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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Structural Certification of Human-Rated Inflatable Space Structures

This paper details the results of an initial study to develop a certification plan for human-rated inflatable space structures, including guidelines for qualification testing. Habitable softgoods inflatables are multi-layered shell structures that use high-strength webbing, cordage and broadcloth fabric to carry the skin loads of a variety of volumetric shapes and structural architectures. The primary objectives of this study are to define the key parameters that affect these structures and propose a statistically robust approach to defining safety and knockdown factors based on test and analysis. Current NASA standards for habitable inflatable space structures use a factor of safety of 4, which was inherited from airship design criteria. An updated approach to defining a design factor, taking into account material strength variability, load variability in the article, number of test samples, and damage and degradation effects is specified. Accurate analytical modeling of these structures is hindered by the difficulty of obtaining accurate and consistent material data due to load-history- dependent, nonlinear load versus strain behavior. A building block approach to certification is detailed that uses stochastic modeling and statistical test design and analysis to address the unique challenges these high-strength softgoods structures present. Human-rated inflatable modules are a transformative capability for launching much larger habitable volumes into space than is possible with rigid shell structures. This research aims to provide the framework for certifying these structures for future human space exploration missions.

Jones, Thomas C.↗
DOE OSTI2020

The carboxylation status of osteocalcin has important consequences for its structure and dynamics

The carboxylation status of Osteocalcin (Ocn) not only influences formation and structure in bones but also has important endocrine functions affecting energy metabolism and expenditure. In this study, the role of γ-carboxylation of the glutamate residues in the structure-dynamics-function relationship in Ocn is investigated. Three forms of Ocn, differentially carboxylated at the Glu-17, 21 and 24 residues, along with a mutated form of Ocn carrying Glu/Ala mutations, are modeled and simulated using molecular dynamics (MD) simulation in the presence of calcium ions. Characterization of the global conformational dynamics of Ocn, described in terms of the orientational variations within its 3-helical domain, highlights large structural variations in the non-carboxylated osteocalcin (nOcn). The bi-carboxylated Ocn (bOcn) and tri-carboxylated (tOcn) species, in contrast, display relatively rigid tertiary structures, with the dynamics of most regions strongly correlated. Radial distribution functions calculated for both bOcn and tOcn show long-range ordering of the calcium ion distribution around the carboxylated glutamate (γGlu) residues, likely playing an important role in promoting stability of these Ocns. Additionally, the same calcium ions are observed to coordinate with neighboring γGlu, better shielding their negative charges and in turn stabilizing these systems more than do the singly coordinating calcium ions observed in the case of nOcn. bOcn is also found to exhibit a more helical C-terminal structure, that has been shown to activate its cellular receptor GPRC6A, highlighting the allosteric role of Ocn carboxylation in modulating the stability and binding potential of the active C-terminal. Furthermore, the carboxylation status of Ocn as well and its calcium coordination appear to have a direct influence on Ocn structure and dynamics, possibly leading to the known differences in Ocn biological function.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2012

Algorithms for Determining Physical Responses of Structures Under Load

Ultra-efficient real-time structural monitoring algorithms have been developed to provide extensive information about the physical response of structures under load. These algorithms are driven by actual strain data to measure accurately local strains at multiple locations on the surface of a structure. Through a single point load calibration test, these structural strains are then used to calculate key physical properties of the structure at each measurement location. Such properties include the structure s flexural rigidity (the product of the structure's modulus of elasticity, and its moment of inertia) and the section modulus (the moment of inertia divided by the structure s half-depth). The resulting structural properties at each location can be used to determine the structure s bending moment, shear, and structural loads in real time while the structure is in service. The amount of structural information can be maximized through the use of highly multiplexed fiber Bragg grating technology using optical time domain reflectometry and optical frequency domain reflectometry, which can provide a local strain measurement every 10 mm on a single hair-sized optical fiber. Since local strain is used as input to the algorithms, this system serves multiple purposes of measuring strains and displacements, as well as determining structural bending moment, shear, and loads for assessing real-time structural health. The first step is to install a series of strain sensors on the structure s surface in such a way as to measure bending strains at desired locations. The next step is to perform a simple ground test calibration. For a beam of length l (see example), discretized into n sections and subjected to a tip load of P that places the beam in bending, the flexural rigidity of the beam can be experimentally determined at each measurement location x. The bending moment at each station can then be determined for any general set of loads applied during operation.

