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At least 649 records · Page 36

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NASA NTRS1972

Some surface characteristics and gas interactions of Apollo 14 fines and rock fragments.

Comprehensive survey of the physical surface characteristics of Apollo 14 fines, two fragments of a breccia (14321), and a crystalline rock (14310). The survey was carried out with optical and both scanning and transmission electron microscopy and by studying the adsorption of a variety of gases including nitrogen, hydrogen, and water vapor. Our objective in the optical microscope study was to relate the visible geological and petrological features to the surface properties. Electron microscopy particularly helped relate surface roughness and particle fusion to gas adsorption and pore structure. The fine sample (14163,111) had a surface area of 0.210 sq m/g and a helium density of 2.9 g/cc. Similar values have been observed with breccia fragments. Other observations include physical adsorption of molecular hydrogen at low temperatures and of water vapor at ambient temperatures. It is concluded that these particular lunar materials, while capable of adsorbing water vapor, do not retain it for any significant time at low pressures, nor, under lunar conditions, is there any indication of absorption or penetration.

Cadenhead, D. A.↗

NASA NTRS1973

The end of the iron-core age.

The terrestrial planets aggregated essentially from small particles, to begin as solid cool bodies with the same general compositions, and there is no possibility of an iron-core developing within any of them at any stage. Their differing internal and surface properties receive ready explanation from their different masses which determine whether the pressures within are sufficient to bring about phase-changes. The claim that the terrestrial core can be identified by means of shock-wave data as nickel-iron is based on theoretical misconception, whereas the actual seismic data establish an uncompressed-density value much lower than any such mixture could have. The onset of the Ramsey phase-change in the earth takes the form of a rapid initial collapse to produce a large core in metallic state which thereafter continues to grow secularly as a result of radioactive heating and leads to reduction of surface-area at long last adequate to account for folded and thrusted mountain-building.

Lyttleton, R. A.↗

NASA NTRS1973

Evaluation of aerodynamic heating uncertainties for Space Shuttle.

The uncertainty in heating predictions derived from ground test data correlations has been used to define the corresponding uncertainties in TPS weight for the Space Shuttle. A completely reusable Shuttle system consisting of an aluminum heat sink booster and orbiter with reusable surface insulation for thermal protection was evaluated. The largest contribution to the uncertainty in the weight of the thermal protection system for the orbiter occurred on lower surface areas due to heating and boundary layer transition uncertainties. Extension of this work to the current Shuttle system concept showed reduced weight uncertainty for the external tank compared to the reusable booster.

Masek, R. V.↗

NASA NTRS1973

Jovian satellite - Satellite eclipses and occultations.

Toward the end of 1973 and in the first part of 1974, when the planes of the orbits of the four large Galilean satellites cross the sun and the earth, satellite-satellite eclipses and occultations will occur. Calculations indicate that during this period 350 such events will occur, most of them potentially observable. From observation of a few of these events the ephemerides of the satellites can be improved, radii and limb darkening curves determined, and crude information about the degree and extent of albedo fluctuations deduced. If a concerted effort were made and a large fraction of these events carefully observed, it would be possible to invert the light curves to obtain albedo maps of most of the surface area at a typical resolution of about 100 km for JI and JII and somewhat poorer for JIII and JIV.

Brinkmann, R. T.↗

NASA NTRS1973

Oxygen consumption measurements during continual centrifugation of mice.

A simple method is described for measurement of metabolism of conscious, unrestrained animals, during chronic centrifugation or other conditions of isolation (23.75 hr/day) from the investigators in an essentially normal atmospheric environment for as long as seven days. This involves telemetry of pressure changes in a metabolic chamber. At 7 G's, increased O2 intake lasting two to seven days and a decreased excursion of the day-night difference were measured for male white mice with less effect or even an opposite effect at lower fields. Base-line measurements of metabolic rate per mouse are less affected by animal size than expected from the surface area law.

