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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Light differentially regulates cell division and the mRNA abundance of pea nucleolin during de-etiolation

The abundance of plant nucleolin mRNA is regulated during de-etiolation by phytochrome. A close correlation between the mRNA abundance of nucleolin and mitosis has also been previously reported. These results raised the question of whether the effects of light on nucleolin mRNA expression were a consequence of light effects on mitosis. To test this we compared the kinetics of light-mediated increases in cell proliferation with that of light-mediated changes in the abundance of nucleolin mRNA using plumules of dark-grown pea (Pisum sativum) seedlings. These experiments show that S-phase increases 9 h after a red light pulse, followed by M-phase increases in the plumule leaves at 12 h post-irradiation, a time course consistent with separately measured kinetics of red light-induced increases in the expression of cell cycle-regulated genes. These increases in cell cycle-regulated genes are photoreversible, implying that the light-induced increases in cell proliferation are, like nucleolin mRNA expression, regulated via phytochrome. Red light stimulates increases in the mRNA for nucleolin at 6 h post-irradiation, prior to any cell proliferation changes and concurrent with the reported timing of phytochrome-mediated increases of rRNA abundance. After a green light pulse, nucleolin mRNA levels increase without increasing S-phase or M-phase. Studies in animals and yeast indicate that nucleolin plays a significant role in ribosome biosynthesis. Consistent with this function, pea nucleolin can rescue nucleolin deletion mutants of yeast that are defective in rRNA synthesis. Our data show that during de-etiolation, the increased expression of nucleolin mRNA is more directly regulated by light than by mitosis.

NASA Program Fundamental Space Biology↗
NASA NTRS1974

Rearward-facing steps in laminar supersonic flows with and without suction

An experimental investigation of heat-transfer and pressure distributions within regions of laminar separated flows produced by two-dimensional rearward-facing steps has been carried out at freestream Mach numbers of around 4 in the range of step height-to-boundary layer thickness varying from 0.1 to 2.4. With no suction from the separated area, the ratio of the maximum post-step heat transfer to the attached-flow values was less than unity. The maximum heating-rate region was located far downstream of the reattachment plate stagnation point. Mass suction from the separated area increased the local heating rates, this effect was however relatively weak for purely laminar flow conditions and the competing effect of the step height clearly predominated. At step heights comparable with boundary-layer thickness, even removing the entire approaching boundary layer was not sufficient to raise the post-step heating rates above the flat-plate values.

Jakubowski, A. K.↗
NASA NTRSDate not supplied

Space Launch System: CLVTOPS Toolchain for SLS Liftoff Separation Analysis

This presentation showcases the unique technical capabilities of the CLVTOPS multi-body flight dynamics tool chain developed by Marshall Space Flight Center (MSFC) for analyzing NASA’s Space Launch System (SLS) liftoff events. The CLVTOPS tool chain integrates high-fidelity simulations, geometric algorithms, advanced data analytics, and post-flight telemetry to demonstrate positive clearance between separating bodies and inform design decisions that enhance mission reliability. Proper liftoff separation is crucial to the success of the launch vehicle’s mission; vehicle impacts with the launch tower and supporting components incur a heightened risk of mission failure. For liftoff analysis, the CLVTOPS tool chain enables the integration of vehicle, launch pad, and environmental input models for the investigation of key clearance effectors. Furthermore, a novel capability of the CLVTOPS tool chain allows for verification and validation of trajectory reconstruction via photogrammetric imagery analysis. The following sections will walk through the tool chain, SLS liftoff ground rules and assumptions, model integration, pre-flight verification, and post-flight validation of the Artemis I mission liftoff event.

CLVTOPS↗
NASA NTRS2003

Hyper-X Stage Separation Trajectory Validation Studies

An independent twelve degree-of-freedom simulation of the X-43A separation trajectory was created with the Program to Optimize Simulated trajectories (POST II). This simulation modeled the multi-body dynamics of the X-43A and its booster and included the effect of two pyrotechnically actuated pistons used to push the vehicles apart as well as aerodynamic interaction forces and moments between the two vehicles. The simulation was developed to validate trajectory studies conducted with a 14 degree-of-freedom simulation created early in the program using the Automatic Dynamic Analysis of Mechanics Systems (ADAMS) simulation software. The POST simulation was less detailed than the official ADAMS-based simulation used by the Project, but was simpler, more concise and ran faster, while providing similar results. The increase in speed provided by the POST simulation provided the Project with an alternate analysis tool. This tool was ideal for performing separation control logic trade studies that required the running of numerous Monte Carlo trajectories.

