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At least 1,315 records · Page 73

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NASA NTRS1985

Computer-assisted image analysis of plant growth, thigmomorphogenesis and gravitropism

A nonintrusive auxonometric system, based on the DARWIN image processor (Telewski et al. 1983 Plant Physiol 72: 177-181), is described and demonstrated in the analysis of gravitropism and thigmomorphogenesis in corn seedlings (Zea mays). Using this system, growth and bending of regularly shaped plants or organs can be quickly and accurately measured without, in any way, interfering with the plant. Furthermore, the growth and bending curves are automatically plotted. Thigmomorphogenesis in the aerial part of corn seedlings involves growth promotion at a low force load and growth retardation at higher force loads. The time courses of the two kinds of response are somewhat different, with retardation occurring immediately after mechanical perturbation and growth promotion taking somewhat longer to begin. Gravitropic experiments show that when dark-grown corn seedlings are placed on their side in the light, the resulting curvature is due to two consecutive morphological mechanisms. In the first instance, lasting for about 15 minutes, the elongation of the bottom edge of the plant accelerates, while the elongation of the top edge remains constant. After that, for the next 1.75 hours, the elongation of the top edge decelerates and stops while that of the bottom edge remains constant at the increased rate for most of the period. The measurements taken from both experiments at relatively high resolution (0.08-0.1 millimeter) show that the growth curves are not smooth but show many small irregularities which may or may not involve micronutations.

Zea mays/growth & development/physiology↗

NASA NTRS2008

Designing a Composable Geometric Toolkit for Versatility in Applications to Simulation Development

Conceived and implemented through the development of probabilistic risk assessment simulations for Project Constellation, the Geometric Toolkit allows users to create, analyze, and visualize relationships between geometric shapes in three-space using the MATLAB computing environment. The key output of the toolkit is an analysis of how emanations from one "source" geometry (e.g., a leak in a pipe) will affect another "target" geometry (e.g., another heat-sensitive component). It can import computer-aided design (CAD) depictions of a system to be analyzed, allowing the user to reliably and easily represent components within the design and determine the relationships between them, ultimately supporting more technical or physics-based simulations that use the toolkit. We opted to develop a variety of modular, interconnecting software tools to extend the scope of the toolkit, providing the capability to support a range of applications. This concept of simulation composability allows specially-developed tools to be reused by assembling them in various combinations. As a result, the concepts described here and implemented in this toolkit have a wide range of applications outside the domain of risk assessment. To that end, the Geometric Toolkit has been evaluated for use in other unrelated applications due to the advantages provided by its underlying design.

Reed, Gregory S.↗

NASA NTRS2009

Objectives and Progress on Integrated Vehicle Ground Vibration Testing for the Ares Launch Vehicles

As NASA begins design and development of the Ares launch vehicles to replace the Space Shuttle and explore beyond low Earth orbit, Integrated Vehicle Ground Vibration Testing (IVGVT) will be a vital component of ensuring that those vehicles can perform the missions assigned to them. A ground vibration test (GVT) is intended to measure by test the fundamental dynamic characteristics of launch vehicles during various phases of flight. During the series of tests, properties such as natural frequencies, mode shapes, and transfer functions are measured directly. This data is then used to calibrate loads and control systems analysis models for verifying analyses of the launch vehicle. The Ares Flight & Integrated Test Office (FITO) will be conducting IVGVT for the Ares I crew launch vehicle at Marshall Space Flight Center (MSFC) from 2011 to 2012 using the venerable Test Stand (TS) 4550, which supported similar tests for the Saturn V and Space Shuttle vehicle stacks.

Tuma, Margaret L.↗

NASA NTRS2010

Wing Leading Edge Concepts for Noise Reduction

This study focuses on the development of wing leading edge concepts for noise reduction during high-lift operations, without compromising landing stall speeds, stall characteristics or cruise performance. High-lift geometries, which can be obtained by conventional mechanical systems or morphing structures have been considered. A systematic aerodynamic analysis procedure was used to arrive at several promising configurations. The aerodynamic design of new wing leading edge shapes is obtained from a robust Computational Fluid Dynamics procedure. Acoustic benefits are qualitatively established through the evaluation of the computed flow fields.