Richards, W. Lance↗
NASA NTRS1981

Low thermal conductance rigidizer for reducing torsional oscillations in cryogenic Dewars

A rigidizer, which provides greater rigidity against torsional oscillations, is highly resistant to radial motions, and has low thermal conductivity, has been developed to decrease vibrational levels affecting infrared detectors operated in cryostats (e.g., HD-3L Dewar) in aircraft such as NASA's Kuiper Airborne Observatory. The rigidizer is composed of two triangular elements and an intermediate support structure which joins them at the centers of their sides. The reentrant design provides a long heat path, while the triangular truss structure provides high rigidity in the horizontal plane. The structure is relatively compliant in the vertical direction, a desirable feature since the internal structure of the Dewar contracts as it cools. Rigidity in the vertical direction is provided by the neck tube. The support structure is quite compact. Several variants of the rigidizer have been fabricated, using flat sheets of G-10 fiberglass epoxy in thicknesses between 0.75-1.5 mm for the upper and lower truss assemblies, and either G-10 or stainless steel for the intermediate structure.

Harper, D. A.↗
NASA NTRS1992

Design of a D-Strut and its application results in the JPL, MIT, and LaRC test beds

High damping at very low magnitudes of vibration is provided by an 'Arched Flexure' D-Strut. Five of these devices have been incorporated in JPL's CSI truss structure, and five more in MIT's interferometer test bed. Two were also temporarily installed in the LaRC CSI test structure. Damping factors in the 50 percent category are being provided at vibration motions as small as 50 nm. The 'Arched Flexure' used in the D-Strut maximizes the volumetric stiffness parameter relative to its axial stiffness. In turn, this enables high damping factors, even in a very rigid truss structure. This paper includes a presentation and discussion of both element and system test data taken at JPL, LaRC, and MIT. Also provided is a detailed description of the D-Strut, the dynamic model, and several graphs showing design parameter variations that will make it possible to evaluate the D-Strut for other applications.

Davis, L. P.↗
DOE OSTI2025

Predicting interface structure using the minima hopping method

Here, we adapt the minima hopping method (MHM) to the problem of interfacial structure prediction and apply it to study a canonical problem, the tilt grain boundaries in SrTiO 3 . Our method employs a hybrid approach by first exploring the potential energy surface (PES) of different grain boundary samplings with an empirical force field, among which the fifteen candidates with lower energies are then refined using ab initio density functional theory (DFT) calculations. During the exploratory stage, we bias the search using a local order parameter to primarily sample various reconstructions in the vicinity of the interface, while preserving the crystallinity of the bulk regions. We further enhance the search by incorporating initial structures with rigid body displacements to account for translational variations between bulk phases, enabling the MHM to effectively generate both stoichiometric and nonstoichiometric SrTiO 3 Σ⁢3(111)[110] and Σ⁢3(112)[110] grain boundaries. From an algorithmic standpoint, MHM outperforms earlier studies based on genetic algorithms (GA) by identifying more stable interfacial structures of several SrTiO 3 grain boundaries. The performance of the present implementation of the MHM approach is primarily limited by exploring an approximate description of the PES with a rather simple Buckingham potential. This limitation leads to variations in performance when compared to approaches utilizing more advanced surrogate PES models, such as direct DFT-PES sampling or GA with the embedded atom method (EAM). Despite the present limitations, the MHM approach is able to yield interfacial structures with comparable or lower interfacial energies in specific cases, such as Σ⁢3(111)[110] Γ=1, ±0.5 and Σ⁢3(112)[110] Γ= ±1, −2, underscoring the robustness of the MHM approach even with a simple approximation of the DFT PES. The MHM interfacial structure prediction method thus offers an efficient approach to understanding the grain boundaries and heterointerfaces at the atomic scale, providing an important prerequisite for effective materials design.

