. This advanced SUT will support NASA s Advanced EMU Evolutionary Concept of a two-sizes-fit-all upper torso for replacement of the current EMU hard upper torso (HUT). Both the passive and nastic sizing system approaches provide astronauts with real-time upper torso sizing, which translates into a more comfortable suit, providing enhanced fit resulting in improved crewmember performance during extravehicular activity. These systems will also benefit NASA by reducing flight logistics as well as overall suit system cost. The nastic sizing system approach provides additional structural redundancy over existing SUT designs by embedding additional coated fabric and uncoated fabric layers. Two sizing systems were selected to build into a prototype SUT: one active and one passive. From manned testing, it was found that both systems offer good solutions to sizing a SUT to fit a crewmember. This new system provided improved suit don/doff over existing spacesuit designs as well as providing better fit at suit operational pressure resulting in improved comfort and mobility. It was found that a SUT with a sizing system may solve several problems that have plagued existing HUT designs, and that a SUT with a sizing system may be a viable option for advanced suit architectures.

Graziosi, David↗
NASA NTRS2019

Electrical Power System Sizing Within the Numerical Propulsion System Simulation

Electrified aircraft propulsion seeks to address ambitious goals in the commercial airline industry, including significant decreases in fuel burn, emissions, noise, and takeoff field length. In order to move these electrified propulsion concepts forward, analysis tools are needed that can model propulsion systems containing both gas turbine and power system components. This work presents the definition of an electric port, a set of electrical power systems tools, and simulation examples for the Numerical Propulsion System Simulation (NPSS) software. NPSS is the industry standard modeling and simulation package for aircraft propulsion systems, and the ability to design, size, integrate, and analyze electric power systems will enable industry efforts towards the development of electrified aircraft propulsion.

aircraft electrification↗
DOE OSTI2020

Heavy flavor dynamics across system size at the LHC

One of the fundamental signatures of the Quark Gluon Plasma has been the suppression of heavy flavor (specifically D mesons), which has been measured via the nuclear modification factor, R AA and azimuthal anisotropies, v n , in large systems. However, multiple competing models can reproduce the same data for R AA to v n . In this talk we break down the competing effects that conspire together to successfully reproduce R AA and v n in experimental data using Trento+v-USPhydro+DAB-MOD. Then using our best fit model we make predictions for R AA and v n across system size for 208 PbPb, 129 XeXe, 40 ArAr, and 16 OO collisions. We find that 0–10% centrality has a non-trivial interplay between the system size and eccentricities such that system size effects are masked in v 2 whereas in 30–50% centrality the eccentricities are approximately constant across system size and, therefore, is a better centrality class to study D meson dynamics across system size.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRSDate not supplied

Architectures of Exoplanetary Systems: Towards a Multi-planet Model for Reproducing the Planet Radius Valley and Intra-system Size Similarity

Multi-planet systems provide crucial insights into the architectures and correlations within planetary systems, which in turn offer clues into their formation and evolution histories. Through the thousands of exoplanet candidates that it discovered, NASA's Kepler mission revealed that systems with multiple transiting planets are common. We describe a new model for inferring the exoplanet population observed by Kepler, which combines a semi-parametric description of planetary systems with a prescription for envelope mass-loss due to photoevaporation. This new model is a"hybrid" of the maximum AMD (angular momentum deficit) model in which the orbital excitations of the planets are drawn by distributing the system's critical AMD (He et al. 2020), and a photoevaporation model for sculpting the observed radius valley (Neil & Rogers 2020). This is an update to the SysSim suite of exoplanet population models derived from forward modeling the Kepler detection pipeline. The hybrid model is constrained by the observed statistics of multi-transiting systems, including additional constraints from the distribution of planet radii and their intra-system size patterns. This model is capable of producing a planet radius valley as well as a preference for planet size similarity. However, we find that the Kepler catalog exhibits features that are even more significant (i.e., it has a deeper observed radius valley and stronger size similarity) than the best-fit model. We use this model to infer the intrinsic planet radius valley as well as the distribution of primordial planet masses and core masses.

kepler↗
NASA NTRS1974

Propulsion system sizing for powered lift and mechanical flap quiet aircraft

A method of propulsion system sizing for mechanical flap and externally blown flap aircraft is demonstrated. Included in this study is the effect of various levels of noise suppression on the aircraft final design characteristics. Both aircraft are sized to operate from a 3000-ft runway and perform the same mission. For each aircraft concept, propulsion system sizing is demonstrated for two different engine cycles - one having a fan pressure ratio of 1.5 and a bypass ratio of 9 and the other having a fan pressure ratio of 1.25 and a bypass ratio of 17.8. The results presented include the required thrust to weight ratio and wing loading and the resulting gross weight and direct operating costs as functions of the engine noise level for each of the four combinations of engine cycles and aircraft concepts.

