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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Hardware acceleration for HPS algorithms in two and three dimensions

We provide a flexible, open-source framework for hardware acceleration, namely massively-parallel execution on general-purpose graphics processing units (GPUs), applied to the hierarchical Poincaré–Steklov (HPS) family of algorithms for building fast direct solvers for linear elliptic partial differential equations. To take full advantage of the power of hardware acceleration, we propose two variants of HPS algorithms to improve performance on two- and three-dimensional problems. In the two-dimensional setting, we introduce a novel recomputation strategy that minimizes costly data transfers to and from the GPU; in three dimensions, we modify and extend the adaptive discretization technique of Geldermans and Gillman [1] to greatly reduce peak memory usage. We provide an open-source implementation of these methods written in JAX, a high-level accelerated linear algebra package, which allows for the first integration of a high-order fast direct solver with automatic differentiation tools. We conclude with extensive numerical examples showing our methods are fast and accurate on two- and three-dimensional problems.

Fast direct solvers↗
DOE OSTI2025

The positron arm of a plasma-based linear collider

Plasma-based acceleration of electrons has produced high-energy beams at high accelerating gradients with a narrow energy spread and high efficiency both in experiments and simulations. Furthermore, it is now being considered as a complementary approach to the use of radiofrequency cavities in next-generation lepton accelerators. However, compared with electrons, plasma-based positron acceleration is at the present time much less advanced. Although high-gradient positron acceleration in a plasma has been achieved, we are one to three orders of magnitude away from delivering the high-quality positron beams needed for a future high-energy linear collider. Here we review the status of plasma-based acceleration of electrons and positrons and discuss the prospects for substantial progress towards developing the positron arm of a plasma-based electron–positron linear collider in the next decade.

Plasma-based accelerators↗
NASA NTRS1994

Design, characterization, and control of the NASA three degree of freedom reaction compensation platform

Increasing research is being done into industrial uses for the microgravity environment aboard orbiting space vehicles. However, there is some concern over the effects of reaction forces produced by moving objects, especially motors, robotic actuators, and astronauts. Reaction forces produced by the movement of these objects may manifest themselves as undesirable accelerations in the space vehicle making the vehicle unusable for microgravity applications. It is desirable to provide compensation for such forces using active means. This paper presents the design and experimental evaluation of the NASA three degree of freedom reaction compensation platform, a system designed to be a testbed for the feasibility of active attenuation of reaction forces caused by moving objects in a microgravity environment. Unique 'linear motors,' which convert electrical current directly into rectilinear force, are used in the platform design. The linear motors induce accelerations of the displacer inertias. These accelerations create reaction forces that may be controlled to counteract disturbance forces introduced to the platform. The stated project goal is to reduce reaction forces by 90 percent, or -20 dB. Description of the system hardware, characterization of the actuators and the composite system, and design of the software safety system and control software are included.

Birkhimer, Craig↗
NASA NTRS1982

Analysis and design of steady transonic flow over airfoils by the method of parametric differentiation

The results reported here are based on applying the method of parametric differentiation (MPD) to transform the nonlinear differential equation governing small-disturbance transonic flow to a linear equation. Implicit approximate factorization and monotone methods were used to accelerate convergence of the linear problem by an order of magnitude over successive line over-relaxation. The relative merits of using MPD are discussed in comparison to conventional small-disturbance applications. Several MPD analyses are performed on an array of airfoils. A design procedure utilizing MPD is discussed and demonstrated for two nonlifting cases.

Halt, D. W.↗
NASA NTRS1990

Computational aspects of sensitivity calculations in linear transient structural analysis

A study was performed focusing on the calculation of sensitivities of displacements, velocities, accelerations, and stresses in linear, structural, transient response problems. One significant goal of the study was to develop and evaluate sensitivity calculation techniques suitable for large-order finite element analyses. Accordingly, approximation vectors such as vibration mode shapes are used to reduce the dimensionality of the finite element model. Much of the research focused on the accuracy of both response quantities and sensitivities as a function of number of vectors used. Two types of sensitivity calculation techniques were developed and evaluated. The first type of technique is an overall finite difference method where the analysis is repeated for perturbed designs. The second type of technique is termed semi-analytical because it involves direct, analytical differentiation of the equations of motion with finite difference approximation of the coefficient matrices. To be computationally practical in large-order problems, the overall finite difference methods must use the approximation vectors from the original design in the analyses of the perturbed models. In several cases this fixed mode approach resulted in very poor approximations of the stress sensitivities. Almost all of the original modes were required for an accurate sensitivity and for small numbers of modes, the accuracy was extremely poor. To overcome this poor accuracy, two semi-analytical techniques were developed. The first technique accounts for the change in eigenvectors through approximate eigenvector derivatives. The second technique applies the mode acceleration method of transient analysis to the sensitivity calculations. Both result in accurate values of the stress sensitivities with a small number of modes and much lower computational costs than if the vibration modes were recalculated and then used in an overall finite difference method.

