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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 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Antenna pattern control using impedance surfaces

During this research period, we have effectively transferred existing computer codes from CRAY supercomputer to work station based systems. The work station based version of our code preserved the accuracy of the numerical computations while giving a much better turn-around time than the CRAY supercomputer. Such a task relieved us of the heavy dependence of the supercomputer account budget and made codes developed in this research project more feasible for applications. The analysis of pyramidal horns with impedance surfaces was our major focus during this research period. Three different modeling algorithms in analyzing lossy impedance surfaces were investigated and compared with measured data. Through this investigation, we discovered that a hybrid Fourier transform technique, which uses the eigen mode in the stepped waveguide section and the Fourier transformed field distributions across the stepped discontinuities for lossy impedances coating, gives a better accuracy in analyzing lossy coatings. After a further refinement of the present technique, we will perform an accurate radiation pattern synthesis in the coming reporting period.

Balanis, Constantine A.↗
NASA NTRS1991

The fueling of active galaxies

Collisions of galaxies are often invoked to explain violent phenomena in the universe. The dynamics of interacting galaxies is intrinsically three-dimensional and involves both gas and stellar dynamics. In general, a computational approach is needed to model galactic collisions. Galaxy encounters are studied using a hybrid N-body/hydrodynamics code, capable of integrating systems of stars, gas, and dark matter in a fully self-consistent manner. These experiments demonstrate that gravitational coupling between gas and stars in galactic interactions can drive most of the gas throughout a galaxy into the nucleus of a merger remnant. The high densities in these gas concentrations are likely to result in strong bursts of star formation. Hence, this process may explain the nuclear starbursts in some systems of interacting galaxies. Further collapse of these gas concentrations can trigger even more intense activity if some gas is eventually accreted by a supermassive black hole. Such an evolutionary sequence may account for some quasars and active galactic nuclei.

Hernquist, Lars↗
NASA NTRS1992

Aerospace applications of SINDA/FLUINT at the Johnson Space Center

SINDA/FLUINT has been found to be a versatile code for modeling aerospace systems involving single or two-phase fluid flow and all modes of heat transfer. Several applications of SINDA/FLUINT are described in this paper. SINDA/FLUINT is being used extensively to model the single phase water loops and the two-phase ammonia loops of the Space Station Freedom active thermal control system (ATCS). These models range from large integrated system models with multiple submodels to very detailed subsystem models. An integrated Space Station ATCS model has been created with ten submodels representing five water loops, three ammonia loops, a Freon loop and a thermal submodel representing the air loop. The model, which has approximately 800 FLUINT lumps and 300 thermal nodes, is used to determine the interaction between the multiple fluid loops which comprise the Space Station ATCS. Several detailed models of the flow-through radiator subsystem of the Space Station ATCS have been developed. One model, which has approximately 70 FLUINT lumps and 340 thermal nodes, provides a representation of the ATCS low temperature radiator array with two fluid loops connected only by conduction through the radiator face sheet. The detailed models are used to determine parameters such as radiator fluid return temperature, fin efficiency, flow distribution and total heat rejection for the baseline design as well as proposed alternate designs. SINDA/FLUINT has also been used as a design tool for several systems using pressurized gasses. One model examined the pressurization and depressurization of the Space Station airlock under a variety of operating conditions including convection with the side walls and internal cooling. Another model predicted the performance of a new generation of manned maneuvering units. This model included high pressure gas depressurization, internal heat transfer and supersonic thruster equations. The results of both models were used to size components, such as the heaters and gas bottles and also to point to areas where hardware testing was needed.

