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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Analytical study of the liquid phase transient behavior of a high temperature heat pipe

The transient operation of the liquid phase of a high temperature heat pipe is studied. The study was conducted in support of advanced heat pipe applications that require reliable transport of high temperature drops and significant distances under a broad spectrum of operating conditions. The heat pipe configuration studied consists of a sealed cylindrical enclosure containing a capillary wick structure and sodium working fluid. The wick is an annular flow channel configuration formed between the enclosure interior wall and a concentric cylindrical tube of fine pore screen. The study approach is analytical through the solution of the governing equations. The energy equation is solved over the pipe wall and liquid region using the finite difference Peaceman-Rachford alternating direction implicit numerical method. The continuity and momentum equations are solved over the liquid region by the integral method. The energy equation and liquid dynamics equation are tightly coupled due to the phase change process at the liquid-vapor interface. A kinetic theory model is used to define the phase change process in terms of the temperature jump between the liquid-vapor surface and the bulk vapor. Extensive auxiliary relations, including sodium properties as functions of temperature, are used to close the analytical system. The solution procedure is implemented in a FORTRAN algorithm with some optimization features to take advantage of the IBM System/370 Model 3090 vectorization facility. The code was intended for coupling to a vapor phase algorithm so that the entire heat pipe problem could be solved. As a test of code capabilities, the vapor phase was approximated in a simple manner.

Roche, Gregory Lawrence↗
NASA NTRS1992

Program For Simulation Of Trajectories And Events

Universal Simulation Executive (USE) program accelerates and eases generation of application programs for numerical simulation of continuous trajectories interrupted by or containing discrete events. Developed for simulation of multiple spacecraft trajectories with events as one spacecraft crossing the equator, two spacecraft meeting or parting, or firing rocket engine. USE also simulates operation of chemical batch processing factory. Written in Ada.

Gottlieb, Robert G.↗
NASA NTRS2002

Minimizing Segregation During the Controlled Directional Solidification of Dendritic Alloys Publication: Metallurgical and Materials Transactions

Gravity-driven thermosolutal convection that arises during controlled directional solidification (DS) of dendritic alloys promotes detrimental macro-segregation (e.g. freckles and steepling) in products such as turbine blades. Considerable time and effort has been spent to experimentally and theoretically investigate this phenomena; although our knowledge has advanced to the point where convection can be modeled and accurately compared to experimental results, little has been done to minimize its onset and deleterious effects. The experimental work demonstrates that segregation can be. minimized and microstructural uniformity promoted when a slow axial rotation is applied to the sample crucible during controlled directional solidification processing. Numerical modeling utilizing continuation and bifurcation methods have been employed to develop accurate physical and mathematical models with the intent of identifying and optimizing processing parameters.

Grugel, R. N.↗
NASA NTRS2010

Fiber-Optic Continuous Liquid Sensor for Cryogenic Propellant Gauging

An innovative fiber-optic sensor has been developed for low-thrust-level settled mass gauging with measurement uncertainty <0.5 percent over cryogenic propellant tank fill levels from 2 to 98 percent. The proposed sensor uses a single optical fiber to measure liquid level and liquid distribution of cryogenic propellants. Every point of the sensing fiber is a point sensor that not only distinguishes liquid and vapor, but also measures temperature. This sensor is able to determine the physical location of each point sensor with 1-mm spatial resolution. Acting as a continuous array of numerous liquid/vapor point sensors, the truly distributed optical sensing fiber can be installed in a propellant tank in the same manner as silicon diode point sensor stripes using only a single feedthrough to connect to an optical signal interrogation unit outside the tank. Either water or liquid nitrogen levels can be measured within 1-mm spatial resolution up to a distance of 70 meters from the optical interrogation unit. This liquid-level sensing technique was also compared to the pressure gauge measurement technique in water and liquid nitrogen contained in a vertical copper pipe with a reasonable degree of accuracy. It has been demonstrated that the sensor can measure liquid levels in multiple containers containing water or liquid nitrogen with one signal interrogation unit. The liquid levels measured by the multiple fiber sensors were consistent with those virtually measured by a ruler. The sensing performance of various optical fibers has been measured, and has demonstrated that they can survive after immersion at cryogenic temperatures. The fiber strength in liquid nitrogen has also been measured. Multiple water level tests were also conducted under various actual and theoretical vibration conditions, and demonstrated that the signal-to-noise ratio under these vibration conditions, insofar as it affects measurement accuracy, is manageable and robust enough for a wide variety of spacecraft applications. A simple solution has been developed to absorb optical energy at the termination of the optical sensor, thereby avoiding any feedback to the optical interrogation unit