Shmilovich, Arvin↗

NASA NTRS2020

Overcoming Dimensionality Barriers in Satellite Data to Elucidate SPECTRAL-SPATIAL-TEMPORAL Trends in the Ocean

The weighted harmonic mean of spectral wavelengths can be used as an index of optical water types that share similar spectral signatures.This technique can be translated to relate spectral shape between sensors of varying spectral resolution.The output along a continuum of color values enables spatio-temporal analysis of subtle spectral shifts.Directional trends in absorption and backscatter data lend a hidden context to changes in water color. Conceptualization of multiple data dimensions is imperative as passive/active sensors grow increasingly sophisticated in nature.

Vandermeulen, Ryan↗

NASA NTRS2019

PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter

Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists because their attributes can be used to determine the properties of the dense matter in their cores. One of the most informative approaches for determining the equation of state (EoS) of this dense matter is to measure both a star’s equatorial circumferential radius Re and its gravitational mass M. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSRJ0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are Re = 13.02+1.24-1.06 km andM = 1.44+0.15-0.14 Mmoon (68%). The independent analysis reported in the companion paper by Riley et al. explores different emitting spot models, but finds spot shapes and locations and estimates of Re and M that are consistent with those found in this work. We show that our measurements of Re and M for PSRJ0030+0451 improve the astrophysical constraints on the EoS of cold, catalyzed matter above nuclear saturation density.

M C Miller↗

NASA NTRSDate not supplied

The Effects to Exposure of Simulated Spaceflight Radiation on Behavioral Health of Male and Female Mice

Exposure to space radiation is a principal consideration of spaceflight missions as risk is leveraged as time and dose—both expected to increase with future missions to the Moon, Mars, and beyond. Previous mission exposure levels, galactic cosmic radiation (GCR) and solar particle events (SPE), have been characterized as increased compared to those natural to Earth and are predicted to cause robust deficits at higher doses and longer durations. The cognitive health implications of this critical difference are understood as risks to mission and crew operations. We examined potential radiation-induced disruptions on brain health through resting-state in-cage behavior. 23–24-week-old male and female mice were exposed to 0 cGy (Sham), 5 cGy, 15 cGy, and 50 cGy via Five-Ion GCR Simulation (H, Si, He, O, Fe) at the NASA Space Radiation Lab in Brookhaven National Labs. Behavioral and cognitive performance were evaluated via frequency/duration of digging, rearing, and grooming within the 72-hour period immediately following irradiation. Additionally, during this time we evaluated nestlet building using a 5-stage Deacon score, rating shredding and shelter assembly of cotton material from untouched (1) to shredded and formed into a crater shape (5). We have observed differences in Deacon score only among the 15 cGy subset. Further comparative performance analysis will be completed evaluating the differences in irradiation effects between male and female mice. These experimental design aspects that allot for gender-inclusivity is supportive of the diversification of future space travel mission plans. Investigating gender differences is an element under our main objective of determining radiation dose-response curves. In brief, these studies identified a space-relevant radiation dose of 15 cGy that that can be utilized for future standardized ground studies on the nervous system.

spaceflight cognition impairment↗

NASA NTRS2021

Variabilities in Pm2.5 and Black Carbon Surface Concentrations Reproduced by Aerosol Optical Properties Estimated by In-Situ Data, Ground Based Remote Sensing and Modeling

Because of the increased temporal and spatial resolutions of the sensors onboard recently launched satellites, satellite-based surface aerosol concentration, which is usually estimated from the aerosol optical depth (AOD), is expected to become a strategic tool for air quality studies in the future. By further exploring the relationships of aerosol concentrations and their optical properties using ground observations, the accuracies of these products can be improved. Here, we analyzed collocated observations of surface mass concentrations of fine particulate matter (PM2.5) and black carbon (BC), as well as columnar aerosol optical properties from a sky radiometer and aerosol extinction profiles obtained by multi-axis differential optical absorption spectroscopy (MAX-DOAS), during the 2019–2020 period. We focused the analyses on a daily scale, emphasizing the role of the ultraviolet (UV) spectral region. Generally, the correlation between the AOD of the fine fraction (i.e., fAOD) and the PM2.5 surface concentration was moderately strong, regardless of considerations of boundary layer humidity and altitude. In contrast, the fAOD of the partial column below 1 km, which was obtained by combining sky radiometer and MAX-DOAS retrievals, better reproduced the variability of the PM2.5 and resulted in a linear relationship. In the same manner, we demonstrated that the absorption AOD of the fine fraction (fAAOD) of the partial column was related to the variability of the BC concentration. Analogous analyses based on aerosol products from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) confirmed these findings and highlighted the importance of the shape of the aerosol profile. Overall, our results indicated a remarkable consistency among the retrieved datasets, and between the datasets and MERRA-2 products. These results confirmed the well-known sensitivity to aerosol absorption in the UV spectral region; they also highlighted the efficacy of combined MAX-DOAS and sky radiometer observations.

