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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Three-Dimensional, Multi-Phase Unsteady Flow of Water Undergoing Multiple Flow Regimes (Free Surface, Droplet, and Fluid Film)

Upgrades to the Mobile Launcher Rainbird nozzles were implemented for the Artemis II launch to increase water flow rates and improve the mobile launcher deck water coverage while minimizing the water throw distance to avoid impacting the Space Launch System (SLS) rocket nozzles. This analysis describes the use of a three-dimensional, multi-phase, free surface transient computational fluid dynamics (CFD) model to simulate the water flowing out through the Rainbird nozzle and ensure compliance with current Artemis requirements. Flow rates, pressures, velocities, nozzle throw distances and coverage areas were analyzed to ensure that system requirements are met. The completed results were used to make necessary modifications to the Ignition Overpressure Protection and Sound Suppression (IOP/SS) system Rainbird design by reshaping the nozzle used in the system.

CFD↗
NASA NTRS1971

Multi-phase, 2-kilowatt, high-voltage, regulated power supply.

Development of a flight configured experimental power supply delivering 2 kw of conditioned power represents a concentrated effort at advancing the state-of-the-art in high voltage power supplies for space application. The power supply described herein was designed for use with the Jet Propulsion Laboratory (JPL) 20 cm Mercury Ion Thruster. However, its modularized design philosophy allows adaptation to various high voltage, high power requirements. Areas of principal concern are design of power and control circuits, performance parameters, packaging, efficiency, and weight.

Garth, D. R.↗
NASA NTRS1986

Dynamic remapping decisions in multi-phase parallel computations

The effectiveness of any given mapping of workload to processors in a parallel system is dependent on the stochastic behavior of the workload. Program behavior is often characterized by a sequence of phases, with phase changes occurring unpredictably. During a phase, the behavior is fairly stable, but may become quite different during the next phase. Thus a workload assignment generated for one phase may hinder performance during the next phase. We consider the problem of deciding whether to remap a paralled computation in the face of uncertainty in remapping's utility. Fundamentally, it is necessary to balance the expected remapping performance gain against the delay cost of remapping. This paper treats this problem formally by constructing a probabilistic model of a computation with at most two phases. We use stochastic dynamic programming to show that the remapping decision policy which minimizes the expected running time of the computation has an extremely simple structure: the optimal decision at any step is followed by comparing the probability of remapping gain against a threshold. This theoretical result stresses the importance of detecting a phase change, and assessing the possibility of gain from remapping. We also empirically study the sensitivity of optimal performance to imprecise decision threshold. Under a wide range of model parameter values, we find nearly optimal performance if remapping is chosen simply when the gain probability is high. These results strongly suggest that except in extreme cases, the remapping decision problem is essentially that of dynamically determining whether gain can be achieved by remapping after a phase change; precise quantification of the decision model parameters is not necessary.

Nicol, D. M.↗
NASA NTRS1976

HAL/S-FC and HAL/S-360 compiler system program description

The compiler is a large multi-phase design and can be broken into four phases: Phase 1 inputs the source language and does a syntactic and semantic analysis generating the source listing, a file of instructions in an internal format (HALMAT) and a collection of tables to be used in subsequent phases. Phase 1.5 massages the code produced by Phase 1, performing machine independent optimization. Phase 2 inputs the HALMAT produced by Phase 1 and outputs machine language object modules in a form suitable for the OS-360 or FCOS linkage editor. Phase 3 produces the SDF tables. The four phases described are written in XPL, a language specifically designed for compiler implementation. In addition to the compiler, there is a large library containing all the routines that can be explicitly called by the source language programmer plus a large collection of routines for implementing various facilities of the language.

Source record↗
NASA NTRS1977

Basic coaxial mass driver reference design

The reference design for a basic coaxial mass driver is developed to illustrate the principles and optimization procedures on the basis of numerical integration by programmable pocket calculators. The four inch caliber system uses a single-coil bucket and a single-phase propulsion track with discrete coils, separately energized by capacitors. An actual driver would use multiple-coil buckets and an oscillatory multi-phase drive system. Even the basic, table-top demonstration system should in principle be able to achieve accelerations in the 1,000 m/sq sec range. Current densities of the order of 25 ka/sq cm, continuously achievable only in superconductors, are carried by an ordinary aluminum bucket coil for a short period in order to demonstrate the calculated acceleration. Ultimately the system can be lengthened and provided with a magnetically levitated, superconducting bucket to study levitation dynamics under quasi-steady-state conditions, and to approach lunar escape velocity in an evacuated tube.

Kolm, H. H.↗
NASA NTRS1980

Variable stream control engine for advanced supersonic aircraft design update

The updating of the engine concept for a second-generation supersonic transport, the variable stream control engine (VSCE), in terms of mechanical design definition and estimated performance is discussed. The design definition reflects technology advancements that improve system efficiency, durability and environments were established. The components unique to the VSCE concept, a high performance duct burner and a low noise coannular nozzle, and the high temperature components are identified as critical technologies. Technology advances for the high temperature components (main combustor and turbines) are also discussed. To address the requirements in this area, the technical approach for undertaking a high temperature validation program is defined. The multi-phased effort would include assorted rig and laboratory tests, then culminate with the demonstration of a flight-type main combustor and single-stage high pressure turbine at operating conditions envisioned for a VSCE.

