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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 1,459 records · Page 81
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Estimation of propulsion-induced effects on transonic flows over a hypersonic configuration

Boundary conditions are formulated for treating selected patches of a subject configuration as inlet or nozzle areas. For subsonic inflow, the mass flow through the inlet is controlled by the exhaust conditions and the effects of mass and heat addition. For supersonic inflow, the exhaust conditions are based on the inlet conditions and on combustion data. These formulations were included into an existing Euler/Navier-Stokes solver. Comparisons with experimental data demonstrate that the resulting software package efficiently permits the assessment of propulsion-induced effects on external flow fields, particularly around highly blended configurations.

Hartwich, Peter M.↗
NASA NTRS1992

Interactions of the space environments with the Long Duration Exposure Facility (LDEF)

The Long Duration Exposure Facility (LDEF) was retrieved from space after 69 months in orbit. Post-retrieval observations of the facility and the 57 experiments that were onboard have revealed unique and valuable observations of the space environments and the interactions of these environments with the LDEF during the prolonged stay. This paper describes the LDEF, the onboard experiments, the flight mission, and what some of the post-retrieval LDEF observations have revealed about the radiation, meteoroids, manmade debris, atomic oxygen, and contamination environments and their effects on spacecraft.

Kinard, William H.↗
NASA NTRS1992

Infrared studies of pre-main-sequence intermediate-mass stars - LkH-Alpha 198

The paper presents FIR scans of LkH-Alpha 198 at 50 and 100 microns along several directions; the observations reveal an extended, roughly spherical source diameter of 33 arcsec, or 20,000 AU, at 100 microns and not more than 10 arcsec, or 15,000 AU, at 50 microns. A luminosity of 250 solar luminosities at a distance of 600 pc is estimated on the basis of a comparison of the observed properties at optical, IR, and millimeter wavelengths with the predictions of radiation transfer models. The optical depth at 100 microns is 0.004-0.006, implying a mass of about 2 solar masses with a radius of 10,000 AU. It is argued that the inner radius of the dusty envelope is rather small, less than about 300 AU (0.5 arcsec), and it may be as small as the dust destruction front: in LkH-Alpha 198 there is no evidence of a large region devoid of grains.

Natta, Antonella↗
NASA NTRS1992

Petrogenesis of mare basalts - A record of lunar volcanism

The classification, sources, and overall petrogenesis of mare basalts are reviewed. All mare basalt analyses are used to define a sixfold classification scheme using TiO2 contents as the primary division. A secondary division is made using Al2O3 contents, and a tertiary division is defined using K contents. Such divisions and subdivisions yield a classification containing 12 categories, of which six are accounted for by the existing Apollo and Luna collections. A variety of postmagma-generation such as fractional crystallization, either alone or combined with wallrock assimilation, are invoked to explain the compositional ranges of the various mare basalt suites. High-Ti mare basalts are found at Apollo 1 and Apollo 17 sites; the A-11 basalts contain lower TiO2 abundances, a considerably larger range in trace-element contents, and the only occurrence of high-Ti/high-K mare basalts. The low-Ti basalts exhibit a wide range of major-and trace-element compositions and require source heterogeneity, fractional crystallization, and some assimilation.

Neal, Clive R.↗
NASA NTRS1991

Star formation - Observations

Star-formation theories can be tested in light of observational evidence of star formation scenarios on the scales of galaxies, Galactic molecular clouds, and individual star-formation regions. Attention is presently given to the relative importance of atomic and molecular gas in star formation, the role of stimulated star formation, the existence of disks around stars undergoing formation, and the effect of spiral density waves. Attention is given to the processes of cloud cores and core collapse. The development of a theory of binary star formation will require the resolution of the issue as to the presence of a disk in the formation scenario, as indicated by the observation of spectral lines at higher resolutions.

