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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Some aspects of flox-methane rocket engine throttling

Four injector designs and two chamber profiles were experimentally evaluated for structural integrity, combustion efficiency, and resistance to combustion instabilities. Vacuum thrust measurements were used as a primary measure of combustion efficiency. Stability rating to test the sensitivity of the injectors to high frequency combustion was conducted, but not extensively. To map the boundary between stable operation and chugging instability, chamber pressure was throttled downward from 689.5 to 206.9 kN/sq m abs (100 to 30 psia). Best operational results were obtained with an injector configuration having no hydraulic swirlers, a 0.00102-m (0.040-in.) recessed FLOX tube, and a nonflared exit in the methane annulus. This injector design exhibited stable combustion and good integrity of hardware, and it exceeded the design goal efficiency (88 percent) at the 10 to 1 throttled condition.

Sokolowski, D. E.↗
NASA NTRS1973

Moonquakes, meteoroids, and the state of the lunar interior

Analysis of data returned from the four stations of the Apollo Seismic Network has revealed that the lunar interior can be divided into two major zones: a rigid, dynamically inactive outer shell, about 1000 km thick (the lunar lithosphere); and a relatively weak central zone (the lunar asthenosphere) in which partial melting is probable. The transition between these two zones is gradual. Seismic activity within the moon is far below that of the earth. The small moonquakes that do occur originate near the base of the lithosphere, and appear to fall within two major belts. Tidal energy appears to be an important, if not the dominant, source of energy released as moonquakes. A secular component of moonquake energy release may result from slight thermal expansion or contraction of the moon, weak convection in the asthenosphere, or secular recession of the moon from the earth. Lack of shallow moonquake activity implies that the moon is neither expanding nor contracting at an appreciable rate at present.

Latham, G.↗
NASA NTRS1974

Ablative thermal protection for space tug multipass, aerobraking entry

Analytical studies had found the employment of an aerobraking trajectory for return of a reusable Space Tug from geosynchronous missions to be feasible and practical. To establish the minimum-weight ablative dome heat shield, trajectories involving 2 and 30 perigee passes were investigated both analytically and by plasma arc testing. Silicone-base ablators with densities of 15, 30, and 50 lb/cu ft were selected for evaluation. All models withstood the multipass exposures without deleterius surface recession or char erosion. Dome heat shield weights based on optimum ablative compositions indicated that ablators are a highly efficient thermal protection system for these missions.

Strauss, E. L.↗
NASA NTRS1974

Volume reflecting heat shields for entry into the giant planet atmospheres

The performance of a volume reflecting or backscattering silica heat shield is examined for an entry probe into the severe radiative environments of Saturn, Uranus, and Jupiter. The governing equations for the material response are solved numerically and include the effects of temperature-dependent thermal properties, temperature- and wavelength-dependent radiative properties, and surface recession caused by thermochemical ablation. The influence of the scattering properties on backface temperature is examined, and results are presented which show the required heat-shield thickness for the entry trajectories selected.

Howe, J. T.↗
NASA NTRS1974

An investigation of environmental factors associated with the current and proposed jetty systems at Belle Pass, Louisiana

The history of the existing jetty system at Belle Pass was investigated to determine its past effect on the littoral currents and beach erosion. Present flow patterns and erosion rates were also studied, along with the prevailing recession rates of local beaches not influenced by the jetty system. Aerial photographs and maps were used in conjunction with periodic hydraulic measurements, ground observations, and physical measurements of beach erosion. A scale model was constructed to further the study of flow patterns and velocities. It is shown that the existing jetty has not adversely affected the coastline in the area; erosive processes have been retarded by the jetty and its companion groin. Future erosion patterns are predicted, and projected effects of the proposed jetty system are given.

Dantin, E. J.↗
NASA NTRS1974

Application of ERTS-1 data to the protection and management of New Jersey's coastal environment

The author has identified the following significant results. Quasi-operational information products for coastal zone management have been prepared using ERTS-1 imagery and collateral aerial photography. These products were applied to the practical regulation, protection, and management of New Jersey's coastal environment. Procedures were developed for the operational use of ERTS-1 data products within New Jersey's Department of Environmental Protection. Successful analysis and product preparation for operational needs centered on four major coastal resource problem areas: (1) detection of environmental changes in coastal areas, (2) siting of ocean outfalls, (3) monitoring of offshore waste disposal, and (4) calculation of recession rates along the Atlantic Shore. The utility and monetary benefits derived from ERTS and aircraft imagery for each problem area have been determined. The NJDEP estimates the possibility of $620,000 yearly savings through the use of an operational ERTS system and a one-time savings of $2.8 million on current or planned projects if a truly operational ERTS type satellite were available.

