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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

High-performance carbon nanotube electronic ratchets

The rapid advancements in low-power portable/wearable electronic devices require concurrent development of technologies that can provide power without the need for bulky, heavy battery storage. Electronic ratchets, asymmetric transistor-based devices that can convert AC signals or electronic noise into DC power, have been proposed as one solution to this growing need. Here, the recent demonstration of conjugated polymer-based electronic ratchets offers a route toward lightweight, flexible power sources for portable applications. Here we demonstrate the fabrication of the first electronic ratchets where the active channel component consists of semiconducting single-walled carbon nanotubes (s-SWCNTs), which can transform electronic noise or AC signals to a stable DC current with higher output power (up to ca. 14 mW for a chemically doped device) than their polymer-based analogs. We also show that patterning of the dopant profile in the s-SWCNT channel enables reasonable power conversion performance (ca. 3.5 mW) with improved stability relative to homogeneously doped devices. Our findings demonstrate the promise for s-SWCNT electronic ratchets as energy harvesting devices for portable, low-power applications.

ENGINEERING,MATERIALS SCIENCE,NANOSCIENCE AND NANO↗
NASA NTRS1982

Performance and load data from Mod-0A and Mod-1 wind turbine generators

Experimental data, together with supporting analysis, are presented on the power conversion performance and blade loading of large, horizontal-axis wind turbines tested at electric utility sites in the U.S. Four turbine rotor configurations, from 28 to 61 meters in diameter, and data from five test sites are included. Performance data are presented in the form of graphs of power and system efficiency versus free-stream wind speed. Deviations from theoretical performance are analyzed statistically. Power conversion efficiency averaged 0.34 for all tests combined, compared with 0.31 predicted. Round blade tips appeared to improve performance significantly. Cyclic blade loads were normalized to develop load factors which can be used in the design of rotors with rigid hubs.

Spera, D. A.↗
NASA NTRSDate not supplied

Coupled Reactor and Engine Nuclear Thermal Propulsion Modeling Methodology

The design and development process of a Nuclear Thermal Propulsion (NTP) system requires extensive multiphysics modeling to couple the neutron physics and thermal feedback effects to determine the reactor’s power shape. Propulsion system performance codes utilize this power shape to determine NTP key performance parameters. While the power shape is heavily dependent on the temperature profile and geometry of the reactor, many analyses either assume a constant power shape, or use neutronics analysis to determine a power shape for a specific reactor configuration. The development of a coupling interface for a propulsion system performance code and a Monte Carlo neutron transport code (OpenMC) allows for the reactor power shape to be calculated in an iteration loop. The interface utilizes a file share system to transfer geometry dimensions, temperatures, and material identifiers to OpenMC, which is used to perform a neutron transport simulation of a design like the government Testing Reference Design reactor. The interface is then able to post-process the results from OpenMC and use the same file share system to share a power shape and other important neutron transport parameters to the system performance code. Initial results show that neglecting the changes to power shape when comparing reactor configurations can yield inaccurate results. Furthermore, utilizing propellants other than hydrogen gas can cause significant changes to the power shape, and thus, the thermal performance of a specific reactor design. This methodology is being expanded to allow for multiple families of NTP reactors to be analyzed, including block moderator, particle bed, and NERVA-derived reactors.

multiphysics coupling↗
NASA NTRSDate not supplied

Coupled Reactor and Engine Nuclear Thermal Propulsion Modeling Methodology

The design and development process of a Nuclear Thermal Propulsion (NTP) system requires extensive multiphysics modeling to couple the neutron physics and thermal feedback effects to determine the reactor’s power shape. Propulsion system performance codes utilize this power shape to determine NTP key performance parameters. While the power shape is heavily dependent on the temperature profile and geometry of the reactor, many analyses either assume a constant power shape, or use neutronics analysis to determine a power shape for a specific reactor configuration. The development of a coupling interface for a propulsion system performance code and a Monte Carlo neutron transport code (OpenMC) allows for the reactor power shape to be calculated in an iteration loop. The interface utilizes a file share system to transfer geometry dimensions, temperatures, and material identifiers to OpenMC, which is used to perform a neutron transport simulation of a design like the government Testing Reference Design reactor. The interface is then able to post-process the results from OpenMC and use the same file share system to share a power shape and other important neutron transport parameters to the system performance code. Initial results show that neglecting the changes to power shape when comparing reactor configurations can yield inaccurate results. Furthermore, utilizing propellants other than hydrogen gas can cause significant changes to the power shape, and thus, the thermal performance of a specific reactor design. This methodology is being expanded to allow for multiple families of NTP reactors to be analyzed, including block moderator, particle bed, and NERVA-derived reactors.