Ewert, Michael K.↗
NASA NTRS1993

A critical analysis of the accuracy of several numerical techniques for combustion kinetic rate equations

A detailed analysis of the accuracy of several techniques recently developed for integrating stiff ordinary differential equations is presented. The techniques include two general-purpose codes EPISODE and LSODE developed for an arbitrary system of ordinary differential equations, and three specialized codes CHEMEQ, CREK1D, and GCKP4 developed specifically to solve chemical kinetic rate equations. The accuracy study is made by application of these codes to two practical combustion kinetics problems. Both problems describe adiabatic, homogeneous, gas-phase chemical reactions at constant pressure, and include all three combustion regimes: induction, heat release, and equilibration. To illustrate the error variation in the different combustion regimes the species are divided into three types (reactants, intermediates, and products), and error versus time plots are presented for each species type and the temperature. These plots show that CHEMEQ is the most accurate code during induction and early heat release. During late heat release and equilibration, however, the other codes are more accurate. A single global quantity, a mean integrated root-mean-square error, that measures the average error incurred in solving the complete problem is used to compare the accuracy of the codes. Among the codes examined, LSODE is the most accurate for solving chemical kinetics problems. It is also the most efficient code, in the sense that it requires the least computational work to attain a specified accuracy level. An important finding is that use of the algebraic enthalpy conservation equation to compute the temperature can be more accurate and efficient than integrating the temperature differential equation.

Radhadrishnan, Krishnan↗
NASA NTRS1993

Performances of a date dissemination code on telephone lines using commercial modems

A coded time/date information dissemination system (CTD), based on telephone lines and commercial modems, is now in its experimental phase in Italy at IEN. This service, born from a cooperation with other metrological laboratories (TUG, Austria, SNT, Sweden, VSL, The Netherlands), represents an attempt towards an European standardization. Some results of an experimental analysis in which a few modems were tested, both in laboratory conditions and connected to the telephone network, in order to evaluate the timing capability of the system are given. When the system is used in a one-way mode, in many practical cases the modems delay turns out to be the main factor which limits the accuracy, even more than the telephone line delays. If the two-way mode is used, the modems asymmetry, i.e., the delay difference between transmission and reception, is almost always the most important source of uncertainty, provided the link is not including a space segment. Comparing the widely used V.22 modems to the old V.21 ones, the latters turn out to be better both in delay time (30-100 ms V.22, and 7-15 ms V.21) and asymmetry (10-50 micro-s V.22, and 10 ms V.22). Time transfer accuracies of 10 micron-s (same turn) to 100 micro-s (long distance calls) were obtained in two-way mode with commercial V.21 modems.

Cordara, F.↗
NASA NTRS1993

Reduced gravity multibody dynamics testing

The Final Report on reduced gravity multibody dynamics testing is presented. Tests were conducted on board the NASA KC-135 RGA in Houston, Texas. The objective was to analyze the effects of large angle rotations on flexible, multi-segmented structures. The flight experiment was conducted to provide data which will be compared to the data gathered from ground tests of the same configurations. The flight and ground tested data will be used to validate the TREETOPS software, software which models dynamic multibody systems, and other multibody codes. The flight experiment consisted of seven complete flights on board the KC-135 RGA during two one-week periods. The first period of testing was 4-9 Apr. 1993. The second period of testing was 13-18 Jun. 1993.

Sillanpaa, Meija↗
NASA NTRS1993

A Performance Prediction Model for a Fault-Tolerant Computer During Recovery and Restoration

The modeling and design of a fault-tolerant multiprocessor system is addressed. In particular, the behavior of the system during recovery and restoration after a fault has occurred is investigated. Given that a multicomputer system is designed using the Algorithm to Architecture to Mapping Model (ATAMM), and that a fault (death of a computing resource) occurs during its normal steady-state operation, a model is presented as a viable research tool for predicting the performance bounds of the system during its recovery and restoration phases. Furthermore, the bounds of the performance behavior of the system during this transient mode can be assessed. These bounds include: time to recover from the fault (t(sub rec)), time to restore the system (t(sub rec)) and whether there is a permanent delay in the system's Time Between Input and Output (TBIO) after the system has reached a steady state. An implementation of an ATAMM based computer was developed with the Generic VHSIC Spaceborne Computer (GVSC) as the target system. A simulation of the GVSC was also written based on the code used in ATAMM Multicomputer Operating System (AMOS). The simulation is in turn used to validate the new model in the usefulness and accuracy in tracking the propagation of the delay through the system and predicting the behavior in the transient state of recovery and restoration. The model is validated as an accurate method to predict the transient behavior of an ATAMM based multicomputer during recovery and restoration.

