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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

A Spreadsheet Simulation Tool for Terrestrial and Planetary Balloon Design

During the early stages of new balloon design and development, it is necessary to conduct many trade studies. These trade studies are required to determine the design space, and aid significantly in determining overall feasibility. Numerous point designs then need to be generated as details of payloads, materials, mission, and manufacturing are determined. To accomplish these numerous designs, transient models are both unnecessary and time intensive. A steady state model that uses appropriate design inputs to generate system-level descriptive parameters can be very flexible and fast. Just such a steady state model has been developed and has been used during both the MABS 2001 Mars balloon study and the Ultra Long Duration Balloon Project. Using Microsoft Excel's built-in iteration routine, a model was built. Separate sheets were used for performance, structural design, materials, and thermal analysis as well as input and output sheets. As can be seen from figure 1, the model takes basic performance requirements, weight estimates, design parameters, and environmental conditions and generates a system level balloon design. Figure 2 shows a sample output of the model. By changing the inputs and a few of the equations in the model, balloons on earth or other planets can be modeled. There are currently several variations of the model for terrestrial and Mars balloons, as well there are versions of the model that perform crude material design based on strength and weight requirements. To perform trade studies, the Visual Basic language built into Excel was used to create an automated matrix of designs. This trade study module allows a three dimensional trade surface to be generated by using a series of values for any two design variables. Once the fixed and variable inputs are defined, the model automatically steps through the input matrix and fills a spreadsheet with the resulting point designs. The proposed paper will describe the model in detail, including current variations. The assumptions, governing equations, and capabilities will be addressed. Detailed examples of the model in practice will also be used.

Raquea, Steven M.↗
NASA NTRS2001

Multi-Level Analysis of Pulsed Detonation Engines

The present study explores some issues concerning the operational performance of pulsed detonation engines. Zero-, one- and two-dimensional, transient models are employed in a synergistic manner to elucidate the various characteristics that can be expected from each level of analysis. The zero-dimensional model provides rapid parametric trends that help to identify the global characteristics of pulsed detonation engines. The one-dimensional model adds key wave propagation issues that are omitted in the zero-dimensional model and helps to assess its limitations. Finally, the two-dimensional model allows estimates of the first-order multi-dimensional effects and provides an initial multi-dimensional end-correction for the one-dimensional model. The zero-dimensional results indicate that the pulsed detonation engine is competitive with a rocket engine when exhausting to vacuum conditions. At finite back pressures, the PDE out-performs the rocket if the combustion pressure rise from the detonation is added to the chamber pressure in the rocket. If the two peak pressures are the same, the rocket performance is higher. Two-dimensional corrections added to the one-dimensional model result in a modest improvement in predicted specific impulse over the constant pressure boundary condition.

Ebrahimi, Houshang B.↗
NASA NTRS2007

Estimation Filter for Alignment of the Spitzer Space Telescope

A document presents a summary of an onboard estimation algorithm now being used to calibrate the alignment of the Spitzer Space Telescope (formerly known as the Space Infrared Telescope Facility). The algorithm, denoted the S2P calibration filter, recursively generates estimates of the alignment angles between a telescope reference frame and a star-tracker reference frame. At several discrete times during the day, the filter accepts, as input, attitude estimates from the star tracker and observations taken by the Pointing Control Reference Sensor (a sensor in the field of view of the telescope). The output of the filter is a calibrated quaternion that represents the best current mean-square estimate of the alignment angles between the telescope and the star tracker. The S2P calibration filter incorporates a Kalman filter that tracks six states - two for each of three orthogonal coordinate axes. Although, in principle, one state per axis is sufficient, the use of two states per axis makes it possible to model both short- and long-term behaviors. Specifically, the filter properly models transient learning, characteristic times and bounds of thermomechanical drift, and long-term steady-state statistics, whether calibration measurements are taken frequently or infrequently. These properties ensure that the S2P filter performance is optimal over a broad range of flight conditions, and can be confidently run autonomously over several years of in-flight operation without human intervention.