multiphysics coupling↗
DOE OSTI2022

Characterizing particle-based thermal storage performance using optical methods for use in next generation concentrating solar power plants

Concentrating Solar Power (CSP) generation is an attractive option for low-emission power generation; however, the high costs of thermal storage associated with concentrating solar create a large barrier for their use and adaptation into modern life. Lowering their operation costs, while maintaining high thermal storage and transfer performance is essential. Solid particle-based heat exchange systems can reduce CSP cost but are often less efficient. Efforts to increase their performance have led to use of binary size particle mixes. Presented is an optical-based thermal analysis technique used to measure near-wall thermal conductivity of particle beds essential in determining their heat exchanger efficiency. Modulated Photothermal Radiometry is used to make dynamic temperature measurements, allowing for the extraction of the most relevant thermal properties like thermal conductivity, specific heat, and effusivity. The system uses a modulated laser source causing a damped periodic heat flux, resulting in a frequency and thermal property dependent surface temperature, of which is measured using radiometry. Lock-In techniques are used to extrapolate the amplitude of the signal. Plotting the amplitude against the root angular frequency allows for effusivity measurement by ratio to a known sample. Using specific heat measurements from literature and density measurements, the thermal conductivity of the particle mixes can be calculated. The simplicity of MPTR to probe through the depth of the bed is ideal for use in CSP for dynamic thermal performance monitoring.

Corona, Javier↗
NASA NTRS1993

Hollow cathode heater development for the Space Station plasma contactor

A hollow cathode-based plasma contactor has been selected for use on the Space Station. During the operation of the plasma contactor, the hollow cathode heater will endure approximately 12000 thermal cycles. Since a hollow cathode heater failure would result in a plasma contactor failure, a hollow cathode heater development program was established to produce a reliable heater design. The development program includes the heater design, process documents for both heater fabrication and assembly, and heater testing. The heater design was a modification of a sheathed ion thruster cathode heater. Three heaters have been tested to date using direct current power supplies. Performance testing was conducted to determine input current and power requirements for achieving activation and ignition temperatures, single unit operational repeatability, and unit-to-unit operational repeatability. Comparisons of performance testing data at the ignition input current level for the three heaters show the unit-to-unit repeatability of input power and tube temperature near the cathode tip to be within 3.5 W and 44 degrees C, respectively. Cyclic testing was then conducted to evaluate reliability under thermal cycling. The first heater, although damaged during assembly, completed 5985 ignition cycles before failing. Two additional heaters were subsequently fabricated and have completed 3178 cycles to date in an on-going test.

Soulas, George C.↗
NASA NTRS1995

TROPIX Power System Architecture

This document contains results obtained in the process of performing a power system definition study of the TROPIX power management and distribution system (PMAD). Requirements derived from the PMADs interaction with other spacecraft systems are discussed first. Since the design is dependent on the performance of the photovoltaics, there is a comprehensive discussion of the appropriate models for cells and arrays. A trade study of the array operating voltage and its effect on array bus mass is also presented. A system architecture is developed which makes use of a combination of high efficiency switching power convertors and analog regulators. Mass and volume estimates are presented for all subsystems.