Xu. Wei↗
NASA NTRS2004

Model of Mixing Layer With Multicomponent Evaporating Drops

A mathematical model of a three-dimensional mixing layer laden with evaporating fuel drops composed of many chemical species has been derived. The study is motivated by the fact that typical real petroleum fuels contain hundreds of chemical species. Previously, for the sake of computational efficiency, spray studies were performed using either models based on a single representative species or models based on surrogate fuels of at most 15 species. The present multicomponent model makes it possible to perform more realistic simulations by accounting for hundreds of chemical species in a computationally efficient manner. The model is used to perform Direct Numerical Simulations in continuing studies directed toward understanding the behavior of liquid petroleum fuel sprays. The model includes governing equations formulated in an Eulerian and a Lagrangian reference frame for the gas and the drops, respectively. This representation is consistent with the expected volumetrically small loading of the drops in gas (of the order of 10 3), although the mass loading can be substantial because of the high ratio (of the order of 103) between the densities of liquid and gas. The drops are treated as point sources of mass, momentum, and energy; this representation is consistent with the drop size being smaller than the Kolmogorov scale. Unsteady drag, added-mass effects, Basset history forces, and collisions between the drops are neglected, and the gas is assumed calorically perfect. The model incorporates the concept of continuous thermodynamics, according to which the chemical composition of a fuel is described probabilistically, by use of a distribution function. Distribution functions generally depend on many parameters. However, for mixtures of homologous species, the distribution can be approximated with acceptable accuracy as a sole function of the molecular weight. The mixing layer is initially laden with drops in its lower stream, and the drops are colder than the gas. Drop evaporation leads to a change in the gas-phase composition, which, like the composition of the drops, is described in a probabilistic manner

Bellan, Josette↗
NASA NTRS2011

Crack Growth Behavior in the Threshold Region for High Cyclic Loading

The present studies show that fanning in the threshold regime is likely caused by other factors than a plastic wake developed during load shedding. The cause of fanning at low R-values is a result of localized roughness, mainly formation of a faceted crack surface morphology , plus crack bifurcations which alters the crack closure at low R-values. The crack growth behavior in the threshold regime involves both crack closure theory and the dislocation theory of metals. Research will continue in studying numerous other metal alloys and performing more extensive analysis, such as the variation in dislocation properties (e.g., stacking fault energy) and its effects in different materials.

Forman, R.↗
NASA NTRS2014

An Analysis and Review of Measures and Relationships in Space Transportation Affordability

The affordability of transportation to or from space is of continued interest across numerous and diverse stakeholders in our aerospace industry. Such an important metric as affordability deserves a clear understanding among stakeholders about what is meant by affordability, costs, and related terms, as otherwise it's difficult to see where specific improvements are needed or where to target specific investments. As captured in the famous words of Lewis Carroll, "If you don't know where you are going, any road will get you there". As important as understanding a metric may be, with terms such as costs, prices, specific costs, average costs, marginal costs, etc., it is equally important to understand the relationship among these measures. In turn, these measures intermingle with caveats and factors that introduce more measures in need of a common understanding among stakeholders. These factors include flight rates, capability, and payload. This paper seeks to review the costs of space transportation systems and the relationships among the many factors involved in costs from the points of view of diverse decision makers. A decision maker may have an interest in acquiring a single launch considering the best price (along with other factors in their business case), or an interest in many launches over time. Alternately, a decision maker may have a specific interest in developing a space transportation system that will offer certain prices, or flight rate capability, or both, at a certain up-front cost. The question arises for the later, to reuse or to expend? As it is necessary in thinking about the future to clearly understand the past and the present, this paper will present data and graphics to assist stakeholders in visualizing trends and the current state of affairs in the launch industry. At all times, raw data will be referenced (or made available separately) alongside detailed explanations about the data, so as to avoid the confusion or misleading conclusions that occur more often than not with complex graphs or statements when such context is lacking.

