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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

Validation of Universal Cryogenic Flow Boiling Correlations in Thermal Desktop for Liquid Hydrogen

Developing accurate models of two-phase cryogenic flow will reduce risk and reduce margins for future NASA vehicles such as the Nuclear Thermal Propulsion (NTP) system. Currently there is a need for more accurate, direct cryogenic data-anchored models for various boiling and two-phase phenomena. The focus of the current work is on modeling steady state cryogenic flow boiling in the transfer line that connects a propellant storage tank to an engine or customer receiver tank. This paper presents Thermal Desktop model validation results against several historical liquid hydrogen (LH2) heated tube experiments that cover a wide range of inlet conditions, mass flux, and heat flux. New universal cryogenic flow boiling correlations were recently developed and anchored to the largest cryogenic flow boiling database assembled in the world to-date. The new universal correlations are patched together and implemented into Thermal Desktop to compare model performance against the built-in flow boiling correlations. Axial wall temperature predictions as a function of preponderant parameters like heat flux, mass flux, inlet pressure, inlet quality, tube diameter, etc. using the two sets of flow boiling correlations are compared against the experimental data. Overall, the Thermal Desktop model with the new universal cryogenic flow boiling correlations demonstrates an improvement in predictive performance over the Thermal Desktop model using built-in correlations for both wall temperature and location of critical heat flux compared to the data for LH2 flow boiling in heated tubes.

cryogenic propellant transfer↗
NASA NTRS2011

Functional Task Test: 2. Spaceflight-Induced Cardiovascular Change and Recovery During NASA's Functional Task Test

The overall objective of the functional task test (FTT) is to correlate spaceflight-induced physiological adaptations with changes in performance of high priority exploration mission-critical tasks. This presentation will focus on the recovery from fall/stand test (RFST), which measures the cardiovascular response to the transition from the prone posture (simulated fall) to standing in normal gravity, as well as heart rate (HR) during 11 functional tasks. As such, this test describes some aspects of spaceflight-induced cardiovascular deconditioning and the course of recovery in Space Shuttle and International Space Station (ISS) astronauts. The sensorimotor and neuromuscular components of the FTT are described in two separate abstracts: Functional Task Test 1 and 3.

Phillips, Tiffany↗
NASA NTRS2006

The Molecular Ecology of Guerrero Negro: Justifying the Need for Environmental Genomics

The record of life on the only planet where it is known to exist is contained in the biogeochemical processes that organisms catalyze for their survival, in the compounds that they produce, and in their phylogenetic (evolutionary) relationships to each other. We manipulated sulfate and nutrient concentrations in intact microbial mats over periods of time up to a year. The objectives of the manipulations were: 1) characterize the diversity of process-associated functional genes; 2) understand environmental conditions leading to shifts in microbial guilds; 3) monitor/identify competitive responses of organisms sharing a metabolic niche. Characterization of functional genes associated with carbon (mcrA), nitrogen (nifH, nirK) and sulfur (dsrkB) cycling performed to date provided insight into the diversity and metabolic potential of the system; however, we only identified broad scale correlations between gene abundances and changes in mat physiology. For instance, increases in methane production by mats subjected to lowered sulfate and salinity concentrations were correlated with an observed increase in abundance of hydrogenotroph-like mcrA genes. However, due to low sequence similarity to any cultured isolates, phylogenetic associations only allow order level taxonomic commentary, preventing any associations being made on the cellular level. In each of the genes characterized from these experiments, a significant portion of sequences recovered show minimal phylogenetic affiliation to cultured organisms, preventing any understanding of inter-community dynamics and the functional capacities of these unknown organisms. Environmental genomics may provide insight into mat systems by allowing the correlation of functional genes with phylogenetic markers.

Smith, Jason M.↗
NASA NTRS2005

Surveillance system and method having an adaptive sequential probability fault detection test

System and method providing surveillance of an asset such as a process and/or apparatus by providing training and surveillance procedures that numerically fit a probability density function to an observed residual error signal distribution that is correlative to normal asset operation and then utilizes the fitted probability density function in a dynamic statistical hypothesis test for providing improved asset surveillance.

Herzog, James P.↗
NASA NTRS2006

Surveillance system and method having an adaptive sequential probability fault detection test

System and method providing surveillance of an asset such as a process and/or apparatus by providing training and surveillance procedures that numerically fit a probability density function to an observed residual error signal distribution that is correlative to normal asset operation and then utilizes the fitted probability density function in a dynamic statistical hypothesis test for providing improved asset surveillance.