Tartabini, Paul V.↗
NASA NTRS1991

Muscle ultrastructural changes from exhaustive exercise performed after prolonged restricted activity and retraining in dogs

The effect of exhaustive treadmill exercise on ultrastructural changes in the quadriceps femoris muscle was studied in 7 normal, healthy dogs, before and after restricted activity (RA), and following a subsequent 2 month treadmill exercise retraining period for the 5 mo group. Mean time to exhaustion in the 2 mo group decreased from 177 + or - 22 min before to 90 + or - 32 min after RA. Retraining increased tolerance to 219 + or - 73 min; 24 pct. above the before RA and 143 pct. above the after RA time. After RA exhaustion time in the 5 mo group was 25 and 45 min. Before RA, pre-exercise muscle structure was normal and post exercise there was only slight swelling of mitochondria. After RA, pre-exercise, numerous glycogen granules and lipid droplets appeared in the muscle fibers, mitochondria were smaller, and sarcoplasmic reticulum channels widened; post exercise these changes were accentuated and some areas were devoid of glycogen, and there was fiber degradation. After 5 mo RA pre-exercise there were more pronounced changes; mitochondria were very small and dense, there were many lipid droplets, myofibrils were often separated, and the fibers appeared edematous and degenerating; post exercise the sarcoplasmic reticulum was swollen, no glycogen was present, and there was marked swelling and deformation of mitochondria. After retraining, both pre-exercise and post exercise there was still evidence of fiber degeneration. Thus, susceptibility of active skeletal muscle structures and subcellular elements, e.g., mitochondria, to the action of damaging factors occurring during exhaustive exercise is enhanced considerably by prolonged disuse.

Nazar, K.↗
NASA NTRS2006

Assessment of Postflight Locomotor Performance Utilizing a Test of Functional Mobility: Strategic and Adaptive Responses

Space flight induces adaptive modification in sensorimotor function, allowing crewmembers to operate in the unique microgravity environment. This adaptive state, however, is inappropriate for a terrestrial environment. During a re-adaptation period upon their return to Earth, crewmembers experience alterations in sensorimotor function, causing various disturbances in perception, spatial orientation, posture, gait, and eye-head coordination. Following long duration space flight, sensorimotor dysfunction would prevent or extend the time required to make an emergency egress from the vehicle; compromising crew safety and mission objectives. We are investigating two types of motor learning that may interact with each other and influence a crewmember's ability to re-adapt to Earth's gravity environment. In strategic learning, crewmembers make rapid modifications in their motor control strategy emphasizing error reduction. This type of learning may be critical during the first minutes and hours after landing. In adaptive learning, long-term plastic transformations occur, involving morphological changes and synaptic modification. In recent literature these two behavioral components have been associated with separate brain structures that control the execution of motor strategies: the strategic component was linked to the posterior parietal cortex and the adaptive component was linked to the cerebellum (Pisella, et al. 2004). The goal of this paper was to demonstrate the relative contributions of the strategic and adaptive components to the re-adaptation process in locomotor control after long duration space flight missions on the International Space Station (ISS). The Functional Mobility Test (FMT) was developed to assess crewmember s ability to ambulate postflight from an operational and functional perspective. Sixteen crewmembers were tested preflight (3 sessions) and postflight (days 1, 2, 4, 7, 25) following a long duration space flight (approx 6 months) on the ISS. We have further analyzed the FMT data to characterize strategic and adaptive components during the postflight readaptation period. Crewmembers walked at a preferred pace through an obstacle course set up on a base of 10 cm thick medium density foam (Sunmate Foam, Dynamic Systems, Inc., Leicester, NC). The 6.0m X 4.0m course consisted of several pylons made of foam; a Styrofoam barrier 46.0cm high that crewmembers stepped over; and a portal constructed of two Styrofoam blocks, each 31cm high, with a horizontal bar covered by foam and suspended from the ceiling which was adjusted to the height of the crewmember s shoulder. The portal required crewmembers to bend at the waist and step over a barrier simultaneously. All obstacles were lightweight, soft and easily knocked over. Crewmembers were instructed to walk through the course as quickly and as safely as possible without touching any of the objects on the course. This task was performed three times in the clockwise direction and three times in the counterclockwise direction that was randomly chosen. The dependent measures for each trial were: time to complete the course (seconds) and the number of obstacles touched or knocked down. For each crewmember, the time to complete each FMT trial from postflight days 1, 2, 4, 7 and 25 were further analyzed. A single logarithmic curve using a least squares calculation was fit through these data to produce a single comprehensive curve (macro). This macro curve composed of data spanning 25 days, illustrates the re-adaptive learning function over the longer time scale term. Additionally, logarithmic curves were fit to the 6 data trials within each individual post flight test day to produce 5 separate daily curves. These micro curves, produced from data obtained over the course of minutes, illustrates the strategic learning function exhibited over a relative shorter time scale. The macro curve for all subjects exhibited adaptive motor learning patterns over the 25 day period. Howev, 9/16 crewmembers exhibited significant strategic motor learning patterns in their micro curves, as defined by m > 1 in the equation of the line y=m*LN(x) +b. These data indicate that postflight recovery in locomotor function involves both strategic and adaptive mechanisms. Future countermeasures will be designed to enhance both recovery processes.

