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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 775 records · Page 43

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NASA NTRS1977

Thrust reverser design studies for an over-the-wing STOL transport

Aerodynamic and acoustics analytical studies were conducted to evaluate three thrust reverser designs for potential use on commercial over-the-wing STOL transports. The concepts were: (1) integral D nozzle/target reverser, (2) integral D nozzle/top arc cascade reverser, and (3) post exit target reverser integral with wing. Aerodynamic flowpaths and kinematic arrangements for each concept were established to provide a 50% thrust reversal capability. Analytical aircraft stopping distance/noise trade studies conducted concurrently with flow path design showed that these high efficiency reverser concepts are employed at substantially reduced power settings to meet noise goals of 100 PNdB on a 152.4 m sideline and still meet 609.6 m landing runway length requirements. From an overall installation standpoint, only the integral D nozzle/target reverser concept was found to penalize nacelle cruise performance; for this concept a larger nacelle diameter was required to match engine cycle effective area demand in reverse thrust.

Ammer, R. C.↗

NASA NTRS1980

Low thrust vehicle concept study

Low thrust chemical (hydrogen-oxygen) propulsion systems configured specifically for low acceleration orbit transfer of large space systems were defined. Results indicate that it is cost effective and least risk to combine the OTV and stowed spacecraft in a single 65 K Shuttle. The study shows that the engine for an optimized low thrust stage (1) does not require very low thrust; (2) 1-3 K thrust range appears optimum; (3) thrust transient is not a concern; (4) throttling probably not worthwhile; and (5) multiple thrusters complicate OTV/LSS design and aggravate LSS loads. Regarding the optimum vehicle for low acceleration missions, the single shuttle launch (LSS and expendable OTV) is most cost effective and least risky. Multiple shuttles increase diameter 20%. The space based radar structure short OTV (which maximizes space available for packaged LSS) favors use of torus tank. Propellant tank pressures/vapor residuals are little affected by engine thrust level or number of burns.

Source record↗

NASA NTRS1981

Performance of large inert-gas thrusters

The performance of large inert-gas thrusters is predicted based on present knowledge of ion optics performance and discharge chamber operation. Calculated performance data are given for argon and xenon propellants. The effect of varying propellant utilization and thruster diameter is discussed and the optimum choice of beam diameter for very large systems is indicated for low, intermediate, and high specific impulses. Optimum discharge chamber depths are also specified. Although detailed design considerations may modify the predictions, the general trends indicated should still be useful for directing future technology efforts and evaluating mission studies involving large thrusters.

Kaufman, H. R.↗

NASA NTRS1957

Experimental Droplet Impingement on Four Bodies of Revolution

The rate and. area of cloud droplet impingement on four bodies of revolution were obtained experimentally in the NACA Lewis icing tunnel with a dye-tracer technique. The study included spheres, ellipsoidal forebodies of fineness ratios of 2.5 and 3.0, and a conical forebody of 300 included angle and covered a range of angles of attack from 0? to 60 and rotational speeds up to 1200 rpm. The data were obtained at an airspeed of 157 knots and are correlated by dimensionless impingement parameters. In general, the experimental data show that the local and total impingement rates and impingement limits of bodies of revolution are primarily functions of the modified inertia parameters, the body shape, and fineness ratio. Both the local impingement rate and impingement limits depend upon the angle of attack. Rotation of the bodies had a negligible effect on the impingement characteristics except for an averaging effect at angle of attack. For comparable diameters the bluffer bodies had the largest total impingement efficiency, but the finer and sharper bodies had the largest values of maximum local impingement efficiency and, in most cases, the largest limits of impingement. In most cases, the impingement characteristics were less than those calculated from theoretical trajectories; in general, however, fairly good agreement was obtained between the experimental and theoretical impingement characteristics.

Lewis, James P.↗

NASA NTRS1982

Wire blade development for Fixed Abrasive Slicing Technique (FAST) slicing

A low cost, effective slicing method is essential to make ingot technology viable for photovoltaics in terrestrial applications. The fixed abrasive slicing technique (FAST) combines the advantages of the three commercially developed techniques. In its development stage FAST demonstrated cutting effectiveness of 10 cm and 15 cm diameter workpieces. Wire blade development is still the critical element for commercialization of FAST technology. Both impregnated and electroplated wire blades have been developed; techniques have been developed to fix diamonds only in the cutting edge of the wire. Electroplated wires show the most near term promise and this approach is emphasized. With plated wires it has been possible to control the size and shape of the electroplating, it is expected that this feature reduces kerf and prolongs the life of the wirepack.

