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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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NASA NTRSDate not supplied

Parametric Mechanism Design Through Numerical Optimization and Physics Simulation

Design-Build-Test approaches for developing spaceflight hardware are prohibitively time and cost intensive and often lead to suboptimal mechanism designs. Approaches that couple machine learning and high-fidelity physics simulation could eliminate the need for hardware prototyping and dramatically accelerate the engineering design cycle, ultimately reducing cost. This work presents a modular NASA-developed toolchain to optimize hardware mechanisms in a virtual environment using numerical optimization and multi-body physics simulation. The toolchain enables multi-objective optimization, generates parametric CAD files that can be further post-processed by an end user, and can be expanded to optimize full systems and non-mechanical parameters such as feedback control variables. We demonstrate the toolchain through an independently verifiable design problem that optimizes wheel radius to achieve a desired linear velocity in a rigid-body physics environment when the wheel rotates at a constant angular speed, and then post-process the parametric CAD file of the optimal design generated by the tool before ultimately manufacturing it via 3D printing. We end with a discussion of how the toolchain can incorporate other analysis tools, including finite element analysis, computational fluid dynamics, and granular media simulations.

Optimization↗
NASA NTRSDate not supplied

An Optimization-Based Toolchain for Parametric Mechanism Design

Design-Build-Test approaches for developing spaceflight hardware are prohibitively time and cost intensive and often lead to suboptimal mechanism designs. Approaches that couple machine learning and high-fidelity physics simulation could eliminate the need for hardware prototyping and dramatically accelerate the engineering design cycle, ultimately reducing cost. This work presents a modular NASA-developed toolchain to optimize hardware mechanisms in a virtual environment using numerical optimization and multi-body physics simulation. The toolchain enables multi-objective optimization, generates parametric CAD files that can be further post-processed by an end user, and can be expanded to optimize full systems and non-mechanical parameters such as feedback control variables. We demonstrate the toolchain through an independently verifiable design problem that optimizes wheel radius to achieve a desired linear velocity in a rigid-body physics environment when the wheel rotates at a constant angular speed, and then post-process the parametric CAD file of the optimal design generated by the tool before ultimately manufacturing it via 3D printing. We end with a discussion of how the toolchain can incorporate other analysis tools, including finite element analysis, computational fluid dynamics, and granular media simulations.

Optimization↗
NASA NTRSDate not supplied

Optimization-Based Parametric Design via High-Fidelity Simulation: Overview + Examples

Design-Build-Test approaches for developing spaceflight hardware are prohibitively time and cost intensive and often lead to suboptimal mechanism designs. Approaches that couple machine learning and high-fidelity physics simulation could eliminate the need for hardware prototyping and dramatically accelerate the engineering design cycle, ultimately reducing cost. This talk presents a modular NASA-developed toolchain to optimize hardware mechanisms in a virtual environment using numerical optimization and multi-body physics simulation and includes example applications related to rigid wheel design for autonomous rovers and computational fluid dynamics.

optimization↗
NASA NTRSDate not supplied

A Flexible Multibody Approach to Space Launch System Liftoff Pad Separation with Umbilical Disconnect

A flexible multibody dynamic framework is applied to the Space Launch System (SLS) liftoff Coupled Loads Analysis (CLA), enabling computational efficiencies and systematic inclusion of components and various nonlinearities. The objective of this work is to simulate the SLS liftoff transient pad separation event inclusive of umbilical disconnects. The vehicle stacking preloads and cryogenically induced preloads, due to the fueling of the Core Stage (CS), are integrated via specialized deformed coupling procedure to ensure full capture of the liftoff transient event. The Vehicle Stabilizer System (VSS) hydraulic struts are nonlinear and provide amplitude dependent damping, significantly contributing to the liftoff transient event. Ground Extensible Columns (EC) provide additional stiffness and preloads on the Mobile Launcher (ML), also significantly contributing to the liftoff transient. An advanced Henkel-Mar algorithm, with separation and re-contact, thus tracking the potential post separation re-contact between the booster aft skirt and ML, the umbilicals and vehicle, and ground EC separation. For this system level nonlinear dynamic simulation, the flexible multibody framework provides a systematic approach for the addition of component specific algorithms to enforce nonlinearities. This multibody framework is similar to an object-oriented programming language integrating classes of associated subroutines. As such, the complexities associated with the nonlinear CLA are greatly reduced, facilitating simplified bookkeeping as well as accelerating the execution of the nonlinear time-domain simulations.

