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At least 721 records · Page 40

All sources NASA NTRS DOE OSTI

DOE OSTI2024

Particles scattering in a HVDC gun

The Electron Ion Collider (EIC) hadron cooling electron source will utilize a high average current, high voltage DC gun ,aiming to generate 1nC, 100 mA average current, and 1mm-mrad normalized emittance[1]. One of the challenges in designing and operating the HVDC gun is the occurrence of undesired "ghost" particles that disrupt the gun's operation. In other words, the high voltage power supply (HVPS) trips more frequently when pushing to higher current.

43 PARTICLE ACCELERATORS↗

DOE OSTI2024

Fabrication of a Liner Assembly for the MARVEL Microreactor

A liner assembly for an intermediate heat exchanger within the MARVEL microreactor at Idaho National Laboratory has been fabricated using laser-based additive manufacturing. The liner design includes challenging features such as long thin walls, overhangs, and tight geometric tolerances. Two versions of the liner assembly, one full length and the other shortened, were printed from several materials (316L SS, Inconel 625, and Inconel 718) using four powder-based laser printers (AddUp BeAM Modulo 400 DED, EOS 290M LPBF, GE Concept M2, and GE Concept Xline 2000R LPBF) located at the Manufacturing Demonstration Facility of Oak Ridge National Laboratory. Dimensional accuracy, print time, and powder utilization have been evaluated to help assess the feasibility of these AM approaches to liner fabrication. Based on this assessment, a potentially cost-effective pathway for fabrication has been proposed.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Catalysis Driven by Confined Hot Carriers at the Liquid/Metal/Zeolite Interface

In chemical industry controlling the activity and selectivity of a chemical conversion process is of immense importance. Traditionally, dissipation of thermal energy drives transformation of reactants, which may lead to formation of a variety of products; it remains a key challenge to design a process that dissociation and formation of specific chemical bonds can be triggered to form certain desirable products with very high selectivity, preferably at low temperatures. Introduction of light-sensitive solid materials into catalysis provides a powerful, alternate strategy for this purpose.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Augmenting LLM-Based Agents for Improved Performance in Pentesting and Commissioning Operational Technology in Critical Infrastructure

Artificial intelligence (AI), and more specifically large language models (LLMs) have the potential for use in penetration testing (“pentesting”) against devices, networks, and computer systems in information technology (IT). We explore the possibility of extending pentesting from IT systems to operational technology (OT) systems, which are more obscure than IT systems in their protocols and design. A challenge therefore exists when applying pretrained LLMs to OT systems as corpora are likely to underrepresent OT systems in comparison to other more prevalent systems. We evaluate augmentations of LLMs with various methods, especially retrieval augmented generation (RAG), to improve performance of the LLMs in the OT domain. In addition to pentesting, some of the testing of these OT devices may include commissioning to ensure that the newly installed devices work correctly. Our framework may also be applied in such cases.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2022

High Order Wall-Modeled Large-Eddy Simulation on Mixed Unstructured Meshes

In the present study, an algebraic equilibrium wall model previously developed for hexahedral elements is extended to handle mixed meshes including prismatic, tetrahedral, and pyramidal elements in the context of a discontinuous high-order method. This extension is needed for complex geometries, for which high-order mixed elements (e.g., tetrahedral and pyramidal elements) are often necessary near solid walls to avoid meshing challenges. Various design decisions are discussed to achieve the best performance on massively parallel CPU/GPU architectures for a production-level high-order large-eddy simulation solver based on the flux reconstruction/correction procedure via reconstruction method, hpMusic. The extension to other elements is first evaluated using a benchmark channel flow problem at various Reynolds numbers. After that, flow over the NASA high-lift Common Research Model (CRM-HL) from the 4th AIAA High-lift Prediction Workshop is computed to further test the new implementation. Computational results at the third- and fourth-order accuracies are compared with experimental data.