Stoughton, John W.↗
NASA NTRS1993

Software engineering methodologies and tools

Over the years many engineering disciplines have developed, including chemical, electronic, etc. Common to all engineering disciplines is the use of rigor, models, metrics, and predefined methodologies. Recently, a new engineering discipline has appeared on the scene, called software engineering. For over thirty years computer software has been developed and the track record has not been good. Software development projects often miss schedules, are over budget, do not give the user what is wanted, and produce defects. One estimate is there are one to three defects per 1000 lines of deployed code. More and more systems are requiring larger and more complex software for support. As this requirement grows, the software development problems grow exponentially. It is believed that software quality can be improved by applying engineering principles. Another compelling reason to bring the engineering disciplines to software development is productivity. It has been estimated that productivity of producing software has only increased one to two percent a year in the last thirty years. Ironically, the computer and its software have contributed significantly to the industry-wide productivity, but computer professionals have done a poor job of using the computer to do their job. Engineering disciplines and methodologies are now emerging supported by software tools that address the problems of software development. This paper addresses some of the current software engineering methodologies as a backdrop for the general evaluation of computer assisted software engineering (CASE) tools from actual installation of and experimentation with some specific tools.

Wilcox, Lawrence M.↗
NASA NTRS1994

Thermal/Structural Tailoring of Engine Blades (T/STAEBL) User's manual

The Thermal/Structural Tailoring of Engine Blades (T/STAEBL) system is a computer code that is able to perform numerical optimizations of cooled jet engine turbine blades and vanes. These optimizations seek an airfoil design of minimum operating cost that satisfies realistic design constraints. This report documents the organization of the T/STAEBL computer program, its design and analysis procedure, its optimization procedure, and provides an overview of the input required to run the program, as well as the computer resources required for its effective use. Additionally, usage of the program is demonstrated through a validation test case.

Brown, K. W.↗
NASA NTRS1994

Matrix evaluation of science objectives

The most fundamental objective of all robotic planetary spacecraft is to return science data. To accomplish this, a spacecraft is fabricated and built, software is planned and coded, and a ground system is designed and implemented. However, the quantitative analysis required to determine how the collection of science data drives ground system capabilities has received very little attention. This paper defines a process by which science objectives can be quantitatively evaluated. By applying it to the Cassini Mission to Saturn, this paper further illustrates the power of this technique. The results show which science objectives drive specific ground system capabilities. In addition, this process can assist system engineers and scientists in the selection of the science payload during pre-project mission planning; ground system designers during ground system development and implementation; and operations personnel during mission operations.

Wessen, Randii R.↗
NASA NTRS1996

CFD Analysis of the 24-inch JIRAD Hybrid Rocket Motor

A series of multispecies, multiphase computational fluid dynamics (CFD) analyses of the 24-inch diameter joint government industry industrial research and development (JIRAD) hybrid rocket motor is described. The 24-inch JIRAD hybrid motor operates by injection of liquid oxygen (LOX) into a vaporization plenum chamber upstream of ports in the hydroxyl-terminated polybutadiene (HTPB) solid fuel. The injector spray pattern had a strong influence on combustion stability of the JIRAD motor so a CFD study was initiated to define the injector end flow field under different oxidizer spray patterns and operating conditions. By using CFD to gain a clear picture of the flow field and temperature distribution within the JIRAD motor, it is hoped that the fundamental mechanisms of hybrid combustion instability may be identified and then suppressed by simple alterations to the oxidizer injection parameters such as injection angle and velocity. The simulations in this study were carried out using the General Algorithm for Analysis of Combustion SYstems (GALACSY) multiphase combustion codes. GALACSY consists of a comprehensive set of droplet dynamic submodels (atomization, evaporation, etc.) and a computationally efficient hydrocarbon chemistry package built around a robust Navier-Stokes solver optimized for low Mach number flows. Lagrangian tracking of dispersed particles describes a closely coupled spray phase. The CFD cases described in this paper represent various levels of simplification of the problem. They include: (A) gaseous oxygen with combusting fuel vapor blowing off the walls at various oxidizer injection angles and velocities, (B) gaseous oxygen with combusting fuel vapor blowing off the walls, and (C) liquid oxygen with combusting fuel vapor blowing off the walls. The study used an axisymmetric model and the results indicate that the injector design significantly effects the flow field in the injector end of the motor. Markedly different recirculation patterns are observed in the vaporization chamber as the oxygen velocity and/or spray pattern is varied. The ability of these recirculation patterns to stabilize the diffusion flame above the surface of the solid fuel gives a plausible explanation for the experimentally determined combustion stability characteristics of the JIRAD motor, and suggests how combustion stability can be assured by modifications to the injector design.