Bowles, J. V.↗
DOE OSTI2020

System-size scan of D meson R AA and v n using PbPb, XeXe, ArAr, and OO collisions at energies available at the CERN Large Hadron Collider

Here, experimental measurements indicate no suppression (e.g. R pPb ~ 1) but a surprisingly large D meson v 2 was measured in pPb collisions. In order to understand these results we use Trento+v-USPhydro+DAB-MOD to make predictions and propose a system size scan at the LHC involving 208 PbPb, 129 XeXe, 40 ArAr, and 16OO collisions. We find that the nuclear modification factor approaches unity as the system size is decreased, but nonetheless, in the 0–10% most central collisions v 2 {2} is roughly equivalent regardless of system size. These results arise from a rather non-trivial interplay between the shrinking path length and the enhancement of eccentricities in small systems at high multiplicity. Finally, we also find a surprising sensitivity of D mesons v 2 {2} in 0–10% at p T = 2–10 GeV to the slight deformation of 129 Xe recently found at LHC.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2007

Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT)

An effort was initiated by NASA/JSC in 2001 to develop an Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT) for the sizing of Extravehicular Activity System (EVAS) architecture and studies. Its intent was to support space suit development efforts and to aid in conceptual designs for future human exploration missions. Its basis was the Life Support Options Performance Program (LSOPP), a spacesuit and portable life support system (PLSS) sizing program developed for NASA/JSC circa 1990. EVAS_SAT estimates the mass, power, and volume characteristics for user-defined EVAS architectures, including Suit Systems, Airlock Systems, Tools and Translation Aids, and Vehicle Support equipment. The tool has undergone annual changes and has been updated as new data have become available. Certain sizing algorithms have been developed based on industry standards, while others are based on the LSOPP sizing routines. The sizing algorithms used by EVAS_SAT are preliminary. Because EVAS_SAT was designed for use by members of the EVA community, subsystem familiarity on the part of the intended user group and in the analysis of results is assumed. The current EVAS_SAT is operated within Microsoft Excel 2003 using a Visual Basic interface system.

Brown, Cheryl B.↗
DOE OSTI2023

Large-scale molecular dynamics simulations of bubble collapse in water: Effects of system size, water model, and nitrogen

Molecular dynamics simulations in the microcanonical ensemble are performed to study the collapse of a bubble in liquid water using the single-site mW and the four-site TIP4P/2005 water models. To study system size effects, simulations for pure water systems are performed using periodically replicated simulation boxes with linear dimensions, L, ranging from 32 to 512 nm with the largest systems containing 8.7 × 10 6 and 4.5 × 10 9 molecules for the TIP4P/2005 and mW water models, respectively. The computationally more efficient mW water model allows us to reach converging behavior when the bubble dynamics results are plotted in reduced units, and the limiting behavior can be obtained through linear extrapolation in L –1 . Qualitative differences are observed between simulations with the mW and TIP4P/2005 water models, but they can be explained by the models’ differences in predicted viscosity and surface tension. Although bubble collapse occurs on time scales of only hundreds of picoseconds, the system sizes used here are sufficiently large to obtain bubble dynamics consistent with the Rayleigh–Plesset equation when using the models’ thermophysical properties as input. For the conditions explored here, extreme heating of the interfacial water molecules near the time of collapse is observed for the larger mW water systems (but the model underpredicts the viscosity), whereas heating is less pronounced for the TIP4P/2005 water systems because its larger viscosity contribution slows the collapse dynamics. The presence of nitrogen within the bubble only starts to affect bubble dynamics near the very end of the initial collapse, leading to an incomplete collapse and strong rebound for the mW water model. Although nitrogen is non-condensable at 300 K, it becomes highly compressed and reaches a liquid-like density near the collapse point. We find that the dissolution of nitrogen is much slower than the movement of the collapsing water front, and the re-expansion of the dense nitrogen droplet gives rise to bubble rebound. The incompatibility of the collapse and dissolution time scales should be considered for continuum-scale modeling of bubble dynamics. Finally, we also confirm that the diffusion coefficient for dissolved nitrogen is insensitive to pressure as the liquid transitions from a compressed to a stretched state.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

D Meson Sensitivity to a System Size Scan at LHC

Experimental measurements in pA collisions indicate no D meson suppression (R pPb ~ 1) but a surprisingly large v 2 . To better understand these results we propose a system size scan at the LHC involving 16 OO, 40 ArAr, 129 XeXe and 208 PbPb collisions. Using Trento+ v-USPhydro+DAB-MOD to make predictions, we find that the R AA tends towards unity when the system size is decreased, but nonetheless, in the most central collisions v 2 {2} is almost independent of the colliding system. Furthermore, these results are analyzed in light of path length and initial eccentricity variations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size

Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for kinetic passing electron dynamics and is known to generate stationary $E\times B$ zonal flow shear layers at radial locations near low-order mode rational surfaces (Weikl et al. Phys. Plasmas, vol. 25, 2018, 072305). Here, we find that self-interaction, in fact, plays a very significant role in also generating fluctuating zonal flows, which is critical to regulating turbulent transport throughout the radial extent. Unlike the usual picture of zonal flow drive in which microinstability eigenmodes coherently amplify the flow via modulational instabilities, the self-interaction drive of zonal flows from these eigenmodes are uncorrelated with each other. It is shown that the associated shearing rate of the fluctuating zonal flows therefore reduces as more toroidal modes are resolved in the simulation. In simulations accounting for the full toroidal domain, such an increase in the density of toroidal modes corresponds to an increase in the toroidal system size, leading to a finite system size effect that is distinct from the well-known profile shearing effect.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRSDate not supplied

Validation of the NASA Electrical Power System – Sizing and Analysis Tool (EPS-SAT)

The electrification of aircraft propulsion systems has opened the design space for engineers by allowing for unique and highly specialized propulsion system and vehicle designs. NASA developed the Electrical Power System – Sizing and Analysis Tool (EPS-SAT) to conduct high-level trade studies and sensitivity studies on the various propulsion system designs that can be implemented in electrified aircraft. The results of these studies would be used to better direct investment dollars and determine strengths and weaknesses of propulsion system designs. In this paper, the results of the EPS-SAT tool were validated with hardware data extracted from the NASA Revolutionary Vertical Lift Technology (RVLT) Advanced Reconfigurable Electric Aircraft Lab (AREAL). Updated performance maps were added to the EPS-SAT library so that high-fidelity results could be calculated.

Patrick A. Hanlon↗
NASA NTRS1984

Stand-alone flat-plate photovoltaic power systems: System sizing and life-cycle costing methodology for Federal agencies

A simple methodology to estimate photovoltaic system size and life-cycle costs in stand-alone applications is presented. It is designed to assist engineers at Government agencies in determining the feasibility of using small stand-alone photovoltaic systems to supply ac or dc power to the load. Photovoltaic system design considerations are presented as well as the equations for sizing the flat-plate array and the battery storage to meet the required load. Cost effectiveness of a candidate photovoltaic system is based on comparison with the life-cycle cost of alternative systems. Examples of alternative systems addressed are batteries, diesel generators, the utility grid, and other renewable energy systems.

Borden, C. S.↗
NASA NTRS2019

Thermal System Sizing Comparison of a PEM and Solid Oxide Fuel Cell Systems on Mars

Power production is a key aspect to any Mars mission. One method for providing power throughout the day/night cycle, or to satisfy short-duration high-output power needs, is to utilize a regenerative fuel cell system for providing energy storage and nighttime or supplemental power. This study compares the total system mass for two types of fuel cell systems, proton exchange membrane (PEM) and solid oxide (SO), sized to provide 10 kW of electrical output power in the Mars environment. Two operating locations were examined; one near the equator at 4 °S latitude and one the higher northern latitude of 48°N. The systems were sized to operate throughout the year at these locations, where the radiator was sized for the worst-case warm condition and the insulation was sized for the worst-case cold condition. Using the selected system parameters, the results for both latitudes showed that the lightest system was the SO fuel cell with a PEM electrolyzer. This was mainly due to the higher operational temperature of the SO system enabled a significantly smaller radiator mass compared to that of the PEM fuel cell system. However, there was a significant difference in mass for the PEM system when operated near the equator as compared to the higher northern latitude. For the 10-kW output system this difference in mass was just under 100 kg.

Fuel Cells↗
DOE OSTI2022

System size and flavour dependence of chemical freeze-out temperatures in ALICE data from pp, pPb and PbPb collisions at LHC energies

We present the system size and flavour dependence of the chemical freeze-out temperature (T ch ) at vanishing baryo-chemical potential calculated via thermal fits to experimental yields for several multiplicity classes in pp, pPb and PbPb collisions measured by ALICE. Using the Thermal-FIST Hadron Resonance Gas model package, we compare the quality of fits across various treatments of strangeness conservation under different freeze-out conditions as a function of the charged particle multiplicity density $\langle$dN ch /d η $\rangle$. Additionally, we examine how the anti-hadron to pion yield ratios of light and strange baryons, as well as the φ meson, evolve within a flavour-dependent model. Through a unique twotemperature chemical freeze-out approach, we show that flavour dependence of T ch in a Strangeness Canonical Ensemble leads to a natural explanation of strangeness enhancement from small to large systems at LHC energies without requiring any non-equilibrium particle production at small $\langle$dN ch /d η $\rangle$.

79 ASTRONOMY AND ASTROPHYSICS↗