Evans, Neal J., II↗
NASA NTRS1991

Degradation of materials properties in space-overview of LDEF (Long Duration Exposure Facility)

This paper presents an overview of the initial observations of the Long Duration Exposure Facility and, in particular, the degradation of the onboard materials. The LDEF was retrieved from space on January 12, 1990, during the Space Shuttle STS Mission 32 after having remained in space for almost 6 years. Ongoing studies of this retrieved hardware are providing a wealth of basic science data on the environments of near-earth space and the synergistic effects of these space environments on a large array of typical spacecraft materials and systems.

Kinard, William H.↗
NASA NTRS1992

Navier-Stokes prediction of large-amplitude delta-wing roll oscillations characterizing wing rock

High-incidence vortical flow about a 65-deg sweep delta wing undergoing static roll and large-amplitude, high-rate-of-roll oscillations is simulated numerically using the time-dependent, three-dimensional, Reynolds-averaged, Navier-Stokes equations. Turbulent computations are presented for static roll angles up through 42 degrees. The effects of roll angle on the vortex aerodynamics are discussed, and the solution accuracy is evaluated by comparison with experimental data. The effects of grid refinement and zonal boundary condition treatment on solution accuracy are assessed at zero roll angle. Numerical simulation of a forced periodic roll motion is also presented.

Chaderjian, Neal M.↗
NASA NTRS1992

Galileo completing VEEGA - A mid-term report

In December Galileo will complete its Venus-Earth-Earth-Gravity Assist (VEEGA) mission phase and will be placed on a direct trajectory to Jupiter arriving in December 1995. Galileo will be the first aircraft to orbit Jupiter and send a probe into its atmosphere and will perform an intensive and comprehensive investigation of the planet. Observations made during the October 1991 encounter with the asteroid Gaspra are discussed. The observation plan to be used for earth and moon observations during the December 1992 gravity assist encounter is described. The Galileo High-Gain Antenna (HGA) deployment anomaly status is reported and future corrective actions are outlined. The low-gain antenna contingency mission to be implemented if the HGA cannot be deployed is described and overall performance and status of the space craft are discussed. The selected tour for the Galileo Jupiter satellite-gravity-assist orbital tour is described and the decision rationale for performing the August 1993 asteroid Ida flyby option is presented.

O'Neil, William J.↗
NASA NTRS1993

Add/Compare/Select Circuit For Rapid Decoding

Prototype decoding system operates at 200 Mb/s. ACS (add/compare/select) gate array is highly integrated emitter-coupled-logic circuit implementing arithmetic operations essential to Viterbi decoding of convolutionally encoded data signals. Principal advantage of circuit is speed. Operates as single unit performing eight additions and finds minimum of eight sums, or operates as two independent units, each performing four additions and finding minimum of four sums. Flexibility enables application to variety of different codes. Includes built-in self-testing circuitry, enabling unit to be tested at full speed with help of only simple test fixture.

Budinger, James M.↗
NASA NTRS1992

Active cooling from the sixties to NASP

Vehicles, such as the X-15 or National Aero-Space Plane, traveling at hypersonic speeds through the earth's atmosphere experience aerodynamic heating. The heating can be severe enough that a thermal protection system is required to limit the temperature of the vehicle structure. Although several categories of thermal protection systems are mentioned briefly, the majority of this paper describes convectively cooled structures for large areas. Convective cooling is a method of limiting structural temperatures by circulating a coolant through the vehicle structure. Efforts to develop convectively cooled structures during the past 30 years--from early engine structures, which were intended to be tested on the X-15, to structural--are described. Many of the lessons learned from these research efforts are presented.

Kelly, H. Neale↗
NASA NTRS1990

First International Microgravity Laboratory

This colorful booklet presents capsule information on every aspect of the International Microgravity Laboratory (IML). As part of Spacelab, IML is divided into Life Science Experiments and Materials Science Experiments. Because the life and materials sciences use different Spacelab resources, they are logically paired on the IML missions. Life science investigations generally require significant crew involvement, and crew members often participate as test subjects or operators. Materials missions capitalize on these complementary experiments. International cooperation consists in participation by the European Space Agency, Canada, France, Germany, and Japan who are all partners in developing hardware and experiments of IML missions. IML experiments are crucial to future space ventures, like the development of Space Station Freedom, the establishment of lunar colonies, and the exploration of other planets. Principal investigators are identified for each experiment.

