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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 235 records · Page 13

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NASA NTRS1994

Heart Rate Variability During Early Adaptation to Space

A recent report hypothesized that episodes of space motion sickness (SMS) were reliably associated with low frequency oscillations (less than 0.03 to less than 0.01 Hz) in heart rate variability. This paper archives a large data set for review of investigators in this field which may facilitate the evaluation of this hypothesis. Continuous recording of Electro-cardiography (ECG) and other measures were made for 6 to 12 hours per day (waking hours) of six Shuttle crewmembers for the first 3 mission days of two separate Shuttle flights. Spectral analyses of heart rate variability during approximately 200 hours of inflight is presented. In addition, nearly 200 hours of data collected on these same individuals during ground tests prior to the mission are presented. The Purpose of this Publication is to document the incidence of low frequency oscillations of heart rate in 4 people exposed to microgravity over a period of five days. In addition, this report contains spectral analyses of heart rate data collected on these same individuals during ground-based mission simulations. By archiving these data in this manner, it is our intention to make this information available to other investigators interested in studying this phenomena.

Toscano, W. B.↗

NASA NTRS2004

Greenland Glacier Albedo Variability

The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo variability in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.

Source record↗

NASA NTRS2008

Modifications to Axially Symmetric Simulations Using New DSMC (2007) Algorithms

Several modifications aimed at improving physical accuracy are proposed for solving axially symmetric problems building on the DSMC (2007) algorithms introduced by Bird. Originally developed to solve nonequilibrium, rarefied flows, the DSMC method is now regularly used to solve complex problems over a wide range of Knudsen numbers. These new algorithms include features such as nearest neighbor collisions excluding the previous collision partners, separate collision and sampling cells, automatically adaptive variable time steps, a modified no-time counter procedure for collisions, and discontinuous and event-driven physical processes. Axially symmetric solutions require radial weighting for the simulated molecules since the molecules near the axis represent fewer real molecules than those farther away from the axis due to the difference in volume of the cells. In the present methodology, these radial weighting factors are continuous, linear functions that vary with the radial position of each simulated molecule. It is shown that how one defines the number of tentative collisions greatly influences the mean collision time near the axis. The method by which the grid is treated for axially symmetric problems also plays an important role near the axis, especially for scalar pressure. A new method to treat how the molecules are traced through the grid is proposed to alleviate the decrease in scalar pressure at the axis near the surface. Also, a modification to the duplication buffer is proposed to vary the duplicated molecular velocities while retaining the molecular kinetic energy and axially symmetric nature of the problem.

Liechty, Derek S.↗

NASA NTRS2010

On-Orbit Prospective Echocardiography on International Space Station Crew

Introduction A prospective trial of echocardiography was conducted on of six crewmembers onboard the International Space Station. The main objective was to determine the efficacy of remotely guided tele-echocardiography, including just-in-time e-training methods and determine what "space normal" echocardiographic data is. Methods Each crewmember operator (n=6) had 2-hour preflight training. Baseline echocardiographic data were collected 55 to 167days preflight. Similar equipment was used in each 60-minute in-flight session (mean microgravity exposure - 114 days (34 -- 190)). On Orbit ultrasound operators used an e-learning system within 24h of these sessions. Expert assistance was provided using ultrasound video downlink and two-way voice. Testing was repeated 5 to 16 days after landing. Separate ANOVA was used on each echocardiographic variable (n=33). Within each ANOVA, three tests were made: a) effect of mission phase (preflight, in-flight, post flight); b) effect of echo technician (two technicians independently analyzed the data); c) interaction between mission phase and technician. Results Nine rejections of the null hypothesis (mission phase or technician or both had no effect) were discovered and considered for follow up. Of these, six rejections were for significant technician effects, not as a result of space flight. Three rejections of the null hypothesis (Aortic Valve time velocity integral, Mitral E wave Velocity and heart rate) were attributable to space flight, however determined not to be clinically significant. No rejections were due to the interaction between technician and space flight. Conclusion No consistent clinically significant effects of long-duration space flight were seen in echocardiographic variables of the given group of subjects.