Manner, David B.↗
NASA NTRS1980

Evaluation of solar thermal power plants using economic and performance simulations

An energy cost analysis is presented for central receiver power plants with thermal storage and point focusing power plants with electrical storage. The present approach is based on optimizing the size of the plant to give the minimum energy cost (in mills/kWe hr) of an annual plant energy production. The optimization is done by considering the trade-off between the collector field size and the storage capacity for a given engine size. The energy cost is determined by the plant cost and performance. The performance is estimated by simulating the behavior of the plant under typical weather conditions. Plant capital and operational costs are estimated based on the size and performance of different components. This methodology is translated into computer programs for automatic and consistent evaluation.

El-Gabawali, N.↗
NASA NTRS1998

Low-Power CO2 Compression Technology

Presently, the most feasible processes for extracting oxygen from the Martian atmosphere either require or are much more efficient if the atmospheric CO2 feed is provided at pressures well above the Martian ambient. Electrical power for performing the desired compression is likely to be an extremely limited resource on the Mars surface. Even if "cheap" nuclear power is available at a central site/launch facility where rocket propellent and oxidant are manufactured, life support applications needing oxygen production capabilities, such as rovers, portable life support, and remote or independent exploration stations, will benefit from extremely low-power atmospheric compression technology, such as the one discussed here. Our experiments show the potential of one very low-power approach to performing CO2 compression that uses the Mars diurnal temperature cycle to drive a heat engine. The 1 kg compressor has been tested over an extended period in a Mars environmental simulation chamber that mimics the composition, pressure, and temperature cycles that can occur on the Martian surface. The simple design, which has very few moving parts and can easily be scaled to larger or smaller sizes, produces a CO2 stream at a rate of 100 g/ day at a quality and pressure suitable for a variety of oxygen production processes.

Finn, John E.↗
DOE OSTI2022

Resilience Design Patterns: A Structured Approach to Resilience at Extreme Scale (V.2.0)

Reliability is a serious concern for future extreme-scale high-performance computing (HPC) systems. Projections based on the current generation of HPC systems and technology roadmaps suggest the prevalence of very high fault rates in future systems. The errors resulting from these faults will propagate and generate various kinds of failures, which may result in outcomes ranging from result corruptions to catastrophic application crashes. Therefore, the resilience challenge for extreme-scale HPC systems requires coordination between various hardware and software technologies that are capable of handling a broad set of fault models at accelerated fault rates. Also, due to practical limits on power consumption in future HPC systems, they are likely to embrace innovative architectures, increasing the levels of hardware and software complexities. Therefore, the techniques that seek to improve resilience must navigate the complex trade-off space between resilience and the overheads to power consumption and performance. While the HPC community has developed various resilience solutions, application-level techniques as well as system-based solutions, the solution space of HPC resilience techniques remains fragmented. There are no formal methods to integrate the various HPC resilience techniques into composite solutions, nor are there methods to holistically evaluate the adequacy and efficacy of such solutions in terms of their protection coverage, and their performance & power efficiency characteristics. Additionally, few implementations of current resilience solutions are portable to newer architectures and software environments that will be deployed on future systems. We developed a new structured approach to the management of HPC resilience using the concept of resilience-based design patterns. In general, a design pattern is a repeatable solution to a commonly occurring problem. We identified the well-known solutions that are commonly used to deal with faults, errors and failures in HPC systems. In the initial design patterns specification (version 1.0), we described the various solutions, which address specific problems in the design of resilient HPC environments, in the form of patterns. Each pattern describes a problem caused by a fault, error or failure event in an HPC environment, and then describes the core of the solution of the problem in such a way that this solution may be adapted to different systems and implemented at different layers of the system stack. The catalog of these resilience design patterns provides designers with a collection of design elements. To construct complete resilience solutions using combinations of various patterns, we defined a framework that enhances HPC designers' understanding of the important constraints and the opportunities for the design patterns to be implemented and deployed at various layers of the system stack. The design framework is also useful for establishing interfaces and mechanisms to coordinate flexible fault management across hardware and software components, as well as to consider the trade-off between performance, resilience, and power consumption when constructing a solution. The resilience design patterns specification version 1.1 included more detailed explanations of the pattern solutions, the context in which the patterns are applicable, and the implications for hardware or software design. It also provided several additional examples and detailed case studies to demonstrate the use of patterns to build realistic solutions. In version 1.2 of the specification document, we have improved the pattern descriptions, including graphical representations of the pattern components. These improvements are largely based on critical comments, feedback and suggestions received from pattern experts and readers of the previous versions of the specification. The pattern classification has been modified to further clarify the relationships between pattern categories. This version of the specification also introduces a pattern language for resilience design patterns. The pattern language presents the patterns in the catalog as a network, revealing the relations among the resilience patterns. The language provides designers with the means to explore alternative techniques for handling a specific fault model that may have different efficiency and complexity characteristics. Using the pattern language also enables the design and implementation of comprehensive resilience solutions as a set of interconnected resilience patterns that can be instantiated across layers of the system stack. The overall goal of this work is to provide hardware and software designers, as well as the users and operators of HPC systems, a systematic methodology for the design and evaluation of resilience technologies in HPC systems that keep scientific applications running to a correct solution in a timely and cost-efficient manner despite frequent faults, errors, and failures of various types. Version 2.0 expands the resilience design pattern classification and catalog to include self-stabilization patterns and reliability, availability and performance models for each structural pattern.

