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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Satellite Constellation Cost Modeling: An Aggregate Model

Satellite constellations and Distributed Spacecraft Mission (DSM) architectures offer unique benefits to Earth observation scientists and unique challenges to cost estimators. The Cost and Risk (CR) module of the Tradespace Analysis Tool for Constellations (TAT-C) being developed by NASA Goddard seeks to address some of these challenges by providing a new approach to cost modeling, which aggregates existing Cost Estimating Relationships (CER) from respected sources, cost estimating best practices, and data from existing and proposed satellite designs. Cost estimation through this tool is approached from two perspectives: parametric cost estimating relationships and analogous cost estimation techniques. The dual approach utilized within the TAT-C CR module is intended to address prevailing concerns regarding early design stage cost estimates, and offer increased transparency and fidelity by offering two preliminary perspectives on mission cost. This work outlines the existing cost model, details assumptions built into the model, and explains what measures have been taken to address the particular challenges of constellation cost estimating. The risk estimation portion of the TAT-C CR module is still in development and will be presented in future work. The cost estimate produced by the CR module is not intended to be an exact mission valuation, but rather a comparative tool to assist in the exploration of the constellation design tradespace. Previous work has noted that estimating the cost of satellite constellations is difficult given that no comprehensive model for constellation cost estimation has yet been developed, and as such, quantitative assessment of multiple spacecraft missions has many remaining areas of uncertainty. By incorporating well-established CERs with preliminary approaches to approaching these uncertainties, the CR module offers more complete approach to constellation costing than has previously been available to mission architects or Earth scientists seeking to leverage the capabilities of multiple spacecraft working in support of a common goal.

Science Data Processing↗
NASA NTRS2020

An Algorithm for Characterization of Fiber Aggregation in Composite Microstructures

Composite structures are susceptible to localized flaws, or variability, that drive global failure. To capture this variance, a multiscale model needs to be introduced that not only accurately represents the statistical nature of the composite microstructure but is also efficient. At the microscale, fiber aggregation creates local stress concentrations, where failure is likely to occur sooner than expected. A method of rapid microstructure generation, in conjunction with cluster characterization, is examined to develop accurate reproductions of 2D composite cross-sections. Parameterization of shape and size of fiber clusters is used to characterize representative volume elements. The discrete element method is used to generate pseudo-microstructures. The clustering parameters from the pseudo- and actual microstructure arrangements (obtained from micrographs) can be compared to determine the validity of the representative volume element generated with the discrete element method. Results show a promising approach to evaluating randomness of fiber distributions and how to accurately recreate microstructures for strength analysis.

Carbon fiber↗
NASA NTRS2024

The Potassium Isotope Composition of Aggregate Material From Asteroid Bennu

NASA’s OSIRIS-REx mission re-turned material from asteroid Bennu on September 24, 2023, marking the first time a U.S. mission has delivered asteroid samples to Earth, and the largest asteroid sample return to date. Due to the pristine nature of these primitive carbonaceous-rich samples, they allow us a rare opportunity to study our solar system’s formation to a degree not previously possible. Isotopes of moderately volatile elements (MVEs) have been recently developed as robust tracers for tracking different volatilization events within our Solar System. Of the MVEs, K has gained significant interest in recent years due to its ideal chemical and physical properties combined with technique improvements. Due to this, several recent studies have investigated the K isotope systematics within bulk chondrites and found an isotopic dichotomy be-tween the carbonaceous and non-carbonaceous chondrites (Figure 1), likely reflecting their different reservoirs which formed in the inner and outer protoplanetary disk respectively. Furthermore, systematic K isotope variations across the different carbonaceous chondrite groups and correlations with mass independent isotope systems such as Cr, Ti, and Ni, have also been observed. As a result, establishing the K isotope composition of bulk Bennu can be used to test the mission hypothesis that “Bennu’s parent asteroid accreted in the outer protoplanetary disk, beyond Jupiter, as recorded by distinct isotopic anomalies in a variety of elements” . In addition to early solar system processes, K isotopes can also be fractionated by space weathering as shown by comparisons between mature and immature lunar regolith. The degree of K isotope fractionation caused by space weathering correlates with the regolith maturity index and is an order of magnitude larger than what is observed in bulk meteorite samples which have not undergone strong space weathering processes. As such, the K isotope systematics of Bennu samples could provide an independent assessment of regolith maturity of the asteroid surface, helping to directly test the mission hypothesis that “Space weathering changed the chemistry and mineralogy of optically active surfaces” . In order to test both this hypothesis, and the hypothesis relating to Bennu’s accretion location, we aim to conduct high-precision K isotope analysis on bulk Bennu aggregates.