Warren, L. E.↗
DOE OSTI2025

Dual aging pathways of Cu-SSZ-13 SCR catalysts: Hydrothermal vs. sulfur-induced deactivation

Hydrothermal aging (HTA) and chemical poisoning are two primary factors contributing to the real-world degradation of Cu-SSZ-13 SCR catalysts. Investigating field-returned samples offers valuable insights into performance degradation caused by these mechanisms. However, the simultaneous presence of both deactivation pathways complicates the isolation of their individual effects in post-mortem analyses. In this study, we separately prepared model Cu-SSZ-13 SCR catalysts subjected to hydrothermal-aging and sulfur-induced chemical poisoning. Using various characterization techniques, we elucidated the specific role of each aging process in catalyst deactivation and compared the results to real-world field-aged catalysts. Our findings show that hydrothermal aging at 650 °C for 100 h caused dealumination of the zeolite framework but no significant CuO x cluster formation. In contrast, sulfur aging (via sulfur exposure, calcination at 550 °C, and desulfation up to 750 °C) led to CuO x formation without any observable dealumination. On model catalysts, sulfur poisoning was found to reduce Cu mobility and the amount of active Cu sites, thus degrading catalyst activity. Although some activity was recovered upon desulfation, a portion of the initial catalyst activity remained irreversibly lost due to CuO x formation. We demonstrate that this occurs because sulfated species impede the ability of multi-nuclear Cu species (e.g., Cu dimers) to split back into their isolated form, leading to CuSO 4 -clusters that oxidatively desulfate to CuO x species. This degradation pathway explains the significant reduction in activity of field-aged samples, where substantial CuSO 4 -cluster accumulation leads to reduced active Cu and subsequent conversion to CuO x . Furthermore, the conclusions from model catalysts were extended directly to field-aged commercial samples, elucidating the decline in activity and chemical properties during field deployment.

Catalyst Deactivation↗
DOE OSTI2024

Multidimensional images and aberrations in STEM

Recent advances in scanning transmission electron microscopy (STEM) have led to increased development of multi-dimensional STEM imaging modalities and novel image reconstruction methods. This interest arises because the main electron lens in a modern transmission electron microscope usually has a diffraction-space information limit that is significantly better than the real-space resolution of the same lens. This state-of-affairs is sometimes shared by other scattering methods in modern physics and contributes to a broader excitement surrounding multidimensional techniques that scan a probe while recording diffraction-space images, such as ptychography and scanning nano-beam diffraction. However, the contrasting resolution in the two spaces raises the question as to what is limiting their effective performance. Here, we examine this paradox by considering the effects of aberrations in both image and diffraction planes, and likewise separate the contributions of pre- and post-sample aberrations. In conclusion, this consideration provides insight into aberration-measurement techniques and might also indicate improvements for super-resolution techniques.