Hamilton, Douglas R.↗

NASA NTRS1974

Recent advances in satellite observations of solar variability and global atmospheric ozone

A description is given of the temporal behavior of the sun as an ultraviolet variable star in relation to daily zonal means of atmospheric ozone from the total amount to that above the 10-mb and 4-mb pressure levels. A significant correlation has been observed between enhancements in the ultraviolet solar irradiances and terrestrial passages of the solar magnetic field sector boundary structure. However, it has not yet been possible to separate solar from the dynamical effects on the variability in the zonal means of ozone. Attention is given to global changes in ozone which have been derived from the satellite observations in terms of season, solar variability, and major stratospheric disturbances such as stratospheric warmings.

Heath, D. F.↗

NASA NTRS1979

Effect of lip and centerbody geometry on aerodynamic performance of inlets for tilting-nacelle VTOL aircraft

Inlets for tilt-nacelle VTOL aircraft must operate over a wide range of incidence angles and engine weight flows without internal flow separation. Wind tunnel tests of scale model inlets were conducted to evaluate the effectiveness of three geometric variables to provide this capability. Increasing the lip contraction ratio increased the separation angle at all engine weight flows. The optimum axial location of the centerbody occurred when its leading edge was located just downstream of the inlet lip. Compared with a short centerbody, the optimum location of the centerbody resulted in an increase in separation angle at all engine weight flows. Decreasing the lip major-to-minor-axis ratio increased the separation angle at the lower engine weight flows.

Burley, R. R.↗

NASA NTRS1979

Effect of lip and centerbody geometry on aerodynamic performance of inlets for tilting-nacelle VTOL aircraft

Burley, R. R.↗

NASA NTRS1986

Heat and mass transfer in porous media phase separation at temperatures below the lambda-point of He-4

Newtonian fluid motion, coupled to heat transfer via latent heat of phase transition, is well known from numerous studies of condensation and boiling. Considerably less knowledge is available for vapor-liquid phase separation in the absence of gravity effect on the transport phenomena. The present studies are focused on heat and mass transfer associated with vapor-liquid phase separation required for long-term storage of the cryogen liquid He II in space vessels. Though space conditions are the dominant mode of interest in advanced equipment, e.g. IR telescopes, the systems may be operated in principle during terrestrial conditions. The latter are considered in the present work. It emphasizes the linear regime including an extrapolation based on variable thermophysical properties. Data taken with a phase separation approach show departures from the linear regime prediction. They agree with a transport equation proposed for the nonlinear, turbulent regime.

Yuan, S. W. K.↗

NASA NTRS2003

Computational Study of Axisymmetric Off-Design Nozzle Flows

Computational Fluid Dynamics (CFD) analyses of axisymmetric circular-arc boattail nozzles operating off-design at transonic Mach numbers have been completed. These computations span the very difficult transonic flight regime with shock-induced separations and strong adverse pressure gradients. External afterbody and internal nozzle pressure distributions computed with the Wind code are compared with experimental data. A range of turbulence models were examined, including the Explicit Algebraic Stress model. Computations have been completed at freestream Mach numbers of 0.9 and 1.2, and nozzle pressure ratios (NPR) of 4 and 6. Calculations completed with variable time-stepping (steady-state) did not converge to a true steady-state solution. Calculations obtained using constant timestepping (timeaccurate) indicate less variations in flow properties compared with steady-state solutions. This failure to converge to a steady-state solution was the result of using variable time-stepping with large-scale separations present in the flow. Nevertheless, time-averaged boattail surface pressure coefficient and internal nozzle pressures show reasonable agreement with experimental data. The SST turbulence model demonstrates the best overall agreement with experimental data.

DalBello, Teryn↗

NASA NTRS1995

The morphogenic features of otoconia during larval development of Cynops pyrrhogaster, the Japanese red-bellied newt

Otoconia are calcified protein matrices within the gravity-sensing organs of the vertebrate vestibular system. Mammalian otoconia are barrel-shaped with triplanar facets at each end. Reptilian otoconia are commonly prismatic or fusiform in shape. Amphibians have all three otoconial morphologies, barrel-shaped otoconia within the utricle, with prismatic and fusiform otoconia in the saccule. Scanning electron microscopy revealed a sequential appearance of all three otoconial morphologies during larval development of the newt, Cynops pyrrhogaster. The first otoconia appear within a single, developing otolith, and some resemble adult barrel-shaped otoconia. As the larvae hatch, around stages 39-42, the single otolith divides into two anatomically separate regions, the utricle and saccule, and both contain otoconia similar to those seen in the single otolith. Throughout development, these otoconia may have variable morphologies, with serrated surfaces, or circumferential striations with either separated facets or adjacent facets in the triplanar end-regions. Small fusiform otoconia occur later, at stage 51, and only in the saccule. Prismatic otoconia appear later still, at stage 55, and again only in the saccule. Thus, although prismatic otoconia are the most numerous in adult newts, it is the last vestibular otoconial morphology to be expressed.