K Wang↗
NASA NTRS2024

Transmission Electron Microscopy of Carbonaceous Matter in Bennu Aggregate Samples

Preliminary analyses of regolith samples from asteroid Bennu show high bulk carbon abundances (~4.7 wt.%). The organic matter is readily apparent in scanning electron microscopy (SEM), transmission electron microscopy (TEM), and NanoSIMS observations. A major objective of the OSIRIS-REx mission is to understand the nature and origin of the pre-biotic organic matter inventory in Bennu samples. Here we report on TEM studies of indigenous organic matter in Bennu aggregate samples.

L P Keller↗
NASA NTRS2026

Molecular Inventory and Comparative Organic Profiling of A Homogenized Aggregate Sample From Asteroid (101955) Bennu

Evaluating the distribution and diversity of solvent-soluble organic molecules in extraterrestrial materials provide information about the physicochemical environments where prebiotic chemistry occurred and is essential for assessing the inventory of prebiotic compounds available to the early Earth. In this work, we conducted a comprehensive molecular characterization of solvent-soluble organic compounds in a homogenized aggregate sample (ID: OREX-800107-128) of unsorted regolith from asteroid (101955) Bennu returned by NASA’s OSIRIS-REx mission. Using two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HRMS), we identified 87 organic compounds across several molecular classes, including alkanes, polycyclic aromatic hydrocarbons, and nitrogen-, oxygen-, and sulfur-bearing species. Comparison with the organic inventory of CI (Orgueil), C2-ungrouped (Tagish Lake and Tarda), and CM2 (Murchison) carbonaceous chondrites revealed that Bennu sample OREX-800107-128 is most similar to Tagish Lake and Tarda yet compositionally distinct from all of these meteorites. This Bennu sample exhibits a relatively high abundance of low-molecular-weight aromatics (e.g., toluene), pyridine derivatives, and sulfur species such as dimethyl sulfite, consistent with episodic low-temperature aqueous alteration. The presence of these organic compounds suggests that this material experienced chemically diverse processes in the parent body conducive to complex organic synthesis, including aldol condensation reactions responsible for N- and O-bearing compounds. We also compared the molecular distributions of this Bennu sample and previously analyzed samples from (162173) Ryugu to assess potential common origins between these two carbonaceous asteroids. Bennu shows more chemically diverse and nitrogen-rich organic materials than Ryugu. While both asteroids share broadly similar primitive compositions, the observed chemical differences indicate distinct evolutionary histories within a likely common formation environment though whether Bennu and Ryugu derive from a single compositionally heterogeneous parent body or from multiple closely related progenitors remains unresolved. Further detailed comparative analyses of material from Bennu, Ryugu, and specific carbonaceous meteorites (e.g., Tagish Lake and Tarda) will provide new insights into how the N-rich molecular profile observed in Bennu samples was formed and evolved in the outer Solar System.

sample return↗
DOE OSTI2017

Feedback-Based Projected-Gradient Method For Real-Time Optimization of Aggregations of Energy Resources: Preprint

This paper develops an online optimization method to maximize the operational objectives of distribution-level distributed energy resources (DERs) while adjusting the aggregate power generated (or consumed) in response to services requested by grid operators. The design of the online algorithm is based on a projected-gradient method, suitably modified to accommodate appropriate measurements from the distribution network and the DERs. By virtue of this approach, the resultant algorithm can cope with inaccuracies in the representation of the AC power, it avoids pervasive metering to gather the state of noncontrollable resources, and it naturally lends itself to a distributed implementation. Optimality claims are established in terms of tracking of the solution of a well-posed time-varying optimization problem.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

SolSmart Webinar - Community Choice Aggregation & Solar Development

This webinar focuses on community choice aggregation (CCA) as a potential strategy for local governments to achieve their clean energy goals. The webinar provides an overview of what CCA is, how it works, and considerations for local governments interested in establishing or participating in a CCA program. The webinar will highlight case studies from CCAs across the U.S. that support local renewable energy development. This webinar provides one AICP CM continuing education credit. Who: Ben Butterwoth, Senior Associate, The Cadmus Group; Megan Lynch, Analyst, The Cadmus Group; Jenna Famular, Communications Manager, MCE Clean Energy; Meghan Shaw, Outreach Director for Cambridge Energy Alliance, City of Cambridge; Daniel Falk, Project Manager, The Solar Foundation