affordability↗
NASA NTRS2020

QWIPs, SLS, Landsat and the International Space Station

In 1988 DARPA provided funding to NASA’s Goddard Space Flight Center to support the development of GaAs Quantum Well Infrared Photodetectors (QWIP). The goal was to make a single element photodetector that might be expandable to a two-dimensional array format. Ultimately, this led to the development of a 128 x 128 element array in collaboration with AT&T Bell Labs and Rockwell Science Center in 1990. We continued to develop numerous generations of QWIP arrays most recently resulting in the multi-QWIP focal plane for the NASA-US Geological Survey (USGS) Landsat 8 mission launched in 2013 and a similar instrument on the Landsat 9 mission to be launched in 2020. Toward the end of the Landsat 8 QWIP-based Thermal Infrared Sensor (TIRS) instrument the potential of the newly developed Strained Layer Superlattice (SLS) detector array technology became of great interest to NASA for three primary reasons: 1) higher operating temperature; 2) broad spectral response and; 3) higher sensitivity. We have collaborated extensively with QmagiQ, LLC and Northwestern University to further pursue and advance the SLS technology ever since we started back in 2012. In December of 2018 we launched the first SLS-based IR camera system to the International Space Station on board the Robotic Refueling Mission #3 (RRM3). This paper will describe the evolution of QWIP technology leading to the current development of SLS-based imaging systems at the Goddard Space Flight Center over the past 30 years.

Jhabvala, M.↗
NASA NTRS2021

A Computational Analysis of Boundary Layer Instability over the BOLT Configuration

The complex boundary layer flow over the BOLT flight configuration is known to exhibit multiple and potentially interacting instability mechanisms. This paper represents a continuation of our numerical investigation of the flow instabilities over the main test surface of the BOLT configuration by using state-of-the-art tools in multidimensional instability analysis. Specifically, the paper extends our previous computations by considering the separate effects of a nonzero angle-of-attack and a nonzero yaw on the modal instability characteristics of the boundary layer streaks adjacent to the minor-axis symmetry plane. At a selected condition from the ascent part of the anticipated flight trajectory, either type of departure from the design condition is shown to have a considerable impact on the structure of the laminar basic state and, hence, also on the amplification characteristics of the instability waves. A broader set of computations, including N-factor predictions for the relevant instabilities, will be presented in the final paper.

Boundary layer transition↗
NASA NTRS2021

A Computational Analysis of Boundary Layer Instability over the BOLT Configuration

The complex boundary layer flow over the BOLT flight configuration is known to exhibit multiple and potentially interacting instability mechanisms. This paper represents a continuation of our numerical investigation of the flow instabilities over the main test surface of the BOLT configuration by using state-of-the-art tools in multidimensional instability analysis. Specifically, the paper extends our previous computations by considering the separate effects of a nonzero angle of attack and a nonzero yaw on the modal instability characteristics of the boundary layer streaks adjacent to the minor-axis symmetry plane, specifically near both ends of the azimuthal region of a thick boundary layer in the middle, where this region rapidly changes to a thinner boundary layer on either side. At the t = 28.8767 s condition from the ascent part of the anticipated flight trajectory with a flight Mach number of M ∞ = 5.53 and unit Reynolds number of 4.25 x 10 6 /m, either type of departure from the design condition is shown to have a considerable impact on the structure of the basic state rollup within the region of interest and, hence, also on the amplification characteristics of instability waves within the resulting streaks. Yet, for a yaw angle of β = 4 degrees, the computations indicate only a slight reduction with respect to the peak N-factor of nearly 11 at the design condition of zero degrees yaw and zero degrees angle of attack. In contrast, an angle of attack equal to α = 4 degrees, the peak N-factor decreases to nearly 6 on the leeward side and increases above 16 on the windward side, making the onset of transition highly likely on the windward side. Computations also highlight the role of streak instabilities that originate as Mack mode disturbances and also demonstrate the potential pitfalls in using surface pressure sensors alone to gauge the magnitude of instability amplification.