Liang, Pak-Yan↗
NASA NTRS1996

Pulse Detonation Engine Air Induction System Analysis

A preliminary mixed-compression inlet design concept for potential pulse-detonation engine (PDE) powered supersonic aircraft was defined and analyzed. The objectives of this research were to conceptually design and integrate an inlet/PDE propulsion system into a supersonic aircraft, perform time-dependent CFD analysis of the inlet flowfield, and to estimate the installed PDE cycle performance. The study was baselined to a NASA Mach 5 Waverider study vehicle in which the baseline over/under turboramjet engines were replaced with a single flowpath PDE propulsion system. As much commonality as possible was maintained with the baseline configuration, including the engine location and forebody lines. Modifications were made to the inlet system's external ramp angles and a rotating cowl lip was incorporated to improve off-design inlet operability and performance. Engines were sized to match the baseline vehicle study's ascent trajectory thrust requirement at Mach 1.2. The majority of this study was focused on a flight Mach number of 3.0. The time-dependent Navier Stokes CFD analyses of a two-dimensional approximation of the inlet was conducted for the Mach 3.0 condition. The Lockheed Martin Tactical Aircraft Systems-developed FALCON CFD code with a two equation 'k-1' turbulence model was used. The downstream PDE was simulated by an array of four sonic nozzles in which the flow areas were rapidly varied in various opening/closing combinations. Results of the CFD study indicated that the inlet design concept operated successfully at the Mach 3.0 condition, satisfying mass capture, total pressure recovery, and operability requirements. Time-dependent analysis indicated that pressure and expansion waves from the simulated valve perturbations did not effect the inlet's operability or performance.

Pegg, R. J.↗
NASA NTRS1996

STS-79 Flight Day 3

On this third day of the STS-79 mission, the flight crew, Cmdr. William F. Readdy, Pilot Terrence W. Wilcutt, Mission Specialists, Thomas D. Akers, John E. Blaha, Jay Apt, and Carl E. Walz, start another busy day on orbit activating experiments in the Spacehab module. Readdy and Wilcutt are seen conducting two rendezvous burns while other crew members are seen working in the Spacehab module. The Active Rack Isolation System, or ARIS, is tended to by Walz, who performs a minor maintenance procedure on one of ARIS' vibration-damping pushrods while Akers works with an inventory management system using a bar code reader to more effectively keep track of items that will be transferred back and forth between the Shuttle and the Mir. Apt continues work with a furnace which heats to nearly 1,600 degrees centigrade to melt metal samples for study after the flight. Apt also provides a television tour of the Spacehab, which is twice its normal size for this flight to allow extra room for science experiments and logistical items slated for transfer to Mir.

Source record↗
NASA NTRS1996

GPS Multipath Fade Measurements to Determine L-Band Ground Reflectivity Properties

In personal satellite communications, especially when the line-of-sight is clear, ground specular reflected signals along with direct signals are received by low gain, almost omni-directional subscriber antennas. A six-channel, C/A code processing, global positioning system (GPS) receiver with an almost omni-directional patch antenna was used to take measurements over three types of ground to characterize 1.575 GHz specular ground reflections and ground dielectric properties. Fade measurements were taken over grass, asphalt, and lake water surfaces by placing the antenna in a vertical position at a fixed height from the ground. Electrical characteristics (conductivity and dielectric constant) of these surfaces (grass, asphalt, lake water) were obtained by matching computer simulations to the experimental results.