Engineering↗

DOE OSTI2025

Advancements in Heat Transfer and Fluid Mechanics (Fundamentals and Applications)

Thermo-fluid science is a foundational discipline for numerous mechanical systems, particularly in energy production and building equipment, where thermal and mechanical energy transfer play critical roles. Advancements in heat transfer and fluid mechanics have significantly enhanced these systems, driving progress in associated market sectors. For instance, evaporator and condenser coils are essential for optimizing vapor compression cycles in building equipment. Heat pumps used for space and water heating constitute a major share of building systems, with microchannel heat exchanger technology at the forefront of these innovations. It is worth mentioning that advancements in heat transfer and fluid mechanics significantly alleviate the challenge of designing energy-efficient building equipment. The development of research techniques has contributed significantly to the advancement of science; for example, in the experimental field, non-intrusive measurement techniques such as Particle Image Velocimetry (PIV) are now capable of resolving flow behavior in a 3D format for different length and time scales.

42 ENGINEERING↗

DOE OSTI2024

Semi-Lagrangian nodal discontinuous Galerkin method for the BGK model

In this work, we propose a semi-Lagrangian (SL) nodal discontinuous Galerkin (DG) solver for the BGK equation. The BGK model was introduced by Bhatnagar, Gross, and Krook [1] as a relaxation model for the fundamental Boltzmann equation [5], which describes the kinetic dynamic of rarefied gases with a probability distribution function. The challenges of designing efficient numerical schemes for the Boltzmann equation mainly come from its high dimensionality and complicated nonlinear collision operator. The BGK model gains interests since it has much lower computational cost, due to the relatively simple structure of the relaxation operator in replacement of the collision operator, while simultaneously preserving several important physical properties, such as macroscopic quantities and dissipation of entropy.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2023

Strategies for conservative and non-conservative monotone remapping on the sphere

Abstract. Monotonicity is an important property of remapping operators for coupled weather and climate models. However, it is often challenging to design highly accurate operators that avoid the generation of new extrema or keep a remapped field between physically prescribed bounds. To that end, this paper explores several traditional and novel approaches for both conservative and non-conservative monotone remapping on the sphere. The accuracy and effectiveness of these algorithms are evaluated in the context of several different real and idealized fields and meshes.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1974

Space Shuttle S-band antenna system

The NASA Space Shuttle Orbiter presents some very challenging antenna design problems for the S-band Orbiter to ground and Orbiter to relay satellite communications links. The line of sight to the ground and/or relay satellite during the various mission phases dictates an almost omni-directional coverage requirement, but the circuit margins require at least a 3 dB gain over this same coverage region. In addition, the environmental conditions imposed by the Orbiter mission dictate a flush mounted rugged antenna design. A number of potential antenna designs have been evaluated and found not to meet the Orbiter requirements. A small passive array of cavity backed spirals was found to offer the most potential to meet the design requirements. New circuit margin requirements presently under study have forced the consideration of the use of an active transmit/receive phased array design that considerably complicates the antenna design, but provides more than 10 dB of additional gain for circuit margin improvement.

Walton, M. D.↗

NASA NTRS1975

Large Space Telescope - Orbital crew EV maintenance operations

The paper shows that orbital EV maintenance by the crew has a tremendous impact on several areas of the program, including operations, Shuttle interfaces, support equipment rendezvous and berthing, checkout and verification, levels of servicing achievable, logistics and spares and scientific instruments in order to permit changeout and possible future refurbishment. To achieve on-orbit EV maintenance, such challenges as designing for suited-astronaut access to all subsystem equipment elements, minimization for contamination, handling of extremely sensitive instruments, development of translation techniques, and use of existing GFE and hardware must be faced early in the preliminary design and operations analysis phases. All studies to date indicate that on-orbit EV manned maintenance of the LST (Large Space Telescope) is not only feasible but can be designed to be readily within the capability of the EV functioning astronaut. Both 1-g and neutral buoyancy man-in-the-loop simulations further support this point.

Fisher, H. T.↗

NASA NTRS1987

System architecture of MMIC-based large aperture arrays for space application

The persistent trend to use millimeter-wave frequencies for satellite communications presents the challenge to design large-aperture phased arrays for space applications. These arrays, which comprise 100 to 10,000 elements, are now possible due to the advent of lightwave technology and the availability of monolithic microwave integrated circuits. In this paper, system aspects of optically controlled array design are studied. In particular, two architectures for a 40 GHz array are outlined, and the main system-related issues are examined: power budget, synchronization in frequency and phase, and stochastic effects.

