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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Research on the thermal history of the moon

Lunar thermal history modelling is used to demonstrate that a realistic computer simulation can be used to predict major and minor element concentrations, thickness of the lunar crust, and intensity of volcanic activity as a function of time. The models which are most consistent with the observations include: (1) a high surface temperature and low interior temperature during the very early lunar history; (2) high near-surface radioactivity and relatively low radioactivity in the interior; and (3) a molten zone formed at or near the surface which gradually migrates downward with time. Lunar magnetic anomaly calculations show that large anomalies measured at some of the landing sites and above some points on the surface cannot be caused by mere basalts but are consistent with valley fillings of Cayley-like material with a remanent magnetization of about 0.0002 emu/gm.

Source record↗
NASA NTRS1975

Analysis of liquid-metal-jet impingement cooling in a corner region and for a row of jets

A conformal mapping method was used to analyze liquid-metal-jet impingement heat transfer. The jet flow region and energy equation are transformed to correspond to uniform flow in a parallel plate channel with nonuniform heat addition along a portion of one wall. The exact solution for the wall-temperature distribution was obtained in the transformed channel, and the results are mapped back into the physical plane. Two geometries are analyzed. One is for a single slot jet directed either into an interior corner formed by two flat plates, or over the external sides of the corner; the flat plates are uniformly heated, and the corner can have various included angles. The heat-transfer coefficient at the stagnation point at the apex of the plates is obtained as a function of the corner angle, and temperature distributions are calculated along the heated walls. The second geometry is an infinite row of uniformly spaced parallel slot jets impinging normally against a uniformly heated plate. The heat-transfer behavior is obtained as a function of the spacing between the jets. Results are given for several jet Peclet numbers from 5 to 50.

Siegel, R.↗
NASA NTRS1989

Surface grid generation for flowfield applications using B-spline surfaces

The adequate discretization of the flowfield domain in structured grid techniques depends on the body surface, the zones, and the interior grid. Attention is presently given to the problem of obtaining a versatile surface-definition and grid-generation technique; a general surface grid-generation technique is presented which develops three-dimensional patches from point data. The grid is generated on a two-dimensional field on the basis of either a direct or inverse interpolation procedure. It is then mapped onto physical space to yield the surface grid.

Atwood, Christopher A.↗
NASA NTRS2008

Towards Verification of Unstructured-Grid Solvers

New methodology for verification of finite-volume computational methods using unstructured grids is presented. The discretization order properties are studied in computational windows, easily constructed within a collection of grids or a single grid. Tests are performed within each window and address a combination of problem-, solution-, and discretization/grid-related features affecting discretization error convergence. The windows can be adjusted to isolate particular elements of the computational scheme, such as the interior discretization, the boundary discretization, or singularities. Studies can use traditional grid-refinement computations within a fixed window or downscaling, a recently-introduced technique in which computations are made within windows contracting toward a focal point of interest. Grids within the windows are constrained to be consistently refined, allowing a meaningful assessment of asymptotic error convergence on unstructured grids. Demonstrations of the method are shown, including a comparative accuracy assessment of commonly-used schemes on general mixed grids and the identification of local accuracy deterioration at boundary intersections. Recommendations to enable attainment of design-order discretization errors for large-scale computational simulations are given.

Thomas, James L.↗
NASA NTRS1993

Origin of high-Ti lunar ultramafic glasses

A series of high pressure melting experiments were performed on a synthetic analog of the Apollo 14 Black Glass. At 15 kb and 1400 C, olivine is the liquidus phase. At 25 kb and 1450 C, orthopyroxene and Cr-spinel crystallize. A multiple saturation point with olivine + orthopyroxene + spinel on the liquidus occurs at 20 kb and 1440 C. It was proposed that the high-Ti ultramafic glass evolved from a low-Ti Green Glass generated deep in the lunar interior that assimilated shallow-level, late stage cumulates of magma ocean differentiation. Heat for assimilation is provided by superheat of the low-Ti magma and melts high-Ca pyroxene and ilmenite cumulates at a depth of 100 km. This model is a variant of that proposed by Hubbard and Minear and rejected by Ringwood and Kesson.