NASA Discipline Neuroscience↗

NASA NTRS1992

Estimation of surface heat and moisture fluxes over a prairie grassland. II - Two-dimensional time filtering and site variability

The behavior of in situ measurements of surface fluxes obtained during FIFE 1987 is examined by using correlative and spectral techniques in order to assess the significance of fluctuations on various time scales, from subdiurnal up to synoptic, intraseasonal, and annual scales. The objectives of this analysis are: (1) to determine which temporal scales have a significant impact on areal averaged fluxes and (2) to design a procedure for filtering an extended flux time series that preserves the basic diurnal features and longer time scales while removing high frequency noise that cannot be attributed to site-induced variation. These objectives are accomplished through the use of a two-dimensional cross-time Fourier transform, which serves to separate processes inherently related to diurnal and subdiurnal variability from those which impact flux variations on the longer time scales. A filtering procedure is desirable before the measurements are utilized as input with an experimental biosphere model, to insure that model based intercomparisons at multiple sites are uncontaminated by input variance not related to true site behavior. Analysis of the spectral decomposition indicates that subdiurnal time scales having periods shorter than 6 hours have little site-to-site consistency and therefore little impact on areal integrated fluxes.

Crosson, William L.↗

NASA NTRS1970

Study of process variables associated with manufacturing hermetically sealed nickel-cadium cells Quarterly report, 23 May - 23 Aug. 1970

Separator materials, ceramic to metal seals, cell plate polarization and impregnation processes, and plaque sintering data for study of variables in manufacture of nickel cadmium cells

Carr, E. S.↗

NASA NTRSDate not supplied

Batch Effect Correction Methods for NASA GeneLab Transcriptomic Datasets

RNA sequencing (RNA-seq) data from space biology experiments promise to yield invaluable insights into the effects of spaceflight on terrestrial biology. However, sample numbers from each study are low due to limited crew availability, hardware, and space. To increase statistical power, spaceflight RNA-seq datasets from different missions are often aggregated together. However, this can introduce technical variation or "batch effects", often due to differences in sample handling, sample processing, and sequencing platforms. Several computational methods have been developed to correct for technical batch effects, thereby reducing their impact on true biological signals. In this study, we combined 7 mouse liver RNA-seq datasets from NASA GeneLab (part of the NASA Open Science Data Repository) to evaluate several common batch effect correction methods (ComBat and ComBat-seq from the sva R package, and Median Polish, Empirical Bayes, and ANOVA from the MBatch R package). We quantitatively evaluated the ability of these methods to correct for technical batch variables in space biology RNA-seq data using the following criteria: BatchQC, principal component analysis, dispersion separability criterion, log fold change correlation, and differential gene expression analysis. Each batch variable / correction method combination was then assessed using a custom scoring approach to identify the optimal correction method for the combined dataset, by geometrically probing the space of all allowable scoring functions to yield an aggregate volume-based scoring measure. Finally, we describe the way in which the GeneLab multi-study analysis and visualization portal will allow users to examine the presence or absence of batch effects using multiple metrics. If the user chooses to perform batch effect correction, the scoring approach described here can be implemented to identify the optimal correction method to use for their specific combined dataset prior to analysis.

Lauren M. Sanders↗

NASA NTRS1994

Airfoil optimization by the one-shot method

An efficient numerical approach for the design of optimal aerodynamic shapes is presented in this paper. The objective of any optimization problem is to find the optimum of a cost function subject to a certain state equation (Governing equation of the flow field) and certain side constraints. As in classical optimal control methods, the present approach introduces a costate variable (Language multiplier) to evaluate the gradient of the cost function. High efficiency in reaching the optimum solution is achieved by using a multigrid technique and updating the shape in a hierarchical manner such that smooth (low-frequency) changes are done separately from high-frequency changes. Thus, the design variables are changed on a grid where their changes produce nonsmooth (high-frequency) perturbations that can be damped efficiently by the multigrid. The cost of solving the optimization problem is approximately two to three times the cost of the equivalent analysis problem.