Greene, William H.↗
DOE OSTI2025

Capacitated p -hub approach for park-and-ride facility location problem under nested logit demand function: polyhedral approaches

By generalizing the unconstrained p-hub approach for the park-and-ride (P&R) facility location problem under the multinomial logit demand function, the capacitated p-hub approach for the problem under the nested logit demand function captures a broader range of real-world cases. To solve this problem optimally, we introduce a mixed-integer linear program and accelerate its solution by enhancing the branch-and-cut procedure. To address the problem at a large scale, we introduce two other polyhedral approaches: variable neighborhood search (VNS) and adaptive randomized rounding (ARR). Downtown areas in Seoul have a high modal share of public transportation and congested road traffic, yet P&R has not been widely implemented. Therefore, we apply the ARR procedure to solve a real-world problem using traffic and geographic data from the Seoul metropolitan area. ARR performs better than VNS and addresses real-world cases. The solutions obtained by ARR present a phased expansion plan that encourages policymakers to start installing a small number of P&Rs immediately.

Capacitated p-hub approach↗
DOE OSTI2024

Image plate multi-scan response to fusion protons in the range of 1–14 MeV

Image plates (IPs) are a quickly recoverable and reusable radiation detector often used to measure proton and x-ray fluence in laser-driven experiments. Recently, IPs have been used in a proton radiography detector stack on the OMEGA laser, a diagnostic historically implemented with CR-39, or radiochromic film. The IPs used in this and other diagnostics detect charged particles, neutrons, and x-rays indiscriminately. IPs detect radiation using a photo-stimulated luminescence (PSL) material, often phosphor, in which electrons are excited to metastable states by ionizing radiation. Protons at MeV energies deposit energy deeper into the IP compared with x rays below ∼20 keV due to the Bragg peak present for protons. This property is exploited to discriminate between radiation types. Doses of mono-energetic protons between 1.7 and 14 MeV are applied to IPs using the MIT linear electrostatic ion accelerator. This paper presents the results from consecutive scans of IPs irradiated with different proton energies. The PSL ratios between subsequent scans are shown to depend on proton energy, with higher energy protons having lower PSL ratios for each scan. This finding is separate from the known energy dependence in the absolute sensitivity of IPs. The results can be compared to complimentary work on x rays, showing a difference between protons and x rays, forging a path to discriminate between proton and x-ray fluence in mixed radiation environments.

Instruments & Instrumentation↗
DOE OSTI2025

Experimental and computational study of phase space dynamics in strongly coupled plasmas with steep density gradients

Understanding how plasmas thermalize when density gradients are steep remains a fundamental challenge in plasma physics, with direct implications for fusion experiments and astrophysical phenomena. Standard hydrodynamic models break down in these regimes, and kinetic theories make predictions that have never been directly tested. Here, we present the first detailed phase-space measurements of a strongly coupled plasma as it evolves from sharp density gradients to thermal equilibrium. Using laser-induced fluorescence imaging of an ultracold calcium plasma, we track the complete ion distribution function f(x,v,t). We discover that commonly used kinetic models (Bhatnagar–Gross–Krook and Lenard–Bernstein) overpredict thermalization rates, even while correctly capturing the initial counterstreaming plasma formation. Our measurements reveal that the initial ion acceleration response scales linearly with electron temperature, and that the simulations underpredict the initial ion response. In our geometry we demonstrate the formation of well-controlled counterpropagating plasma beams. This experimental platform enables precision tests of kinetic theories and opens new possibilities for studying plasma stopping power and flow-induced instabilities in strongly coupled systems.

Bergeson, Scott (ORCID:0000000231249226)↗
DOE OSTI2025

ORNL/Restricted-Alternating-Anderson-Picard

Implementation in the programming language Julia of the Restricted Alternating Anderson Picard (AAP) acceleration for (non)-linear fixed point iterations.

Barnafi, NicolásAlejandro [Pontifica Universidad C↗
NASA NTRS1977

Vestibular functions and sleep in space experiments

Physical indices of sleep were continuously monitored in an owl monkey living in a chamber continuously rotating at a constant angular velocity. The electrophysiological data obtained from chronically implanted electrodes was analyzed to determine the chronic effects of vestibular stimulation on sleep and wakefulness cycles. The interaction of linear and angular acceleration on the vestibulo-ocular reflex was investigated in three rhesus monkeys at various angular accelerations.

Perachio, A. A.↗
NASA NTRS1980

Electric-car simulation

PARAMET, interactive simulation program for parametric studies of electric vehicles, guides user through simulation by menu and series of prompts for input parameters. Program considers aerodynamic drag, rolling resistance, linear and rotational acceleration, and road gradient as forces acting on vehicle.