97 MATHEMATICS AND COMPUTING↗
NASA NTRSDate not supplied

The Effects of Arcing Ejecta on Space Suit Materials from ISS RPCM Hot Mate/Demate During EVA

Onboard ISS, taking systems off-line when powering down to perform servicing on Remote Power Control Modules (RPCMs) introduces operational risk. An investigation lead by the NASA Engineering and Safety Center (NESC) was performed by a multi-center team to assess the safety of performing on-orbit replacement of RPCMs without powering down. This investigation revealed the potential for molten metal particulate generation in the event of an arcing occurrence. As RPCM replacement can be performed outside ISS during an Extra Vehicular Activity (EVA), it is necessary to assess the effects of this molten metal ejecta contact with the Extravehicular Mobility Unit (EMU) Space Suit Assembly (SSA) during an arcing event. A test was devised to mimic arcing ejecta contact with samples representing various SSA cross-sections. Four areas of the SSA were chosen for test to represent the majority of the SSA cross-sections. Testing was conducted by the University of California, Riverside that generated the molten metal particles, included varying composition, size and temperature, and dropped them onto the surface of the various SSA cross-sections. Exposed SSA materials were then evaluated for degree of damage, penetration, and thermal conductance through the cross-section by ILC Dover. Results showed that the SSA Glove is most susceptible to damage from arcing events. This data will be used to make risk management decisions for future RPCM servicing operations. This testing also demonstrated the durability of the SSA design and materials to exposure to extreme environments

Linda S Hewes↗
NASA NTRSDate not supplied

The Effects of Arcing Ejecta on Space Suit Materials from ISS RPCM Hot Mate/Demate During EVA

Onboard ISS, taking systems off-line when powering down to perform servicing on Remote Power Control Modules (RPCMs) introduces operational risk. An investigation lead by the NASA Engineering and Safety Center (NESC) was performed by a multi-center team to assess the safety of performing on-orbit replacement of RPCMs without powering down. This investigation revealed the potential for molten metal particulate generation in the event of an arcing occurrence. As RPCM replacement can be performed outside ISS during an Extra Vehicular Activity (EVA), it is necessary to assess the effects of this molten metal ejecta contact with the Extravehicular Mobility Unit (EMU) Space Suit Assembly (SSA) during an arcing event. A test was devised to mimic arcing ejecta contact with samples representing various SSA cross-sections. Four areas of the SSA were chosen for test to represent the majority of the SSA cross-sections. Testing was conducted by the University of California, Riverside that generated the molten metal particles, included varying composition, size and temperature, and dropped them onto the surface of the various SSA cross-sections. Exposed SSA materials were then evaluated for degree of damage, penetration, and thermal conductance through the cross-section by ILC Dover. Results showed that the SSA Glove is most susceptible to damage from arcing events. This data will be used to make risk management decisions for future RPCM servicing operations. This testing also demonstrated the durability of the SSA design and materials to exposure to extreme environments.