Fethke, W.↗

NASA NTRS1951

Experimental Investigation of Air-Cooled Turbine Blades in Turbojet Engine. 7: Rotor-Blade Fabrication Procedures

An experimental investigation was conducted to determine the cooling effectiveness of a wide variety of air-cooled turbine-blade configurations. The blades, which were tested in the turbine of a - commercial turbojet engine that was modified for this investigation by replacing two of the original blades with air-cooled blades located diametrically opposite each other, are untwisted, have no aerodynamic taper, and have essentially the same external profile. The cooling-passage configuration is different for each blade, however. The fabrication procedures were varied and often unique. The blades were fabricated using methods most suitable for obtaining a small number of blades for use in the cooling investigations and therefore not all the fabrication procedures would be directly applicable to production processes, although some of the ideas and steps might be useful. Blade shells were obtained by both casting and forming. The cast shells were either welded to the blade base or cast integrally with the base. The formed shells were attached to the base by a brazing and two welding methods. Additional surface area was supplied in the coolant passages by the addition of fins or tubes that were S-brazed. to the shell. A number of blades with special leading- and trailing-edge designs that provided added cooling to these areas were fabricated. The cooling effectiveness and purposes of the various blade configurations are discussed briefly.

Long, Roger A.↗

NASA NTRS1975

Liquid sample processor

Processor is automatic and includes series of extraction tubes packed with fibrous absorbent material of large surface area. When introduced into these tubes, liquid test samples become completely absorbed by packing material as thin film.

Jahnsen, V. J.↗

NASA NTRS1974

Deployable pressurized cell structure for a micrometeoroid detector

This disclosure comprises a plurality of individual pressurized cells which are caused to leak in response to a micrometeoroid penetration, the leak being sensed by appropriate instrumentation. The plurality of cells may be rolled into a compact arrangement such that the volume of the micrometeoroid detector is small and therefore readily packed in a payload of a launch vehicle. Once the payload is placed in orbit, the rolled up cells can be released, pressurized and provide a relatively rigid, large surface area for detecting micrometeoroid penetration.

Kinard, W. H.↗

NASA NTRS1974

Bibliography on aircraft fire hazards and safety. Volume 1: Hazards. Part 1: Key numbers 1 to 817

Ignition temperatures of n-hexane, n-octane, n-decane, JP-6 jet fuel, and aircraft engine oil MIL-7-7808 (0-60-18) were determined in air using heated Pyrex cylinders and Nichrome wires, rods, or tubes. Ignition temperature varied little with fuel-air ratio, but increased as the size of the heat source was decreased. Expressions are given which define the variation of the hot surface ignition temperatures of these combustibles with the radius and the surface area of the heat source. The expressions are applicable to stagnant or low velocity flow conditions (less than 0.2 in./sec.). In addition, the hot gas ignition temperatures of the combustible vapor-air mixtures were determined with jets of hot air. These ignition temperatures also varied little with fuel-air ratio and increased as the diameter of the heat sources was decreased.

Pelouch, J. J., Jr.↗

NASA NTRS1974

Conductive elastomeric extensometer

An extensometer was used for measuring surface area changes of the human body caused by expansion and contraction of the body. A relatively thin and wide strain responsive conductive elastomeric band was adapted for application to a part of the body, such as around a limb or the trunk of the body. The elastomeric band is incorporated as a resistor in a balanced bridge circuit. Expansion or contraction of the portion of the body on which the elastomeric band is applied causes a change in the resistance of the band and a resultant imbalance of the bridge circuit. The output of the amplifier in volts is suitable for proving the desired reading through a recorder, oscilloscope or voltmeter.

Gause, R. L.↗

NASA NTRS1974

Thailand national programme of the Earth Resources Technology Satellite

The author has identified the following significant results. Intensive interpretation of ERTS-1 scenes covering agricultural regions near Bangkok, backed up by ground surveys and low altitude reconnaissance flights, has established that the major agricultural crops of Thailand can be positively differentiated, and in most cases identified, after some experience has been gained, by examination of ERTS-1 imagery. A country-wide survey of remaining forest cover will be completed during 1974. MSS band 5 and band 7 and white positive transparencies were found to be the most desirable medium for identification of geological structure. The Royal Irrigation Department conducted a pilot study to examine the possibility of determining water reservoir capacity from surface area measurements derived from ERTS-1 images.