Hunt, R. B.↗
NASA NTRS1983

A simulation investigation of the effects of engine-and thrust-response characteristics on helicopter handling qualities

A multi-phase program is being conducted to study, in a generic sense and through ground simulation, the effects of engine response, rotor inertia, rpm control, excess power, and vertical damping on specific maneuvers included in nap-of-the-Earth (NOE) operations. The helicopter configuration with an rpm-governed gas-turbine engine are considered. Handling-qualities-criteria data are considered in light of aspects peculiar to rotary-wing and NOE operations. The results of three moving-based piloted simulation studies are summarized and the frequency, characteristics of the helicopter thrust response which set it apart from other VTOL types are explained. Power-system response is affected by both the engine-governor response and the level of rotor inertia. However, results indicate that with unlimited power, variations in engine response can have a significant effect on pilot rating, whereas changes in rotor inertia, in general, do not. The results also show that any pilot interaction required to maintain proper control can significantly degrade handling qualities. Data for variations in vertical damping and collective sensitivity are compared with existing handling-qualities specifications, MIL-F-83300 and AGARD 577, and show a need for higher minimums for both damping and sensitivity for the bob-up task. Results for cases of limited power are also shown.

Corless, L. D.↗
NASA NTRS1984

Observations of Highly-ionized Interstellar Iron

The spectra of 24 stars, including 5 at distances d 200 pc, have been observed in the regions of the coronal Fe X lambda 6375 and Fe X lambda 5303 lines at detection limits near an equivalent width of 1 mA in the best cases. In general agreement with predictions based on a multi-phase model of the interstellar medium, no absorption which can be attributed to Fe X or Fe X4 ions in hot interstellar gas emitting the soft X-ray background is seen in any of these spectra, except for two. Toward lambda Cephei an absorption line near lambda 6375 is measured with an equivalent width of 8.1 + or - 2 mA, a width corresponding to 20 + or - 5 km/sec or a temperature T or = (0.5 + or - 0.25) x 10 to the 6th power K, and, if it is caused by Fe X ions, a radial velocity of -355 km/sec. On that hypothesis, the interstellar gas constitutes at least 63% of the column density of gas along this light path.

Hobbs, L. M.↗
NASA NTRS1984

High altitude chemically reacting gas particle mixtures. Volume 1: A theoretical analysis and development of the numerical solution

The overall contractual effort and the theory and numerical solution for the Reacting and Multi-Phase (RAMP2) computer code are described. The code can be used to model the dominant phenomena which affect the prediction of liquid and solid rocket nozzle and orbital plume flow fields. Fundamental equations for steady flow of reacting gas-particle mixtures, method of characteristics, mesh point construction, and numerical integration of the conservation equations are considered herein.

Smith, S. D.↗
NASA NTRS1985

A stagnation pressure probe for droplet-laden air flow

It is often of interest in a droplet-laden gas flow to obtain the stagnation pressure of both the gas phase and the mixture. A flow-decelerating probe (TPF), with separate, purged ports for the gas phase and the mixture and with a bleed for accumulating liquid at the closed end, has been developed. Measurements obtained utilizing the TPF in a nearly isothermal air-water droplet mixture flow in a smooth circular pipe under various conditions of flow velocity, pressure, liquid concentration and droplet size are presented and compared with data obtained under identical conditions with a conventional, gas phase stagnation pressure probe (CSP). The data obtained with the CSP and TPF probes are analyzed to determine the applicability of the two probes in relation to the multi-phase characteristics of the flow and the geometry of the probe.

Murthy, S. N. B.↗
NASA NTRS1988

Glass: A source of data leading to constraints on the volcanic, impact, and atmospheric histories of Mars

Volcanism and impact are important processes on Mars. Both mechanisms can produce glasses. Criteria exist for distinguishing between impact glasses and volcanic glasses. Owing to the single-phase nature of glass, tiny pieces (approximately 50-micrometer diameter) are as compositionally representative as larger pieces, in contrast to multi-phase crystalline samples, such as basalts. The thesis of this abstract is that glasses may be common in the Martian regolith and should be a high-priority sample owing to their combination of: (1) low representative mass, and (2) high content of information.