Kavak, Adnan↗
NASA NTRS1997

Analyses of Technology for Solid State Coherent Lidar

Over past few years, considerable advances have been made in the areas of the diode-pumped, eye-safe, solid state lasers and room temperature, wide bandwidth, semiconductor detectors operating in the near-infrared region. These advances have created new possibilities for the development of reliable and compact coherent lidar systems for a wide range of applications. This research effort is aimed at further developing solid state coherent lidar technology for remote sensing of atmospheric processes such as wind, turbulence and aerosol concentration. The work performed by the UAH personnel under this Delivery Order concentrated on design and analyses of laboratory experiments and measurements, and development of advanced lidar optical subsystems in support of solid state laser radar remote sensing systems which are to be designed, deployed, and used to measure atmospheric processes and constituents. Under this delivery order, a lidar breadboard system was designed and analyzed by considering the major aircraft and space operational requirements. The lidar optical system was analyzed in detail using SYNOPSIS and Code V optical design packages. The lidar optical system include a wedge scanner and the compact telescope designed by the UAH personnel. The other major optical components included in the design and analyses were: polarizing beam splitter, routing mirrors, wave plates, signal beam derotator, and lag angle compensator. This lidar system is to be used for demonstrating all the critical technologies for the development of a reliable and low-cost space-based instrument capable of measuring global wind fields. A number of laboratory experiments and measurements were performed at the NASA/MSFC Detector Characterization Facility, previously developed by the UAH personnel. These laboratory measurements include the characterization of a 2-micron InGaAs detectors suitable for use in coherent lidars and characterization of Holographic Optical Element Scanners. UAH personnel actively participated in the development of performance and operational requirements for the development of the high pulse energy transmitter laser and frequency-agile local oscillator laser, that are in-progress at NASA Langley Research Center and Jet Propulsion Laboratory.

Amzajerdian, Farzin↗
NASA NTRS2004

Modular Engine Noise Component Prediction System (MCP) Program Users' Guide

This is a user's manual for Modular Engine Noise Component Prediction System (MCP). This computer code allows the user to predict turbofan engine noise estimates. The program is based on an empirical procedure that has evolved over many years at The Boeing Company. The data used to develop the procedure include both full-scale engine data and small-scale model data, and include testing done by Boeing, by the engine manufacturers, and by NASA. In order to generate a noise estimate, the user specifies the appropriate engine properties (including both geometry and performance parameters), the microphone locations, the atmospheric conditions, and certain data processing options. The version of the program described here allows the user to predict three components: inlet-radiated fan noise, aft-radiated fan noise, and jet noise. MCP predicts one-third octave band noise levels over the frequency range of 50 to 10,000 Hertz. It also calculates overall sound pressure levels and certain subjective noise metrics (e.g., perceived noise levels).

Golub, Robert A.↗
NASA NTRS2005

Proceedings of the 2004 NASA/ONR Circulation Control Workshop, Part 1

As technological advances influence the efficiency and effectiveness of aerodynamic and hydrodynamic applications, designs and operations, this workshop was intended to address the technologies, systems, challenges and successes specific to Coanda driven circulation control in aerodynamics and hydrodynamics. A major goal of this workshop was to determine the 2004 state-of-the-art in circulation control and understand the roadblocks to its application. The workshop addressed applications, CFD, and experiments related to circulation control, emphasizing fundamental physics, systems analysis, and applied research. The workshop consisted of 34 single session oral presentations and written papers that focused on Naval hydrodynamic vehicles (e.g. submarines), Fixed Wing Aviation, V/STOL platforms, propulsion systems (including wind turbine systems), ground vehicles (automotive and trucks) and miscellaneous applications (e.g., poultry exhaust systems and vacuum systems). Several advanced CFD codes were benchmarked using a two-dimensional NCCR circulation control airfoil. The CFD efforts highlighted inconsistencies in turbulence modeling, separation and performance predictions.

Jones, Gregory S.↗
NASA NTRS1995

The Next Generation of Space Telemetry and Telecommand Standards

Standardizing the exchange of data through communications channels that connect spacecraft with their ground systems reduces costs. Efficient coding and packetization promote the automated, error-free transfer of data.

Galileo Near Infrared Mapping Spectrometer NIMS Ju↗