Bickford, Randall L.↗
NASA NTRS2008

Surveillance System and Method having an Adaptive Sequential Probability Fault Detection Test

System and method providing surveillance of an asset such as a process and/or apparatus by providing training and surveillance procedures that numerically fit a probability density function to an observed residual error signal distribution that is correlative to normal asset operation and then utilizes the fitted probability density function in a dynamic statistical hypothesis test for providing improved asset surveillance.

Bickford, Randall L.↗
NASA NTRS1992

The form of spin orbitals for open-shell restricted Hartree-Fock reference functions

A new set of spin orbitals is proposed for single-reference correlation procedures based on an open-shell restricted Hartree-Fock (RHF) reference function. The spatial parts of the new spin orbitals are from an open-shell RHF calculation. These spin orbitals form a complete, orthonormal set. The RHF single determinant based on these spin orbitals is an S sub 2 eigenfunction, but a linear combination of S sub z eigenfunctions. The advantage of these spin orbitals is that equations for perturbation theory or coupled-cluster theory are symmetric in the spin indices and hence the number of independent parameters to be determined is dramatically reduced.

Jayatilaka, Dylan↗
NASA NTRS1995

Noise correlations in cosmic microwave background experiments

Many analysis of microwave background experiments neglect the correlation of noise in different frequency of polarization channels. We show that these correlations, should they be present, can lead to serve misinterpretation of an experiment. In particular, correlated noise arising from either electronics or atmosphere may mimic a cosmic signal. We quantify how the likelihood function for a given experiment varies with noise correlation, using both simple analytic models and actual data. For a typical microwave background anisotropy experiment, noise correlations at the level of 1% of the overall noise can seriously reduce the significance of a given detection.

Dodelson, Scott↗
NASA NTRS2013

Bulk Insolation Models as Predictors for Locations for High Lunar Hydrogen Concentrations

In this study we consider the bulk effects of surface illumination on topography (insolation) and the possible thermodynamic effects on the Moon's hydrogen budget. Insolation is important as one of the dominant loss processes governing distributions of hydrogen volatiles on the Earth, Mars and most recently Mercury. We evaluated three types of high latitude > 65 deg., illumination models that were derived from the Lunar Observing Laser Altimetry (LOLA) digital elevation models (DEM)'s. These models reflect varying accounts of solar flux interactions with the Moon's near-surface. We correlate these models with orbital collimated epithermal neutron measurements made by the Lunar Exploration Neutron Detector (LEND). LEND's measurements derive the Moon's spatial distributions of hydrogen concentration. To perform this analysis we transformed the topographic model into an insolation model described by two variables as each pixels 1) slope and 2) slope angular orientation with respect to the pole. We then decomposed the illumination models and epithermal maps as a function of the insolation model and correlate the datasets.

Hydrogen Concentrations↗
NASA NTRS2017

Spaceflight Effects on Neurocognitive Performance: Extent, Longevity and Neural Bases

We are conducting ongoing experiments in which we are performing structural and functional magnetic resonance brain imaging to identify the relationships between changes in neurocognitive function and neural structural alterations following a six month International Space Station mission. Our central hypothesis is that measures of brain structure, function, and network integrity will change from pre to post spaceflight. Moreover, we predict that these changes will correlate with indices of cognitive, sensory, and motor function in a neuroanatomically selective fashion. Our interdisciplinary approach utilizes cutting edge neuroimaging techniques and a broad ranging battery of sensory, motor, and cognitive assessments that are conducted pre flight, during flight, and post flight to investigate potential neuroplastic and maladaptive brain changes in crewmembers following long-duration spaceflight. Success in this endeavor would 1) result in identification of the underlying neural mechanisms and operational risks of spaceflight-induced changes in behavior, and 2) identify whether a return to normative behavioral function following re-adaptation to Earth's gravitational environment is associated with a restitution of brain structure and function or instead is supported by substitution with compensatory brain processes. We have collected data on several crewmembers and preliminary findings will be presented. Eventual comparison to results from our parallel bed rest study will enable us to parse out the multiple mechanisms contributing to any spaceflight-induced neural structural and behavioral changes that we observe.

Seidler, R. D.↗
NASA NTRS2005

Prediction of Turbulence-Generated Noise in Unheated Jets: JeNo Technical Manual (Version 1.0) - Part 1

The model-based approach, used by the JeNo code to predict jet noise spectral directivity, is described. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. A Reynolds-averaged Navier-Stokes (RANS) solution yields the required mean flow for the solution of the propagation Green s function in a locally parallel flow. The RANS solution also produces time- and length-scales needed to model the non-compact source, the turbulent velocity correlation tensor, with exponential temporal and spatial functions. It is shown that while an exact non-causal Green s function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at low to moderate Mach numbers, the polar directivity of radiated sound is not entirely captured by this Green s function at high subsonic and supersonic acoustic Mach numbers. Results presented for unheated jets in the Mach number range of 0.51 to 1.8 suggest that near the peak radiation angle of high-speed jets, a different source/Green s function convolution integral may be required in order to capture the peak observed directivity of jet noise. A sample Mach 0.90 heated jet is also discussed that highlights the requirements for a comprehensive jet noise prediction model.

