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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Computer simulation of supersonic rarefied gas flow in the transition region, about a spherical probe; a Monte Carlo approach with application to rocket-borne ion probe experiments

This report describes a Monte Carlo simulation of transition flow around a sphere. Conditions for the simulation correspond to neutral monatomic molecules at two altitudes (70 and 75 km) in the D region of the ionosphere. Results are presented in the form of density contours, velocity vector plots and density, velocity and temperature profiles for the two altitudes. Contours and density profiles are related to independent Monte Carlo and experimental studies, and drag coefficients are calculated and compared with available experimental data. The small computer used is a PDP-15 with 16 K of core, and a typical run for 75 km requires five iterations, each taking five hours. The results are recorded on DECTAPE to be printed when required, and the program provides error estimates for any flow field parameter.

Horton, B. E.↗
NASA NTRS1973

V/STOL tilt rotor aircraft study. Volume 9: Piloted simulator evaluation of the Boeing Vertol model 222 tilt rotor aircraft

The results of a real time piloted simulation to investigate the handling qualities and performance of a tilting rotor aircraft design are presented. The aerodynamic configuration of the aircraft is described. The procedures for conducting the simulator evaluation are reported. Pilot comments of the aircraft handling qualities under various simulated flight conditions are included. The time histories of selected pilot maneuvers are shown.

Rosenstein, H.↗
NASA NTRS1973

The electric field in the vicinity of a photo-emitting plate in a plasma

Knowledge of the electric field in the vicinity of a spacecraft provides necessary corrections to measurements of ambient fields and charged particle fluxes and a required parameter to understand the motion of dust particles and grains around the spacecraft. The complex problem of the entire electric field, needed for grain transport calculations, is treated for the one-dimensional case. By approximations to the analysis of a photo-emitting plate immersed in a dilute plasma, explicit expressions for the potential and the electric field were derived. The two classes of implicit solutions for the potential reported by them are shown to yield essentially identical results for the conditions in our solar system. The values were obtained following assumptions of a later paper by Guernsey and Fu, in which the emitted photoelectron distribution is taken as Maxwellian. These results are compared with a simple model due to Grand and Tunaley, wherein the effect of the dilute plasma is neglected entirely.

Barengoltz, J.↗
NASA NTRS1973

Chemical composition of Apollo 15, 16, and 17 samples

The authors analyzed 22 Apollo 15 samples, 21 Apollo 16 samples, 4 Luna 20 samples, and 6 Apollo 17 samples for 26 to 30 major, minor, and trace elements by instrumental neutron activation analysis (INAA). Major attention is given to Apollo 16 results and recent Apollo 17 data. The roster of elements via INAA has been extended to include Nd, Ni, Ir, and Au in the Apollo 16 and 17 samples. The latter three elements are highly abundant in these samples. Sample preparation, activation conditions, and the detailed INAA analytical procedure are essentially the same as reported by Laul and Schmitt (1973).

Laul, J. C.↗
NASA NTRS1975

The experimental clean combustor program: Description and status to November 1975

The generation of technology was studied for the development of advanced commercial CTOL aircraft engines with lower exhaust emissions than current aircraft. The program is in three phases. Phase 1, already completed, consisted of screening tests of low pollution combustor concepts. Phase 2, currently in progress, consists of test rig refinement of the most promising combustor concepts. Phase 2 test results are reported. Phase 3, also currently in progress, consists of incorporating and evaluating the best combustors as part of a complete engine. Engine test plans and pollution sampling techniques are described in this report. Program pollution goals, specified at engine idle and take-off conditions, are idle emission index value of 20 and 4 for carbon monoxide (CO) and total unburned hydrocarbons (THC), respectively, and at take-off are an oxides of nitrogen (NOx) emission index level of 10 and a smoke number of 15. Pollution data were obtained at all engine operating conditions. Results are presented in terms of emission index and also in terms of the Environmental Protection Agency's 1979 Standards Parameter.

Niedzwiecki, R. W.↗
NASA NTRS1975

An improved method for measuring the magnetic inhomogeneity shift in hydrogen masers

The reported method makes it possible to conduct all maser frequency measurements under conditions of low magnetic field intensity for which the hydrogen maser is most stable. Aspects concerning the origin of the magnetic inhomogeneity shift are examined and the available approaches for measuring this shift are considered, taking into account certain drawbacks of currently used methods. An approach free of these drawbacks can be based on the measurement of changes in a parameter representing the difference between the number of atoms in the involved states.