Mcmahan, Tracy↗
NASA NTRS1992

Oxidation processes in magneto-optic and related materials

The surface oxidation processes of thin films of magneto-optic materials, such as the rare-earth transition metal alloys have been studied, starting in ultrahigh vacuum environments, using surface analysis techniques, as a way of modeling the oxidation processes which occur at the base of a defect in an overcoated material, at the instant of exposure to ambient environments. Materials examined have included FeTbCo alloys, as well as those same materials with low percentages of added elements, such a Ta, and their reactivities to both O2 and H2O compared with materials such as thin Fe films coated with ultrathin adlayers of Ti. The surface oxidation pathways for these materials is reviewed, and XPS data presented which indicates the type of oxides formed, and a critical region of Ta concentration which provides optimum protection.

Lee, Paul A.↗
NASA NTRS1992

The Apollo 17 mare basalts: Serenely sampling Taurus-Littrow

As we are all aware, the Apollo 17 mission marked the final manned lunar landing of the Apollo program. The lunar module (LM) landed approximately 0.7 km due east of Camelot Crater in the Taurus-Littrow region on the southwestern edge of Mare Serenitatis. Three extravehicular activities (EVA's) were performed, the first concentrating around the LM and including station 1 approximately 1.1 km south-southeast of the LM at the northwestern edge of Steno Crater. The second traversed approximately 8 km west of the LM to include stations 2, 3, 4, and 5, and the third EVA traversed approximately 4.5 km to the northwest of the LM to include stations 6, 7, 8, and 9. This final manned mission returned the largest quantity of lunar rock samples, 110.5 kg/243.7 lb, and included soils, breccias, highland samples, and mare basalts. This abstract concentrates upon the Apollo 17 mare basalt samples.

Neal, Clive R.↗
NASA NTRS1992

Using Apollo 17 high-Ti mare basalts as windows to the lunar mantle

The Apollo 17 high-Ti mare basalts are derived from source regions containing plagioclase that was not retained in the residue. Ilmenite appears to remain as a residual phase, but plagioclase is exhausted. The open-system behavior of the type B2 basalts results in slightly higher Yb/Hf and La/Sm ratios. The nature of the added component is not clear, but may be a KREEP derivative or residue. The recognition of plagioclase in the source(s) of these basalts suggests that the location of the source region(s) would be more likely to be less than 150 km (i.e., closer to the plagioclase-rich crust), which would allow incorporation of plagioclase into the source through incomplete separation of crustal feldspar.

Neal, Clive R.↗
NASA NTRS1991

Direct solar pumping of semiconductor lasers: A feasibility study

The primary goals of the feasibility study are the following: (1) to provide a preliminary assessment of the feasibility of pumping semiconductor lasers in space directly focused sunlight; and (2) to identify semiconductor laser structures expected to operate at the lowest possible focusing intensities. It should be emphasized that the structures under consideration would provide direct optical-to-optical conversion of sunlight into laser light in a single crystal, in contrast to a configuration consisting of a solar cell or battery electrically pumping a current injection laser. With external modulation, such lasers may prove to be efficient sources for intersatellite communications. We proposed to develop a theoretical model of semiconductor quantum-well lasers photopumped by a broadband source, test it against existing experimental data where possible, and apply it to estimating solar pumping requirements and identifying optimum structures for operation for operation at low pump intensities. This report outlines our progress toward these goals. Discussion of several technical details are left to the attached summary abstract.

Anderson, Neal G.↗
NASA NTRS1993

Candidate Technologies for the Integrated Health Management Program

The purpose of this report is to assess Vehicle Health Management (VHM) technologies for implementation as a demonstration. Extensive studies have been performed to determine technologies which could be implemented on the Atlas and Centaur vehicles as part of a bridging program. This paper discusses areas today where VHM can be implemented for benefits in reliability, performance, and cost reduction. VHM Options are identified and one demonstration is recommended for execution.

Johnson, Neal F., Jr.↗