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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Use of KC-135 parabolic flights to determine if brief changes in the gravity field can influence the phase and/or period of the circadian clock

In February 1994 a total of 10 hampsters flew on two separate KC-135 flights. On one flight, 25 animals experienced 31 parabolas, thus going through 31 cycles of hypergravity (up to about 1.8 G). On the other flight, the animals were exposed to 43 parabolas. fifty additional animals served as ground based controls and were treated in the same fashion as the experimental animals. The profiles of plasma GH, corisol and coricosterone from representative parabolic flight and ground control animals during pre-flight, in-flight, and post-flight conditions are depicted.

Turek, Fred W.↗
NASA NTRS1996

Parabolic aircraft solidification experiments

A number of solidification experiments have been utilized throughout the Materials Processing in Space Program to provide an experimental environment which minimizes variables in solidification experiments. Two techniques of interest are directional solidification and isothermal casting. Because of the wide-spread use of these experimental techniques in space-based research, several MSAD experiments have been manifested for space flight. In addition to the microstructural analysis for interpretation of the experimental results from previous work with parabolic flights, it has become apparent that a better understanding of the phenomena occurring during solidification can be better understood if direct visualization of the solidification interface were possible. Our university has performed in several experimental studies such as this in recent years. The most recent was in visualizing the effect of convective flow phenomena on the KC-135 and prior to that were several successive contracts to perform directional solidification and isothermal casting experiments on the KC-135. Included in this work was the modification and utilization of the Convective Flow Analyzer (CFA), the Aircraft Isothermal Casting Furnace (ICF), and the Three-Zone Directional Solidification Furnace. These studies have contributed heavily to the mission of the Microgravity Science and Applications' Materials Science Program.

Workman, Gary L.↗
NASA NTRS1996

Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for Aircraft Acoustic Nacelle Design

An explicit finite difference iteration scheme is developed to study harmonic sound propagation in aircraft engine nacelles. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

Baumeister, Kenneth J.↗
NASA NTRS1996

Parallelization of a Parabolized Navier-Stokes Solver with a Design Optimizer

The design of future supersonic aircraft, such as the High Speed Civil Transport (HSCT), will rely heavily on computational methods for aircraft design and the prediction of the complex aerodynamics encountered in flight. Parabolized Navier-Stokes (PNS) equation flow solvers are recognized as efficient and accurate computational tools for the solution of supersonic and hypersonic flow-fields, while design optimizers have the potential to be valuable tools within the overall design process. Presently, however, the execution of the flow solver in conjunction with a design optimizer presents a computationally intensive and formidable problem. To meet the challenges and increasing demand for multidisciplinary numerical tools which are faster, more robust and provide greater functionality, alternative strategies are explored to increase computational throughput by coupling a design optimizer and flow solver in a parallel processing environment. To address this problem the parallel processing of a PNS flow solver with a nonlinear constraint design optimizer is investigated as an alternative computational method.

Pallis, J. M.↗
NASA NTRS1996

Time-Dependent Parabolic Finite Difference Formulation for Harmonic Sound Propagation in a Two-Dimensional Duct with Flow

An explicit finite difference real time iteration scheme is developed to study harmonic sound propagation in aircraft engine nacelles. To reduce storage requirements for future large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable for a harmonic monochromatic sound field, a parabolic (in time) approximation is introduced to reduce the order of the governing equation. The analysis begins with a harmonic sound source radiating into a quiescent duct. This fully explicit iteration method then calculates stepwise in time to obtain the 'steady state' harmonic solutions of the acoustic field. For stability, applications of conventional impedance boundary conditions requires coupling to explicit hyperbolic difference equations at the boundary. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

Kreider, Kevin L.↗
NASA NTRS1996

Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for the Convective Wave Equation

An explicit finite difference iteration scheme is developed to study harmonic sound propagation in ducts. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

Baumeister, K. J.↗
NASA NTRS1961

The Drag Coefficient of Parabolic Bodies of Revolution Operating at Zero Cavitation Number and Zero Angle of Yaw

The form-drag coefficient of parabolic bodies of revolution with fineness ratios greater than 1 operating at zero angle of yaw and zero cavitation number is determined both theoretically and experimentally. Agreement between theory and experiment is very good, The theoretical form-drag coefficient of paraboloids is about half the form-drag coefficient of cones of comparable fineness ratio.