Reinhardt, V. S.↗
NASA NTRS1981

Solar heating for an observatory--Lincoln, Nebraska

Report describes solar-energy system for 50 seat observatory that provides 60 percent of space heating needs. System includes 9 flat-plate collectors, rock storage bin, blowers, controls, ducting, and auxiliary natural-gas furnace; it has five operation modes. Net energy savings were 11.31 million Btu for 12 months, or equivalent of 1.9 barrels of oil. Report appendixes list performance factor definitions, performance equations, and average area weather conditions.

Source record↗
NASA NTRS1982

Studies on wind tunnel straighteners

Tests using small-scale straighteners are reported. The studies allowed conclusions on the most favorable depth relationships, flow conditions behind the straightener and on the drag. The ways an obliquely hitting airflow is deflected by a straightener are examined. In addition the flow drag was measured and the manner in which the individual air columns emanating from the holes unite to form a homogeneous speed field was investigated.

Schultz-Grunow, F.↗
NASA NTRS1983

Condensation of solids in space. Isotope fractionation in the model system C-O

The reported chemical fractionation of a single isotope O-16 under simulated space conditions provides the first experimental proof for the hypothesis that the oxygen isotopic anomaly (and other similar anomalies) seen in meteorites is a product of chemical fractionation in interstellar or circumstellar space. Work proposed on this subject was discontinued because a peer review determined that such effects could not possibly exist and that continued support of this project would be a wasted effort. A bibliography is included of articles generated during research in this area.

Arrhenius, G.↗
NASA NTRS1989

Two-beam coupling gain in undoped GaAs with applied dc electric field and moving grating

Experimental results of two-beam coupling gain efficiency in an undoped, semiinsulating GaAs crystal are reported. The highest gain coefficient measured is about 4.5/cm under the condition of an applied electric field of 13 kV/cm and a grating periodicity of 20 microns. The experimental results and theoretical calculations are in reasonable agreement with each other.

Liu, Duncan T. H.↗
NASA NTRS1991

Effect of flange bolt preload on Space Shuttle main engine high pressure oxidizer turbopump housing analysis

Cracks at the seal fillet flange and the strut pilot groove of primary turbine drain passage of the space shuttle main engine (SSME) high pressure oxidizer turbopump (HPOTP) were observed and reported. Stress information for critical structural components in the SSME under actual conditions is necessary for design and life prediction analysis. However, little information is available about the stress distribution at this location under various combinations of loadings and environments. Thus, a stress analysis was conducted to determine an influence of the various operation and installation loads on the stresses of the HPOTP main mounting flange. To do this, a 3-D finite element model of the HPOTP housing was generated. A fairly comfortable margin of stresses at the flange fillet with respect to the yield stress of Inconel 718 is shown. However, it was revealed that the bending stress arising from the housing flange bolt preloads could significantly affect the stress distribution at the strut pilot groove of primary turbine drain passage in the HPOTP housing. Consequently, the information obtained from the present 3-D analysis results should be useful in guiding the development of the SSME HPOTP.

Min, J. B.↗
NASA NTRS1992

Emission spectra of selected SSME elements and materials

Stennis Space Center (SSC) is pursuing the advancement of experimental techniques and theoretical developments in the field of plume spectroscopy for application to rocket development testing programs and engine health monitoring. Exhaust plume spectral data for the Space Shuttle Main Engine (SSME) are routinely acquired. The usefulness of this data depends upon qualitative and quantitative interpretation of spectral features and their correlation with the engine performance. A knowledge of the emission spectral characteristics of effluent materials in the exhaust plume is essential. A study of SSME critical components and their materials identified 30 elements and 53 materials whose engine exhaust plume spectral might be required. The most important were evaluated using SSC's Diagnostic Testbed Facility Thruster (DTFT), a 1200-lbf, liquid oxygen/gaseous hydrogen rocket engine which very nearly replicates the temperature and pressure conditions of the SSME exhaust plume in the first Mach diamond. This report presents the spectral data for the 10 most important elements and 27 most important materials which are strongly to moderately emitting in the DTFT exhaust plume. The covered spectral range is 300 to 426 nm and the spectral resolution is 0.25 nm. Spectral line identification information is provided and line interference effects are considered.