Delano, J. W.↗
NASA NTRS1989

Multibody modeling and verification

A summary of a ten week project on flexible multibody modeling, verification and control is presented. Emphasis was on the need for experimental verification. A literature survey was conducted for gathering information on the existence of experimental work related to flexible multibody systems. The first portion of the assigned task encompassed the modeling aspects of flexible multibodies that can undergo large angular displacements. Research in the area of modeling aspects were also surveyed, with special attention given to the component mode approach. Resulting from this is a research plan on various modeling aspects to be investigated over the next year. The relationship between the large angular displacements, boundary conditions, mode selection, and system modes is of particular interest. The other portion of the assigned task was the generation of a test plan for experimental verification of analytical and/or computer analysis techniques used for flexible multibody systems. Based on current and expected frequency ranges of flexible multibody systems to be used in space applications, an initial test article was selected and designed. A preliminary TREETOPS computer analysis was run to ensure frequency content in the low frequency range, 0.1 to 50 Hz. The initial specifications of experimental measurement and instrumentation components were also generated. Resulting from this effort is the initial multi-phase plan for a Ground Test Facility of Flexible Multibody Systems for Modeling Verification and Control. The plan focusses on the Multibody Modeling and Verification (MMV) Laboratory. General requirements of the Unobtrusive Sensor and Effector (USE) and the Robot Enhancement (RE) laboratories were considered during the laboratory development.

Wiens, Gloria J.↗
NASA NTRS1990

Numerical analysis of bipropellant combustion in orbit maneuvering vehicle thrust chamber

The combustion and aerodynamic processes of liquid-liquid bipropellant; monomethylhydrazine and nitrogen tetroxide in the combustion chamber of a variable thrust engine (VTE) have been examined to assess the flow structure, combustion characteristics, and wall heat transfer under the simulated engine operations at two power levels. The Generalized Elliptic Multi-phase flow with Chemical reaction, Heat transfer and Interfacial Processes (GEM-CHIP) code and the Bipropellant Combustion (BICOMB) code, which is the GEMCHIP algorithm reformulated in the frame work of a body fitted coordinate system, have been used for the numerical study. Combustion flow structure with non-premixed type injection that simulates the impingement type injector is predicted and the results are compared with that of the premixed injector.

Chiu, H. H.↗
NASA NTRS1990

Analysis and design of a high power, digitally-controlled spacecraft power system

The progress to date on the analysis and design of a high power, digitally controlled spacecraft power system is described. Several battery discharger topologies were compared for use in the space platform application. Updated information has been provided on the battery voltage specification. Initially it was thought to be in the 30 to 40 V range. It is now specified to be 53 V to 84 V. This eliminated the tapped-boost and the current-fed auto-transformer converters from consideration. After consultations with NASA, it was decided to trade-off the following topologies: (1) boost converter; (2) multi-module, multi-phase boost converter; and (3) voltage-fed push-pull with auto-transformer. A non-linear design optimization software tool was employed to facilitate an objective comparison. Non-linear design optimization insures that the best design of each topology is compared. The results indicate that a four-module, boost converter with each module operating 90 degrees out of phase is the optimum converter for the space platform. Large-signal and small-signal models were generated for the shunt, charger, discharger, battery, and the mode controller. The models were first tested individually according to the space platform power system specifications supplied by NASA. The effect of battery voltage imbalance on parallel dischargers was investigated with respect to dc and small-signal responses. Similarly, the effects of paralleling dischargers and chargers were also investigated. A solar array and shunt model was included in these simulations. A model for the bus mode controller (power control unit) was also developed to interface the Orbital replacement Unit (ORU) model to the platform power system. Small signal models were used to generate the bus impedance plots in the various operating modes. The large signal models were integrated into a system model, and time domain simulations were performed to verify bus regulation during mode transitions. Some changes have subsequently been incorporated into the models. The changes include the use of a four module boost discharger, and a new model for the mode controller, which includes the effects of saturation. The new simulations for the boost discharger show the improvement in bus ripple that can be achieved by phase-shifted operation of each of the boost modules.

Lee, F. C.↗
NASA NTRS1991

Measurements and predictions of a liquid spray from an air-assist nozzle

Droplet size and gas velocity were measured in a water spray using a two-component Phase/Doppler Particle Analyzer. A complete set of measurements was obtained at axial locations from 5 to 50 cm downstream of the nozzle. The nozzle used was a simple axisymmetric air-assist nozzle. The sprays produced, using the atomizer, were extremely fine. Sauter mean diameters were less than 20 microns at all locations. Measurements were obtained for droplets ranging from 1 to 50 microns. The gas phase was seeded with micron sized droplets, and droplets having diameters of 1.4 microns and less were used to represent gas-phase properties. Measurements were compared with predictions from a multi-phase computer model. Initial conditions for the model were taken from measurements at 5 cm downstream. Predictions for both the gas phase and the droplets showed relatively good agreement with the measurements.

Bulzan, Daniel L.↗
NASA NTRS1991

Global water cycle

The primary objective is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates changes on both global and regional scales. The following subject areas are covered: (1) water vapor variability; (2) multi-phase water analysis; (3) diabatic heating; (4) MSU (Microwave Sounding Unit) temperature analysis; (5) Optimal precipitation and streamflow analysis; (6) CCM (Community Climate Model) hydrological cycle; (7) CCM1 climate sensitivity to lower boundary forcing; and (8) mesoscale modeling of atmosphere/surface interaction.

Robertson, Franklin R.↗