Alessandro Damiani↗

NASA NTRSDate not supplied

Improvements to the Simulated CubeSpark Satellite Constellation and Their Effects on Lightning Geolocation Accuracy from Orbit

The CubeSpark mission concept is being developed as a constellation of up to six satellites in low-Earth orbit (LEO) for high resolution 3D lightning mapping using optical and radio frequency (RF) sensors. Individual lightning VHF signals are simulated from Earth’s atmosphere through the ionosphere to each satellite, using their arrival times to reconstruct source locations. Here we present recent updates to these simulations based on improved ionospheric modeling, with a focus on the expected three-dimensional resolution. These studies include testing from the equator up to high latitudes, with varying vertical total electron content (vTEC), and using between one and six orbiting stations. In addition to the more robust ionosphere model, the constellation formation has also been updated to reduce its resulting errors and increase the effective range of VHF geolocation from space. The goals of CubeSpark include mapping thundercloud charge structure as well as lightning channel lengths relevant to climatology, meteorology, and more. These applications require location uncertainty less than 1-2 km in each dimension. This improved algorithm shows sufficient resolution up to high latitudes, including significantly larger areas having 3D resolution less than 1 km. Analysis of the distributions of biases in simulated arrival times has also revealed the unexpected relationship between the shape of those distributions and the resulting uncertainties. This work helps to refine our understanding of the sources of error in lightning geolocation and reinforces the potential for post-processing improvements in this and other similar systems.

Lightning↗

NASA NTRS1986

Simulation and analysis of antennas radiating in a complex environment

A numerical procedure for computing the high-frequency radiation patterns of antennas mounted on curved surfaces is described. The procedure utilizes the uniform geometrical theory of diffraction to examine the antenna system's performance, which is dependent on antenna radiation patterns. Composite ellipsoid models of fuselage shapes are developed and the formation of geodesic paths on the models is studied; the shape of the fuselage affects the radiation patterns. The actual field radiated by the source and scattered by the structure is calculated using the ray field technique. The numerical solution is applied to the analysis of the antenna radiation patterns of a military aircraft, private aircraft, and the Space Shuttle orbiter. Good correlation between the calculated and measured radiation patterns is noted verifying the usefulness and accuracy of the numerical procedure.

Kim, J. J.↗

NASA NTRS1990

Configuration design sensitivity analysis of built-up structures

In the design of complex built-up structures that are made of truss, beam, membrane, shell, and solid, there are five different kinds of design variables: material property, sizing, shape, configuration, and topological variables. Previous research has shown that the improvement in performances obtained by altering the configuration of structural components can be much more significant than those obtained when the geometry is assumed to be fixed. Using the variational approach, a unified design sensitivity was developed for the first three kinds of design variables, and was further extended recently in many structural analysis problems such as nonlinear, structural dynamics, and frequency response analysis. A continuum design sensitivity analysis method is developed for the configuration design variable of built-up structures.

Choi, Kyung K.↗

NASA NTRS1980

An investigation of the cratering-induced motions occurring during the formation of bowl-shaped craters

The effects of the dynamic processes which occur during crater formation were examined using small hemispherical high-explosive charges detonated in a tank which had one wall constructed of a thick piece of clear plexiglas. Crater formation and the motions of numerous tracer particles installed in the cratering medium at the medium-wall interface were viewed through the wall of this quarter-space tank and recorded with high-speed cameras. Subsequent study and analysis of particle motions and events recorded on the film provide data needed to develop a time-sequence description of the formation of a bowl-shaped crater. Tables show the dimensions of craters produced in a quarter-space tank compared with dimensions of craters produced in normal half-space tanks. Crater growth rate summaries are also tabulated.

