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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 811 records · Page 45

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NASA NTRS1975

Test evaluation of potential heatshield contamination of an outer planet probe's gas sampling system

The feasibility of retaining the heat shield for outer planet probes was investigated as a potential source of atmospheric sample contamination by outgassing. The onboard instruments which are affected by the concept are the pressure sensor, temperature sensor, IR detector, nephelometer, and gas sampling instruments. It was found that: (1) The retention of the charred heatshield and the baseline atmospheric sampling concepts are compatible with obtaining noncontaminated atmospheric samples. (2) Increasing the sampling tube length so that it extends beyond the viscous boundary layer eliminates contamination of the atmospheric sample. (3) The potential for contamination increases with angle of attack.

Kessler, W. C.↗

NASA NTRS1975

Analytical study of spacecraft deposition contamination by internal reflection spectroscopy

The in-situ vacuum chamber designed around the IRE was tested under vacuum. The contamination analyzer system was tested using two liquid contaminant materials. The analysis of the contaminants on the SL-4 rendezvous window shows that the material has methyl silicone, hydroxyl, and carbonyl radicals. The analysis of the outgassing material from Shuttle TPS shows silicone as the primary product.

Mookherji, T. K.↗

NASA NTRS1975

Evaluation and study of advanced optical contamination, deposition, measurement, and removal techniques

A program is described to design, fabricate and install an experimental work chamber assembly (WCA) to provide a wide range of experimental capability. The WCA incorporates several techniques for studying the kinetics of contaminant films and their effect on optical surfaces. It incorporates the capability for depositing both optical and contaminant films on temperature-controlled samples, and for in-situ measurements of the vacuum ultraviolet reflectance. Ellipsometer optics are mounted on the chamber for film thickness determinations, and other features include access ports for radiation sources and instrumentation. Several supporting studies were conducted to define specific chamber requirements, to determine the sensitivity of the measurement techniques to be incorporated in the chamber, and to establish procedures for handling samples prior to their installation in the chamber. A bibliography and literature survey of contamination-related articles is included.

Linford, R. M. F.↗

NASA NTRS1975

Value contamination avoidance devices

Mechanical redesign methods were used to minimize contamination damage of conventional fluid components and a contamination separator device was developed for long term reusable space vehicles. These were incorporated into an existing 50.8 mm poppet valve and tested for damage tolerance in a full size open loop flow system with gaseous and liquid nitrogen. Cyclic and steady flow conditions were tested with particles of 125 to 420 micrometers aluminum oxide dispersed in the test fluids. Nonflow life tests (100,000 cycles) were made with two valve configurations in gaseous hydrogen. The redesigned valve had an acceptable cycle life and improved tolerance to contamination damage when the primary sealing surfaces were coated with thin coatings of hard plastic (Teflon S and Kynar). Analytical studies and flow testing were completed of four different versions of the separator. overall separation efficiencies in the 55-90% range were measured with these non-optimum configurations.

Endicott, D. L.↗

NASA NTRS1975

Contamination control in hybrid microelectronic modules. Part 3: Specifications for coating material and process controls

Resin systems for coating hybrids prior to hermetic sealing are described. The resin systems are a flexible silicone junction resin system and a flexible cycloaliphatic epoxy resin system. The coatings are intended for application to the hybrid after all the chips have been assembled and wire bonded, but prior to hermetic sealing of the package. The purpose of the coating is to control particulate contamination by immobilizing particles and by passivating the hybrid. Recommended process controls for the purpose of minimizing contamination in hybrid microcircuit packages are given. Emphasis is placed on those critical hybrid processing steps in which contamination is most likely to occur.

Himmel, R. P.↗

NASA NTRS1976

Molecular contamination study by interaction of a molecular beam with a platinum surface

The capability of molecular beam scattering from a solid surface is analyzed for identification of molecular contamination of the surface. The design and setup of the molecular beam source and the measuring setup for the application of a phase sensitive measuring technique for the determination of the scattered beam intensity are described. The scattering distributions of helium and nitrogen molecular beams interacting with a platinum surface were measured for different amounts of contamination from diffusion pump oil for surface temperatures ranging from 30 to 400 C. The results indicate the scattering of molecular beams from a platinum surface is a very sensitive method for detecting surface contamination.

