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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Effect of Pt Doping on Nucleation and Crystallization in Li2O.2SiO2 Glass: Experimental Measurements and Computer Modeling

Heterogeneous nucleation and its effects on the crystallization of lithium disilicate glass containing small amounts of Pt are investigated. Measurements of the nucleation frequencies and induction times with and without Pt are shown to be consistent with predictions based on the classical nucleation theory. A realistic computer model for the transformation is presented. Computed differential thermal analysis data (such as crystallization rates as a function of time and temperature) are shown to be in good agreement with experimental results. This modeling provides a new, more quantitative method for analyzing calorimetric data.

Narayan, K. Lakshmi↗
NASA NTRS2015

Great New Insights from Failed Experiments, Unanticipated Results and Embracing Controversial Observations

Experimental data and observations, whether telescopic or analytical, are never wrong, though data derived from such sources can be misinterpreted or applied inappropriately to derive conclusions that are incorrect. Given that nature always behaves according to the laws of physics and chemistry, rather than according to currently popular models and theories, experimental results should always be considered correct even when the results are far from those that one might initially expect. We discuss a number of cases where the results of experiments, even one carried out as a simple calibration measure, produced wildly different results that generally required many years of effort or contemplation to understand. On the positive side, exploration of the circumstances that produced the errant results often led to new and interesting insights concerning processes that might occur in natural environments and that were well worth the effort involved. Specifically, we show how an experiment that "failed" due to a broken conductor led to experiments that made the first refractory oxide solids containing mass independently fractionated oxygen isotopes and to 1998 predictions of the oxygen isotopic composition of the sun that were confirmed by the analysis of Genesis samples in 2011. We describe a calibration experiment that unexpectedly produced single magnetic domain iron particles. We discuss how tracking down a persistent source of "contamination" in experiments intended to produce amorphous iron and magnesium silicate smokes led to a series of studies on the synthesis of carbonaceous grain coatings that turn out to be very efficient Fischer-Tropsch catalysts and have great potential for trapping the planetary noble gases found in meteorites. We describe how models predicting the instability of silicate grains in circumstellar environments spurred new measurements of the vapor pressure of SiO partially based on previous experiments showing unexpected but systematic non-equilibrium behavior instead of the anticipated equilibrium products resembling meteoritic minerals. We trace the process that led from observations of the presence of crystalline minerals detected in the comae of some comets to the 1999 prediction of large-scale circulation of materials from the hot, innermost regions of the solar nebula out to the cold dark nebular environments where comets form. This large-scale circulation was ultimately confirmed by analyses of highly refractory Stardust samples collected from the Kuiper Belt Comet Wild 2. Finally we discuss a modern and still unresolved conflict between the assumptions built into three well known processes: the CO Self Shielding Model for mass independent isotopic fractionation of oxygen in solar system solids, rapid and thorough mixing within the solar nebula, and the efficient conversion of CO into organic coatings and volatiles on the surfaces of nebular grains via Fischer-Tropsch-type processes.

controversial↗
NASA NTRS1992

Swept shock/boundary layer interaction experiments in support of CFD code validation

Research on the topic of shock wave/turbulent boundary-layer interaction was carried out during the past three years at the Penn State Gas Dynamics Laboratory. This report describes the experimental research program which provides basic knowledge and establishes new data on heat transfer in swept shock wave/boundary-layer interactions. An equilibrium turbulent boundary-layer on a flat plate is subjected to impingement by swept planar shock waves generated by a sharp fin. Five different interactions with fin angle ranging from 10 deg to 20 deg at freestream Mach numbers of 3.0 and 4.0 produce a variety of interaction strengths from weak to very strong. A foil heater generates a uniform heat flux over the flat plate surface, and miniature thin-film-resistance sensors mounted on it are used to measure the local surface temperature. The heat convection equation is then solved for the heat transfer distribution within an interaction, yielding a total uncertainty of about +/- 10 percent. These experimental data are compared with the results of numerical Navier-Stokes solutions which employ a k-epsilon turbulence model. Finally, a simplified form of the peak heat transfer correlation for fin interactions is suggested.

Settles, G. S.↗
NASA NTRS1986

Interface of the transport systems research vehicle monochrome display system to the digital autonomous terminal access communication data bus

An upgrade of the transport systems research vehicle (TSRV) experimental flight system retained the original monochrome display system. The original host computer was replaced with a Norden 11/70, a new digital autonomous terminal access communication (DATAC) data bus was installed for data transfer between display system and host, while a new data interface method was required. The new display data interface uses four split phase bipolar (SPBP) serial busses. The DATAC bus uses a shared interface ram (SIR) for intermediate storage of its data transfer. A display interface unit (DIU) was designed and configured to read from and write to the SIR to properly convert the data from parallel to SPBP serial and vice versa. It is found that separation of data for use by each SPBP bus and synchronization of data tranfer throughout the entire experimental flight system are major problems which require solution in DIU design. The techniques used to accomplish these new data interface requirements are described.