Joel W Sills Jr.↗
NASA NTRS1973

Fatigue of supersonic transport materials using simulated flight-by-flight loading

Methods to reduce the fatigue test time for structural materials which are candidates for supersonic transport airplanes were investigated by conducting real-time and accelerated fatigue tests. The tests employed sequences of stresses and temperatures to simulate the flights of a Mach 3 transport airplane. Some of the simulated flights were altered to determine the effect of the design mean stress and the number of stress cycles per flight on fatigue life. Salt solution was also applied in other tests. Notched Ti-8Al-1Mo-1V and Ti-6Al-4V were used in the investigation.

Imig, L. A.↗
NASA NTRS1994

A mechanism to produce a dawn-dusk component of plasma flow during magnetic reconnection in the magnetotail

Magnetic reconnection between antiparallel field lines in the magnetotail is generally thought to produce plasma acceleration in the earthward-tailward direction. However, measurements of the plasma velocity in the magnetotail during substorm activity sometimes reveal a dawn-dusk component of plasma flow. In this paper, we show that a dawn-dusk component of plasma acceleration may be produced during reconnection if the neutral line is not perpendicular to the magnetic field. In this case, Magnetohydrodynamic (MHD) simulations show that reconnection between antiparallel field lines will initially produce plasma acceleration that is nearly parallel to the neutral line because the magnetic tension force is not opposed by a pressure gradient force in this direction. As the magnetic field topology evolves to a steady state, the plasma flow direction rotates until it is nearly parallel to the plane that initially contained the antiparallel magnetic field lines before reconnection (hereafter referred to as the initial field plane). However, the time required to reach a steady state (typically several hundred seconds in the magnetotail region) may be greater than the time during which the reconnection process is active. Consequently, bursts of plasma flow with a dawn-dusk component may occur in the magnetotail. The initial acceleration along the neutral line depends on the angle theta (sub B) between the neutral line and the initial field plane, with the largest burst of plasma flow along the neutral line occuring when theta (s ub B) = 45 degs.

Hawkins, J. G.↗
NASA NTRS2021

Spatially Separated Electron and Proton Beams in a Simulated Solar Coronal Jet

Magnetic reconnection is widely accepted to be a major contributor to non-thermal particle acceleration in the solar atmosphere. In this paper we investigate particle acceleration during the impulsive phase of a coronal jet, which involves bursty reconnection at a magnetic null point. A test-particle approach is employed, using electromagnetic fields from a magnetohydrodynamic simulation of such a jet. Protons and electrons are found to be accelerated non-thermally both downwards toward the domain’s lower boundary and the solar photosphere, and outwards along the axis of the coronal jet and into the heliosphere. A key finding is that a circular ribbon of particle deposition on the photosphere is predicted, with the protons and electrons concentrated in different parts of the ribbon. Furthermore, the outgoing protons and electrons form two spatially separated beams parallel to the axis of the jet, signatures that may be observable inin-situobservations of the heliosphere.

