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At least 1,387 records · Page 77

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NASA NTRSDate not supplied

Foundational Concepts in Simulation-Based Resilience Analysis and Design

Resilience is a topic of increasing interest–with ever-present calls from policymakers to increase the resilience of complex systems and infrastructure. However, resilience as a concept can be confusing, because of a lack of a common unified definition and frame of reference. Sometimes it can appear as if resilience analysis is merely duplicating other, more mature fields such as safety, reliability, or risk, while other times it seems as if resilience is providing an “alternative” view with limited rigor. To better understand the resilience concept (and its relation to the broader field of risk management), this paper will present the perspective of simulation-based resilience analysis and design, including some of the foundational precepts and resultant concepts defining the resilience concept. It will further present the motivation for using simulation to understand resilience and highlight some ongoing work and research challenges in this area. From this frame of reference, one can better understand the field of resilience, including how different aspects and definitions of resilience relate to each other, and how resilience relates to broader design considerations and practices.

resilience↗

NASA NTRSDate not supplied

Enhancing Future Commercial Space Stations: Applying ISS Insights to Environmental Control and Life Support Systems (ECLSS) Development

The expansion of space exploration to commercial space stations represents a shift from government-led endeavors to a new competitive era driven by private companies and innovative forces. The journey to actualize these celestial outposts is fraught with difficulties, including the intricate establishment of Environmental Control and Life Support systems (ECLSS) within these commercial space stations. By applying the insights gleaned from the ISS, particularly during the initial conceptual design phase of the commercial developments, there is an opportunity to circumvent some of the teething issues and optimize the development process. Furthermore, applying insights from the ISS ECLSS design, development, test, and maintenance phases has the potential to enhance system compatibility and mitigate the challenges associated with upgrading a fixed design. This approach can lead to lower costs due to fewer iterations and streamlined processes. This paper will conduct an in-depth evaluation of the ECLS system from both system and operational perspectives with the aim to provide a knowledge capture for early-stage design considerations to bolster the development of sustainable, efficient, and habitable commercial space stations.

ISS↗

NASA NTRSDate not supplied

Foundational Concepts in Simulation-Based Resilience Analysis and Design

resilience↗

NASA NTRSDate not supplied

A New Test Methodology for Evaluating Fire Risk Due to Electrical Faults in Oxygen-Enriched Environments

This paper discusses a new test methodology for assessing the safe use of materials found in spacecraft that may be exposed to electrical faults, as performed at the NASA White Sands Test Facility. “Wire-break” testing, modeled after the Cleveland Open Cup method, identifies the conditions under which pyrolyzed material transitions from a brief flash to a propagating flame. The approach focuses on fuel mass liberated through pyrolysis, mixed with oxygen, and ignited by a piloted ignition (spark due to fusion of wire) to achieve flame propagation with the least energy. The test approach attempts to find energy density thresholds derived using I²t values from current-induced heating of various test materials and wire characteristics. The application of the data provides a useful approach to mitigating fire risks in space systems by correlating threshold data to real-world designs and scaling factors, including oxygen pressure, wire diameter, heat sinking, and contained smoke volume. Several case studies, including Apollo missions and hypothetical scenarios, illustrate practical applications of these thresholds to enhance fire safety design considerations in space environments.

methodology↗

NASA NTRSDate not supplied

Assessment of a Surface Propellant Transportation System Concept for Operations on Mars

NASA is working to define the architecture needed for a Mars exploration campaign. One potential architecture option allows for pre-deployment of essential cargo and equipment to support a crew landing, including the pre-positioning of a Mars Ascent Vehicle (MAV). This MAV is likely to represent the largest single payload that must be landed on the Martian surface. Its size would be influenced by the amount of mass that state-of-the-art Entry, Descent, and Landing (EDL) systems would be capable of placing on Mars. One possible method of increasing the usable size of the MAV without exceeding available EDL capabilities is to land the MAV without its ascent propellant on board. Following such a method may necessitate a strategy to acquire sufficient ascent propellant to allow a crew to safely depart the Martian surface. This paper describes a conceptual return propellant strategy that uses a liquid transportation skid, or pallet, to be used in conjunction with a rover mobility system to transfer cryogenic propellant, consisting of oxygen and methane, across the Martian surface from a delivery lander to the MAV to enable its launch. Design considerations, concept of operations, and rover energetics will be discussed in this paper.

