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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Electron beam irradiation of thinned backside illuminated CCDs

The physical properties of backside illuminated surface channel CCD arrays and a pixel buried channel CCD array when bombarded with electrons were studied. The devices were mounted in a high vacuum system and irradiated with electrons generated by an electron gun. Basic measurements of EBS gain, dead voltage, transfer efficiency and dark current were performed to verify proper device operation. The surface channel devices were then irradiated with electrons of up to 8 keV energy for up to 98 hours while the buried channel device was irradiated with electrons.

Borsuk, G. M.↗
NASA NTRS1977

Techniques for increasing boron fiber fracture strain

Improvement in the strain-to-failure of CVD boron fibers is shown possible by contracting the tungsten boride core region and its inherent flaws. The results of three methods are presented in which etching and thermal processing techniques were employed to achieve core flaw contraction by internal stresses available in the boron sheath. After commercially and treatment induced surface flaws were removed from 203 micrometers (8 mil) fibers, the core flaw was observed to be essentially the only source of fiber fracture. Thus, fiber strain-to-failure was found to improve by an amount equal to the treatment induced contraction on the core flaw. Commercial feasibility considerations suggest as the most cost effective technique that method in which as-produced fibers are given a rapid heat treatment above 700 C. Preliminary results concerning the contraction kinetics and fracture behavior observed are presented and discussed both for high vacuum and argon gas heat treatment environments.

Dicarlo, J. A.↗
NASA NTRS1977

Techniques for increasing boron fiber fracture strain

Improvement in the strain-to-failure of chemical-vapor-deposition boron fibers is shown possible by contracting the tungsten boride core region and its inherent flaws. Results of three methods are presented in which etching and thermal-processing techniques were employed to achieve core flaw contraction by internal stresses available in the boron sheath. After commercially and treatment-induced surface flaws were removed from 203-micron (8-mil) fibers, the core flaw was observed to be essentially the only source of fiber fracture. Thus, fiber strain-to-failure was found to improve by an amount equal to the treatment-induced contraction on the core flaw. To date, average fracture strains and stresses greater than 1.4% and 5.5 GN/sq m (800 ksi), respectively, have been achieved. Commercial feasibility considerations suggest as the most cost-effective technique that method in which as-produced fibers are given a rapid heat treatment above 700 C. Preliminary results concerning the contraction kinetics and fracture behavior observed with this technique are presented and discussed for both high-vacuum and argon-gas heat-treatment environments.

Dicarlo, J. A.↗
NASA NTRS1979

Two-position wax-motor rotary actuator

Two position rotary actuator rotates shaft by precisely 180 deg and rotates it back on command. Mechanism consumes 11 watts of power and functions over wide range of temperatures under high vacuum for long unattended periods. Light weight device may be used to flip magnetometer for calibration in magnetic field.

Stange, W. C.↗
NASA NTRS1977

Friction and wear of single-crystal and polycrystalline maganese-zinc ferrite in contact with various metals

Sliding friction experiments were conducted with single-crystal (SCF) and hot-pressed polycrystalline (HPF) manganese-zinc ferrite in contact with various metals. Results indicate that the coefficients of friction for SCF and HPF are related to the relative chemical activity of those metals in high vacuum. The more active the metal, the higher the coefficient of friction. The coefficients of friction for both SCF and HPF were the same and much higher in vacuum than in argon at atmospheric pressure. All the metals tested transferred to the surface of both SCF and HPF in sliding. Both SCF and HPF exhibited cracking and fracture with sliding. Cracking in SCF is dependent on crystallographic characteristics. In HPF, cracking depends on the orientation of the individual crystallites.

Miyoshi, K.↗
NASA NTRS1978

Measurement of the time-temperature dependent dynamic mechanical properties of boron/aluminum composites

A flexural vibration test and associated equipment were developed to accurately measure the low strain dynamic modulus and damping of composite materials from -200 C to over 500 C. The basic test method involves the forced vibration of composite bars at their resonant free-free flexural modes in a high vacuum cryostat furnace. The accuracy of these expressions and the flexural test was verified by dynamic moduli and damping capacity measurements on 50 fiber volume percent boron/aluminum (B/Al) composites vibrating near 2000 Hz. The phase results were summarized to permit predictions of the B/Al dynamic behavior as a function of frequency, temperature, and fiber volume fraction.