Nuss, H. E.↗

NASA NTRS1976

Optimization of contaminated oxide inversion layer solar cell

Contaminated oxide cells have been fabricated with efficiencies of 8.6% with values of I sub sc = 120 ma, V sub oc = .54 volts, and curve factor of .73. Attempts to optimize the fabrication step to yield a higher output have not been successful. The fundamental limitation is the inadequate antireflection coating afforded by the silicon dioxide coating used to hold the contaminating ions. Coatings of SiO, therefore, were used to obtain a good antireflection coating, but the thinness of the coatings prevented a large concentration of the contaminating ions, and the cells was weak. Data of the best cell were .52 volts V sub oc, 110 ma I sub sc, .66 CFF and 6.7% efficiency.

Call, R. L.↗

NASA NTRS1976

Preliminary study of contaminant particulates around Skylab

Techniques originally developed for the Skylab T025 contamination experiment were applied to S052 white-light coronagraph data in a preliminary study to investigate particulates around Skylab. Periods were selected which contained some contamination, even though there were no apparent dumps or vents during these periods. Velocity and size distributions were determined from optical data for particles within 200 meters of the spacecraft. Both photographic (61 particle tracks) and video (34 particles) observations yield an upper limit on particle radius of 100 micrometers. Selected photometric data from the S073 zodiacal light experiment during mission SL-2 were also examined for evidence of contamination.

Schuerman, D. W.↗

NASA NTRS1977

Monopropellant thruster exhaust plume contamination measurements

The potential spacecraft contaminants in the exhaust plume of a 0.89N monopropellant hydrazine thruster were measured in an ultrahigh quartz crystal microbalances located at angles of approximately 0 deg, + 15 deg and + or - 30 deg with respect to the nozzle centerline. The crystal temperatures were controlled such that the mass adhering to the crystal surface at temperatures of from 106 K to 256 K could be measured. Thruster duty cycles of 25 ms on/5 seconds off, 100 ms on/10 seconds off, and 200 ms on/20 seconds off were investigated. The change in contaminant production with thruster life was assessed by subjecting the thruster to a 100,000 pulse aging sequence and comparing the before and after contaminant deposition rates. The results of these tests are summarized, conclusions drawn, and recommendations given.

Baerwald, R. K.↗

NASA NTRS1978

NASA charging analyzer program: A computer tool that can evaluate electrostatic contamination

A computer code, the NASA Charging Analyzer Program (NASCAP), was developed to study the surface charging of bodies subjected to geomagnetic substorm conditions. This program will treat the material properties of a surface in a self-consistent manner and calculate the electric fields in space due to the surface charge. Trajectories of charged particles in this electric field can be computed to determine if these particles enhance surface contamination. A preliminary model of the Spacecraft Charging At The High Altitudes (SCATHA) satellite was developed in the NASCAP code and subjected to a geomagnetic substorm environment to investigate the possibility of electrostatic contamination. The results indicate that differential voltages will exist between the spacecraft ground surfaces and the insulator surfaces. The electric fields from this differential charging can enhance the contamination of spacecraft surfaces.

Stevens, N. J.↗

NASA NTRS1978

Effect of filtration on rolling-element-bearing life in contaminated lubricant environment

Fatigue tests were conducted on groups of 65 millimeter-bore ball bearings under four levels of filtration with and without a contaminated MIL-L-23699 lubricant. The baseline series used noncontaminated oil with 49 micron absolute filtration. In the remaining tests contaminants of the composition found in aircraft engine filters were injected into the filter's supply line at a constant rate of 125 milligrams per bearing-hour. The test filters had absolute particle removal ratings of 3, 30, 49, and 105 microns (0.45, 10, 30, and 70 microns nominal), respectively. Bearings were tested at 15,000 rpm under 4580 newtons radial load. Bearing life and running tract condition generally improved with finer filtration. The 3 and 30 micron filter bearings in a contaminated lubricant had statistically equivalent lives, approaching those from the baseline tests. The experimental lives of 49 micron bearings were approximately half the baseline bearing's lives. Bearings tested with the 105 micron filter experienced wear failures. The degree of surface distress, weight loss, and probable failure mode were found to be dependent on filtration level, with finer filtration being clearly beneficial.