Propellant↗

NASA NTRSDate not supplied

Enabling Smart Urban Airspaces through Distributed Sensing Technologies

Distributed sensing systems offer potential for enhancing safety and efficiency in urban airspaces and low-altitude metropolitan flight corridors. These systems leverage sensor networks to provide real-time airspace monitoring, situational awareness, and data for decision-making. This paper examines application of distributed sensing and smart airspace concepts to enable advanced urban flight, focusing on critical need applications such as airspace monitoring, corridor surveillance, precision navigation, and hazard avoidance. Benefits such as improved monitoring and increased situational awareness of activity within the urban airspace are considered alongside challenges in system design and implementation. This paper summarizes an ongoing effort to study the feasibility and effectiveness of distributed sensing systems for enabling urban airspace operations. Current research and design considerations are summarized, and a proposed roadmap for future work is presented.

Corey A Ippolito↗

NASA NTRSDate not supplied

Assessment of a Surface Propellant Transportation System Concept for Operations on Mars

NASA is working to define the architecture needed for a Mars exploration campaign. One potential architecture option allows for pre-deployment of essential cargo and equipment to support a crew landing, including the pre-positioning of a Mars Ascent Vehicle (MAV). This MAV is likely to represent the largest single payload that must be landed on the Martian surface. Its size would be influenced by the amount of mass that state-of-the-art Entry, Descent, and Landing (EDL) systems would be capable of placing on Mars. One possible method of increasing the usable size of the MAV without exceeding available EDL capabilities is to land the MAV without its ascent propellant on board. Following such a method may necessitate a strategy to acquire sufficient ascent propellant to allow a crew to safely depart the Martian surface. This presentation describes a conceptual return propellant strategy that uses a liquid transportation skid, or pallet, to be used in conjunction with a rover mobility system to transfer cryogenic propellant, consisting of oxygen and methane, across the Martian surface from a delivery lander to the MAV to enable its launch. Design considerations, concept of operations, and rover energetics will be discussed in this presentation.

Surface↗

NASA NTRSDate not supplied

The Space Weather Follow On – Lagrange 1 Mission

The Space Weather Follow On – Lagrange 1 (SWFO-L1) Observatory will be situated in a Sun-Earth L1 Lissajous orbit with the goal of providing continuous measurements of the space environment and observations of the Sun’s outer atmosphere, and contributing to accurate forecasts of space weather disturbances. Unique to the SWFO-L1 mission are challenges of a rideshare launch, immoderate momentum management delta-V residuals, and spacecraft maneuver design considerations, resulting in specialized operational approach, management, and support.

cislunar↗

NASA NTRSDate not supplied

The Space Weather Follow On – Lagrange 1 Mission

Dynamical Systems↗

DOE OSTI2020

The Future of Zero Energy Buildings: Produce, Respond, Regenerate: Preprint

The zero energy buildings concept is more than 20 years old, and the paradigm shift from buildings as energy consumers to buildings as energy producers is underway. Buildings also consume land and material resources, however, with attendant environmental impacts. Another paradigm is emerging: a built environment that produces energy and is environmentally responsive and regenerative. This paper investigates an updated framework for thinking about zero energy buildings that includes discussions of prioritizing renewables; determining on-site versus off-site generation; exploring how and when buildings should use energy; and balancing renewables, storage, and energy efficiency. Buildings are typically connected to the utility grid and the utility grid develops largely in response to the built environment. If more buildings’ real time electricity use aligned with renewable generation, more renewables would be added to the grid. Ultimately, the goal for zero energy buildings will be to use 100% renewables, 100% of the time, matching loads with energy storage and renewable generation at each discrete timestep over a year. This target is beyond the current zero energy definitions, which focus on an annual balance of renewable supply and energy demand and use the grid to “store” excess production to make up for hours without sufficient on-site renewable generation. This paper expands this upgraded concept and outlines simple metrics to evaluate the alignment of renewable sources and storage with building loads. This process can provide insights on building design considerations, including the use of flexible loads and optimal resource management.

ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION↗

DOE OSTI2021

Cryogenic Electronics development for High Energy Physics

In the quest to study the fundamental nature of matterand the universe, High Energy Physics (HEP) experimentsoften operate in extreme conditions that lie well outside thestandard operating range of integrated circuits. Two prominentexamples of such extreme environments are the irradiationlevels experienced at high luminosity colliders, as well asoperation at cryogenic temperatures. Cryogenic electronicsis a broad term that encompasses circuits operating at temperatures below the standard operating limit (-55°C in the caseof military grade electronics), all the way down to millikelvin,as in the case of superconducting circuits. Cryogenic circuitshave a long history and have found applications in abroad spectrum of applications, such as infrared focal planearrays, PET, quantum science. While CMOS circuits have beenreliably operated at deep cryogenic temperatures (<4.2K),this article focuses on applications down to liquid Nitrogen(77K), and provides an overview on the design considerations,benefits, and unique challenges pertaining to cryogenic CMOSICs for large HEP experiments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Towards Generic Parallel Programming in Computer Science Education with Kokkos

Parallel patterns, views, and spaces are promising abstractions to capture the programmer's intent as well as the contextual information that can be used by an underlying runtime to efficiently map software to parallel hardware. These abstractions can be valuable in cases where an algorithm must accommodate requirements of code and performance portability across hardware architectures and vendor programming models. Kokkos is a parallel programming model for host- and accelerator architectures that relies on these abstractions and targets these requirements. It consists of a pure C++ interface, a specification, and a programming library. The programming library exposes patterns and types and maps them to an underlying abstract machine model. The abstract machine model offers a generic view of parallel hardware. While Kokkos is gaining popularity in large-scale HPC applications at some DOE laboratories, we believe that the implemented concepts are of interest to a broader audience including academia as they may contribute to a generic, vendor, and architecture-independent education of parallel programming. In this work, we give an insight into the design considerations of this programming model and list important abstractions. Further, we document best practices obtained from giving virtual classes on Kokkos and give pointers to resources that the reader may consider valuable for a lecture on generic parallel programming for students with preexisting knowledge on this matter.

Ciesko, Jan↗

DOE OSTI2021

High efficiency multi-junction small-molecule photovoltaic devices

High efficiency multi-junction small-molecule organic photovoltaic devices and methods of fabricating the same are disclosed herein. Design considerations for improving spectral coverage and light-harvesting efficiency using the multi-junction devices are also disclosed.

Forrest, Stephen R.↗

DOE OSTI2021

Multiplexing-Based Flyback Converter for Multi-Port USB Power Delivery with True Power-Sharing

Universal serial bus power delivery (USB-PD) chargers are more attractive to consumers with multiple output ports. Existing multiple port charger designs take multi-stage approach thus increase power loss and charger size. Also, ports are normally designed with different power capability thus the high-power port becomes under-used if the connected device is fully charged while the other lower power ports cannot take over the unused power. This is mainly limited by the power architecture design. This paper addresses this issue by presenting a multiplexing based multi-port quasi-resonant flyback converter. The design achieves true power-sharing with high efficiency, small size, and simple analog implementation. This paper discusses the operating principle and design considerations. A GaN-based 60 W dual port charger verifies the proposed scheme while achieving 76% size reduction and 1% efficiency improvement than state-of-the-art.

Xue, Lincoln↗

DOE OSTI2022

First survey of centimeter-scale AC-LGAD strip sensors with a 120 GeV proton beam

We present the first beam test results with centimeter-scale AC-LGAD strip sensors, using the Fermilab Test Beam Facility and sensors manufactured by the Brookhaven National Laboratory. Sensors of this type are envisioned for applications that require large-area precision 4D tracking coverage with economical channel counts, including timing layers for the Electron Ion Collider (EIC), and space-based particle experiments. A survey of sensor designs is presented, with the aim of optimizing the electrode geometry for spatial resolution and timing performance. Several design considerations are discussed towards maintaining desirable signal characteristics with increasingly larger electrodes. The resolutions obtained with several prototypes are presented, reaching simultaneous 18 micron and 32 ps resolutions from strips of 1 cm length and 500 micron pitch. With only slight modifications, these sensors would be ideal candidates for a 4D timing layer at the EIC.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2024

Enhancing Electrochemical CO2 Conversion by Controlling Electrocatalysts' Structure