Khattak, C. P.↗

NASA NTRS1983

Precise thermal control test demonstration on simulated space telescope main ring

A simulated section of the main ring of the Space Telescope, (ST) the part that holds the primary mirror, was manufactured and tested for thermal stability characteristics in a complex structural assembly. The other telescope subassemblies are also mounted on the main ring, which is constructed of a titanium alloy. The entire ring is wrapped in heater elements around the outside diameter to reduce the external temperature gradient effects by two orders of magnitude. A thermal vacuum test was performed using a stainless steel alloy tailored to represent the titanium ring's thermal characteristics. The tests examined the thermal performance and controllability of the test ring, the effects of a 24-hr slew manuever that produced worst-case environment changes, hot and cold simulation of predicted ST orbital thermal environments, and the effects of heater failure. Pointing and thermal control features were verified, but a heater failure on the 'on' side was found to quickly lead to exceeding the thermal design limits.

Bettini, R. G.↗

NASA NTRS1984

Opacification of high temperature fibrous insulation

A study was conducted to determine the merits of adding particulate materials to silica fiber felts to increase their resistance to the passage of thermal radiation. Laboratory samples containing 5, 10, and 15 percent of chromium oxide, silicon carbide, and titanium dioxide were prepared and evaluated in accordance with ASTM C-518 thermal conductivity test method at 425 C (800 F) mean temperature. The titania particles averaging 3-4 micrometers in diameter were found to be the most effective. This was followed by a short plant run, in order to confirm the initial results on the laboratory samples. These samples were tested according to ASTM C-201 High Temperature Calorimeter from 93 C to 760 C (200 F to 1400 F) mean temperature. The ten percent by weight of titania resulted in an optimum effectiveness, and reduced the conductivity over 20% at 760 C (1400 F).

Miller, W. C.↗

NASA NTRS1983

The Uranian satellites and Hyperion - New spectrophotometry and compositional implications

New reflectance spectra at 3.5 percent resolution have been obtained for Ariel, Titania, Oberon, and Hyperion in the 0.8 to 1.6-micron spectrum region. The new spectra show no absorptions other than the 1.5 micron water-ice feature (within the precision of the data), and demonstrate extension into the 0.8- to 1.6 micron region of the 1.5- to 2.5 micron spectral similarity ofo Ariel to Hyperion (Brown and Cruikshank, 1983). The new data confirm the presence of a dark, spectrally bland component on/in the water-ice surfaces of the Uranian satellites, which, with some reservations, has spectral similarities to the dark substance on the leading side of lapetus and the dark material on/in the surface of Hyperion, as well as other dark, spectrally neutral substances such as charcoal. Attempts were made to match the spectra of Ariel, Titania, and Oberon with additive reflectance mixes (aeral coverage) of fine-grained water frost and various dark components such as charcoal, lampblack, and charcoal-water-ice mixtures. The results were broad limits on the amounts of possible areal coverage of a charcoal-like spectral component on the surfaces of the Uranian satellites, but the data are not of sufficient precision to conclusively determine whether the dominant mode of contaminant dispersal is areal or voluminal. The effect of highly variegated albedos on the diameters derived by Brown, Cruikshank, and Morrison (1982) is found to be small.

Brown, R. H.↗

NASA NTRS1988

Strawman Optical Reception Development Antenna (SORDA)

A strawman design of a ground-based station for receiving optical communications from deep space is presented. This strawman will serve as a basis for further study and design refinement. The recommendation to build rather than to use an existing facility is explained. Parameters of the design were selected to postulate a workable system, starting with a 10 m diameter, hexagonally segmented, f/0.5 primary mirror. The effects of variations of design parameters on performance and cost are discussed. Some design formulas are included. An electro-optical functional block diagram is presented and discussed. Cost calculations are based on a previous cost model for the hardware or on typical construction costs per unit area for several types of facilities. Other cost factors are included in the usual way for Construction of Facilities. The ratio of high and low reasonable values was less than a factor of 2, with a best estimate of under $16,000,000.

Kerr, E. L.↗

NASA NTRS1991

Medium power hydrogen arcjet performance

An experimental investigation was performed to evaluate hydrogen arcjet operating characteristics in the range of 1 to 4 kW. A series of nozzles were operated in modular laboratory thrusters to examine the effects of geometric parameters such as constrictor diameter and nozzle divergence angle. Each nozzle was tested over a range of current and mass flow rates to explore stability and performance. In the range of mass flow rates and power levels tested, specific impulse values between 650 and 1250 sec were obtained at efficiencies between 30 and 40 percent. The performance of the two larger half angle (20, 15 deg) nozzles was similar for each of the two constrictor diameters tested. The nozzles with the smallest half angle (10 deg) were difiicult to operate. A restrike mode of operation was identified and described. Damage in the form of melting was observed in the constrictor region of all the nozzle inserts tested. Arcjet ignition was also difficult in many tests and a glow discharge mode that prevents starting was identified.