density functional theory↗
NASA NTRSDate not supplied

Inflatable Softgoods Testing Capability Development for Habitation

The Habitation Systems Development Office (HP40) at NASA Marshall Space Flight Center supports systems engineering, integration, and project management for next generation space habitats. The office is responsible for formulation activities for Lunar Surface Habitat and Mars Transit Habitat. HP40 also manages commercial partnerships for exploration habitat development. The Lunar Surface Habitat is intended to initially support a minimum of two crew on the lunar surface for an approximately 30-day mission, with the ability to accommodate four crew for short durations. The Mars Transit Habitat will transport four crew to and from Mars orbit on a potentially 1,200 day mission. Both concepts are envisioned to leverage inflatable softgoods as the primary structural material for the habitation portion of the architecture. Inflatable softgoods are a complex, multi-material system consisting of multiple layers which perform specific functions. A bladder layer (polymer) contains the habitat’s atmosphere. The bladder is indexed to a woven restraint layer, usually Kevlar or Vectran, which serves as the structural layer. The remaining outer layers are for micro-meteoroid orbital debris (MMOD) shielding, protection from atomic Oxygen (if the material system is to be deployed in low earth orbit), and thermal insulation. The primary advantage of inflatable softgoods is that they can offer a larger volume per unit mass relative to a rigid metal structure. Inflatable softgoods have a strong development heritage within NASA, beginning with work in the 1960s in partnership with Goodyear Aerospace and continuing with Johnson Space Center’s TransHab project in the 1990s . Some development efforts subsequently transitioned into the private sector to mature the material technology for flight applications, including human habitation. In August 2022, NASA published its guidelines for certification of crewed inflatable softgoods structures (JSC-67721). This document outlines a series of tests which will be needed to certify inflatable softgoods material systems for use in crewed mission applications. It includes burst testing at the subscale and full-scale to determine the ultimate burst pressure of the softgoods architecture. Creep (long term deformation of the material under stress) is a key failure mode which must be characterized. Creep testing at the component and module levels is also recommended to generate time to failure curves and verify that the inflatable system has a predicted operational life which exceeds mission parameters. ET (Test Engineering) at MSFC and HP40 have worked together to establish softgoods testing capabilities for the center. This includes the ability to conduct module level burst tests and creep tests. The poster will highlight these capabilities and provide examples of testing which has been performed to date by ET. NASA MSFC anticipates that these test capabilities will continue to offer critical support for companies pursuing inflatable softgoods for exploration applications (lunar surface habitation, Mars transit) as well as commercial low earth orbit platforms.

habitation↗
DOE OSTI2022

Compatibility of Fuel System Elastomers and Plastics with a Fast-Pyrolysis Oil (Bio-oil) at Room Temperature

Herein the compatibility of a fast-pyrolysis bio-oil with 17 elastomer and 21 plastic materials common to fuel storage, dispensing, and delivery systems was assessed by measuring volume and hardness. Diesel was used as the baseline for comparison. The elastomer and plastic specimens were exposed to the test fuels at 23 °C. The exposure times were 4 and 16 weeks for the elastomers and plastics, respectively. The elastomers (except for silicone and styrene butadiene) exhibited pronounced swelling in the bio-oil. This was especially true for the fluorocarbons and acrylonitrile rubbers. For the elastomers, a strong correlation between polarity and volume swell was observed. Compositional and structural analysis on one of the fluorocarbon materials showed that the bio-oil was less effective at extracting phthalate additives than the diesel. However, the crystallinity of a fluorocarbon was altered by the bio-oil. Unlike the elastomers, the plastic materials were less impacted by exposure to the bio-oil. This finding is attributed to their denser and more rigid molecular structures (compared to the elastomers). Notable swelling did occur in the nylons, but this swelling was attributed to water absorption rather than polarity. Comparison with previous studies showed that the observed swelling was lower for both the elastomers and the plastics. Solubility (and hence swell) increases with temperature, and because this study was conducted at 23 °C rather than 50 °C, the reduced temperature is responsible for the lower swell levels.