14 SOLAR ENERGY↗
DOE OSTI2018

Data-Driven Network Reduction and Aggregation with DERs for Outage Management

A novel approach exploiting the growing number of Distributed Energy Resources (DERs) to enhance distribution system resiliency is presented. After a power outage, DERs and loads are aggregated into switch-level equivalent models, preserving, at the same time, controllability information to enable real-time outage management analysis. Pre-fault smart-meters measurements are used as inputs for Artificial Neural Networks and Cold Load Pick-Up (CLPU) modeling to obtain short-term load forecast, while an optimal restoration analysis is carried out to determine restored network topology and utility-controlled loads and DERs set-points

Menazzi, Matteo↗
DOE OSTI2022

Integration of Microgrids, DER Aggregators, and DERMS with ADMS

Distributed energy resource (DER) management and control is disjointed, siloed, and at times conflicting. Behind-the-meter (BTM) assets can provide significant flexibility but are poorly integrated with the grid. Centralized control methods alone are not scalable. The objective is to develop and demonstrate an architecture that: provides reliable, resilient, and secure grid services; enables scalable, near-real-time management of utility- and small-scale DERs; supports transactive control, aggregation, and direct control of DERs; and incorporates existing utility management systems.

ADMS↗
DOE OSTI2013

Investigation of metal ion extraction and aggregate formation combining acidic and neutral organophosphorous reagents

In the present study, we investigate how varying mixtures of tri-n-butyl phosphate (TBP) and dibutyl phosphate (HDBP) results in enhanced extraction of lanthanum(III), La{sup 3+}, and dysprosium(III), Dy{sup 3+}. Water and metal ion extraction were carefully monitored as a function of TBP:HDBP mole ratio.In addition to these techniques, EXAFS was used to determine the coordination environment of the metal ion in this system. To produce the necessary signal, a concentration of 1.25*10{sup -3} M La{sup 3+} and Dy{sup 3+} was used. Although previous studies of synergistic extraction of metal cations using combinations of neutral and acidic reagents explain the enhanced extraction by increased dehydration of the metal ion and the formation of mixed extractant complexes, our evidence for the increased water extraction coupled with the aggregate formation suggests a reverse micellar aspect to synergism in the system containing TBP and HDBP. It is quite possible that both of these phenomena contribute to our system behavior. The EXAFS data shows that, based on coordination numbers alone, several possible structures may exist. From this study, we cannot provide a definitive answer as to the nature of extraction in this system or the exact complex formed during extraction.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Dyes in dye aggregate systems—engineering J, K, and dye packing

The present disclosure is directed to designing dyes and methods to alter the parameters controlling the dipole-dipole coupling of dyes bound to a nucleotide oligomer architecture, which are used to propagate excitons for use in next generation room temperature quantum information systems. The disclosed dyes and methods are directed to changing the dye stability, symmetry, overlap, and steric hindrance of the dyes to fine tune aggregate systems.

Knowlton, William B.↗
DOE OSTI2016

Modeling the Effect of Evaporative Flux and Colloidal Aggregation on Crud Deposition

