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At least 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

High alumina (HA) and very high potassium (VHK) basalt clasts from Apollo 14 breccias. I - Mineralogy and Petrology - Evidence of crystallization from evolving magmas

The mineralogy and petrography of very high potassium (VHK) and high alumina (HA) basalts from the Apollo 14 site provide an insight into their magmatic evolution. Generally, their parageneses are similar, with olivine and chromite the early liquidus phases, followed by plagioclase and pyroxene, which crystallized together. Although late-stage ilmenite and FeNi metal occur in both VHK and HA samples, the VHKs also crystallize K-feldspar and Fa-rich olivine. Zoning of constituent minerals is similar for both basalt types, demonstrating that the parental magmas for both HA and VHK basalts became enriched in K, Na, Ca, Fe, and Ti and depleted in Mg and Al as crystallization proceeded. Enrichment of K in the VHK basalts is above that expected from normal fractional crystallization.

Neal, C. R.↗
NASA NTRS1989

High alumina (HA) and very high potassium (VHK) basalt clasts from Apollo 14 breccias. II - Whole rock geochemistry - Further evidence for combined assimilation and fractional crystallization within the lunar crust

The understanding of basalt petrogenesis at the Apollo 14 site has increased markedly due to the study of 'new' samples from breccia 'pull-apart' efforts. Whole-rock compositions of 26 new high alumina (HA) and 7 very high potassium (VHK) basalts emphasize the importance of combined assimilation and fractional crystallization in a lunar regime. Previously formulated models for HA and VHK basalt petrogenesis are modified in order to accomodate these new data, although modeling parameters are essentially the same. The required range in HA basalt compositions is generated by the assimilation of KREEP by a 'primitive' parental magma. The VHK basalts can be generated by three parental HA basalts assimilating granite. Results indicate that VHK basalt compositions are dominated by the parental magma, and only up to 8 percent granite assimilation is required. This modeling indicates that at least three VHK basalt flows must be present at the Apollo 14 site.

Neal, C. R.↗
NASA NTRS1989

The nature and barium partitioning between immiscible melts - A comparison of experimental and natural systems with reference to lunar granite petrogenesis

Elemental partitioning between immiscible melts has been studied using experimental liquid-liquid Kds and those determined by analysis of immiscible glasses in basalt mesostases in order to investigate lunar granite petrogenesis. Experimental data show that Ba is partitioned into the basic immiscible melt, while probe analysis results show that Ba is partitioned into the granitic immiscible melt. It is concluded that lunar granite of significant size can only occur in a plutonic or deep hypabyssal environment.

Neal, C. R.↗
NASA NTRS1989

Explicit-explicit subcycling with non-integer time step ratios for structural dynamic systems

An explicit-explicit subcycling procedure for the finite element analysis of structural dynamics is developed. This procedure has relaxed the usual constraint of requiring integer time step ratios for adjacent nodal groups. This allows for greater advantage to be taken of local stability criteria, and thus improves the efficiency of the explicit time integrator. Example problems are included to demonstrate the accuracy and stability of the method.

Neal, Mark O.↗
NASA NTRS1988

Plasma motor generator tether system for orbit reboost

This paper describes a comprehensive study of an electrodynamic tether used as a Plasma Motor Generator (PMG). The paper summarizes the work performed in the study and includes: (1) a detailed design of a 2 kW PMG tether system to be used for orbit reboost, (2) the selection of the Orbiting Maneuvering Vehicle (OMV) and the European Retrievable Carrier (EURECA) as the primary candidate spacecraft to host the experimental system, (3) analysis of the integration of the PMG tether system with these two spacecraft, (4) the simulation of the deployment of the tether, and (5) an engineering design and development plan leading to a flight demonstration of this PMG tether.

Hulkower, Neal D.↗
NASA NTRS1989

Human mononuclear cell function after 4 C storage during 1-G and microgravity conditions of spaceflight

To investigate the possibility of restoring immune competence of crewmembers during a prolonged spaceflight by infusions of autologous blood components, the effect of storage at 4 C aboard Space Shuttle Columbia (Mission 61-c) on the activity of human peripheral blood mononuclear cells (PBMNCs), stored as leukocyte concentrates in autologous plasa, was investigated. The results of preflight storage at 4 C demonstrated a progressive daily loss in mitogen-stimulated protein synthesis, and thymidine uptake, as well as a progressive reduction in the percentage of PBMNCs expressing cell-surface phenotype markers. The ability of PBMNCs stored at 4 C for 8 d in Columbia's middeck, to become activated and proliferate in vitro was similar to that of cells that remained for 7 d on ground.