09 BIOMASS FUELS↗
DOE OSTI2021

New interaction potentials for alkaline earth silicate and borate glasses

New interaction potentials were developed for molecular dynamics simulations to study the role of Mg and Ca in modifying the structure and properties of alkaline earth silicates and borates. Competition between the depolymerization of the silica network and the formation of new bonds between oxygen atoms and modifiers leads to the enhancement of the elastic moduli with increasing modifier content in alkaline earth silicate glasses. Compared with calcium silicate, the higher elastic moduli of magnesium silicate result from a higher connectivity of the overall glass network due to the incorporation of fourfold coordinated magnesium and a more rigid connection between oxygen atoms and modifiers. In contrast to the silicates, the effect of modifier on the elastic moduli of alkaline earth borates is dominated by the formation of fourfold coordinated boron (N 4 ). Calcium borate with higher N 4 shows a more rigid network structure and higher elastic moduli.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Conformational and oligomeric states of SPOP from small-angle X-ray scattering and molecular dynamics simulations

Speckle-type POZ protein (SPOP) is a substrate adaptor in the ubiquitin proteasome system, and plays important roles in cell-cycle control, development, and cancer pathogenesis. SPOP forms linear higher-order oligomers following an isodesmic self-association model. Oligomerization is essential for SPOP’s multivalent interactions with substrates, which facilitate phase separation and localization to biomolecular condensates. Structural characterization of SPOP in its oligomeric state and in solution is, however, challenging due to the inherent conformational and compositional heterogeneity of the oligomeric species. Here, we develop an approach to simultaneously and self-consistently characterize the conformational ensemble and the distribution of oligomeric states of SPOP by combining small-angle X-ray scattering (SAXS) and molecular dynamics (MD) simulations. We build initial conformational ensembles of SPOP oligomers using coarse-grained molecular dynamics simulations, and use a Bayesian/maximum entropy approach to refine the ensembles, along with the distribution of oligomeric states, against a concentration series of SAXS experiments. Our results suggest that SPOP oligomers behave as rigid, helical structures in solution, and that a flexible linker region allows SPOP’s substrate-binding domains to extend away from the core of the oligomers. Additionally, our results are in good agreement with previous characterization of the isodesmic self-association of SPOP. In the future, the approach presented here can be extended to other systems to simultaneously characterize structural heterogeneity and self-assembly.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

On the Structural Origin of Fast Li-Ion Cycling in Tetragonal Bronze-Type Nb 8 W 9 O 47

Bronze and bronze-derived, mixed metal oxides are materials of growing interest for lithium-ion battery anodes due to their high-rate capabilities and the potential for high energy densities via multielectron redox. We report on the synthesis and electrochemical properties of the tetragonal tungsten bronzetype phase Nb 8 W 9 O 47 and our investigation into the structural evolution of this phase upon lithium (de)intercalation, with particular attention to how it relates to the fast-cycling capabilities. Electrochemical cycling shows Nb 8 W 9 O 47 can achieve greater than one Li + per transition metal at rates of C/2 or slower and maintains a capacity equivalent to 0.65 Li + per transition metal at a rate of 20C. Sequential Rietveld analysis of operando X-ray diffraction data reveals anisotropic changes to the unit cell parameters during discharge, accompanied by an off-centering of the transition metals within their octahedral environments. While higher capacities can be accessed below 1.2 V, cells discharged to 1.0 V exhibit a significant expansion of the unit cell volume and reduced Coulombic efficiencies. This report suggests that rigid crystal structures incapable of undergoing polyhedral rotational deformations can instead exploit displacive distortions of the transition metal redox center to enable fast Li-ion cycling with minimal atomic rearrangements.