Khavaran, Abbas↗
NASA NTRS2006

SOFTC: A Software Correlator for VLBI

SOFTC is an advanced software implementation of a signal correlator for very-long-baseline interferometry (VLBI) for measuring positions of natural celestial objects and distant spacecraft. Because of increases in processing speeds of general-purpose computers, software VLBI correlators have become viable alternatives to hardware ones. The input to SOFTC consists of digitized samples of raw VLBI-antenna received- signal voltages. Optionally, SOFTC also tracks calibration tones superimposed on the received signals. The outputs of SOFTC are (1) phases and amplitudes as functions of time and frequency for cross-correlated received signals and (2) phases and amplitudes as functions of time, station, and tone number for the calibration tones. SOFTC was created to be as accurate as possible, capable of processing essentially any VLBI data, pass strong debugging tests, have a simple user interface, and have no platform dependencies. SOFTC is written modularly in the C programming language. The great advantage of implementing a correlator in software, in contradistinction to hardware, is that it becomes relatively easy and much less expensive and time-consuming to adapt, modify, improve, and update the correlator.

Lowe, Stephen↗
NASA NTRS2002

Enabling Computational Nanotechnology through JavaGenes in a Cycle Scavenging Environment

A genetic algorithm procedure is developed and implemented for fitting parameters for many-body inter-atomic force field functions for simulating nanotechnology atomistic applications using portable Java on cycle-scavenged heterogeneous workstations. Given a physics based analytic functional form for the force field, correlated parameters in a multi-dimensional environment are typically chosen to fit properties given either by experiments and/or by higher accuracy quantum mechanical simulations. The implementation automates this tedious procedure using an evolutionary computing algorithm operating on hundreds of cycle-scavenged computers. As a proof of concept, we demonstrate the procedure for evaluating the Stillinger-Weber (S-W) potential by (a) reproducing the published parameters for Si using S-W energies in the fitness function, and (b) evolving a "new" set of parameters using semi-empirical tightbinding energies in the fitness function. The "new" parameters are significantly better suited for Si cluster energies and forces as compared to even the published S-W potential.

Globus, Al↗
NASA NTRS2000

Fractal correlation properties of R-R interval dynamics and mortality in patients with depressed left ventricular function after an acute myocardial infarction

BACKGROUND: Preliminary data suggest that the analysis of R-R interval variability by fractal analysis methods may provide clinically useful information on patients with heart failure. The purpose of this study was to compare the prognostic power of new fractal and traditional measures of R-R interval variability as predictors of death after acute myocardial infarction. METHODS AND RESULTS: Time and frequency domain heart rate (HR) variability measures, along with short- and long-term correlation (fractal) properties of R-R intervals (exponents alpha(1) and alpha(2)) and power-law scaling of the power spectra (exponent beta), were assessed from 24-hour Holter recordings in 446 survivors of acute myocardial infarction with a depressed left ventricular function (ejection fraction </=35%). During a mean+/-SD follow-up period of 685+/-360 days, 114 patients died (25.6%), with 75 deaths classified as arrhythmic (17.0%) and 28 as nonarrhythmic (6.3%) cardiac deaths. Several traditional and fractal measures of R-R interval variability were significant univariate predictors of all-cause mortality. Reduced short-term scaling exponent alpha(1) was the most powerful R-R interval variability measure as a predictor of all-cause mortality (alpha(1) <0.75, relative risk 3.0, 95% confidence interval 2.5 to 4.2, P<0.001). It remained an independent predictor of death (P<0.001) after adjustment for other postinfarction risk markers, such as age, ejection fraction, NYHA class, and medication. Reduced alpha(1) predicted both arrhythmic death (P<0.001) and nonarrhythmic cardiac death (P<0.001). CONCLUSIONS: Analysis of the fractal characteristics of short-term R-R interval dynamics yields more powerful prognostic information than the traditional measures of HR variability among patients with depressed left ventricular function after an acute myocardial infarction.