Herczfeld, P. R.↗

NASA NTRS1988

Handling Flight-Research Data In Real Time

Researchers at widely separated locations able to participate in tests and analyze data immediately. Basic data-handling needs common: Communicates with vehicle, pilot, and test team; Acquires, computes, and displays data; knows exact location of research vehicle at all times. Continuing challenge for designers and operators of ground support facilities to perform tasks in real time and present integrated results to research team in real time. Paper presents several approaches to satisfaction of requirements of representative types of aircraft research programs at NASA Western Aeronautical Test Range of Ames Research Center.

Moore, Archie L.↗

NASA NTRS1987

Telescope structures - An evolutionary overview

A development history is presented for telescope structural support materials, design concepts, equatorial and altazimuthal orientational preferences, and mechanical control system structural realizations. In the course of 50 years after Galileo, the basic configurations of all reflecting telescopes was set for the subsequent 300 years: these were the Cassegrain, Gregorian, and Newtonian designs. The challenge of making a lightweight ribbed pyrex glass primary mirror for the 5-m Palomar telescope was met by von Karman's use of finite element analysis. Attention is given to the prospects for a 20-m deployable space-based reflecting telescope.

Meinel, Aden B.↗

NASA NTRS1987

System architecture of MMIC-based large aperture arrays for space applications

Herczfeld, P. R.↗

NASA NTRS1988

International interface design for Space Station Freedom - Challenges and solutions

The definition of interfaces for the International Space Station is discussed, with a focus on negotiations between NASA and ESA. The program organization and division of responsibilities for the Space Station are outlined; the basic features of physical and functional interfaces are described; and particular attention is given to the interface management and documentation procedures, architectural control elements, interface implementation and verification, and examples of Columbus interface solutions (including mechanical, ECLSS, thermal-control, electrical, data-management, standardized user, and software interfaces). Diagrams, drawings, graphs, and tables listing interface types are provided.

Mayo, Richard E.↗

NASA NTRS1989

The Space Station Freedom - International cooperation and innovation in space safety

The Space Station Freedom (SSF) being developed by the United States, European Space Agency (ESA), Japan, and Canada poses novel safety challenges in design, operations, logistics, and program management. A brief overview discloses many features that make SSF a radical departure from earlier low earth orbit (LEO) space stations relative to safety management: size and power levels; multiphase manned assembly; 30-year planned lifetime, with embedded 'hooks and scars' forevolution; crew size and skill-mix variability; sustained logistical dependence; use of man, robotics and telepresence for on-orbit maintenance of station and free-flyer systems; closed-environment recycling; use of automation and expert systems; long-term operation of collocated life-sciences and materials-science experiments, requiring control and segregation of hazardous and chemically incompatible materials; and materials aging in space.

Rodney, George A.↗

NASA NTRS1991

Overview Of Aerothermodynamics Of Hypersonic Flight

Paper reviews recent developments in technology of hypersonic flight. Notes renewed interest including proposals for commercial hypersonic transport and atmospheric-braking orbital-transfer vehicles. Considers flight environments in which such aircraft operate, fluid-dynamic and chemical phenomena of hypersonic flight, computational challenges to designers and developers of aircraft and power-plants, and difficulties of validating computer models of hypersonic phenomena.

Chapman, Gary T.↗

NASA NTRS1991

The effect of a type 3 and type 4 shock/shock interaction on heat transfer in the stagnation region

One of the major engineering challenges in designing the National Aerospace Plane, NASP, is to overcome augmented heating on the intake cowl lip from shock/shock interactions. The shock/shock interaction arises when the bow shock from the craft's nose interferes with the bow shock from the cowl lip. Considering only the region immediately around the cowl lip, the problem geometry may be simplified as that of an oblique shock impinging on a bow shock from a circular cylinder. Edney classified six different interference patterns resulting from an oblique-shock/curved bow-shock interaction. Of these six types, type 3 and 4 are most significant in that augmented surface heat transfer may be ten to thirty times greater than the case without the shock/shock interaction. The objective was to begin to develop a mathematical model which is capable of predicting the effect of a type 3 and 4 shock/shock interaction in the stagnation region of an arbitrary 2-D body. This model must be capable of predicting the maximum surface heat flux and the surface stagnation point pressure once the outer (effectively inviscid) flowfield is given. Therefore, it must capture the unsteady physics of the impinging shear layer.

Wilson, Dennis↗