Hoglund, Eric R.↗
NASA NTRS1986

Simulation of self-induced unsteady motion in the near wake of a Joukowski airfoil

The unsteady Navier-Stokes analysis is shown to be capable of analyzing the massively separated, persistently unsteady flow in the post-stall regime of a Joukowski airfoil for an angle of attack as high as 53 degrees. The analysis has provided the detailed flow structure, showing the complex vortex interaction for this configuration. The aerodynamic coefficients for lift, drag, and moment were calculated. So far only the spatial structure of the vortex interaction was computed. It is now important to potentially use the large-scale vortex interactions, an additional energy source, to improve the aerodynamic performance.

Ghia, K. N.↗
NASA NTRS1993

Finite element large deflection random response of thermally buckled plates

The governing nonlinear equations of motion are derived for a rectangular isotropic plate subjected to a combined thermal-acoustic loading. The thermal loading is taken to be a steady state temperature distribution, and the acoustic loading is considered to be a stationary Gaussian pressure with zero mean and uniform magnitude and phase over the plate surface. With these types of loads, the thermal-acoustic analysis can be separated into two problems: (1) thermal post-buckling; and (2) random vibration of the thermally buckled plate. Since both analyses are nonlinear, iterative techniques are used to solve each. For the random vibration analysis, the method of equivalent linearization is used; both auto- and cross-correlation terms are included. Results obtained using the present formulation are compared with previous classical equivalent linearization results.

Locke, J. E.↗
NASA NTRS1992

Simulation of ASTER data using AVIRIS images

The Advanced Thermal Emission and Reflectance Radiometer (ASTER) is a joint Japanese/US imaging instrument scheduled to fly on the first Earth Observing System (EOS) platform in 1998. The complement of scanners includes a visible, three channel module with forward-looking stereo capability, a six channel short wavelength infrared module, and a five channel thermal module. As part of the definition phase for the instrument design, AVIRIS data was used to simulate the short wave infrared (SWIR) bands to investigate the effects of widening two of the bands to increase the signal-to-noise ratio (SNR) versus loss of spectral separability due to uncertainty in the post-launch band positions.

Abrams, Michael↗
NASA NTRS1995

NASA Safety Standard: Guidelines and Assessment Procedures for Limiting Orbital Debris

Collision with orbital debris is a hazard of growing concern as historically accepted practices and procedures have allowed man-made objects to accumulate in orbit. To limit future debris generation, NASA Management Instruction (NMI) 1700.8, 'Policy to Limit Orbital Debris Generation,' was issued in April of 1993. The NMI requires each program to conduct a formal assessment of the potential to generate orbital debris. This document serves as a companion to NMI 1700.08 and provides each NASA program with specific guidelines and assessment methods to assure compliance with the NMI. Each main debris assessment issue (e.g., Post Mission Disposal) is developed in a separate chapter.

Source record↗
NASA NTRS1997

Coupling of Sph and Finite Element Codes for Multi-Layer Orbital Debris Shield Design

Particle-based hydrodynamics models offer distinct advantages over Eulerian and Lagrangian hydrocodes in particular shock physics applications. Particle models are designed to avoid the mesh distortion and state variable diffusion problems which can hinder the effective use of Lagrangian and Eulerian codes respectively. However conventional particle-in-cell and smooth particle hydrodynamics methods employ particles which are actually moving interpolation points. A new particle-based modeling methodology, termed Hamiltonian particle hydrodynamics, was developed by Fahrenthold and Koo (1997) to provide an alternative, fully Lagrangian, energy-based approach to shock physics simulations. This alternative formulation avoids the tensile and boundary instabilities associated with standard smooth particle hydrodynamics formulations and the diffusive grid- to-particle mapping schemes characteristic of particle-in-cell methods. In the work described herein, the method of Fahrenthold and Koo has been extended, by coupling the aforementioned hydrodynamic particle model to a hexahedral finite element based description of the continuum dynamics. The resulting continuum model retains all of the features (including general contact-impact effects) of Hamiltonian particle hydrodynamics, while in addition accounting for tensile strength, plasticity, and damage effects important in the simulation of hypervelocity impact on orbital debris shielding. A three dimensional, vectorized, and autotasked implementation of the extended particle method described here has been coded for application to orbital debris shielding design. Source code for the pre-processor (PREP), analysis code (EXOS), post-processor (POST), and rezoner (ZONE), have been delivered separately, along with a User's Guide describing installation and application of the software.