Non-NASA Center↗
NASA NTRS2011

Can Functional Cardiac Age be Predicted from ECG in a Normal Healthy Population

In a normal healthy population, we desired to determine the most age-dependent conventional and advanced ECG parameters. We hypothesized that changes in several ECG parameters might correlate with age and together reliably characterize the functional age of the heart. Methods: An initial study population of 313 apparently healthy subjects was ultimately reduced to 148 subjects (74 men, 84 women, in the range from 10 to 75 years of age) after exclusion criteria. In all subjects, ECG recordings (resting 5-minute 12-lead high frequency ECG) were evaluated via custom software programs to calculate up to 85 different conventional and advanced ECG parameters including beat-to-beat QT and RR variability, waveform complexity, and signal-averaged, high-frequency and spatial/spatiotemporal ECG parameters. The prediction of functional age was evaluated by multiple linear regression analysis using the best 5 univariate predictors. Results: Ignoring what were ultimately small differences between males and females, the functional age was found to be predicted (R2= 0.69, P < 0.001) from a linear combination of 5 independent variables: QRS elevation in the frontal plane (p<0.001), a new repolarization parameter QTcorr (p<0.001), mean high frequency QRS amplitude (p=0.009), the variability parameter % VLF of RRV (p=0.021) and the P-wave width (p=0.10). Here, QTcorr represents the correlation between the calculated QT and the measured QT signal. Conclusions: In apparently healthy subjects with normal conventional ECGs, functional cardiac age can be estimated by multiple linear regression analysis of mostly advanced ECG results. Because some parameters in the regression formula, such as QTcorr, high frequency QRS amplitude and P-wave width also change with disease in the same direction as with increased age, increased functional age of the heart may reflect subtle age-related pathologies in cardiac electrical function that are usually hidden on conventional ECG.

Schlegel, Todd↗
NASA NTRS1973

Hydrogen and hydrocarbon diffusion flames in a weightless environment

An experimental investigation was performed on laminar hydrogen-, ethylene-, and propylene-air diffusion burning in a weightless environment. The flames burned on nozzles with radii ranging from 0.051 to 0.186 cm with fuel Reynolds numbers at the nozzle exit from 9 to 410. Steady-state diffusion flames existed in a weightless environment for all the fuels tested. A correlation was obtained for their axial length as a function of Schmidt number, Reynolds numbers, and stoichiometric mole fraction. The maximum flame radii were correlated with the ratio of nozzle radius to average fuel velocity. The flames of ethylene and propylene on nozzles with radii 0.113 or larger appeared to be constantly changing color and/or length throughout the test. No extinguishment was observed for any of the gases tested within the 2.2 seconds of weightlessness.

Haggard, J. B., Jr.↗
NASA NTRS1980

A lower limit on the magnitude of the companion to HDE 226868 /Cygnus X-1/

High-precision digital spectra of the HDE 226868/Cygnus X-1 system have been obtained at a variety of orbital phases, using a Digicon photon counting array at the coude focus of the Lick Shane reflector. The spectra have been cross-correlated to search for evidence for the existence of a luminous stellar companion to HDE 226868, as has been suggested by several models where the secondary star is not a black hole. We find no evidence for such a star and place a lower limit on the difference between HDE 226868 and its companion of 4 magnitudes. This limit rules out all of the models for the Cygnus X-1 system calculated by Avni and Bahcall which include main-sequence stars as secondaries rather than black holes. A merit function generally useful for cross-correlation of digital spectra is described.

Shafter, A. W.↗
NASA NTRS2017

Effects of One Year of Spaceflight on Neurocognitive Function

It is known that spaceflight adversely affects human sensorimotor function. With interests in longer duration deep space missions it is important to understand microgravity dose-response relationships. NASA's One Year Mission project allows for comparison of the effects of one year in space with those seen in more typical six month missions to the International Space Station. In the Neuromapping project we are performing structural and functional magnetic resonance brain imaging to identify the relationships between changes in neurocognitive function and neural structural alterations following a six month International Space Station mission. Our central hypothesis is that measures of brain structure, function, and network integrity will change from pre- to post-spaceflight. Moreover, we predict that these changes will correlate with indices of cognitive, sensory, and motor function in a neuroanatomically selective fashion. Our interdisciplinary approach utilizes cutting edge neuroimaging techniques and a broad-ranging battery of sensory, motor, and cognitive assessments that are conducted pre-flight, during flight, and post-flight to investigate potential neuroplastic and maladaptive brain changes in crewmembers following long-duration spaceflight. With the one year mission we had one crewmember participate in all of the same measures pre-, per- and post-flight as in our ongoing study. During this presentation we will provide an overview of the magnitude of changes observed with our brain and behavioral assessments for the one year crewmember in comparison to participants that have completed our six month study to date.

Seidler, R. D.↗