Boundary layer transition↗
NASA NTRS2021

A Computational Analysis of Boundary Layer Instability over the BOLT Configuration (Effect of Nonzero AoA and Yaw)

The complex boundary layer flow over the BOLT flight configuration is known to exhibit multiple and potentially interacting instability mechanisms. This paper represents a continuation of our numerical investigation of the flow instabilities over the main test surface of the BOLT configuration by using state-of-the-art tools in multidimensional instability analysis. Specifically, the paper extends our previous computations by considering the separate effects of a nonzero angle of attack and a nonzero yaw on the modal instability characteristics of the boundary layer streaks adjacent to the minor-axis symmetry plane, specifically near both ends of the azimuthal region of a thick boundary layer in the middle, where this region rapidly changes to a thinner boundary layer on either side. At the t = 28.8767 s condition from the ascent part of the anticipated flight trajectory with a flight Mach number of M ∞ = 5.53 and unit Reynolds number of 4.25 x 10 6 /m, either type of departure from the design condition is shown to have a considerable impact on the structure of the basic state rollup within the region of interest and, hence, also on the amplification characteristics of instability waves within the resulting streaks. Yet, for a yaw angle of β = 4 degrees, the computations indicate only a slight reduction with respect to the peak N-factor of nearly 11 at the design condition of zero degrees yaw and zero degrees angle of attack. In contrast, an angle of attack equal to α = 4 degrees, the peak N-factor decreases to nearly 6 on the leeward side and increases above 16 on the windward side, making the onset of transition highly likely on the windward side. Computations also highlight the role of streak instabilities that originate as Mack mode disturbances and also demonstrate the potential pitfalls in using surface pressure sensors alone to gauge the magnitude of instability amplification.

Boundary layer transition↗
NASA NTRSDate not supplied

Comparison of Daily, Monthly (Lunar), Yearly, Decadal, Quarter-Century, Half-Century, and Centurial Shoreline Change Rates at the Kennedy Space Center, Cape Canaveral, Florida, USA

The Kennedy Space Center (KSC) is North America’s premier spaceport and provides crucial access to space for both government and private entities. The National Aeronautics and Space Administration (NASA) facilities are clustered along a 12 km active shoreline at Cape Canaveral, Florida, USA, with the entire NASA and US Space Force station (SF) shoreline stretching over 32 km (Figure 1). Several Launch Complexes (LC’s) including the modern heavy lift facilities are only a few tens of meters from the active shoreline and are imminently threatened by continued sea level rise and ongoing coastal erosion. The space center was built on the northern part of Cape Canaveral. Images collected in 1943 show that Apollo Heavy Lift Launch Complexes were built in swales on ground that was at or below sea level with Launch Complex 39B constructed on a paleo inlet (Figures 2 and 3). Today the Heavy Lift Launch Complexes are ~220 meters from the shoreline with the area between the complexes retreating at the highest rates along the cape (Figure 4). To better understand the intersection of environmental concerns, limited budgets for shoreline protection, and sheltering critical infrastructure; NASA, The University of Florida, United States Geological Survey (USGS), National Park Service (NPS) and contractors have and continue to conduct numerous studies to characterize and understand the shoreline evolution and rates of change at KSC. This project aims to better understand and visualize the temporal and spatial variability of change along the NASA shoreline beyond a simple point to point solution.

Richard MacKenzie III↗
NASA NTRSDate not supplied

NASA Sustainable Flight National Partnership Panel

The National Aeronautics and Space Administration (NASA) Aeronautics Mission Directorate (ARMD) Hybrid Thermally Efficient Core (HyTEC) Project within the Advanced Air Vehicles Program (AAVP) is focused on accelerating the development of small-core turbofan engine technologies to advance the next entry into service (EIS) single-aisle aircraft having 25,000-35,000 lb. thrust class engines. The goal is to accelerate the development of key engine technologies with improvements in efficiency, durability, performance, and hybridization in order to meet the next EIS single-aisle aircraft expected in the 2030s. The HyTEC Project technology portfolio includes High Pressure Compressor, High Pressure Turbine, Advanced Materials, Hybrid Electric and Compact Combustor (includes operation with Sustainable Aviation Fuels (SAF)). The individual technologies were industry partner proposed and defined where HyTEC selected technologies to cost share with the industry partner. The first phase of the project has matured some and continues to mature numerous technologies to a Technology Readiness Level (TRL) 4-5, which will then be integrated into an advanced small core demonstration. The results of completed efforts have been successful, and projections toward project performance metrics of all Phase 1 technologies indicates significant progress toward meeting the requirements. The core demonstration will integrate many of these technologies into a large-scale ground demonstration that will take them to TRL 6 and enable industry to transition the technologies into the next single-aisle engine architecture. The demonstration goal is to meet the project performance metrics that signify a compact engine core with substantial efficiency and durability improvements over a year 2020 baseline. The core demonstration has been awarded with a cost-share partnership and will take place by the end of 2028.