Fahrenthold, Eric P.↗
NASA NTRS2000

Overcoming Dynamic Disturbances in Imaging Systems

We develop and discuss a methodology with the potential to yield a significant reduction in complexity, cost, and risk of space-borne optical systems in the presence of dynamic disturbances. More robust systems almost certainly will be a result as well. Many future space-based and ground-based optical systems will employ optical control systems to enhance imaging performance. The goal of the optical control subsystem is to determine the wavefront aberrations and remove them. Ideally reducing an aberrated image of the object under investigation to a sufficiently clear (usually diffraction-limited) image. Control will likely be distributed over several elements. These elements may include telescope primary segments, telescope secondary, telescope tertiary, deformable mirror(s), fine steering mirror(s), etc. The last two elements, in particular, may have to provide dynamic control. These control subsystems may become elaborate indeed. But robust system performance will require evaluation of the image quality over a substantial range and in a dynamic environment. Candidate systems for improvement in the Earth Sciences Enterprise could include next generation Landsat systems or atmospheric sensors for dynamic imaging of individual, severe storms. The technology developed here could have a substantial impact on the development of new systems in the Space Science Enterprise; such as the Next Generation Space Telescope(NGST) and its follow-on the Next NGST. Large Interferometric Systems of non-zero field, such as Planet Finder and Submillimeter Probe of the Evolution of Cosmic Structure, could benefit. These systems most likely will contain large, flexible optomechanical structures subject to dynamic disturbance. Furthermore, large systems for high resolution imaging of planets or the sun from space may also benefit. Tactical and Strategic Defense systems will need to image very small targets as well and could benefit from the technology developed here. We discuss a novel speckle imaging technique with the potential to separate dynamic aberrations from static aberrations. Post-processing of a set of image data, using an algorithm based on this technique, should work for all but the lowest light levels and highest frequency dynamic environments. This technique may serve to reduce the complexity of the control system and provide for robust, fault-tolerant, reduced risk operation. For a given object, a short exposure image is "frozen" on the focal plane in the presence of the environmental disturbance (turbulence, jitter, etc.). A key factor is that this imaging data exhibits frame-to-frame linear shift invariance. Therefore, although the Point Spread Function is varying from frame to frame, the source is fixed; and each short exposure contains object spectrum data out to the diffraction limit of the imaging system. This novel speckle imaging technique uses the Knox-Thompson method. The magnitude of the complex object spectrum is straightforward to determine by well-established approaches. The phase of the complex object spectrum is decomposed into two parts. One is a single-valued function determined by the divergence of the optical phase gradient. The other is a multi-valued function determined by the circulation of the optical phase gradient-"hidden phase." Finite difference equations are developed for the phase. The novelty of this approach is captured in the inclusion of this "hidden phase." This technique allows the diffraction-limited reconstruction of the object from the ensemble of short exposure frames while simultaneously estimating the phase as a function of time from a set of exposures.