Ross Pallister↗
NASA NTRS1994

Centrifugal acceleration of the polar wind

The effect of parallel ion acceleration associated with convection was first applied to energization of test particle polar ions by Cladis (1986). However, this effect is typically neglected in 'self-consistent' models of polar plasma outflow, apart from the fluid simulation by Swift (1990). Here we include approximations for this acceleration, which we broadly characterize as centrifugal in nature, in our time-dependent, semikinetic model of polar plasma outflow and describe the effects on the bulk parameter profiles and distribution functions of H+ and O+. For meridional convection across the pole the approximate parallel force along a polar magnetic field line may be written as F(sub cent, pole) = 1.5m(E(sub i))/B(sub i))squared (r(squared)/r(sup 3)(sub i)) where m is ion mass, r is geometric distance; and E(sub i), B(sub i) and r(sub i) refer to the electric and magnetic field magnitudes and geocentric distance at the ionosphere, respectively. For purely longitudinal convection along a constant L shell the parallel force is F(cent. long) = F(sub cent, pole)(1 - (r/(r(sub i)L))(sup 3/2)/(1 - 3r/(4 r(sub i)L))(sup 5/2). For high latitudes the difference between these two cases is relatively unimportant below approximately 5 R(sub E). We find that the steady state O+ bulk velocities and parallel temperatures strongly increase and decrease, respectively, with convection strength. In particular, the bulk velocities increase from near 0 km/s at 4000 km altitude to approximately 10 km/s at 5 R(sub E) geocentric distance for 50-mV/m ionospheric convection electric field. However, the centrifugal effect on the steady O+ density profiles depends on the exobase ion and electron temperatures: for low-base temperatures (T(sub i) = T(sub e) = 3000 K) the O+ density at high altitudes increases greatly with convection, while for higher base temperatures (T(sub i) = 5000 K, T(sub e) = 9000 K), the high-altitude O+ density decreases somewhat as convection is enhanced. The centrifugal force further has a pronounced effect on the escaping O+ flux, especially for cool exobase conditions; as referenced to the 4000-km altitude, the steady state O+ flux increases from 10(exp 5) ions/sq cm/s when the ionospheric convection field E(sub i) = 0 mV/m to approximately 10(exp 7) ions/sq cm/s when E(sub i) = 100 mV/m. The centrifugal effect also decreases the time scale for approach to steady-state. For example, in the plasma expansion for T(sub i) = T(sub e) = 3000 K, the O+ density at 7 R(sub E) reaches only 10(exp -7) of it final value approximately 1.5 hours after expansion onset for E(sub i) = 0. For meridional convection driven by E(sub i) = 50 mV/m, the density at the same time after initial injection is 30-50% of its asymptotic level. The centrifugal acceleration described here is a possible explanation for the large (up to approximately 10 km/s or more) o+ outflow velocities observed in the midlatitude polar magnetosphere with the Dynamics Explorer 1 and Akebono spacecraft.

Horwitz, J. L.↗
NASA NTRS2016

Decompression Sickness During Simulated Low Pressure Exposure is Increased with Mild Ambulation Exercise

Musculoskeletal activity accelerates inert gas elimination during oxygen breathing prior to decompression (prebreathe), but may also promote bubble formation (nucleation) and increase the risk of decompression sickness (DCS). The timing, pattern and intensity of musculoskeletal activity are likely critical to the net effect. The NASA Prebreathe Reduction Program (PRP) combined oxygen prebreathe and exercise preceding a 4.3 psia exposure in non-ambulatory subjects (a microgravity analog) to produce two protocols now used by astronauts preparing for extravehicular activity - one employing cycling and non-cycling exercise (CEVIS: 'cycle ergometer vibration isolation system') and one relying on non-cycling exercise only (ISLE: 'in-suit light exercise'). Current efforts investigate whether light exercise normal to 1 G environments increases the risk of DCS over microgravity simulation.

Pollock, N. W.↗
NASA NTRS2015

Galactic Cosmic Ray Simulator at the NASA Space Radiation Laboratory

The external Galactic Cosmic Ray (GCR) spectrum is significantly modified when it passes through spacecraft shielding and astronauts. One approach for simulating the GCR space radiation environment is to attempt to reproduce the unmodified, external GCR spectrum at a ground based accelerator. A possibly better approach would use the modified, shielded tissue spectrum, to select accelerator beams impinging on biological targets. NASA plans for implementation of a GCR simulator at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory will be discussed.

Norbury, John W.↗
NASA NTRS1994

Numerical Simulation Of Cutting Of Gear Teeth

Shapes of gear teeth produced by gear cutters of specified shape simulated computationally, according to approach based on principles of differential geometry. Results of computer simulation displayed as computer graphics and/or used in analyses of design, manufacturing, and performance of gears. Applicable to both standard and non-standard gear-tooth forms. Accelerates and facilitates analysis of alternative designs of gears and cutters. Simulation extended to study generation of surfaces other than gears. Applied to cams, bearings, and surfaces of arbitrary rolling elements as well as to gears. Possible to develop analogous procedures for simulating manufacture of skin surfaces like automobile fenders, airfoils, and ship hulls.