Bayard, David↗
NASA NTRS2010

CECE: Expanding the Envelope of Deep Throttling Technology in Liquid Oxygen/Liquid Hydrogen Rocket Engines for NASA Exploration Missions

As one of the first technology development programs awarded by NASA under the Vision for Space Exploration, the Pratt & Whitney Rocketdyne (PWR) Deep Throttling, Common Extensible Cryogenic Engine (CECE) program was selected by NASA in November 2004 to begin technology development and demonstration toward a deep throttling, cryogenic engine supporting ongoing trade studies for NASA s Lunar Lander descent stage. The CECE program leverages the maturity and previous investment of a flight-proven hydrogen/oxygen expander cycle engine, the PWR RL10, to develop and demonstrate an unprecedented combination of reliability, safety, durability, throttlability, and restart capabilities in high-energy, cryogenic, in-space propulsion. The testbed selected for the deep throttling demonstration phases of this program was a minimally modified RL10 engine, allowing for maximum current production engine commonality and extensibility with minimum program cost. Four series of demonstrator engine tests have been successfully completed between April 2006 and April 2010, accumulating 7,436 seconds of hot fire time over 47 separate tests. While the first two test series explored low power combustion (chug) and system instabilities, the third test series investigated and was ultimately successful in demonstrating several mitigating technologies for these instabilities and achieved a stable throttling ratio of 13:1. The fourth test series significantly expanded the engine s operability envelope by successfully demonstrating a closed-loop control system and extensive transient modeling to enable lower power engine starting, faster throttle ramp rates, and mission-specific ignition testing. The final hot fire test demonstrated a chug-free, minimum power level of 5.9%, corresponding to an overall 17.6:1 throttling ratio achieved. In total, these tests have provided an early technology demonstration of an enabling cryogenic propulsion concept with invaluable system-level technology data acquisition toward design and development risk mitigation for future lander descent main engines.

Giuliano, Victor J.↗
NASA NTRS2005

Using Dynamic Simulations and Automated Decision Tools to Design Lunar Habitats

This paper describes the role of transient simulations, heuristic techniques, and closed loop integrated control in designing and sizing habitat life support systems. The integration of these three elements allows for more accurate requirements to be derived in advance of hardware choices. As a test case, we used a typical lunar surface habitat. Large numbers of habitat configurations were rapidly tested and evaluated using automated decision support tools. Through this process, preliminary sizing for habitat life support systems were derived. Our preliminary results show that by using transient simulations and closed loop control , we substantially reduced the system mass required to meet mission goals. This has greater implications for general systems analyses and for life support systems. It is likely that transient models, realtime integrated control, and other analyses capable of capturing the uncertainties of systems can be useful for systems analyses much earlier in the system development life cycle than has previously been considered.

Bell, Scott↗
NASA NTRS2014

Temperature Control with Two Parallel Small Loop Heat Pipes for GLM Program

The concept of temperature control of an electronic component using a single Loop Heat Pipe (LHP) is well established for Aerospace applications. Using two LHPs is often desirable for redundancy/reliability reasons or for increasing the overall heat source-sink thermal conductance. This effort elaborates on temperature controlling operation of a thermal system that includes two small ammonia LHPs thermally coupled together at the evaporator end as well as at the condenser end and operating "in parallel". A transient model of the LHP system was developed on the Thermal Desktop (TradeMark) platform to understand some fundamental details of such parallel operation of the two LHPs. Extensive thermal-vacuum testing was conducted with two thermally coupled LHPs operating simultaneously as well as with only one LHP operating at a time. This paper outlines the temperature control procedures for two LHPs operating simultaneously with widely varying sink temperatures. The test data obtained during the thermal-vacuum testing, with both LHPs running simultaneously in comparison with only one LHP operating at a time, are presented with detailed explanations.

0000↗
NASA NTRS2005

Transient Catalytic Combustor Model With Detailed Gas and Surface Chemistry

In this work, we numerically investigate the transient combustion of a premixed gas mixture in a narrow, perfectly-insulated, catalytic channel which can represent an interior channel of a catalytic monolith. The model assumes a quasi-steady gas-phase and a transient, thermally thin solid phase. The gas phase is one-dimensional, but it does account for heat and mass transfer in a direction perpendicular to the flow via appropriate heat and mass transfer coefficients. The model neglects axial conduction in both the gas and in the solid. The model includes both detailed gas-phase reactions and catalytic surface reactions. The reactants modeled so far include lean mixtures of dry CO and CO/H2 mixtures, with pure oxygen as the oxidizer. The results include transient computations of light-off and system response to inlet condition variations. In some cases, the model predicts two different steady-state solutions depending on whether the channel is initially hot or cold. Additionally, the model suggests that the catalytic ignition of CO/O2 mixtures is extremely sensitive to small variations of inlet equivalence ratios and parts per million levels of H2.