Meehan, Richard↗
NASA NTRS1989

The implementation and operation of a variable-response electronic throttle control system for a TF-104G aircraft

During some flight programs, researchers have encountered problems in the throttle response characteristics of high-performance aircraft. To study and to help solve these problems, the National Aeronautics and Space Administration Ames Research Center's Dryden Flight Research Facility (Ames-Dryden) conducted a study using a TF-104G airplane modified with a variable-response electronic throttle control system. Ames-Dryden investigated the effects of different variables on engine response and handling qualities. The system provided transport delay, lead and lag filters, second-order lags, command rate and position limits, and variable gain between the pilot's throttle command and the engine fuel controller. These variables could be tested individually or in combination. Ten research flights were flown to gather data on engine response and to obtain pilot ratings of the various system configurations. The results should provide design criteria for engine-response characteristics. The variable-response throttle components and how they were installed in the TF-104G aircraft are described. How the variable-response throttle was used in flight and some of the results of using this system are discussed.

Neal, Bradford↗
NASA NTRS1990

Navier-Stokes predictions of the flowfield around the F-18 (HARV) wing and fuselage at large incidence

In support of the NASA High Alpha Technology Program, Navier-Stokes solutions have been obtained using the Chimera overset grid scheme for flow over the wing, fuselage, and wing leading-edge extension (LEX) of the F/A-18 High Alpha Research Vehicle (HARV) at high incidence. Solutions are also presented for flow over the fuselage forebody at high angles of attack. The solutions are for turbulent flows at high-Reynolds-number flight-test conditions, and are compared with available qualitative and quantitative experimental data. Comparisons of predicted surface flow patterns, off-surface flow visualization, and surface-pressure distributions are in good agreement with flight-test data. The ability of the numerical method to predict the bursting of the LEX vortex as it encounters the adverse pressure gradient field of the wing is demonstrated, and the capability of predicting high-angle-of-attack aerodynamics around realistic aircraft configurations is established.

Cummings, Russell M.↗
NASA NTRS1990

Unsteady transonic Navier-Stokes computations for an oscillating wing using single and multiple zones

Modern jet transports and maneuvering tactical fighters operating in the transonic regime often give rise to time-dependent fluid physics that interact with flexible structural components, e.g., vortical flow, shocks, and separation. Efficient computational fluid dynamic (CFD) methods are required to study such computationally intensive problems. In this work a numerical method is presented to address this problem. Time-dependent, compressible, Navier-Stokes equations are used to simulate unsteady transonic flow about a three-dimensional rigid wing undergoing a forced periodic motion in angle of attack. An efficient, implicit, diagonal algorithm is utilized because of its low operation count per time step compared to other methods that solve systems of block matrix equations. The formal time accuracy is addressed theoretically and demonstrated numerically by comparison of computational results with experimental data. A zonal grid approach, capable of treating complex geometries, is presented and its time accuracy is demonstrated by comparing a zonal computation with a single grid computation and experimental data.

Chaderjian, Neal M.↗
NASA NTRS1990

Supersonic convection

Numerical simulations with high spatial resolution are used to study that the combined effects of stratification, pressure gradients, and nonadiabatic processes can lead to the formation of regions of supersonic motions near the upper thermal boundary layer. Within these regions, the dynamics is dominated by nonstationary shock structures. These form near the downflow sites and propagate upstream along the boundary layer to the upflow regions where they weaken and eventually disappear. The shock cycle, consisting of the formation, propagation, and disappearance of shock structures, has a time scale comparable to the sound crossing time over a portion of the convective cell, giving rise to vigorous time dependence in the convection.