Chapman, C. P.↗
NASA NTRS1980

Electrofluidic accelerometer

Electrofluidic accelerometer senses components of linear and angular acceleration field. Typical application of such acceleration is as active controlling element in airplane autopilot. In contrast to conventional accelerometers, electrofluidic accelerometer is lightweight, small, inexpensive, rugged, and requires little power. It consists of two temperature sensors on opposite sides of heating element. Sensors detect temperature gradient created by acceleration field on fluid; when device is accelerated, gradient changes because of bouyant force on hotter (thus lighter) portion of fluid.

Hewes, D. E.↗
NASA NTRS1981

Superconducting tensor gravity gradiometer

The employment of superconductivity and other material properties at cryogenic temperatures to fabricate sensitive, low-drift, gravity gradiometer is described. The device yields a reduction of noise of four orders of magnitude over room temperature gradiometers, and direct summation and subtraction of signals from accelerometers in varying orientations are possible with superconducting circuitry. Additional circuits permit determination of the linear and angular acceleration vectors independent of the measurement of the gravity gradient tensor. A dewar flask capable of maintaining helium in a liquid state for a year's duration is under development by NASA, and a superconducting tensor gravity gradiometer for the NASA Geodynamics Program is intended for a LEO polar trajectory to measure the harmonic expansion coefficients of the earth's gravity field up to order 300.

Paik, H. J.↗
NASA NTRS1982

Cyclotron resonance effects on stochastic acceleration of light ionospheric ions

The production of energetic ions with conical pitch angle distributions along the auroral field lines is a subject of considerable current interest. There are several theoretical treatments showing the acceleration (heating) of the ions by ion cyclotron waves. The quasi-linear theory predicts no acceleration when the ions are nonresonant. In the present investigation, it is demonstrated that the cyclotron resonances are not crucial for the transverse acceleration of ions by ion cyclotron waves. It is found that transverse energization of ionospheric ions, such as He(+), He(++), O(++), and O(+), is possible by an Electrostatic Hydrogen Cyclotron (EHC) wave even in the absence of cyclotron resonance. The mechanism of acceleration is the nonresonant stochastic heating. However, when there are resonant ions both the total energy gain and the number of accelerated ions increase with increasing parallel wave number.

Singh, N.↗
NASA NTRS1988

Recursive Dynamic Equations For Two Robot Arms In A Closed Chain

Paper discusses use of difference equations from Kalman filtering and Bryson-Frazier smoothing to solve equations of forward dynamics of closed chain of robot-arm links. "Forward dynamics" is computation of linear and angular accelerations of joints between links, given set of applied or prescribed joint torques. Paper lays foundation for potential use of filtering and smoothing techniques in dynamics of robots and in design of controls for robots.

Rodriguez, Guillermo↗
NASA NTRS1987

Hormonal responses of metoclopramide-treated subjects experiencing nausea or emesis during parabolic flight

The concentrations of adrenocorticotropic hormone (ACTH), vasopressin (AVP), epinephrine (EPI), and norepinephrine (NE) in 22 subjects administered 10 to 20 mg of metoclopramide prior to parabolic flight are measured. The effect of metoclopramide on motion sickness is examined. It is observed that metoclopramide is ineffective in the modulation of motion sickness due to stressful linear and angular acceleration and orbital flight, and it does not affect serum hormones prior to parabolic flight. It is detected that the serum level of AVP declines following emesis induced by parabolic flight and stressful angular acceleration; the serum levels of ACTH and EPI are elevated by parabolic flight and stressful angular acceleration; and serum NE is significantly elevated immediately following emesis. The possible roles of these hormones in the etiology of space motion sickness are discussed.

Kohl, Randall L.↗
NASA NTRS1992

Laboratory demonstrations of superconducting gravity and inertial sensors for space and airborne gravity measurements

The paper describes the superconducting gravity gradiometers (SGGs) and superconducting accelerometers being developed at the University of Maryland, which take advantage of many exotic properties of superconductivity to obtain the required low noise, high stability, and large dynamic range. Results of laboratory demonstrations of some of these instruments are presented together with the design and operating principles. Particular attention is given to the three-axis Model II SGG and a six-axis superconducting accelerometer model (Model I SSA). Model II SGG, after a residual common-mode balance, exhibited a noise level of 0.05/sq rt Hz above 0.1 Hz and a 1/f-squared noise below 0.1 Hz. All six channels of Model I SSA operated simultaneously with linear and angular acceleration noise levels of 3 x 10 exp -10 g(E)/sq rt Hz and 5 x 10 exp -8 rad/sec per sec per sq rt Hz, respectively.

Paik, Ho J.↗