During the last few years lot of research has been conducted to investigate and predict the Crud deposition in PWRs. One of the common findings of various experimental and computational studies is that thickness or amount of crud deposits is directly related to evaporative flux maps. Evaporation driven deposition profile on the surfaces takes different forms, i.e. from ring to disk shapes during initial stages and in the form of porous to impervious continuous layers covering the hot fuel surface at the later stages. The amount and thickness of these deposits although are directly related to evaporative flux, the relationship is much complex and can be dependent upon several other factors. A popular problem relating evaporative flux to particulate deposition has been well studied in the form of drying of sessile colloidal drops. It was proposed that, this phenomenon is due to a geometrical constraint: the free surface, constrained by a pinned contact line squeezes the fluid outwards to compensate for evaporative losses and thereby transporting particles to the contact line. Later on a quantitative relationship between evaporative flux and deposition rate was proposed and validated by the same group, which showed power-law relationship. Deposition studies conducted with controlled concentration of particles with subcooled nucleate boiling also showed a power-law relationship rather than a simpler linear relationship whereas physics of evaporation would tend to concentrate particles at linear rate. In a typical subcooled nucleate boiling system, bubble growth and departure time is of the order 1-2 ms, measured experimentally. Diffusion time constant for dilute spherical metallic colloids such as crud particulates, generally present as particulate in process piping, range from 0.0025-2.5 sec in water for a size range 0.1-1.0 μm. Colloidal behavioral characteristics during the growth of bubbles can be computed with escape time constant at collision, which is dependent on effective Hamaker constant. For minimum effective Hamaker constant of Hematite is -2.5 kT and diffusion time constant τ = 0.0025 sec, escape time constant is computed as Kramer rule, τexp[A/kT] magnitude is 0.03 sec or 30 ms. This clearly indicates that evaporation will cause particles to come together and they cannot escape at a fast enough rate which would lead them to form agglomerates. Therefore both effects of evaporative flux in conjunction with the agglomeration kinetics must be considered for modeling the crud deposition if the evaporative flux is known. In this paper, we propose a phenomenological model of colloidal transport and aggregation with evaporative flux. The dynamic of particles interactions while drying of sessile colloidal drops is developed by coupling general transport equation with Smoluchowshki Coagulation equation. Crud deposition on the nuclear fuel has been a serious problem with severe consequences in nuclear power plants. In several studies it has been consistently reported that crud deposition is directly related to evaporative flux on the nuclear fuel surfaces. However, it has not been established how to quantify the deposition rates of crud type particulates if the evaporative flux is known. This complex multiphysics problem is similar to coffee-ring effect, where the governing physics is understood more clearly. In this work, a simplified geometry is used to model the effects of evaporative flux acting at a boundary on the colloidal concentration. The effect of this condition on change in concentration is shown numerically. Further, agglomeration is suspected to play a significant role in high evaporative flux such as bubble nucleation. The coagulation kinetics is modeled using uniform particle distribution and the effective total concentration of colloids including original particles and agglomerates is studied. Once this model is validated with a simple separate effect experiments, it can be integrated to large scale PWR models of evaluating evaporative flux and chemistry models developed by Electrical Power Research Institute (EPRI). (authors)

42 ENGINEERING↗
DOE OSTI2025

Quantifying Message Aggregation Optimisations for Energy Savings in PGAS Models

Upon breaking past the exascale barrier, HPC systems are facing their greatest challenge yet - a power wall that must be addressed through new methods in both hardware and software. While energy costs are becoming a major issue at all levels, of particular concern is that of the network, as the relative cost of moving data is increasing faster than ever. The partitioned global address space (PGAS) model is critical within certain HPC domains, but is known to suffer from the small message problem, where irregular many-to-many access patterns result in congesting the network with excessive numbers of small messages. To address this, the conveyor aggregation library was developed to defer individual messages and group them for subsequent bulk processing. In this paper, we investigate its impact on energy use related to the network, with a focus on the Slingshot 11 interconnect. We will demonstrate that this strategy is not only highly performant, but also crucial to reducing energy footprints to remain within target power envelopes.

Welch, Aaron [ORNL]↗
DOE OSTI2026

Measurement-informed Dynamic Aggregation of Distribution Systems

This paper proposes a measurement-informed dynamic aggregation methodology in order to create equivalent representations of distribution systems that are compatible with large-scale transmission analysis. By optimizing an equivalent feeder parameters using time-series measurements of active power, reactive power, and voltage at the Point of Interconnection (POI), the approach yields simplified yet dynamically accurate equivalents. Implemented in PSCAD with models of photovoltaic–battery systems, three-phase motors, and static loads, the method employs hybrid differential evolution and bounded least-squares optimization laying the foundation for for real-time state estimation and optimized sensor placement in distribution networks.

Ahmed, Kazi Ishrak [University of Tennessee, Knoxv↗
DOE OSTI2016

Room-Temperature Micron-Scale Exciton Migration in a Stabilized Emissive Molecular Aggregate

We report 1.6 ± 1 μm exciton transport in self-assembled supramolecular light-harvesting nanotubes (LHNs) assembled from amphiphillic cyanine dyes. We stabilize LHNs in a sucrose glass matrix, greatly reducing light and oxidative damage and allowing the observation of exciton–exciton annihilation signatures under weak excitation flux. Fitting to a one-dimensional diffusion model, we find an average exciton diffusion constant of 55 ± 20 cm 2 /s, among the highest measured for an organic system. We develop a simple model that uses cryogenic measurements of static and dynamic energetic disorder to estimate a diffusion constant of 32 cm 2 /s, in agreement with experiment. We ascribe large exciton diffusion lengths to low static and dynamic energetic disorder in LHNs. We argue that matrix-stabilized LHNS represent an excellent model system to study coherent excitonic transport.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