Tejwani, Gopal D.↗
NASA NTRS1993

A shadowgraph study of two proposed Shuttle-C launch vehicle configurations

A shadowgraph study concerning two of the proposed Shuttle-C launch vehicle configurations are presented. These shadowgraphs were obtained from a wind tunnel test performed in Marshall Space Flight Center's 14-in trisonic wind tunnel at various angles-of-attack and roll angles over the Mach range of 0.6 to 4.96. Variations in payload bay length were also evaluated. Major flow field phenomena can easily be seen in the shadowgraphs. Shadowgraphs are a valuable resource. They are used in the analysis of the external flow conditions the launch vehicle encounters through the ascent stage of flight. Subsequent reports will contain shadowgraph studies for other launch vehicle configurations also tested in the Marshall Space Flight Center's 14-in trisonic wind tunnel.

Springer, A. M.↗
NASA NTRS1993

Revised prediction of LDEF exposure to trapped protons

The Long Duration Exposure Facility (LDEF) spacecraft flew in a 28.5 deg inclination circular orbit with an altitude in the range from 319.4 to 478.7 km. For this orbital altitude and inclination, two components contribute most of the penetrating charge particle radiation encountered - the galactic cosmic rays and the geomagnetically trapped Van Allen protons. Where shielding is less than 1.0 g/sq cm geomagnetically trapped electrons make a significant contribution. The 'Vette' models together with the associated magnetic field models and the solar conditions were used to obtain the trapped electron and proton omnidirectional fluences reported previously. Results for directional proton spectra using the MSFC anisotropy model for solar minimum and 463 km altitude (representative for the LDEF mission) were also reported. The directional trapped proton flux as a function of mission time is presented considering altitude and solar activity variation during the mission. These additional results represent an extension of previous calculations to provide a more definitive description of the LDEF trapped proton exposure.

Watts, John W.↗
NASA NTRS1956

Tabulated Pressure Data for a Series of Controls on a 60 Degree Delta Wing at Mach Numbers of 1.61 and 2.01

An investigation has been made at Mach numbers of 1.61 and 2.01 and Reynolds numbers from 1.7 X 10 to 7.6 X 10 to determine the pressure distributions over a 60 deg. delta wing having 20 different control configurations. Measurements were made at angles of attack from O deg to 15 deg for control deflections from -30 deg to 30 deg. This report presents the complete tabulated pressure data for the range of test conditions.

Lord, Douglas R↗
NASA NTRS1946

Cylinder-temperature correlation of a single-cylinder liquid-cooled engine

An analysis based on nonboiling forced-convection heat-transfer theory is made of the cooling processes in liquid-cooled engine cylinders. Semiempirical equations that relate the average head and barrel temperatures with the primary engine and coolant parameters are derived. A correlation method based on these equations is applied to data obtained from previously reported investigations, which were conducted over large ranges of engine and coolant conditions with two liquid-cooled cylinders using water and various aqueous ethylene glycol solutions as coolants. Upon evaluation of empirical factors, an equation for the cylinder-head temperature as a function of the engine operating conditions and the flow rate, temperature, and physical properties of the coolants is obtained, which represents the data with good accuracy.

Pinkel, Benjamin↗
NASA NTRS1995

Fiber optic reference frequency distribution to remote beam waveguide antennas

In the NASA/JPL Deep Space Network (DSN), radio science experiments (probing outer planet atmospheres, rings, gravitational waves, etc.) and very long-base interferometry (VLBI) require ultra-stable, low phase noise reference frequency signals at the user locations. Typical locations for radio science/VLBI exciters and down-converters are the cone areas of the 34 m high efficiency antennas or the 70 m antennas, located several hundred meters from the reference frequency standards. Over the past three years, fiber optic distribution links have replaced coaxial cable distribution for reference frequencies to these antenna sites. Optical fibers are the preferred medium for distribution because of their low attenuation, immunity to EMI/IWI, and temperature stability. A new network of Beam Waveguide (BWG) antennas presently under construction in the DSN requires hydrogen maser stability at tens of kilometers distance from the frequency standards central location. The topic of this paper is the design and implementation of an optical fiber distribution link which provides ultra-stable reference frequencies to users at a remote BWG antenna. The temperature profile from the earth's surface to a depth of six feet over a time period of six months was used to optimize the placement of the fiber optic cables. In-situ evaluation of the fiber optic link performance indicates Allan deviation on the order of parts in 10(exp -15) at 1000 and 10,000 seconds averaging time; thus, the link stability degradation due to environmental conditions still preserves hydrogen maser stability at the user locations. This paper reports on the implementation of optical fibers and electro-optic devices for distributing very stable, low phase noise reference signals to remote BWG antenna locations. Allan deviation and phase noise test results for a 16 km fiber optic distribution link are presented in the paper.

Calhoun, Malcolm↗