Curran, Francis M.↗

NASA NTRS1989

Combustion of 316 stainless steel in high-pressure gaseous oxygen

Upward combustion of 316 stainless steel (SS) rods is discussed and a combustion model is presented. The effects of varying oxygen pressure and rod diameter on the rate limiting processes for combustion of 316 SS are evaluated. The rate-limiting steps for combustion up 316 SS rods are shown to be dependent on the incorporation and mass transport of oxygen in the molten mass, and heat transfer between the molten mass and rod. Both these rate-limiting steps are shown to be dependent on rod diameter. Small (d/r/ = 0.051 cm) 316 SS rods are shown to be dependent on convective heat transfer, and larger rods (d/r/ not less than 0.32 cm) are shown to be dependent on oxygen incorporation and mass transport in the molten mass.

Benz, Frank↗

NASA NTRS1991

Medium power hydrogen arcjet performance

An experimental investigation was performed to evaluate hydrogen arcjet operating characteristics in the range of 1 to 4 kW. A series of nozzles were operated in modular laboratory thrusters to examine the effects of geometric parameters such as constrictor diameter and nozzle divergence angle. Each nozzle was tested over a range of current and mass flow rates to explore stability and performance. In the range of mass flow rates and power levels tested, specific impulse values between 650 and 1250 sec were obtained at efficiencies between 30 and 40 percent. The performance of the two larger half angle (20, 15 deg) nozzles was similar for each of the two constrictor diameters tested. The nozzles with the smallest half angle (10 deg) were difficult to operate. A restrike mode of operation was identified and described. Damage in the form of melting was observed in the constrictor region of all the nozzle inserts tested. Arcjet ignition was also difficult in many tests and a glow discharge mode that prevents starting was identified.

Curran, Francis M.↗

NASA NTRS1992

Surface modification of Venus as inferred from Magellan observations of plains

Magellan radar and altimetry data are analyzed to understand the extent to which surface processes, such as impact crater ejecta emplacement, aeolian processes, and weathering, have modified Venusian plains. The analysis focuses on three areas: (1) lava flows of different relative ages in Sedna Planitia to determine the degradation history of Venusian volcanic surfaces; (2) the 65-km-diameter impact crater Stuart to evaluate the effects of ejecta emplacement on plains surfaces; and (3) elevated plains in western Ovda Regio to explore the nature and rate of production of highly reflective surfaces that dominate terrains that are greater than 6054 km in radius.

Arvidson, Raymond E.↗

NASA NTRS1993

Thermomechanical buckling of multilayered composite panels with cutouts

A study is made of the thermomechanical buckling of flat unstiffened composite panels with central circular cutouts. The panels are subjected to combined temperature changes and applied edge loading (or edge displacements). The analysis is based on a first-order shear deformation plate theory. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the plate. Both the stability boundary and the sensitivity coefficients are evaluated. The sensitivity coefficients measure the sensitivity of the buckling response to variations in the different lamination and material parameters of the panel. Numerical results are presented showing the effects of the variations in the hole diameter, laminate stacking sequence, fiber orientation, and aspect ratio of the panel on the thermomechanical buckling response and its sensitivity coefficients.

Noor, Ahmed K.↗

NASA NTRS1995

Thermomechanical postbuckling of multilayered composite panels with cutouts

The results of a study of the detailed thermomechanical postbuckling response characteristics of flat unstiffened composite panels with central circular cutouts are presented. The panels are subjected to combined temperature changes and applied edge loading (or edge displacements). The analysis is based on a first-order shear deformation plate theory. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the plate. The postbuckling displacements, transverse shear stresses, transverse shear strain energy density, and their sensitivity coefficients are evaluated. The sensitivity coefficients measure the sensitivity of the post-buckling response to variations in the different lamination and material parameters of the panel. Numerical results are presented showing the effects of the variations in the hole diameter, laminate stacking sequence, fiber orientation, and aspect ratio of the panel on the thermomechanical postbuckling response and its sensitivity to changes in panel parameters.

Noor, Ahmed K.↗

NASA NTRS1994

Thermomechanical buckling of multilayered composite panels with cutouts

THERMOMECHANICAL BUCKLING↗

NASA NTRS1994

Thermomechanical buckling of multilayered composite panels with cutouts

Noor, Ahmed K.↗

NASA NTRS1997

Empirical models for spacecraft damage from orbital debris penetration and effects on spacecraft survivability

Semi-empirical models of hole diameter and tip-to-tip crack length for different multi-wall shielding systems currently under development for the International Space Station are presented. These equations were developed using light gas gun test data at impact velocities of 6.5 km/s and inhibited shaped charge test data for an impact velocity of 11.3 km/s. These models are incorporated into a survivability analysis using the manned spacecraft crew survivability computer code to determine whether or not module unzipping or crew incapacitation would occur under a specific set of impact conditions.

Williamsen, Joel↗