Young, Eric W.↗
NASA NTRS2000

Overcoming Dynamic Disturbances in Imaging Systems

We develop and discuss a methodology with the potential to yield a significant reduction in complexity, cost, and risk of space-borne optical systems in the presence of dynamic disturbances. More robust systems almost certainly will be a result as well. Many future space-based and ground-based optical systems will employ optical control systems to enhance imaging performance. The goal of the optical control subsystem is to determine the wavefront aberrations and remove them. Ideally reducing an aberrated image of the object under investigation to a sufficiently clear (usually diffraction-limited) image. Control will likely be distributed over several elements. These elements may include telescope primary segments, telescope secondary, telescope tertiary, deformable mirror(s), fine steering mirror(s), etc. The last two elements, in particular, may have to provide dynamic control. These control subsystems may become elaborate indeed. But robust system performance will require evaluation of the image quality over a substantial range and in a dynamic environment. Candidate systems for improvement in the Earth Sciences Enterprise could include next generation Landsat systems or atmospheric sensors for dynamic imaging of individual, severe storms. The technology developed here could have a substantial impact on the development of new systems in the Space Science Enterprise; such as the Next Generation Space Telescope(NGST) and its follow-on the Next NGST. Large Interferometric Systems of non-zero field, such as Planet Finder and Submillimeter Probe of the Evolution of Cosmic Structure, could benefit. These systems most likely will contain large, flexible optormechanical structures subject to dynamic disturbance. Furthermore, large systems for high resolution imaging of planets or the sun from space may also benefit. Tactical and Strategic Defense systems will need to image very small targets as well and could benefit from the technology developed here. We discuss a novel speckle imaging technique with the potential to separate dynamic aberrations from static aberrations. Post-processing of a set of image data, using an algorithm based on this technique, should work for all but the lowest light levels and highest frequency dynamic environments. This technique may serve to reduce the complexity of the control system and provide for robust, fault-tolerant, reduced risk operation. For a given object, a short exposure image is "frozen" on the focal plane in the presence of the environmental disturbance (turbulence, jitter, etc.). A key factor is that this imaging data exhibits frame-to-frame linear shift invariance. Therefore, although the Point Spread Function is varying from frame to frame, the source is fixed; and each short exposure contains object spectrum data out to the diffraction limit of the imaging system. This novel speckle imaging technique uses the Knox-Thompson method. The magnitude of the complex object spectrum is straightforward to determine by well-established approaches. The phase of the complex object spectrum is decomposed into two parts. One is a single-valued function determined by the divergence of the optical phase gradient. The other is a multi-valued function determined by, the circulation of the optical phase gradient-"hidden phase." Finite difference equations are developed for the phase. The novelty of this approach is captured in the inclusion of this "hidden phase." This technique allows the diffraction-limited reconstruction of the object from the ensemble of short exposure frames while simultaneously estimating the phase as a function of time from a set of exposures.

Young, Eric W.↗
NASA NTRS2000

Influence of microgravity on ultrastructure and storage reserves in seeds of Brassica rapa L

Successful plant reproduction under spaceflight conditions has been problematic in the past. During a 122 d opportunity on the Mir space station, full life cycles of Brassica rapa L. were completed in microgravity in a series of three experiments in the Svet greenhouse. Ultrastructural and cytochemical analyses of storage reserves in mature dry seeds produced in these experiments were compared with those of seeds produced during a high-fidelity ground control. Additional analyses were performed on developing Brassica embryos, 15 d post pollination, which were produced during a separate experiment on the Shuttle (STS-87). Seeds produced on Mir had less than 20% of the cotyledon cell number found in seeds harvested from the ground control. Cytochemical localization of storage reserves in mature cotyledons showed that starch was retained in the spaceflight material, whereas protein and lipid were the primary storage reserves in ground control seeds. Protein bodies in mature cotyledons produced in space were 44% smaller than those in the ground control seeds. Fifteen days after pollination, cotyledon cells from mature embryos formed in space had large numbers of starch grains, and protein bodies were absent, while in developing ground control seeds at the same stage, protein bodies had already formed and fewer starch grains were evident. These data suggest that both the late stage of seed development and maturation are changed in Brassica by growth in a microgravity environment. While gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.

NASA Experiment Number 9600004↗
NASA NTRS2004

Cylindrical Asymmetrical Capacitor Devices for Space Applications

An asymmetrical capacitor system is provided which creates a thrust force. The system is adapted for use in space applications and includes a capacitor device provided with a first conductive element and a second conductive element axially spaced from the first conductive element and of smaller axial extent. A shroud supplied with gas surrounds the capacitor device. The second conductive element can be a wire ring or mesh mounted on dielectric support posts affixed to a dielectric member which separates the conductive elements or a wire or mesh annulus surrounding a barrel-shaped dielectric member on which the h t element is also mounted. A high voltage source is connected across the conductive elements and applies a high voltage to the conductive elements of sufficient value to create a thrust force on the system inducing movement thereof.

Jonathan W Campbell↗