Electrochemical reduction of CO2 (CO2R) to valuable, carbon-neutral chemical feedstocks and storable fuels driven by renewable electricity has been recognized as one of the promising pathways to mitigate the greenhouse effect, reduce global demand for fossil fuels, achieve carbon neutrality, and create sustainable energy. Tremendous ongoing efforts have focused on controlling the morphology, composition, structure, size, defects, etc., of the electrocatalysts to improve product selectivity, activity, and durability to approach the feasibility of practical applications (current density higher than 200 mA/cm2 and lifetime ~1,000 hr+). This presentation will discuss how the geometry and surface composition of novel copper- and tin-based catalysts would maximize the CO2 conversion to carbon monoxide and liquid formic acid/formate in both common aqueous H-cell and electrolyzer configurations. Several spectroscopic, microscopic, and electrochemical characterization tools have been utilized to correlate the changes in the structural, physico-chemical, and electronic properties with the catalytic activity. Our work provides additional electrocatalyst design considerations for high-performance CO2 electrolysis.

Nguyen Phan, Thuy Duong↗

DOE OSTI2023

Thermal Analysis of Thermal Shield for PIP-II SSR1 Cryomodule

Fermilab's PIP-II project plans to enhance the onsite accelerator into the world's most intense neutrino beam, bringing Fermilab into the next generation of particle accelerators. The five different types of cryomodules are vital parts of the PIP-II project and each requires numerous engineering analyses to prove operation. For example, the thermal shield of the Single Spoke Resonator-1 (SSR1) cryomodule required a thermal analysis to ensure the design was operating as intended before fabrication commenced. The thermal shield is cooled by the supercritical helium inside of the extrusion and must remain between 45 and 80 Kelvin. The main purpose of the thermal shield is to intercept different high heat loads and thermal radiation and prevent them from reaching the more sensitive internal components. Finite Element Analysis (FEM) was used to determine temperature estimates of the thermal shield based on the location of a variety of heat sources. Results determined temperatures exceeding the design limit around the crucial component of the current leads. Due to superconducting properties, the areas around the current leads cannot surpass 68 Kelvin. Different solutions to the critical high-temperature areas will be proposed. These solutions range from changing the properties of the helium flow to designing an attachment for the thermal shield. Each proposition works as a viable solution, however, each proposition also has its own set of advantages and disadvantages that are described for further design consideration.

43 PARTICLE ACCELERATORS↗

DOE OSTI2024

Non-Electricity Based Renewable Fuels: Theory and Computation for Solar Thermochemical Hydrogen

Dominated by photovoltaics and wind, current renewable energy sources generate mostly electricity, but 80% of the global final energy consumption occurs in form of fuels. Therefore, direct solar fuel generation would be a major breakthrough for the energy transition. Solar thermochemical hydrogen (STCH) is one of the very few potential routes towards scalable renewable fuels, but currently suffers from lack of an oxide working material that could optimally perform energy conversion within the thermodynamic boundary conditions. Theory and computation can contribute in two distinct ways, through materials search and discovery, but also by providing detailed mechanistic models for specific systems so to advance our understanding of possible design strategies. To enable high-throughput materials screening, we developed a defect graph neural network (dGNN) machine learning approach,[1] which accelerates the prediction of defect formation energies by replacing the tedious density functional theory (DFT) supercell calculations for all possible defect sites. This approach enables high-throughput database screening of oxides, which was integrated with thermodynamic modeling to extract the reduction entropies as additional selection criterion for STCH. Once potential candidate materials are identified, detailed models can guide materials design by predicting performance characteristics. One challenge is to quantitatively predict thermochemical equilibria at high concentrations when the redox active defects start to interact with each other, thereby impeding the formation of additional defects. Introducing a model for the free energy of defect interaction, parametrized on the basis of DFT data, we simulated the complete STCH redox cycle for (Sr,Ce)MnO3 alloys, achieving near-quantitative agreement with experimental data.[2] The analysis of these simulations reveals how defect interactions diminish the reduction entropy and H2 yield, suggesting to include these interactions in design considerations. Finally, we revisit the popular van't Hoff method for analyzing reduction enthalpies and entropies. This method is not ideal, as it involves a temperature-dependent convolution of gas-phase and solid-state entropies, causing uncertainties in the same order of magnitude as the physical quantities of interest. To avoid this problem, we suggest a simple alternative approach which can be applied to experimental and simulated data alike.

first-principles calculations↗