Johnson, Virgil E., Jr.↗
NASA NTRS1959

Static Stability Characteristics of Three Thick Wing Models with Parabolic Plan Forms at a Mach Number of 3.11

An experimental investigation has been made to determine the static stability characteristics of three thick wing models with parabolic plan forms at a Mach number of 3.11 for angles of attack from about -6 to 16 deg. The primary variable was aspect ratio, with the plan-form area and the ratio of base height to span kept the same for all three models. All models had stable, linear pitching-moment curves about the quarter chord of the wing mean aerodynamic chord. The model with the lowest aspect ratio attained a maximum untrimmed lift-drag ratio of about 5.0 at an angle of attack of about 8 deg. Increasing the aspect ratio (which was accompanied by an increase in base area because the ratio of the base height to span was kept constant) caused a decrease in maximum lift-drag ratio. All models were directionally stable for the range of angle of attack of the tests. Addition of a vertical tail to the models caused an increase in the directional stability over the angle-of-attack range. In general, the lateral aerodynamic characteristics of the models were not linear functions of angle of attack over any appreciable angle-of-attack range.

Queijo, M. J.↗
NASA NTRS1961

Radiative Heat Transfer During Atmosphere Entry at Parabolic Velocity

Stagnation point radiative heating rates for manned vehicles entering the earth's atmosphere at parabolic velocity are presented and compared with corresponding laminar convective heating rates. The calculations were made for both nonlifting and lifting entry trajectories for vehicles of varying nose radius, weight-to-area ratio, and drag. It is concluded from the results presented that radiative heating will be important for the entry conditions considered.

Yoshikawa, Kenneth K.↗
NASA NTRS1999

A Pseubo-Temporal Multi-Grid Relaxation Scheme for Solving the Parabolized Navier-Stokes Equations

A multi-grid, flux-difference-split, finite-volume code, VULCAN, is presented for solving the elliptic and parabolized form of the equations governing three-dimensional, turbulent, calorically perfect and non-equilibrium chemically reacting flows. The space marching algorithms developed to improve convergence rate and or reduce computational cost are emphasized. The algorithms presented are extensions to the class of implicit pseudo-time iterative, upwind space-marching schemes. A full approximate storage, full multi-grid scheme is also described which is used to accelerate the convergence of a Gauss-Seidel relaxation method. The multi-grid algorithm is shown to significantly improve convergence on high aspect ratio grids.

Morrison, J. H.↗
NASA NTRS1954

Flight Measurements of Average Skin-Friction Coefficients on a Parabolic Body of Revolution (NACA RM-10) at Mach Numbers from 1.0 to 3.7

Measurement of average skin-friction coefficients have been made on six rocket-powered free-flight models by using the boundary-layer rake technique. The model configuration was the NACA RM-10, a 12.2-fineness-ratio parabolic body of revolution with a flat base. Measurements were made over a Mach number range from 1 to 3.7, a Reynolds number range 40 x 10(exp 6) to 170 x 10(exp 6) based on length to the measurement station, and with aerodynamic heating conditions varying from strong skin heating to strong skin cooling. The measurements show the same trends over the test ranges as Van Driest's theory for turbulent boundary layer on a flat plate. The measured values are approximately 7 percent higher than the values of the flat-plate theory. A comparison which takes into account the differences in Reynolds number is made between the present results and skin-friction measurements obtained on NACA RM-10 scale models in the Langley 4- by 4-foot supersonic pressure tunnel, the Lewis 8- by 6-foot supersonic tunnel, and the Langley 9-inch supersonic tunnel. Good agreement is shown at all but the lowest tunnel Reynolds number conditions. A simple empirical equation is developed which represents the measurements over the range of the tests.

Loposer, J. Dan↗
NASA NTRS1961

Experimental Investigation of a High-Speed Hydrofoil with Parabolic Thickness Distribution and an Aspect Ratio of 3

An experimental investigation has been made to determine the hydro-dynamic characteristics of a 10-percent-thick hydrofoil with an aspect ratio of 3 designed to operate with acceptable efficiency at speeds in the neighborhood of 100 knots (169 fps). A cambered hydrofoil model with parabolic thickness distribution was investigated at a depth of chord over a range of angles of attack from -0.5 deg to 4.0 deg and at speeds from 120 to 210 fps. substantially wider range of operation at acceptable lift-drag ratios as well as higher maximum lift-drag-ratio values than did a hydrofoil of similar design with an aspect ratio of 1.