Oswald, Fred B.↗
NASA NTRS2005

Building the Case for SNAP: Creation of Multi-Band, Simulated Images With Shapelets

Dark energy has simultaneously been the most elusive and most important phenomenon in the shaping of the universe. A case for a proposed space-telescope called SNAP (SuperNova Acceleration Probe) is being built, a crucial component of which is image simulations. One method for this is "Shapelets," developed at Caltech. Shapelets form an orthonormal basis and are uniquely able to represent realistic space images and create new images based on real ones. Previously, simulations were created using the Hubble Deep Field (HDF) as a basis Set in one band. In this project, image simulations are created.using the 4 bands of the Hubble Ultra Deep Field (UDF) as a basis set. This provides a better basis for simulations because (1) the survey is deeper, (2) they have a higher resolution, and (3) this is a step closer to simulating the 9 bands of SNAP. Image simulations are achieved by detecting sources in the UDF, decomposing them into shapelets, tweaking their parameters in realistic ways, and recomposing them into new images. Morphological tests were also run to verify the realism of the simulations. They have a wide variety of uses, including the ability to create weak gravitational lensing simulations.

Ferry, Matthew A.↗
NASA NTRS1990

A unique approach to space thermal simulation

The Space Systems Lab of McDonnell Douglas developed several innovative techniques to perform the DELTA Star System thermal vacuum test. Test design constraints included an accelerated test schedule and an ambitious test plan focusing on cyclic absorbed orbital flux simulation. Test design and fabrication was completed in only 4 months, producing a 21 zone computer modeled refectorless lamp array system. Array zone control was based on discreet absorbed flux measurements, provided by adiabatic coupons conceived to eliminate the need for conventional radiometers. Test requirements, methodology, and test thermal model flight data correlation are presented.

Durant, D. Q.↗
NASA NTRSDate not supplied

QuAIL Tools for Benchmarking, Analysis and Quantum Algorithm Development

HybridQ and PySA are open-source tools developed by NASA to support benchmarking, analysis and quantum algorithm development in areas such as simulation, optimization and machine learning. These tools leverage classical hardware acceleration via high-performance computing CPU and GPU architectures and support high-performance computing. HybridQ is a highly extensible platform designed to provide a common framework to integrate multiple state-of-the-art techniques to simulate large scale quantum circuits. PySA is an extensible platform to optimize a classical cost function. We provide an outline of each of these open-source tools and highlight projects using each of these tools in contexts of simulation, optimization and machine learning.

Quantum Computing↗
NASA NTRS1977

Application of system identification to analytic rotor modeling from simulated and wind tunnel dynamic test data, part 2

An introduction to aircraft state and parameter identification methods is presented. A simplified form of the maximum likelihood method is selected to extract analytical aeroelastic rotor models from simulated and dynamic wind tunnel test results for accelerated cyclic pitch stirring excitation. The dynamic inflow characteristics for forward flight conditions from the blade flapping responses without direct inflow measurements were examined. The rotor blades are essentially rigid for inplane bending and for torsion within the frequency range of study, but flexible in out-of-plane bending. Reverse flow effects are considered for high rotor advance ratios. Two inflow models are studied; the first is based on an equivalent blade Lock number, the second is based on a time delayed momentum inflow. In addition to the inflow parameters, basic rotor parameters like the blade natural frequency and the actual blade Lock number are identified together with measurement bias values. The effect of the theoretical dynamic inflow on the rotor eigenvalues is evaluated.

Hohenemser, K. H.↗
NASA NTRS1976

Nonlinear coupling between pulsation and convection in late type stars

A simple idealized nonlinear model applicable to long-period variable stars has been formulated which assumes that the convective envelope of M giants is composed of giant convection cells comparable in size to the stellar radius. The simplicity of this model essentially constitutes a physical analog to the strong dynamic coupling that occurs if the convective envelope of the star undergoes both modes of motion. As shown implicitly in the time scales associated with these motions, the coupling produces asymmetrical fluctuations of the entire star, the mean velocity of which is comparable to the escape velocity of the star at particular values of the ratio of the pulsation and convection time scales. It is suggested that this can account for the mass loss from late-type stars and the circumstellar dust shells that are associated extensively with long-period variables. For critical values of the pulsation and convection time scales, the solutions correspond to the rapid expansion of the entire convective envelope and are the basis of a mechanism that simulates the manner in which pulsating stars ballistically accelerate their convective shells to form planetary nebulae.

Anand, S. P. S.↗