25 ENERGY STORAGE↗
NASA NTRS1996

Mechanism of unassisted ion transport across membrane bilayers

To establish how charged species move from water to the nonpolar membrane interior and to determine the energetic and structural effects accompanying this process, we performed molecular dynamics simulations of the transport of Na+ and Cl- across a lipid bilayer located between two water lamellae. The total length of molecular dynamics trajectories generated for each ion was 10 ns. Our simulations demonstrate that permeation of ions into the membrane is accompanied by the formation of deep, asymmetric thinning defects in the bilayer, whereby polar lipid head groups and water penetrate the nonpolar membrane interior. Once the ion crosses the midplane of the bilayer the deformation "switches sides"; the initial defect slowly relaxes, and a defect forms in the outgoing side of the bilayer. As a result, the ion remains well solvated during the process; the total number of oxygen atoms from water and lipid head groups in the first solvation shell remains constant. A similar membrane deformation is formed when the ion is instantaneously inserted into the interior of the bilayer. The formation of defects considerably lowers the free energy barrier to transfer of the ion across the bilayer and, consequently, increases the permeabilities of the membrane to ions, compared to the rigid, planar structure, by approximately 14 orders of magnitude. Our results have implications for drug delivery using liposomes and peptide insertion into membranes.

NASA Discipline Exobiology↗
NASA NTRSDate not supplied

The Wizard Staff: A Mobile Tool Supporting Human Exploration on The Lunar Surface

The Wizard Staff is a rechargeable, battery powered mobile tool with multiple uses for lunar surface exploration. It supports human activity as a surface survey tool, provides external illumination to enhance safety, delivers networking, communications, and navigation features to remote sites, and assists crew rescue with an emergency beacon and rigid splint structure. As a survey tool, it assists crewed geologic field site exploration with external lights, cameras, and LiDAR to illuminate, map, and record the sample collection process. As a relay station, it provides a surface intranet communications and navigation node for extended exploration far from the lander or habitation module. A separately developed Search-and-Rescue (SAR) handheld device can broadcast a signal to the Gandalf Staff containing crew position and biometric data. The staff then formats the message and sends it orbiting satellite(s) for emergency response via the LunaNET on a dedicated frequency similar to terrestrial applications using an Emergency Position-Indicating Radiobeacon (EPIRB). The staff is designed with an upper and lower segment. Components in the upper segment are the LiDAR, external lighting arrays, cameras, communications equipment, intelligence devices, and user interface for crew operations. The lower segment is a set of FeLiPO4 battery cells packed into the 2” diameter carbon fiber tube. When the battery pack is discharged, a spring connector (designed for the dusty lunar environment) easily disconnects the two segments for replacement with another fully charged battery pack. The lower segment can be used for Incapacitated Crew Rescue (ICR) as a rigid splint. As a stand-alone science platform, the Wizard Staff provides infrastructure for instruments and sensors to record the lunar environment over long periods of time. After a crew installs the components on the lunar surface, the platform delivers data to the lunar lander or base station for analysis. The stand-alone mode requires an auxiliary power source (e.g. solar array) and energy storage system (e.g. battery), so it could also be used as an electrical recharging station. A working prototype of Wizard Staff has been developed with collaboration between NASA (JSC, MSFC, and GSFC), Texas Space Technology Applications and Research (T STAR), and Texas A&M University (TAMU) using $300k of innovation funding in FY’21 and FY’22. The functional staff weights 36# on Earth (6# on the Moon), stands 2.1m tall and delivers external lighting with an array of 40 LED bulbs generating 1460 Lux at 2m range (near field), or 2 Lux at 50m (far field).