Easley, W. C.↗
NASA NTRS2003

Data and Modeling of Dendrites Subject to A Step Change in Pressure (TDSE)

There is considerable interest in dendritic solidification because of the influence dendrites have in the determination of microstructure, and thereby in the physical properties of cast metals and alloys. Current theories and models of dendritic growth generally couple diffusion effects in the melt with the physics of the interface. Data and subsequent analysis prior of the tip growth speed and radii of thermal succinonitrile dendrites in the near-convection free, on-orbit, free-fall environment demonstrate that these theories yield predictions that are reasonably in agreement with the results of experiment. However, data and analysis for assessing the interfacial physics component of theory are not sufficiently detailed or definitive. To study fundamental aspects of dendritic interface stability, we are measuring and modeling the kinetics and morphology of dendrites as they evolve from one well-defined steady state at a pre-set supercooling, through a transient stage, to a different well-defined steady state. More specifically, we subject succinonitrile dendrites, growing under steady-state conditions, to a rapid change in pressure. This leads to a rapid change in thermal driving force from the corresponding change in both the equilibrium melting temperature due to the Clapeyron effect, and a change in the far-field temperature due to adiabatic temperature changes in the bulk liquid and solid. Subsequently, we observe transformations from a well-characterized initial state into a new steady-state. Initial data reveal that the dendrite tip velocity changes almost as fast as the pressure charges, while the tip radius changes occur more slowly, taking from 10 60 seconds depending on the size of the step change and the final supercooling. Computer modeling of this process shows both agreements and disagreements with the experimental data. In making these observations and measurements, we are gaining new understandings of interfacial dynamics and state-selection physics.

Koss, Matthew B.↗
NASA NTRS1994

Dynamic and Thermal Turbulent Time Scale Modelling for Homogeneous Shear Flows

A new turbulence model, based upon dynamic and thermal turbulent time scale transport equations, is developed and applied to homogeneous shear flows with constant velocity and temperature gradients. The new model comprises transport equations for k, the turbulent kinetic energy; tau, the dynamic time scale; k(sub theta), the fluctuating temperature variance; and tau(sub theta), the thermal time scale. It offers conceptually parallel modeling of the dynamic and thermal turbulence at the two equation level, and eliminates the customary prescription of an empirical turbulent Prandtl number, Pr(sub t), thus permitting a more generalized prediction capability for turbulent heat transfer in complex flows and geometries. The new model also incorporates constitutive relations, based upon invariant theory, that allow the effects of nonequilibrium to modify the primary coefficients for the turbulent shear stress and heat flux. Predictions of the new model, along with those from two other similar models, are compared with experimental data for decaying homogeneous dynamic and thermal turbulence, homogeneous turbulence with constant temperature gradient, and homogeneous turbulence with constant temperature gradient and constant velocity gradient. The new model offers improvement in agreement with the data for most cases considered in this work, although it was no better than the other models for several cases where all the models performed poorly.

Schwab, John R.↗
NASA NTRS1988

New Mode For Single-Event Upsets

Report presents theory and experimental data regarding newly discovered mode for single-event upsets, (SEU's) in complementary metal-oxide/semiconductor, static random-access memories, CMOS SRAM's. SEU cross sections larger than those expected from previously known modes given rise to speculation regarding additional mode, and subsequent cross-section measurements appear to confirm speculation.

Zoutendyk, John A.↗
NASA NTRS1974

The protective effect of a constant magnetic field

The protective effect of a constant magnetic field sharply reduced spontaneous lysis of E. coli cells when subjected to ultraviolet radiation. A protective effect of a CMF was found in a study of tissue cultures of normally growing cells (kidney epithelium) and cancer cells (cells from a cancer of the larynx). The protective effect of a CMF is also seen in a combined exposure of tissue cultures to X-rays and CMF energy (strength of the CMF was 2000 oersteds with a gradient of 500 oersteds/cm). The data obtained are of interest to experimental oncology (development of new methods of treating malignant tumors).

Sosunov, A. V.↗
NASA NTRS1979

The supersonic triplet - A new aerodynamic panel singularity with directional properties

A new supersonic triplet singularity has been developed which eliminates internal waves generated by panels having supersonic edges. The triplet is a linear combination of source and vortex distributions which provides the desired directional properties in the flow field surrounding the panel. The theoretical development of the triplet is described, together with its application to the calculation of surface pressure on arbitrary body shapes. Examples are presented comparing the results of the new method with other supersonic panel methods and with experimental data.