Struk, Peter M.↗
NASA NTRS2011

Highlights of Transient Plume Impingement Model Validation and Applications

This paper describes highlights of an ongoing validation effort conducted to assess the viability of applying a set of analytic point source transient free molecule equations to model behavior ranging from molecular effusion to rocket plumes. The validation effort includes encouraging comparisons to both steady and transient studies involving experimental data and direct simulation Monte Carlo results. Finally, this model is applied to describe features of two exotic transient scenarios involving NASA Goddard Space Flight Center satellite programs.

Woronowicz, Michael↗
NASA NTRS2013

Development of an Aeroelastic Modeling Capability for Transient Nozzle Side Load Analysis

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development. Currently there is no fully coupled computational tool to analyze this fluid/structure interaction process. The objective of this study was to develop a fully coupled aeroelastic modeling capability to describe the fluid/structure interaction process during the transient nozzle operations. The aeroelastic model composes of three components: the computational fluid dynamics component based on an unstructured-grid, pressure-based computational fluid dynamics formulation, the computational structural dynamics component developed in the framework of modal analysis, and the fluid-structural interface component. The developed aeroelastic model was applied to the transient nozzle startup process of the Space Shuttle Main Engine at sea level. The computed nozzle side loads and the axial nozzle wall pressure profiles from the aeroelastic nozzle are compared with those of the published rigid nozzle results, and the impact of the fluid/structure interaction on nozzle side loads is interrogated and presented.

Wang, Ten-See↗
NASA NTRSDate not supplied

Validation of Transient Spacecraft Refueling Model with Gateway Breadboard Test Data

The ability to refuel spacecraft on-orbit is a key enabling technology for deep space human exploration. On-orbit refueling requires priming a pressurized liquid propellant from a source tank into fluid transfer lines at vacuum conditions, which could result in excessive surge pressures beyond the system’s qualified operating limits and potentially damage hardware. Therefore, it is imperative to employ numerical models during the development of flight hardware to parametrically characterize system performance over a wide range of operating conditions. Since priming transients are difficult to model accurately, it is important to validate those models with test data. As part of the Gateway bipropellant refueling system development, a simplified fluidic breadboard system was created using water as a simulant for fuel to support early program risk reduction of refueling operations. The objectives of breadboard testing were to gather performance data to characterize and demonstrate critical refueling operations and to validate numerical models that can be extended to predicting flight system performance. A description of the breadboard test system and the results of numerical model validation is presented. The model is shown to have very good agreement with test data.

Brian S Lusby↗
NASA NTRS2000

Observations and Modeling of the Transient General Circulation of the North Pacific Basin

Because of recent progress in satellite altimetry and numerical modeling and the accumulation and archiving of long records of hydrographic and meteorological variables, it is becoming feasible to describe and understand the transient general circulation of the ocean (i.e., variations with spatial scales larger than a few hundred kilometers and time scales of seasonal and longer-beyond the mesoscale). We have carried out various studies in investigation of the transient general circulation of the Pacific Ocean from a coordinated analysis of satellite altimeter data, historical hydrographic gauge data, scatterometer wind observations, reanalyzed operational wind fields, and a variety of ocean circulation models. Broadly stated, our goal was to achieve a phenomenological catalogue of different possible types of large-scale, low-frequency variability, as a context for understanding the observational record. The approach is to identify the simplest possible model from which particular observed phenomena can be isolated and understood dynamically and then to determine how well these dynamical processes are represented in more complex Oceanic General Circulation Models (OGCMs). Research results have been obtained on Rossby wave propagation and transformation, oceanic intrinsic low-frequency variability, effects of surface gravity waves, pacific data analyses, OGCM formulation and developments, and OGCM simulations of forced variability.

McWilliams, James C.↗
NASA NTRS1993

A Frequency-Dependent Q Model Based Upon Transient Rheological Properties of Heterogeneous Materials

Seismic attenuation at low frequency has previously been modeled using two approaches: (1) Examination of all possible microstructural dislocation mechanisms that involve irreversible thermodynamics [Minster and Anderson 1981, P. Trans. R.S. Lond, A, 299]; (2) Parameterized superposition of one-dimensional analogue springs and dashpots, usually consisting of a three-parameter standard linear solid arrangement [Liu et al. 1976, G.J.R.A.S., 47]. The first approach is appealing in that a strong connection is made between micromechanical dissipation and short-term creep that can be studied in the laboratory. The second approach has the advantage of providing a robust 'fit' to actual seismic observations, but has little intrinsic physical content...