Dicarlo, J. A.↗
NASA NTRS1978

Plasma cleaning device

High vacuum cleaning of contaminated surfaces such as hydrocarbon containment films can be accomplished by a plasma cleaning device which includes a plasma discharge housing to permit generation of a plasma in an environment having a higher pressure than the surface which is to be cleaned. A ground electrode and a radio frequency electrode partially surround a quartz plasma tube, for the introduction of an ionizable gas. These electrodes ionize the gas and help generate the plasma. This plasma flows through a non-constrictive aperture, through the plasma discharge housing and then on to the contaminated surface.

Shannon, R. L.↗
NASA NTRS1978

Basic approaches to and tasks of space technology

The high vacuum and weightlessness of outer space offer great possibilities for the new field of space technology. To take advantage of this, it is necessary to study such physical and chemical phenomena as diffusion, surface tension, heat exchange, and crystallization. The research shows the possibility of obtaining materials with a more perfect structure. Methods of treating materials can be used in space which are impossible on earth. Achievements in material science in outer space will have a large impact on the national economy.

Okhotin, A. S.↗
NASA NTRS1978

Measurement of the time-temperature dependent dynamic mechanical properties of boron/aluminum composites

A relatively simple flexural vibration test is developed for accurate measurement of the low-strain dynamic modulus and damping capacity of B/Al composite bar specimens from -200 C to over 500 C. The specimens are prepared from 8-ply unidirectional panels containing 50 volume percent fibers composed of 203-micron commercial boron-on-tungsten fibers. The basic test technique consists of the forced flexural vibration of the composite bar specimens at their two lowest free-free symmetrical resonant modes in a high-vacuum cryostat furnace. Specimen damping is determined from oscilloscope photographs of the free decay obtained after simultaneously removing the resonant drive signal and grounding the vibration-drive electrode. The availability of time-temperature dynamic data coupled with the predictive accuracy of composite theory suggests a future potential for using such data in examining environmental effects on composite macrostructure and microstructure.

Dicarlo, J. A.↗
NASA NTRS1977

European tests on materials outgassing

With a view to international coordination of spacecraft materials, a number of European firms and institutes performed outgassing tests on identical materials at 125 C in high vacuum. The outgassing data obtained with the different types of equipment is presented and both the results and the critical parameters are discussed.

Zwaal, A.↗
NASA NTRS1980

Miniature cyclotron resonance ion source using small permanent magnet

An ion source using the cyclotron resonance principle is described. A miniaturized ion source device is used in an air gap of a small permanent magnet with a substantially uniform field in the air gap of about 0.5 inch. The device and permanent magnet are placed in an enclosure which is maintained at a high vacuum (typically 10 to the minus 7th power) into which a sample gas can be introduced. The ion beam end of the device is placed very close to an aperture through which an ion beam can exit into the apparatus for an experiment.

Anicich, V. G.↗
NASA NTRS1979

Electrostatic beneficiation of ores on the moon surface

The feasibility of the electrostatic beneficiation of lunar ores is studied. It is shown that the lunar environment with its sustained high vacuum, low temperature, and low acceleration of gravity, is suitable for the use of the electrostatic technique with magnetic as well as nonmagnetic ores. Only an initial coarse screening will be required prior to processing, as the lunar soil is already in fine particulate form. The low temperature and the absence of water suggest the use of tribo-electrification for the electric charging of lunar soils.

Inculet, I. I.↗
NASA NTRS1980

Radiometric observations of the 752.033-GHz rotational absorption line of H2O from a laboratory jet

With the aid of a high-resolution two-stage heterodyne radiometer, spectral absorption measurements of the 752.033 GHz line of water vapor were carried out, using a blackbody continuum as a background radiation source for investigating the absorptive properties of the H2O content of high altitude rocket plumes. To simulate this physical situation in a laboratory environment, a small steam jet was operated within a large high-vacuum chamber, with the H2O jet plume traversing the radiometer line of sight. The experiments verified that this rotational line is optically thick, with excitation temperatures below 100 K, in the downstream part of the plume, as predicted by theoretical modelling.