Linda S. Hewes↗
NASA NTRSDate not supplied

A Study of Large Scale Power Extraction and Insertion on Turbofan Performance and Stability

This describes the effects of turbofan power extraction and insertion (augmentation) on engine performance and stability. The purpose of this paper is to present how power augmentation affects a dual spool gas turbine engine cycle where the engine will also be required to provide thrust. The goals for the paper are to describe effective limits of power augmentation and offer strategies, utilizing spool choice and variable geometries, to maximize augmentation effect. While Analysis is general, two potential uses are explored: Power extraction for electrified aircraft propulsion and power insertion for thrust assist. Results of the paper show it is possible to extract over 20% (at 85% max thrust) and gain roughly 12% of maximum thrust through power insertion.

Gas Turbine engines↗
NASA NTRS2010

Test Results of Selected Commercial DC/DC Converters under Cryogenic Temperatures - A Digest

DC/DC converters are widely used in space power systems in the areas of power management and distribution, signal conditioning, and motor control. Design of DC/DC converters to survive cryogenic temperatures will improve the power system performance, simplify design, and reduce development and launch costs. In this work, the performance of nine COTS modular, low-tomedium power DC/DC converters was investigated under cryogenic temperatures. The converters were evaluated in terms of their output regulation, efficiency, and input and output currents. At a given temperature, these properties were obtained at various input voltages and at different load levels. A summary on the performance of the tested converters was given. More comprehensive testing and in-depth analysis of performance under long-term exposure to extreme temperatures are deemed necessary to establish the suitability of these and other devices for use in the harsh environment of space exploration missions.

Patterson, Richard↗
DOE OSTI2024

Modeling the impact of high thermal conductivity paper on the performance and life of power transformers

Degradation of insulation paper is a key contributor to the failure of power transformers. Insulation degradation accelerates at elevated temperatures, which highlights the potential for better thermal management to prolong life. While several studies have analyzed the benefits of high thermal conductivity oil for reducing temperatures inside a transformer, this study is an initial assessment of the benefits of high thermal conductivity paper on transformer life. Blending particulates with cellulosic fibers offers a pathway for high thermal conductivity paper (with good dielectric properties), which can reduce internal temperatures. Presently, life extensions that can be achieved by the use of such thermally conducting papers were estimated, with the thermal conductivity of the paper being the key parameter under study. The analytical-numerical thermal model used in this study was validated against experimental measurements in a distribution transformer, adding confidence to the utility of the model. This model was then used to provide estimates of hot-spot temperature reduction resulting from the use of papers with higher thermal conductivity than baseline. Transformer life was predicted conventionally by tracking the degree of polymerization of paper over time, based on an Arrhenius model. Results indicate that increasing the thermal conductivity of paper from 0.2 W/mK (baseline) to 1W/mK reduces the hot spot temperature by 10°C. While degradation significantly depends on the moisture and oxygen content, the model shows that such a temperature reduction can increase life for all conditions, by as much as a factor of three.

42 ENGINEERING↗
DOE OSTI2022

A 4 kV/120 A SiC Solid-State DC Circuit Breaker Powered By a Load-Independent IPT System

This article introduces a 4 kV/120 A solid-state dc circuit breaker (DCCB) based on discrete SiC mosfets. The DCCB is designed in a five-layer tower structure. Each layer consists of a circular main conduction branch and an attached gate driver. There are two primary benefits of the proposed DCCB. First, it reduces conduction loss with multiple devices in parallel. Second, it achieves an ultrafast response speed with SiC mosfets. Moreover, the gate drivers of the DCCB are powered by a domino inductive power transfer (IPT) system. It achieves the load-independent constant-voltage output characteristics, which means the outputs are immune to load variations. Additionally, an IPT system prototype is implemented to test the power transfer performance. At 500-kHz frequency, the total output power reaches 15.73 W, which is sufficient to power on five gate drivers, with a peak transfer efficiency of 75.4%. The IPT system is tested to power a 4 kV/120 A DCCB prototype. It validates that the DCCB is effective to turn off 120 A current within 3.5 μs.

42 ENGINEERING↗