Yunghans, R. S.↗
NASA NTRS1974

Densitometry of ERTS-1 imagery to access vegetation change

Density measurements of ERTS-1 multispectral scanner (MSS) imagery can be used to evaluate phenological changes in vegetation. It was found that the density ratios for MSS bands 5 and 7 best characterize vegetation change. The ratio increases with vegetative progression and decreases with vegetative recession. The use of a densitometer aperture as small as 0.4 mm does not adversely affect the accuracy of readings on forest sites.

Ashley, M. D.↗
NASA NTRS1976

Rotary broaches

Tool is used for counterboring or backspot facing recesses for boltheads or nuts in difficult-to-reach locations, such as near webs, bosses, or flanges. Two versions of tool have been designed, one for roughing out and another for finishing.

Libertone, C.↗
NASA NTRS1977

Door latch with through-access hole

Innovation allows fully-loaded container to be fastened to rear wall of recessed area. Assembly is designed to carry shear and tension loads. Retractable handle allows for visual verification if door is locked or unlocked.

Dixon, W. F.↗
NASA NTRS1975

Remote sensing in Michigan for land resource management

The utilization of NASA earth resource survey technology as an important aid in the solution of current problems in resource management and environmental protection in Michigan is discussed. Remote sensing techniques to aid Michigan government agencies were used to achieve the following results: (1) provide data on Great Lakes beach recession rates to establish shoreline zoning ordinances; (2) supply technical justification for public acquisition of land to establish the St. John's Marshland Recreation Area; (3) establish economical and effective methods for performing a statewide wetlands survey; (4) accomplish a variety of regional resource management actions in the Upper Peninsula; and (5) demonstrate improved soil survey methods. The project disseminated information on remote sensing technology and provided advice and assistance to a number of users in Michigan.

Lowe, D. S.↗
NASA NTRS1976

Results of tests in the AEDC VKF Tunnel B using the phase change paint technique on 0.04 scale 50 percent forebody models (82-0) of the Rockwell space shuttle orbiter (OH50A)

Model information and data from wind tunnel tests conducted on 0.04 scale 50 percent forebody models of the Space Shuttle Orbiter were presented. These tests were conducted using the phase change paint technique to determine aerodynamic heating rates due to various proturberances and recessions. Angles of attack from 20 deg through 45 deg were investigated at Mach 8.

Quan, M.↗
NASA NTRS1976

Graphite and ablative material response to CO2 laser, carbon-arc, and xenon-arc radiation

The behavior was investigated of graphite and several charring ablators in a variety of high-radiative heat-flux environments. A commercial-grade graphite and nine state-of-the-art charring ablators were subjected to various radiative environments produced by a CO2 laser and a carbon arc. Graphite was also tested in xenon-arc radiation. Heat-flux levels ranged from 10 to 47 MW/sq m. Tests were conducted in air, nitrogen, helium, and a CO2-N2 mixture which simulated the Venus atmosphere. The experimental results were compared with theoretical results obtained with a one-dimensional charring-ablator analysis and a two-dimensional subliming-ablator analysis. Neither the graphite nor the charring ablators showed significant differences in appearance or microstructure after testing in the different radiative environments. The performance of phenolic nylon and graphite was predicted satisfactorily with existing analyses and published material property data. Good agreement between experimental and analytical results was obtained by using sublimation parameters from a chemical nonequilibrium analysis of graphite sublimation. Some charring ablators performed reasonably well and could withstand radiative fluxes of the level encountered in certain planetary entries. Other materials showed excessive surface recession and/or large amounts of cracking and spalling, and appear to be unsuitable for severe radiative environments.