Wagner, T. P.↗
NASA NTRS1999

Internal Heterogeneous Processes in Aluminum Combustion

This paper discusses the aluminum particle combustion mechanism which has been expanded by inclusion of gas dissolution processes and ensuing internal phase transformations. This mechanism is proposed based on recent normal and microgravity experiments with particles formed and ignited in a pulsed micro-arc. Recent experimental findings on the three stages observed in Al particle combustion in air and shows the burning particle radiation, trajectory (streak), smoke cloud shapes, and quenched particle interiors are summarized. During stage I, the radiation trace is smooth and the particle flame is spherically symmetric. The temperature measured using a three-color pyrometer is close to 3000 K. Because it exceeds the aluminum boiling point (2730 K), this temperature most likely characterizes the vapor phase flame zone rather than the aluminum surface. The dissolved oxygen content within particles quenched during stage I was below the detection sensitivity (about 1 atomic %) for Wavelength Dispersive Spectroscopy (WDS). After an increase in the radiation intensity (and simultaneous decrease in the measured color temperature from about 3000 to 2800 K) indicative of the transition to stage II combustion, the internal compositions of the quenched particles change. Both oxygen-rich (approx. 10 atomic %) and oxygen-lean (< 1 %) regions are identified within the particles using back-scattered electron imaging and WDS. During stage II, oscillations are observed in particle radiation and the flame and smoke cloud are distorted from their original spherically-symmetric shape. In stage III, particle radiation continues to exhibit oscillations, but its radiation intensity drops and remains at a nearly constant level. The measured temperature decreases to about 2300 K. Also, larger changes in particle velocities are observed, and oxide caps are found on quenched particle surfaces. While these results showed the correlation between the aluminum particle combustion behavior and the evolution of its internal composition, the change from the spherically symmetric to asymmetric flame shape occurring upon the transition from stage I to stage II combustion could not be understood based only on the fact that dissolved oxygen is detected in the particles. The connection between the two phenomena appeared even less significant because in earlier aluminum combustion studies carried in O2/Ar mixtures, flame asymmetry was not observed as opposed to experiments in air or O2/CO mixtures. It has been proposed that the presence of other gases, i.e., hydrogen, or nitrogen causes the change in the combustion regime.

Dreizin, E. L.↗
NASA NTRS2008

NASA's Earth Science Use of Commercially Availiable Remote Sensing Datasets: Cover Image

The cover image incorporates high resolution stereo pairs acquired from the DigitalGlobe(R) QuickBird sensor. It shows a digital elevation model of Meteor Crater, Arizona at approximately 1.3 meter point-spacing. Image analysts used the Leica Photogrammetry Suite to produce the DEM. The outside portion was computed from two QuickBird panchromatic scenes acquired October 2006, while an Optech laser scan dataset was used for the crater s interior elevations. The crater s terrain model and image drape were created in a NASA Constellation Program project focused on simulating lunar surface environments for prototyping and testing lunar surface mission analysis and planning tools. This work exemplifies NASA s Scientific Data Purchase legacy and commercial high resolution imagery applications, as scientists use commercial high resolution data to examine lunar analog Earth landscapes for advanced planning and trade studies for future lunar surface activities. Other applications include landscape dynamics related to volcanism, hydrologic events, climate change, and ice movement.

Underwood, Lauren W.↗
NASA NTRS2011

Computational Analysis of the Large Scale Low-Boom Supersonic Inlet

This presentation describes two computational fluid dynamic (CFD) analyses done in support of a supersonic inlet test performed at NASA Glenn Research Center in the fall of 2010. The large-scale-low-boom supersonic inlet was designed for a small supersonic aircraft that would cruise at a Mach number of 1.6. It uses an axisymmetric, external compression spike to reduce the Mach number to 0.65 at the fan face. The inlet was tested in the 8x6 supersonic wind tunnel at NASA GRC using conventional pressure probes, pressure sensitive paint, and high-speed schlieren. Two CFD analyses of the inlet were performed before the test, and compared to the experimental data afterwards. Both analyses used the WIND-US code. First, an axisymmetric analysis of the inlet, diffuser, cold pipe, and mass flow plug was performed to predict the performance of the entire system in the wind tunnel. Then a 3-D analysis of the inlet with all its interior struts was performed to predict details of the flow field and effects of angle of attack. Test results showed that the inlet had excellent performance, with a peak total pressure recovery of 96 percent, and a buzz point far outside the engine operating range. The computations agreed very well with the data, with predicted recoveries within 0.3 - 0.5 points of the measurements.

Chima, ROdrick V.↗
NASA NTRS1997

Application of PML Absorbing Boundary Conditions to the Benchmark Problems of Computational Aeroacoustics