Piekutowski, A. J.↗

NASA NTRS1992

Design, analysis, and testing of a metal matrix composite web/flange intersection

An experimental and analytical program to study the local design details of a typical T-shaped web/flange intersection made from a metal matrix composite is described. Loads creating flange bending were applied to specimens having different designs and boundary conditions. Finite element analyses were conducted on models of the test specimens to predict the structural response. The analyses correctly predict failure load, mode, and location in the fillet material in the intersection region of the web and the flange when specimen quality is good. The test program shows the importance of fabrication quality in the intersection region. The full-scale test program that led to the investigation of this local detail is also described.

Biggers, S. B.↗

NASA NTRS2012

HEART Aerothermodynamic Analysis

This paper presents an assessment of the aerothermodynamic environment around an 8.3 meter High Energy Atmospheric Reentry Test (HEART) vehicle. This study generated twelve nose shape configurations and compared their responses at the peak heating trajectory point against the baseline nose shape. The heat flux sensitivity to the angle of attack variations are also discussed. The possibility of a two-piece Thermal Protection System (TPS) design at the nose is also considered, as are the surface catalytic affects of the aeroheating environment of such configuration. Based on these analyses, an optimum nose shape is proposed to minimize the surface heating. A recommendation is also made for a two-piece TPS design, for which the surface catalytic uncertainty associated with the jump in heating at the nose-IAD juncture is reduced by a minimum of 93%. In this paper, the aeroshell is assumed to be rigid and the inflatable fluid interaction effect is left for future investigations.

Mazaheri, Alireza↗

NASA NTRS2013

High-Energy Atmospheric Reentry Test Aerothermodynamic Analysis

Mazaheri, Alireza↗

NASA NTRS2016

Graphical Acoustic Liner Design and Analysis Tool

An interactive liner design and impedance modeling tool comprises software utilized to design acoustic liners for use in constrained spaces, both regularly and irregularly shaped. A graphical user interface allows the acoustic channel geometry to be drawn in a liner volume while the surface impedance calculations are updated and displayed in real-time. A one-dimensional transmission line model may be used as the basis for the impedance calculations.

Howerton, Brian M.↗

NASA NTRS1987

DSS 43 antenna gain analysis for Voyager Uranus encounter: 8.45-GHz radio science data correction

A malfunction of the Deep Space Network (DSN) 64-meter antenna in Australia forced the antenna to operate with a mispositioned subreflector during the Voyager Uranus encounter period (January 24, 1986). Because of changing main reflector shape and quadripod position as a function of elevation angle, the antenna gain and pointing were not as expected, and the 8.45 GHz received signal level changed during the pass. The study described here used the Geometrical Theory of Diffraction (GTD) analysis to determine actual antenna gain and pointing during that period in an attempt to reconstruct the radio science data. It is found that the 1.4 dB of signal variation can be accounted for by antenna geometry changes and pointing error. Suggested modifications to the values measured during the pass are presented. Additionally, an extremely useful tool for the analysis of gravity deformed reflectors was developed for use in future antenna design and analysis projects.

Slobin, S. D.↗

NASA NTRS1999

Cosmic Diffuse Analysis

The final analysis of the COMPTEL cosmic diffuse flux analysis is summarized in the accompanying figure. It shows the intensity of the cosmic diffuse flux spectrum measured jointly between the Virgo region and the South Galactic pole. This spectrum represents flux per unit solid angle over the range of 0.8 to 30 MeV. It contains the first positive measurement of the flux above 10 MeV. The spectrum merges smoothly with that measured with the EGRET instrument, starting at 30 MeV. It also merges smoothly with the latest results of the HEAO-1 measurements. However, the spectrum below is softer than the spectrum above the COMPTEL energy band. In the COMPTEL energy band there must exist a change in spectral shape as the source objects or processes change from the lower energy regime to the higher energy regime. The details of the analysis and the implications and meanings of the results are spelled out in the thesis of Dr. Cheenu Kappadath which is enclosed.

Ryan, James M.↗