Woodward, F. A.↗
NASA NTRS1982

An assessment of preliminary aerodynamic analysis methods for supersonic speeds including high angle-of-attack flow

The problems associated with predicting the aerodynamic loads for moderate supersonic Mach number, high angle-of-attack flows and for high supersonic Mach number flows are addressed. For these large disturbance-type flows, commonly used prediction methods based on linearized theory or on the tangent-wedge method are shown to be generally inadequate. For the preliminary analysis of aerodynamic shapes subjected to these type flows, two methods have recently been developed by combining features of the linearized theory and tangent-wedge method. These two new methods are discussed, and through extensive comparisons with experimental data, are shown to offer an improved prediction capability.

Pittman, J. L.↗
NASA NTRS1987

Single-mode projection filters for identification and state estimation of flexible structures

Single-mode projection filters are developed for eigensystem parameter identification and state estimation from both analytical results and test data. Explicit formulations of these projection filters are derived using the pseudoinverse matrices of the controllabilty and observability matrices in the general sense. A global minimum optimization algorithm is developed to update the filter parameters by using the interval analysis method. Modal parameters can be identified and updated in the global sense within a specified region of parameters by passing the experimental data through the projection filters. For illustration of this new approach, a numerical example is shown by using a one-dimensional global optimization algorithm to estimate modal frequencies and damping.

Huang, Jen-Kuang↗
NASA NTRS1989

Particle kinetic simulation of high altitude hypervelocity flight

A new model for simulating the transfer of energy between the translational and rotational modes was derived for a homogeneous gas of diatomic molecules. The model was developed specifically for use in discrete particle simulation methods where molecular motion and inter-molecular collisions are treated at the molecular level. In such methods it is normal to assume a constant rotational collision number for the entire flowfield. The new model differs in that a temperature dependence is introduced which has been predicted by theory and observed in experiment. The new model is applied to the relaxation of rotational temperature, and is found to produce significant differences in comparison with the model normally employed at both high and low temperatures. Calculations have also been performed for a Mach 7 normal shock wave. Large differences in the solutions are again observed, with the new model offering an improved correspondence to the available experimental data.

Boyd, Iain D.↗
NASA NTRS1991

Classical electron mass and fields 2

Continued here is the development of a model of the electron (HYDRA), which includes rotational and magnetic terms. The atomic electron state is discussed and a comparison is made with a simple harmonic oscillator. Experimental data is reviewed that supports the possibility of a new lepton.

Spaniol, Craig↗
NASA NTRS1992

Classical electron mass and fields. II

Continued here is the development of a model of the electron (HYDRA), which includes rotational and magnetic terms. The atomic electron state is discussed and a comparison is made with a simple harmonic oscillator. Experimental data is reviewed that supports the possibility of a new lepton.

Spaniol, Craig↗
NASA NTRS2004

Integrated Solar System Exploration Education and Public Outreach: Theme, Products and Activities

NASA's Solar System Exploration Program is entering an unprecedented period of exploration and discovery. Its goal is to understand the origin and evolution of the solar system and life within it. SSE missions are operating or in development to study the far reaches of our solar system and beyond. These missions proceed in sequence for each body from reconnaissance flybys through orbiters and landers or rovers to sample returns. SSE research programs develop new instruments, analyze mission data or returned samples, and provide experimental or theoretical models to aid in interpretation.

Lowes, Leslie↗
NASA NTRS2011

Supersonic Retropropulsion Experimental Results from the NASA Langley Unitary Plan Wind Tunnel

A new supersonic retropropulsion experimental effort, intended to provide code validation data, was recently completed in the Langley Research Center Unitary Plan Wind Tunnel Test Section 2 over the Mach number range from 2.4 to 4.6. The experimental model was designed using insights gained from pre-test computations, which were instrumental for sizing and refining the model to minimize tunnel wall interference and internal flow separation concerns. A 5-in diameter 70-deg sphere-cone forebody with a roughly 10-in long cylindrical aftbody was the baseline configuration selected for this study. The forebody was designed to accommodate up to four 4:1 area ratio supersonic nozzles. Primary measurements for this model were a large number of surface pressures on the forebody and aftbody. Supplemental data included high-speed Schlieren video and internal pressures and temperatures. The run matrix was developed to allow for the quantification of various sources of experimental uncertainty, such as random errors due to run-to-run variations and bias errors due to flow field or model misalignments. Preliminary results and observations from the test are presented, while detailed data and uncertainty analyses are ongoing.

Berry, Scott A.↗