Accurate numerical non-reflecting boundary conditions are important in all the proposed benchmark problems of the Second Workshop. Recently, a new absorbing boundary condition has been developed using Perfectly Matched Layer (PML) equations for the Euler equations. In this approach, a region with a width of a few grid points is introduced adjacent to the non-reflecting boundaries. In the added region, Perfectly Matched Layer equations are constructed and applied so that the out-going waves are absorbed inside the layer with little reflection to the interior domain. It will be demonstrated in the present paper that the proposed absorbing boundary condition is quite general and versatile, applicable to radiation boundaries as well as inflow and outflow boundaries. It is also easy to implement. The emphasis of the paper will be on the application of the PML absorbing boundary condition to problems in Categories 1, 2, and 3. In Category 1, solutions of problems 1 and 2 are presented. Both problems are solved using a multi-domain polar grid system. Perfectly Matched Layer equations for a circular boundary are constructed and their effectiveness assessed. In Category 2, solutions of problem 2 are presented. Here, in addition to the radiation boundary conditions at the far field in the axisymmetric coordinate system, the inflow boundary condition at the duct inlet is also dealt with using the proposed Perfectly Match Layer equations. At the inlet, a PML domain is introduced in which the incident duct mode is simulated while the waves reflected from the open end of the duct are absorbed at the same time. In Category 3, solutions of all three problems are presented. Again, the PML absorbing boundary condition is used at the inflow boundary so that the incoming vorticity wave is simulated while the outgoing acoustic waves are absorbed with very little numerical reflection. All the problems are solved using central difference schemes for spatial discretizations and the optimized Low-Dissipation and Low-Dispersion Runge-Kutta scheme for the time integration. Issues of numerical accuracy and efficiency are also addressed.

Hu, Fang Q.↗
NASA NTRS2003

Low Stretch Solid-Fuel Flame Transient Response to a Step Change in Gravity

The effect of a step change in gravity level on the stability of low stretch diffusion flames over a solid fuel is studied both numerically and experimentally. Drop tower experiments have been conducted in NASA Glenn Research Center's 5.2 Zero Gravity Facility. In the experiments burning PMMA cylinders, a dynamic transition is observed when the steadily burning 1g flame is dropped and becomes a 0g flame. To understand the physics behind this dynamic transition, a transient stagnation point model has been developed which includes gas-phase radiation and solid phase coupling to describe this dynamic process. In this paper, the experimental results are compared with the model predictions. Both model and experiment show that the interior of the solid phase does not have time to change significantly in the few seconds of drop time, so the experimental results are pseudo-steady in the gas-phase, but the solid is inherently unsteady over long time scales. The model is also used to examine the importance of fractional heat losses on extinction, which clearly demonstrates that as the feedback from the flame decreases, the importance of the ongoing heat losses becomes greater, and extinction is observed when these losses represent 80% or more of the flame feedback.

Armstrong, J. B.↗
NASA NTRS1978

An interpretation of special and general isotopic anomalies in r-process nuclei

My analysis of new discoveries by McCulloch and Wasserburg of Ba and Nd isotopic anomalies in inclusions of the Allende meteorite argues that (1) these anomalies contain special extinct radioactivities resulting from radioactive decay within grains formed in and ejected from the supernova interior, (2) the inclusions studied are fused assemblies of interstellar grains that were never totally vaporized, and (3) theoretical separation into r and s abundances suggests that fluctuations between r and s components has occurred during the accumulation processes. These points lend support to a new chemical picture of the early solar system that I have developed, although many interpretations remain possible. Measurements of the neutron-capture cross sections of Nd isotopes are urgently needed to experimentally validate these conclusions.

Clayton, D. D.↗
NASA NTRS1987

Inadequacy of single-impulse transfers for path constrained rendezvous

The use of single-impulse techniques to maneuver from point to point about a large space structure (LSS) with an arbitrary geometrical configuration and spin is examined. Particular consideration is given to transfers with both endpoints on the forbidden zone surface. Clohessy-Wiltshire equations of relative motion are employed to solve path constrained rendezvous problems. External and internal transfers between arbitrary points are analyzed in terms of tangential departure and arrival conditions. It is observed that single-impulse techniques are inadequate for transferring about the exterior of any LSS; however, single-impulse transfers are applicable for transfers in the interior of LSSs. It is concluded that single-impulse transducers are not applicable for path constrained rendezvous guidance.

Stern, S. A.↗
NASA NTRS1994

An optimization program based on the method of feasible directions: Theory and users guide

The theory and user instructions for an optimization code based on the method of feasible directions are presented. The code was written for wide distribution and ease of attachment to other simulation software. Although the theory of the method of feasible direction was developed in the 1960's, many considerations are involved in its actual implementation as a computer code. Included in the code are a number of features to improve robustness in optimization. The search direction is obtained by solving a quadratic program using an interior method based on Karmarkar's algorithm. The theory is discussed, focusing on the important and often overlooked role played by the various parameters guiding the iterations within the program. Also discussed is a robust approach for handling infeasible starting points. The code was validated by solving a variety of structural optimization test problems that have known solutions obtained by other optimization codes. It has been observed that this code is accurate and robust: it has solved a variety of problems from different starting points. However, the code is inefficient in that it takes considerable CPU time as compared with certain other available codes. Further work is required to improve its efficiency while retaining its robustness.