Gandalf Staff↗
NASA NTRS2001

Structural Modeling of a Five-Meter Thin Film Inflatable Antenna/Concentrator With Rigidized Support Struts

Dynamic characterization of a non-rigidized thin film inflatable antenna/solar concentrator structure with rigidized composite support struts is described in detail. A two-step finite element modeling approach in MSC/NASTRAN is utilized, consisting of: (1) a nonlinear static pressurization procedure used to obtain the updated stiffness matrix, and (2) a modal "restart" eigen solution that uses the modified stiffness matrix. Unique problems encountered in modeling of this large 5-m lightweight inflatable are identified, including considerable difficulty in obtaining convergence in the nonlinear pressurization solution. It was found that the extremely thin polyimide film material (.001 in or I mil) presents tremendous problems in obtaining a converged solution when internal pressure loading is applied. It was concluded that the ratios of film thickness to other geometric dimensions such as torus cross-sectional and ring diameter and lenticular diameter are the critical parameters for convergence of the pressurization procedure. Comparison of finite element predictions for frequency and mode shapes with experimental results indicated reasonable agreement considering the complexity of the structure, the film-to-air interaction, and the nonlinear material properties of the film. It was also concluded that analysis should be done using different finite element to codes to determine if a more robust and stable solution can be obtained.

Smalley, Kurt B.↗
DOE OSTI2021

Molecular Origin of Strain-Induced Chain Alignment in PDPP-Based Semiconducting Polymeric Thin Films

Donor–acceptor (D–A) type semiconducting polymers have shown great potential for the application of deformable and stretchable electronics in recent decades. However, due to their heterogeneous structure with rigid backbones and long solubilizing side chains, the fundamental understanding of their molecular picture upon mechanical deformation still lacks investigation. Here, the molecular orientation of diketopyrrolopyrrole (DPP)-based D–A polymer thin films is probed under tensile deformation via both experimental measurements and molecular modeling. The detailed morphological analysis demonstrates highly aligned polymer crystallites upon deformation, while the degree of backbone alignment is limited within the crystalline domain. Besides, the aromatic ring on polymer backbones rotates parallel to the strain direction despite the relatively low overall chain anisotropy. Additionally, the effect of side-chain length on the DPP chain alignment is observed to be less noticeable. These observations are distinct from traditional linear-chain semicrystalline polymers like polyethylene due to distinct characteristics of backbone/side-chain combination and the crystallographic characteristics in DPP polymers. Furthermore, a stable and isotropic charge carrier mobility is obtained from fabricated organic field-effect transistors. This study deconvolutes the alignment of different components within the thin-film microstructure and highlights that crystallite rotation and chain slippage are the primary deformation mechanisms for semiconducting polymers.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A renewable lignin-based thermoplastic adhesive for steel joining

Adhesive bonding of metals has become increasingly relevant in recent years due to the demand for reducing weight and improving performance in structural applications such as automobiles and aerospace. We developed renewable thermoplastic adhesives from technical organosolv lignin isolated from hardwood biomass and acrylonitrile butadiene co-polymer rubber (NBR) for joining steel substrates. NBR33, NBR41 and NBR51 with acrylonitrile molar ratios of 33, 41 and 51%, respectively, were blended with lignin to form two-phase thermoplastic adhesives, and their adhesion, viscoelastic and surface properties were measured. Lignin content in the compositions were varied, ranging from 40% to 80% (w/w), to alter toughness, stiffness, and surface energy characteristics of the material. Better interaction or reactivity between the lignin and NBR phases was observed with greater nitrile content in NBR, leading to greater modulus and stiffness of the adhesive. Simultaneously, increasing the proportion of lignin reduced toughness and improved stiffness, with the highest adhesive strength of 13.1 MPa measured in a 60% lignin loading ratio with NBR51. Surface energy measurements revealed that total surface energy (sum of polar and dispersive surface energy) raised with lignin loading, suggesting that both surface energy and matrix strength play a critical role in the adhesive properties of the synthesized materials. A finite element-based cohesive zone model (CZM) was developed and implemented to study the failure strength of the adhesively bonded joint. Here, this study demonstrates the viability of lignin as a valuable building block for adhesives, not only due to its inherent chemical structure and rigidity, but also for its surface energy characteristics.

36 MATERIALS SCIENCE↗