Loewenthal, S. H.↗

NASA NTRS1978

Electric discharge for treatment of trace contaminants

A radio frequency glow discharge reactor is described for removing trace oxidizable contaminants from an oxygen bearing atmosphere. The reaction chamber is defined by an inner metal electrode facing a dielectric backed by an outer conductive electrode. In one embodiment, a conductive liquid forms the conductor of an outer electrode and cools the dielectric. A resonator coupled to a variable radio frequency source generates the high voltages for creating a glow discharge in the chamber at a predetermined pressure whereby the trace contaminants are oxidized into a few simple non-toxic products that may be easily recovered. The corresponding process for removal of trace contaminants from an oxygen-bearing atmosphere with high efficiency independent of the concentration level is also disclosed.

Flamm, D. L.↗

NASA NTRS1978

Experimental investigation of contamination prevention techniques for a cryogenically cooled telescope in earth-orbit

A one-tenth scale model of the Shuttle Infrared Telescope Facility (SIRTF) was constructed to experimentally investigate the feasibility of a helium purge system to reduce contamination on cryogenic surfaces. The on-orbit ambient contaminant environment was simulated with ion beams of N2(+), O(+) and H2O(+). Helium was injected into the model telescope at the simulated plane of the primary optics using two techniques: a) porous plug, b) nozzle. Helium flow rates and telescope pressures were varied to determine the purge effectiveness against potential contaminants. Based on the subscale results, a 90% reduction in O, N2, and H2O at the primary optics of the SIRTF can be obtained using 20 K helium with a pressure of .00001 torr and a flow rate of less than 0.1 g/s.

Hetrick, M. A.↗

NASA NTRS1979

Assessment of shuttle payloads gaseous environment contamination and its control

A prediction is given of the in-orbit gaseous environment and the contamination it could produce on cryogenic and room temperature surfaces of payloads in the shuttle bay. The time varying environment was obtained by the superposition of the calculated shuttle environment for a discrete time and payload induced environments measured in large space chambers. Representative contaminant surface accretions were calculated for flights 1 week and 1 month long for payloads having the largest source of outgassing and an orbit of 200 km. A number of calculations were based on the magnitude of the sources, the molecular natures, the decay rate with time, the sticking coefficients, the view factors, and the temperatures of the surfaces being contaminated. Significant results are reported.

Scialdone, J. J.↗

NASA NTRS1979

Design and development of a trace contaminant removal canister for Spacelab

The paper describes the overall approach used by NASA-MSFC to design and develop a trace contaminant removal canister for Spacelab. The elements of this approach include the establishment of a trace contaminant load model, analysis and testing to define a preliminary design, development testing to verify the adequacy of the selected design, and testing to define a suitable canister location in the transfer tunnel ventilation system. The canister utilizes a catalyst material which is effective in removing carbon monoxide at room temperature, as well as plain and acid treated charcoal. The canister alone will control all contaminants in the load model below their maximum allowable concentration (MAC) levels without assistance from the baseline environmental control system (ECS) except for methyl alcohol and ammonia.

Ray, C. D.↗

NASA NTRS1980

IUS solid rocket motor contamination prediction methods

A series of computer codes were developed to predict solid rocket motor produced contamination to spacecraft sensitive surfaces. Subscale and flight test data have confirmed some of the analytical results. Application of the analysis tools to a typical spacecraft has provided early identification of potential spacecraft contamination problems and provided insight into their solution; e.g., flight plan modifications, plume or outgassing shields and/or contamination covers.

Mullen, C. R.↗

NASA NTRS1979

Contamination control in hybrid microcircuit modules

The influence of chemical and particulate contamination upon the reliability and service life of hybrid microelectronic systems is documented. Several coating systems used include the parylene and Dow Corning silicone (DC90-711). These passivating coatings have potential for decreasing the degradation caused by particulate contaminants in hybrid systems as well as the possible deleterious effect of trapping chemical contaminants which have long term degrading influences upon the performance of the system. The reliability of a representative hybrid microcircuit is enhanced by the coating process.

Kinser, D. L.↗

NASA NTRS1982

Space Shuttle preliminary. Contamination assessment from STS-1 and STS-2

A preliminary assessment of the space shuttle contamination environment was made using data from the first two orbital flight tests, STS-1 and STS-2. Data sources consisted of crew observations during flight, postflight vehicle inspection, and the induced environment contamination monitor which was used on STS-2 and consists of 10 instruments. These instruments are used to measure gas phase contaminants, particle population, humidity, and molecular deposition in the orbiter payload bay during ascent and descent and particle population, molecular deposition, and gas cloud during orbital flight. Results of the measurements described are presented in summary form and indicate low molecular deposition rates for both pressurized and orbital flight.

Leger, L. J.↗