Brewer, W. D.↗
NASA NTRS1976

Method of making hollow elastomeric bodies

Annular elastomeric bodies having intricate shapes are cast by dipping a heated, rotating mandrel into a solution of the elastomer, permitting the elastomer to creep into sharp recesses, drying the coated mandrel and repeating the operation until the desired thickness has been achieved. A bladder for a heart assist pump in which a cylindrical body terminating in flat, sharp horizontal flanges fabricated by this procedure has been subjected to over 2,500 hours of simulated life conditions with no visible signs of degradation.

Broyles, H. F.↗
NASA NTRS1976

Re-examination of compliant wall experiments in air with water substrates

A possible alternative explanation is proposed for compliant wall drag reductions measured in previous investigations. Standing waves were observed to form on the surfaces of compliant wall models in air with water substrates as the freestream velocity was increased from 15 to 30 m/s. These waves resembled sine waves with half of the wave protruding over the upstream portion of the model and the other half being recessed over the downstream end of the model. These data coupled with results of recent drag reduction experiments suggest that standing waves could have caused a shift in the model center of gravity creating a bending moment that was interpreted as a reduction in the skin friction drag.

Hefner, J. N.↗
NASA NTRS1976

Inert gas thrusters

Inert gases are of interest as possible alternatives to the usual electric thruster propellants of mercury and cesium. The multipole discharge chamber investigated was shown capable of low discharge chamber losses and flat ion beam profiles with a minimum of optimization. Minimum discharge losses were 200 to 250 eV/ion for xenon and 300 to 350 eV/ion for argon, while flatness parameters in the plane of the accelerator grid were 0.85 to 0.95. The design used employs low magnetic field strengths, which permits the use of sheet-metal parts. The corner problem of the discharge chamber was resolved with recessed corner anodes, which approximately equalized both the magnetic field above the anodes and the electron currents to these anodes. Argon hollow cathodes were investigated at currents up to about 5 amperes using internal thermionic emitters. Cathode chamber diameter optimized in the 1.0 to 2.5 cm range, while orifices diameter optimized in the 0.5 to 5 mm range. The use of a bias voltage for the internal emitter extended the operating range and facilitated starting. The masses of 15 and 30 cm flight type thrusters were estimated at about 4.2 and 10.8 kg.

Kaufman, H. R.↗
NASA NTRS1977

Reaction diffusion in the nickel-chromium-aluminum and cobalt-chromium-aluminum systems

The effects of MCrAl coating-substrate interdiffusion on oxidation life and the general mutliphase, multicomponent diffusion problem were examined. Semi-infinite diffusion couples that had sources representing coatings and sinks representing gas turbine alloys were annealed at 1,000, 1,095, 1,150, or 1,205 C for as long as 500 hours. The source and sink aluminum and chromium contents and the base metal (cobalt or nickel) determined the parabolic diffusion rate constants of the couples and predicted finite coating lives. The beta source strength concept provided a method (1) for correlating beta recession rate constants with composition; (2) for determining reliable average total, diffusion, and constitutional activation energies; and (3) for calculating interdiffusion coefficients.

Levine, S. R.↗
NASA NTRS1977

Nuclear thermionic converter

Efficient nuclear reactor thermionic converter units are described which can be constructed at low cost and assembled in a reactor which requires a minimum of fuel. Each converter unit utilizes an emitter rod with a fluted exterior, several fuel passages located in the bulges that are formed in the rod between the flutes, and a collector receiving passage formed through the center of the rod. An array of rods is closely packed in an interfitting arrangement, with the bulges of the rods received in the recesses formed between the bulges of other rods, thereby closely packing the nuclear fuel. The rods are constructed of a mixture of tungsten and thorium oxide to provide high power output, high efficiency, high strength, and good machinability.

Phillips, W. M.↗
NASA NTRS1977

Experimental study of error sources in skin-friction balance measurements

An experimental study has been performed to determine potential error sources in skin-friction balance measurements. A floating-element balance, large enough to contain the instrumentation needed to systematically investigate these error sources has been constructed and tested in the thick turbulent boundary layer on the sidewall of a large supersonic wind tunnel. Test variables include element-to-case misalignment, gap size, and Reynolds number. The effects of these variables on the friction, lip, and normal forces have been analyzed. It was found that larger gap sizes were preferable to smaller ones; that small element recession below the surrounding test surface produced errors comparable to the same amount of protrusion above the test surface; and that normal forces on the element were, in some cases, large compared to the friction force.

Allen, J. M.↗