Ashok D. Belegundu↗
NASA NTRS2012

Gravity Recovery and Interior Laboratory (GRAIL) Mission: Status at the Initiation of the Science Mapping Phase

The Gravity Recovery And Interior Laboratory (GRAIL) mission, a component of NASA's Discovery Program, launched successfully from Cape Canaveral Air Force Station on September 10, 2011. The dual spacecraft traversed independent, low-energy trajectories to the Moon via the EL-1 Lagrange point and inserted into elliptical, 11.5-hour polar orbits around the Moon on December 31, 2011, and January 1, 2012. The spacecraft are currently executing a series of maneuvers to circularize their orbits at 55-km mean altitude. Once the mapping orbit is achieved, the spacecraft will undergo additional maneuvers to align them into mapping configuration. The mission is on track to initiate the Science Phase on March 8, 2012.

Zuber, Maria T.↗
NASA NTRSDate not supplied

Ariane 5 Fairing Preparations for James JWST Space Telescope

The James Webb Space Telescope (JWST) is a large, infrared space telescope operating at Lagrange point 2. JWST is a joint effort between NASA, ESA, and CSA and was launched from the Centre Spatial Guyanais (CSG) on an Ariane 5 rocket in December 2021. The Ariane 5 payload faring (PLF), as shown in Figure 1, interior and Vehicle Equipment Bay membranes received multiple cleanings, detailed inspections, and verification sampling to achieve necessary cleanliness levels. Investigation of PLF cleanliness began early in the JWST program to test the Fairing Acoustic Protection (FAP) panels. Initial PLF cleaning was performed at RUAG in Switzerland prior to shipment to the launch site in collaboration with NASA and ESA. The cleaning procedure used at RUAG premises was based on heritage of the PLF cleaning procedure for ESA/Herschel-Planck and NASA/Mars2020 missions on an Atlas V launcher. The Ariane 5 fairing was packaged in a clean manner and inspected and cleaned upon arrival to CSG. Silicon wafers and particle fall out (PFO) plates were used to monitor the internal fairing cleanliness prior to encapsulation. Just after encapsulation, PFO plates and calcium fluoride (CaF2) crystals were placed inside the fairing on a specific tool door for monitoring the cleanliness inside the fairing during the ventilation phase. The fairing itself was specially sealed to protect the inner environment with just a small, doored porthole accessible via diving board for final closeout of the purge interface. Fairing cleanliness was achieved and mitigated contamination distribution upon launch.

James Webb Space Telescope↗
NASA NTRS1990

Asymptotic modal analysis and statistical energy analysis

The sound field of a structural-acoustic enclosure was subject to experimental analysis and theoretical description in order to develop an efficient and accurate method for predicting sound pressure levels in enclosures such as aircraft fuselages. Asymptotic Modal Analysis (AMA) is the method under investigation. AMA is derived from classical modal analysis (CMA) by considering the asymptotic limit of the sound pressure level as the number of acoustic and/or structural modes approaches infinity. Using AMA, results identical to those of Statistical Energy Analysis (SEA) were obtained for the spatially-averaged sound pressure levels in the interior. AMA is systematically derived from CMA and therefore the degree of generality of the end result can be adjusted through the choice of appropriate simplifying assumptions. For example, AMA can be used to obtain local sound pressure levels at particular points inside the enclosure, or to include the effects of varying the size and/or location of the sound source. AMA theoretical results were compared with CMA theory and also with experiment for the case where the structural-acoustic enclosure is a rectangular cavity with part of one wall flexible and vibrating, while the rest of the cavity is rigid.

Dowell, Earl H.↗
NASA NTRS2011

Understanding Space Weather: The Sun as a Variable Star

The Sun is a complex system of systems and until recently, less than half of its surface was observable at any given time and then only from afar. New observational techniques and modeling capabilities are giving us a fresh perspective of the solar interior and how our Sun works as a variable star. This revolution in solar observations and modeling provides us with the exciting prospect of being able to use a vastly increased stream of solar data taken simultaneously from several different vantage points to produce more reliable and prompt space weather forecasts. Solar variations that cause identifiable space weather effects do not happen only on solar-cycle timescales from decades to centuries; there are also many shorter-term events that have their own unique space weather effects and a different set of challenges to understand and predict, such as flares, coronal mass ejections, and solar wind variations

Strong, Keith↗
NASA NTRS2012

Understanding Space Weather: The Sun as a Variable Star

The Sun is a complex system of systems and until recently, less than half of its surface was observable at any given time and then only from afar. New observational techniques and modeling capabilities are giving us a fresh perspective of the solar interior and how our Sun works as a variable star. This revolution in solar observations and modeling provides us with the exciting prospect of being able to use a vastly increased stream of solar data taken simultaneously from several different vantage points to produce more reliable and prompt space weather forecasts. Solar variations that cause identifiable space weather effects do not happen only on solar-cycle timescales from decades to centuries; there are also many shorter-term events that have their own unique space weather effects and a different set of challenges to understand and predict, such as flares, coronal mass ejections, and solar wind variations.

Sun: Corona↗