Tony Nerone↗
NASA NTRS1990

ULTRA-SHARP nonoscillatory convection schemes for high-speed steady multidimensional flow

For convection-dominated flows, classical second-order methods are notoriously oscillatory and often unstable. For this reason, many computational fluid dynamicists have adopted various forms of (inherently stable) first-order upwinding over the past few decades. Although it is now well known that first-order convection schemes suffer from serious inaccuracies attributable to artificial viscosity or numerical diffusion under high convection conditions, these methods continue to enjoy widespread popularity for numerical heat transfer calculations, apparently due to a perceived lack of viable high accuracy alternatives. But alternatives are available. For example, nonoscillatory methods used in gasdynamics, including currently popular TVD schemes, can be easily adapted to multidimensional incompressible flow and convective transport. This, in itself, would be a major advance for numerical convective heat transfer, for example. But, as is shown, second-order TVD schemes form only a small, overly restrictive, subclass of a much more universal, and extremely simple, nonoscillatory flux-limiting strategy which can be applied to convection schemes of arbitrarily high order accuracy, while requiring only a simple tridiagonal ADI line-solver, as used in the majority of general purpose iterative codes for incompressible flow and numerical heat transfer. The new universal limiter and associated solution procedures form the so-called ULTRA-SHARP alternative for high resolution nonoscillatory multidimensional steady state high speed convective modelling.

Leonard, B. P.↗
NASA NTRS2003

On a Non-Reflecting Boundary Condition for Hyperbolic Conservation Laws

A non-reflecting boundary condition (NRBC) for practical computations in fluid dynamics and aeroacoustics is presented. The technique is based on the first principle of non-reflecting, plane wave propagation and the hyperbolicity of the Euler equation system. The NRBC is simple and effective, provided the numerical scheme maintains locally a C(sup 1) continuous solution at the boundary. Several numerical examples in 1D, 2D, and 3D space are illustrated to demonstrate its robustness in practical computations.

Loh, Ching Y.↗
NASA NTRS2003

On a Non-Reflecting Boundary Condition for Hyperbolic Conservation Laws

A non-reflecting boundary condition (NRBC) for practical computations in fluid dynamics and aeroacoustics is presented. The technique is based on the hyperbolicity of the Euler equation system and the first principle of plane (simple) wave propagation. The NRBC is simple and effective, provided the numerical scheme maintains locally a C(sup 1) continuous solution at the boundary. Several numerical examples in ID, 2D and 3D space are illustrated to demonstrate its robustness in practical computations.

Loh, Ching Y.↗
NASA NTRS2015

On the Reconstruction of Palaeo-Ice Sheets: Recent Advances and Future Challenges

Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding mechanisms of global climate change and associated sea-level fluctuations in the past, present and future. The significance of palaeo-ice sheets is further underlined by the broad range of disciplines concerned with reconstructing their behaviour, many of which have undergone a rapid expansion since the 1980s. In particular, there has been a major increase in the size and qualitative diversity of empirical data used to reconstruct and date ice sheets, and major improvements in our ability to simulate their dynamics in numerical ice sheet models. These developments have made it increasingly necessary to forge interdisciplinary links between sub-disciplines and to link numerical modelling with observations and dating of proxy records. The aim of this paper is to evaluate recent developments in the methods used to reconstruct ice sheets and outline some key challenges that remain, with an emphasis on how future work might integrate terrestrial and marine evidence together with numerical modelling. Our focus is on pan-ice sheet reconstructions of the last deglaciation, but regional case studies are used to illustrate methodological achievements, challenges and opportunities. Whilst various disciplines have made important progress in our understanding of ice-sheet dynamics, it is clear that data-model integration remains under-used, and that uncertainties remain poorly quantified in both empirically-based and numerical ice-sheet reconstructions. The representation of past climate will continue to be the largest source of uncertainty for numerical modelling. As such, palaeo-observations are critical to constrain and validate modelling. State-of-the-art numerical models will continue to improve both in model resolution and in the breadth of inclusion of relevant processes, thereby enabling more accurate and more direct comparison with the increasing range of palaeo-observations. Thus, the capability is developing to use all relevant palaeo-records to more strongly constrain deglacial (and to a lesser extent pre-LGM) ice sheet evolution. In working towards that goal, the accurate representation of uncertainties is required for both constraint data and model outputs. Close cooperation between modelling and data-gathering communities is essential to ensure this capability is realised and continues to progress.

Ice sheet reconstruction↗