Ivins, Erik R.↗
NASA NTRS2006

Experimental and Numerical Characterization of Transient Insertion of Heat Flux Gages in a Cylindrical Black Body Cavity at 1100 C

Initial transient thermal models have been developed to simulate a heat flux gage calibration process capable of generating high heat flux levels of interest to reciprocating and gas turbine engine industries as well as the aerospace industry. These transient models are based on existing, experimentally validated, steady state models of the cylindrical blackbody calibration system. The steady state models were modified to include insertion of a heat flux gage into the hot zone of the calibration system and time varying electrical current passing through the resistance heated blackbody. Heat fluxes computed using the initial transient models were compared to experimental measurements. The calculated and measured transient heat fluxes were within 5% indicating that the major physical phenomena in the transient calibration had been captured by the models. The predicted and measured transient heat fluxes were also compared at two different gage insertion depths. These results indicated that there is an optimum insertion position which maximizes heat flux and minimizes cavity disturbance.

Abdelmessih, A. N.↗
NASA NTRS1981

Magnetohydrodynamic models of coronal transients in the meridional plane. IV - Effect of the solar wind

A two-dimensional, time-dependent magnetohydrodynamic model in the meridional plane with and without an ambient solar wind in an ambient radial magnetic field has been used to investigate mass motions associated with coronal transients. It is shown that the solar wind does not significantly affect the general dynamic characteristics of the mass motion. The ambient solar wind, however, increases the velocity of the mass motion and produces a moderate change in the thermodynamic properties of the coronal plasma.

Wu, S. T.↗
NASA NTRS2007

Effect of Insertion of a Heat Flux Gage into a High Temperature Cylindrical Blackbody Cavity on the Gage

Detailed transient thermal models have been developed to simulate a heat flux gage calibration process capable of generating high heat flux levels. These heat flux levels are of interest to the reciprocating and gas turbine engine industries as well as the aerospace industry. The transient models are based on existing, experimentally validated steady state models of a cylindrical blackbody calibration system. The steady state models were modified to include insertion of a heat flux gage into the hot zone of the calibration system, time-varying electrical current that passes through the resistance heated blackbody, and the resulting heating of the heat flux gage. Heat fluxes computed using detailed transient models were compared to experimental measurements. The calculated and measured transient heat fluxes agreed to within 2 percent, indicating that the models had captured the physical phenomena in the transient calibration. The predicted and measured transient heat fluxes were also compared for two different blackbody configurations. The effect of convection on the blackbody extension was evaluated and found to be a minor factor.

Abdelmessih, Amanie N.↗
NASA NTRS1990

A model for the transient magnetospheric response to sudden solar wind dynamic pressure variations

The evidence for transient variations in the solar wind dynamic pressure, their effect on magnetopause boundary motion, and the signatures they produce within the magnetosphere and at high-latitude auroral ground stations, are examined. A qualitative model for the magnetospheric response to such variations explaining a wide variety of transient magnetopause, magnetospheric and ground signatures is proposed, and its applicability is shown. The model is presented as an alternative explanation for many of the signatures previously interpreted as direct on site evidence of patchy, sporadic, magnetic field merging, namely the flux transfer events (FTEs).

Sibeck, D. G.↗
NASA NTRSDate not supplied

Validation of Transient Spacecraft Refueling Model with Gateway Breadboard Test Data

The ability to refuel spacecraft on-orbit is a key enabling technology for deep space human exploration. On-orbit refueling requires priming a pressurized liquid propellant from a source tank into fluid transfer lines at vacuum conditions, which could result in excessive surge pressures beyond the system’s qualified operating limits and potentially damage hardware. Another source of potentially damaging surge pressures is the water hammer transient that occurs when the isolation valves are closed to pause or end the refueling operation. Therefore, it is imperative to employ numerical models during the development of flight hardware to parametrically characterize system performance over a wide range of operating conditions to minimize the risk of exceeding pressure limits during flight. Since rapid pressure transients can be difficult to model accurately, it is important to validate those models with test data. As part of the Gateway bipropellant refueling system development, a simplified fluidic breadboard system was created using water as a simulant for fuel to support early program risk reduction of refueling operations. The objectives of breadboard testing were to gather performance data to characterize and demonstrate critical refueling operations and to validate numerical models that can be extended to predicting flight system performance. A description of the breadboard test article and the results of numerical model validation is presented. The model is shown to have very good agreement with test data.

Refueling↗