Cheosakul, P.↗

NASA NTRS1973

Long-term cryogenic space storage system

Discussion of the design, fabrication and testing of a 225-cu ft spherical cryogenic storage system for long-term subcritical applications under zero-g conditions in storing subcritical cryogens for space vehicle propulsion systems. The insulation system design, the analytical methods used, and the correlation between the performance test results and analytical predictions are described. The best available multilayer insulation materials and state-of-the-art thermal protection concepts were applied in the design, providing a boiloff rate of 0.152 lb/hr, or 0.032% per day, and an overall heat flux of 0.066 Btu/sq ft hr based on a 200 sq ft surface area. A six to eighteen month cryogenic storage is provided by this system for space applications.

Hopkins, R. A.↗

NASA NTRS1974

Sound fields in a lined annular flow duct with lined radial splitters

High attenuation in the inlet duct of fan-jet engines is limited mainly because of two factors: the duct length is short and the frequency is high giving rise to a large duct width to wavelength ratio. Lined radial splitters may be installed. In this configuration not only is the absorbing surface area increased, the acoustic propagation properties in each of the segmented ducts are different to those in a cylindrical or annular duct without radial splitters. Such differences in properties can be used to advantage for mismatching the acoustic source. A lower order spinning mode must propagate as a higher order (integral or fractional) spinning mode. Cut-off phenomena may also be used to advantage. A theoretical modal analysis is made of the sound inside one segment of the annular duct with lined radial splitters.

Mungur, P.↗

NASA NTRS1974

Energy source for comet outbursts

Development of a mechanism explaining the internal source of energy of comet outbursts. A mechanism is proposed which automatically provides a source of particulate matter which creates a huge surface area which contains a substantial percentage of amorphous ice, so that the phase transition of the amorphous ice to a cubic structure provides a release of energy which may be responsible for the outbursts observed in many comets. In addition, the volume into which the transition can propagate is estimated for a spherical comet with a radius of 5 km.

Patashnick, H.↗

NASA NTRS1975

Variable-volume atomic storage vessel for hydrogen masers

Vessel, located in maser cavity, is made from cylindrical, convoluted flexible bellows which can be expanded or contracted along the cylinder axis vertically. Inner surface area remains constant with changing volume, permitting measurement of frequency deviations of excited atoms.

Peters, H. F.↗

NASA NTRS1974

Acceleration processes in the quasi-steady magnetoplasmadynamic discharge

The flow field characteristics within the discharge chamber and exhaust of a quasi-steady magnetoplasmadynamic (MPD) arcjet were examined to clarify the nature of the plasma acceleration process. The observation of discharge characteristics unperturbed by insulator ablation and terminal voltage fluctuations, first requires the satisfaction of three criteria: the use of refractory insulator materials; a mass injection geometry tailored to provide propellant to both electrode regions of the discharge; and a cathode of sufficient surface area to permit nominal MPD arcjet operation for given combinations of arc current and total mass flow. The axial velocity profile and electromagnetic discharge structure were measured for an arcjet configuration which functions nominally at 15.3 kA and 6 g/sec argon mass flow. An empirical two-flow plasma acceleration model is advanced which delineates inner and outer flow regions and accounts for the observed velocity profile and calculated thrust of the accelerator.

Boyle, M. J.↗

NASA NTRS1974

Fast response vanes for sensing flow patterns in helicopter rotor environment

Wind tunnel experiments were conducted on four small-scale flow-direction vanes for the determination of aerodynamic response. The tests were further extended to include a standard sized low-inertia vane currently employed in aircraft flight testing. The four test vanes had different aspect ratios and were about 35 percent of the surface area of the standard vane. The test results indicate satisfactory damping and frequency response for all vanes tested and compare favorably with the standard design.

Barna, P. S.↗

NASA NTRS1975

A fuselage/tank structure study for actively cooled hypersonic cruise vehicles: Active cooling system analysis

The effects of fuselage cross section and structural arrangement on the performance of actively cooled hypersonic cruise vehicles are investigated. An active cooling system which maintains the aircraft's entire surface area at temperatures below 394 K at Mach 6 is developed along with a hydrogen fuel tankage thermal protection system. Thermodynamic characteristics of the actively cooled thermal protection systems established are summarized. Design heat loads and coolant flowrate requirements are defined for each major structural section and for the total system. Cooling system weights are summarized at the major component level. Conclusions and recommendations are included.

Stone, J. E.↗