Cattaneo, Fausto↗
NASA NTRS1989

Physical conditions in molecular clouds

Recent developments have complicated the picture of the physical conditions in molecular clouds. The discoveries of widespread emission from high-J lines of CD and 12-micron IRAS emission have revealed the presence of considerably hotter gas and dust near the surfaces of molecular clouds. These components can complicate interpretation of the bulk of the cloud gas. Commonly assumed relations between column density or mean density and cloud size are called into question by conflicting results and by consideration of selection effects. Analysis of density and density structure through molecular excitation has shown that very high densities exist in star formation regions, but unresolved structure and possible chemical effects complicate the interpretation. High resolution far-IR and submillimeter observations offer a complementary approach and are beginning to test theoretical predictions of density gradients in clouds.

Evans, Neal J., II↗
NASA NTRS1990

Molecular clouds in the outer Galaxy. IV - Studies of star formation

Star formation has been studied in 17 outer Galaxy molecular clouds using the VLA to perform 6 and 20 cm continuum observations to search for H II regions as evidence of massive star formation. IRAS data are used to measure the far-IR luminosity as an indicator of the total star formation rate. H II regions are found to be associated with each of the clouds. The number of ionizing photons required by radio luminosity ranges from 6 x 10 to the 45th/s to 5.5 x 10 to the 49th/s. Far-IR emission was detected from each of the clouds with the range of luminosities being 500 to one million solar. From the data, it is concluded that there is no strong correlation between star formation activity and cloud mass.

Mead, Kathryn N.↗
NASA NTRS1990

The significance of fractional crystallization in the petrogenesis of Apollo 17 Type A and B high-Ti basalts

Whole-rock and mineral analyses of 26 'new' type A and B Apollo 17 basalts are reported. The petrography and mineral chemistry of these basalts are similar to previously reported Apollo 17 basalts. However, these 'new' whole-rock data extend the compositional ranges of previously reported type A and B basalts and require the division of the type B basalts into type B1 and B2 varieties. These three types display similar trends when both major and trace elements are plotted against a fractionation index of Cr/La ratio. Major element compositions of basalts from all three types fall on olivine + Ti oxide control lines. This study demonstrates that Apollo 17 type A, B1, and B2 basalts have a relatively simple petrogenesis, with the only postmagma-generation process being fractional crystallization.

Neal, Clive R.↗
NASA NTRS1990

Astronomical observations with normal incidence multilayer optics - Recent results and future prospects

High-resolution X-ray and EUV images of the solar corona have been obtained with two rocket-borne normal incidence Cassegrain multilayer telescopes. The Cassegrain images correspond to material at about 10 to the 6th K and about 80,000 K. Other images, at somewhat lower resolution, were obtained with Herschelian multilayer telescopes and Wolter-Schwarzschild hybrid grazing incidence/multilayer optical systems. The Cassegrain and Herschelian images are discussed emphasizing the analysis of polar plumes observed at the limb of the sun. The application of specific multilayer techniques to astronomical observations is discussed, emphasizing observations of the sun. Current efforts to develop a comprehensive Multi-Spectral Solar Telescope Array rocket instrument for the study of a wide variety of problems related to the solar atmosphere are reported.

Walker, Arthur B. C., Jr.↗
NASA NTRS1990

Multi-Spectral Solar Telescope Array

This paper descibes the design and the characteristics of the Multispectral Solar Telescope Array (MSSTA), a new rocket spectroheliograph to be launched in August 1990. The MSSTA includes five multilayer Ritchey-Chretien telescopes covering the spectral range 150-300 A and eight multilayer Herschelian telescopes covering the spectral range 40-1550 A, making it possible to obtain spectrohelipgrams over the soft X-ray/extreme UV/FUV spectral range. The MSSTA is expected to obtain information regarding the structure and dynamics of the solar atmosphere in the temperature range 10 to the 4th-10 to the 7th K.

Walker, Arthur B. C., Jr.↗
NASA NTRS1990

Aerodynamic design of the Cal Poly Da Vinci Human-Powered Helicopter

This paper will discuss the methodology used in designing the rotor and drive propellers for the third generation Cal Poly Da Vinci Human-Powered Helicopter. The rotor was designed using a lifting surface, uniform inflow hover analysis code and the propeller was designed using a minimum induced-loss method. Construction, geometry, and operating considerations are discussed as they impact the designs. Optimization of the design performance is also explained. The propellers were tested in a wind tunnel and results are compared with theoretical data. Successful flight tests of the Da Vinci III are discussed.

Larwood, Scott↗