Kuruvila, G.↗

NASA NTRS1995

Airfoil Design and Optimization by the One-Shot Method

An efficient numerical approach for the design of optimal aerodynamic shapes is presented in this paper. The objective of any optimization problem is to find the optimum of a cost function subject to a certain state equation (governing equation of the flow field) and certain side constraints. As in classical optimal control methods, the present approach introduces a costate variable (Lagrange multiplier) to evaluate the gradient of the cost function. High efficiency in reaching the optimum solution is achieved by using a multigrid technique and updating the shape in a hierarchical manner such that smooth (low-frequency) changes are done separately from high-frequency changes. Thus, the design variables are changed on a grid where their changes produce nonsmooth (high-frequency) perturbations that can be damped efficiently by the multigrid. The cost of solving the optimization problem is approximately two to three times the cost of the equivalent analysis problem.

Kuruvila, G.↗

NASA NTRS2019

Uncertainty Analysis of the CE-22 Advanced Nozzle Test Facility

This paper presents methods and results of a detailed measurement uncertainty analysis that was performed for the Advanced Nozzle Test Facility, CE-22, located at the NASA Glenn Research Center. Results for the uncertainty in thrust and flow coefficients, in addition to other variables of interest, are provided. Results are presented separately as random uncertainty (characterizing errors inherent to instrument or measurement environment, impacting repeatability), systematic uncertainty (capturing inaccuracies due to measurement process, calibration, installation effects or other sources which may introduce bias), and total combined uncertainty. The statistical methods and engineering judgments used to estimate elemental uncertainties are described. The analysis tool MANTUS (Measurement Analysis Tool for Uncertainty in Systems) was used to quantify instrumentation system uncertainty, and statistical analysis and engineering judgment were used to quantify other random and systematic uncertainty sources. The Monte Carlo method was used to propagate systematic and random elemental uncertainties to determine the uncertainties of various calculated variables of interest.

data quality↗

NASA NTRS1920

Variable Pitch Propellers

In this report are described four different types of propellers which appeared at widely separated dates, but which were exhibited together at the last Salon de l'Aeronautique. The four propellers are the Chaviere variable pitch propeller, the variable pitch propeller used on the Clement Bayard dirigible, the variable pitch propeller used on Italian dirigibles, and the Levasseur variable pitch propeller.

Source record↗

NASA NTRS2006

Tropospheric and stratospheric ozone from assimilation of Aura data

Ozone is an atmospheric trace gas with multiple impacts on the environment. Global ozone fields are needed for air quality predictions, estimation of the ultraviolet radiation reaching the surface, climate-radiation studies, and may also have an impact on longer-term weather predictions. We estimate global ozone fields in the stratosphere and troposphere by combining the data from EOS Aura satellite with an ozone model using data assimilation. Ozone exhibits a large temporal variability in the lower stratosphere. Our previous work showed that assimilation of satellite data from limb-sounding geometry helps constrain ozone profiles in that region. We assimilated ozone data from the Aura Microwave Limb Sounder (MLS) and the Ozone Monitoring Instrument (OMI) into the ozone system at NASA's Global Modeling and Assimilation Office (GMAO). Ozone is transported within a general circulation model (GCM) which includes parameterizations for stratospheric photochemistry, tropospheric chemistry, and a simple scheme for heterogeneous ozone loss. The focus of this study is on the representation of ozone in the lower stratosphere and tropospheric ozone columns. We plan to extend studies of tropospheric ozone distribution through assimilation of ozone data from the Tropospheric Emission Spectrometer (TES). Comparisons with ozone sondes and occultation data show that assimilation of Aura data reproduces ozone gradients and variability in the lower stratosphere well. We proceed by separating the contributions to temporal changes in the ozone field into those that are due to the model and those that are due to the assimilation of Aura data. The impacts of Aura data are illustrated and their role in the representation of ozone variability in the lower stratosphere and troposphere is shown.

Stajner, I.↗