Dionne, G. F.↗
NASA NTRS1980

Structure and optical properties of evaporated films of the Cr- and V-group metals

Thin films of Cr, Mo, and W rapidly evaporated in high vacuum (5 x 10 to the -7th torr) onto room-temperature substrates show anomalously low reflectance (compared to bulk samples). From electron and X-ray diffraction and electron microscopy, the normal bcc crystal structure is found, but with very fine grains. Columnar grains about 100 A in diameter were separated by a less dense grain-boundary network about 10-A wide. The measured optical conductivity agrees with an inhomogeneous-medium model that assumes the normal crystalline conductivity for the grain interiors, with model parameters that correlate to the observed columnar grain size. In contrast, V and Nb films rapidly evaporated onto room-temperature substrates have the reflectance of bulk crystalline material. On liquid-nitrogen temperature substrates, however, V and Nb have normal bcc crystal structure but with small flat-plate grains, and the same model, with appropriate parameters, accounts for the optical conductivity. The difference between these two groups apparently depends on residual gases segregated at the grain boundaries in the Cr-group films.

Nestell, J. E., Jr.↗
NASA NTRS1981

Three-axis electron-beam test facility

An electron beam test facility, which consists of a precision multidimensional manipulator built into an ultra-high-vacuum bell jar, was designed, fabricated, and operated at Lewis Research Center. The position within the bell jar of a Faraday cup which samples current in the electron beam under test, is controlled by the manipulator. Three orthogonal axes of motion are controlled by stepping motors driven by digital indexers, and the positions are displayed on electronic totalizers. In the transverse directions, the limits of travel are approximately + or - 2.5 cm from the center with a precision of 2.54 micron (0.0001 in.); in the axial direction, approximately 15.0 cm of travel are permitted with an accuracy of 12.7 micron (0.0005 in.). In addition, two manually operated motions are provided, the pitch and yaw of the Faraday cup with respect to the electron beam can be adjusted to within a few degrees. The current is sensed by pulse transformers and the data are processed by a dual channel box car averager with a digital output. The beam tester can be operated manually or it can be programmed for automated operation. In the automated mode, the beam tester is controlled by a microcomputer (installed at the test site) which communicates with a minicomputer at the central computing facility. The data are recorded and later processed by computer to obtain the desired graphical presentations.

Dayton, J. A., Jr.↗
NASA NTRS1976

Review comments of shuttle-based cometary experiments

The experiments considered are in two groups: on-board experiments and overboard experiments. The on-board experiments include the determination of bulk properties and processes (within solids) and observations of exposure panels (near surface phenomena) The overboard experiments consist of analysis of gas/dust shells by observation from the shuttle and observation by sub-satellites. Experimental parameters are discussed with emphasis on work that is unique to low gravity and high vacuum environments.

Odell, C. R.↗
NASA NTRS1981

Materials processing in space: A survey of referred open literature publications

Over 190 reports published in the open literature by workers in the materials processing in space program are listed according to year as well as alphabetically by author. Thirty five reports submitted for publication are also cited. Supported either directly or indirectly by NASA, the research generally pertains to the influence (or lack of influence) of gravity on processes involved in crystal growth, solidification, fluid transport, containerless phenomena, and various separation techniques of interest to the biomedical community. Studies of the possibilities of using the high vacuum in the wake of orbiting vehicles for performing processes involving large heat loads and evolution of gases are also included.

Pentecost, E.↗
NASA NTRS1980

Property changes of a graphite/epoxy composite exposed to nonionizing space parameters

A study has been made of the changes in the mass, thickness and flexural properties of initially wet and dry specimens of graphite/epoxy composite material due to the equivalent of eight weeks of exposure to nonionizing space environmental parameters. The parameters were near and middle solar UV irradiance, high vacuum, and temperature. The flexural properties were not affected by the exposures. Changes occurred to the mass, dimensions, and surface morphology of the specimens which varied with individual and combined parameter exposures. The combined UV and elevated thermal environment had synergistic effects on the properties of the specimens.

Phelps, H. R.↗