Christopher, Kenneth W.↗
NASA NTRS2004

Discontinuous Galerkin Finite Element Method for Parabolic Problems

In this paper, we develop a time and its corresponding spatial discretization scheme, based upon the assumption of a certain weak singularity of parallel ut(t) parallel Lz(omega) = parallel ut parallel2, for the discontinuous Galerkin finite element method for one-dimensional parabolic problems. Optimal convergence rates in both time and spatial variables are obtained. A discussion of automatic time-step control method is also included.

Kaneko, Hideaki↗
NASA NTRS1999

A Pseudo-Temporal Multi-Grid Relaxation Scheme for Solving the Parabolized Navier-Stokes Equations

A multi-grid, flux-difference-split, finite-volume code, VULCAN, is presented for solving the elliptic and parabolized form of the equations governing three-dimensional, turbulent, calorically perfect and non-equilibrium chemically reacting flows. The space marching algorithms developed to improve convergence rate and or reduce computational cost are emphasized. The algorithms presented are extensions to the class of implicit pseudo-time iterative, upwind space-marching schemes. A full approximate storage, full multi-grid scheme is also described which is used to accelerate the convergence of a Gauss-Seidel relaxation method. The multi-grid algorithm is shown to significantly improve convergence on high aspect ratio grids.

White, J. A.↗
NASA NTRS2002

Context-specific adaptation of saccade gain in parabolic flight

Previous studies established that vestibular reflexes can have two adapted states (e.g., gains) simultaneously, and that a context cue (e.g., vertical eye position) can switch between the two states. Our earlier work demonstrated this phenomenon of context-specific adaptation for saccadic eye movements: we asked for gain decrease in one context state and gain increase in another context state, and then determined if a change in the context state would invoke switching between the adapted states. Horizontal and vertical eye position and head orientation could serve, to varying degrees, as cues for switching between two different saccade gains. In the present study, we asked whether gravity magnitude could serve as a context cue: saccade adaptation was performed during parabolic flight, which provides alternating levels of gravitoinertial force (0 g and 1.8 g). Results were less robust than those from ground experiments, but established that different saccade magnitudes could be associated with different gravity levels.

Clinical Trial↗
NASA NTRS2004

High Precision Metrology on the Ultra-Lightweight W 50.8 cm f/1.25 Parabolic SHARPI Primary Mirror using a CGH Null Lens

For potential use on the SHARPI mission, Eastman Kodak has delivered a 50.8cm CA f/1.25 ultra-lightweight UV parabolic mirror with a surface figure error requirement of 6nm RMS. We address the challenges involved in verifying and mapping the surface error of this large lightweight mirror to +/-3nm using a diffractive CGH null lens. Of main concern is removal of large systematic errors resulting from surface deflections of the mirror due to gravity as well as smaller contributions from system misalignment and reference optic errors. We present our efforts to characterize these errors and remove their wavefront error contribution in post-processing as well as minimizing the uncertainty these calculations introduce. Data from Kodak and preliminary measurements from NASA Goddard will be included.

Antonille, Scott↗
NASA NTRS2004

Foot-ground reaction force during resistive exercise in parabolic flight

INTRODUCTION: An interim resistance exercise device (iRED) was designed to provide resistive exercise as a countermeasure to spaceflight-induced loss of muscle strength and endurance as well as decreased bone mineral density. The purpose of this project was to compare foot-ground reaction force during iRED exercise in normal gravity (1 G) vs. microgravity (0 G) achieved during parabolic flight. METHODS: There were four subjects who performed three exercises (squat, heel raise, and deadlift) using the iRED during 1 G and 0 G at a moderate intensity (60% of maximum strength during deadlift exercise). Foot-ground reaction force was measured in the three orthogonal axes (x, y, z) using a force plate, and the magnitude of the resultant force vector was calculated (r = square root(x2 + y2 + z2)). Linear displacement (LD) was measured using a linear transducer. Peak force (Fpeak) and an index of total work (TWi) were calculated using a customized computer program. Paired t-tests were used to test if significant differences (p < or = 0.05) were observed between 1 G and 0 G exercise. RESULTS: Fpeak and TWi measured in the resultant axis were significantly less in 0 G for each of the exercises tested. During 0 G, Fpeak was 42-46% and TWi was 33-37% of that measured during 1 G. LD and average time to complete each repetition were not different from 1 G to 0 G. CONCLUSIONS: Crewmembers who perform resistive exercises during spaceflight that include the movement of a large portion of their body mass will require much greater external resistive force during 0 G than 1 G exercise to provide a sufficient stimulus to maintain muscle and bone mass.

Physical Education and Training↗