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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 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Pulsed plasma thruster contamination studies

The exhaust plume of the one millipound pulsed plasma thruster has a measurable backflow upstream of the nozzle exit plane which may deposit on and degrade the performance of exposed spacecraft surfaces. High speed photographs and Faraday cup measurements suggest that this backflow is predominantly an electrically neutral, relatively low energy vapor. Articulated collimator quartz crystal microbalance measurements of this backflow were made for a thruster with a radically modified nozzle and a flat plate backflow shield, to determine the backflow sensitivity to nozzle design changes. The results are compared with the original nozzle backflow and show a measurable reduction in the backflow directly upstream of the shield.

Rudolph, L. K.↗
NASA NTRS1980

Hydrochloric acid aerosol and gaseous hydrogen chloride partitioning in a cloud contaminated by solid rocket exhaust

Partitioning of hydrogen chloride between hydrochloric acid aerosol and gaseous HCl in the lower atmosphere was experimentally investigated in a solid rocket exhaust cloud diluted with humid ambient air. Airborne measurements were obtained of gaseous HCl, total HCl, relative humidity and temperature to evaluate the conditions under which aerosol formation occurs in the troposphere in the presence of hygroscopic HCl vapor. Equilibrium predictions of HCl aerosol formation accurately predict the measured HCl partitioning over a range of total HCl concentrations from 0.6 to 16 ppm.

Sebacher, D. I.↗
NASA NTRS1981

Effect of chloride contamination in MON-1 propellant on crack growth properties of metals

The effect of a high level of chloride content (800 ppm) in MON-1 propellant on the crack growth properties of seven materials was investigated. Sustained load tests were conducted at 49 C (120 F) temperature with thin gauge tensile specimens having a semi-elliptical surface flaw. Alloys included aluminum 1100, 3003, 5086 and 6061; corrosion resistant steel types A286 and 347; and titanium 6Al-4V. The configurations tested with precracked flaws exposed to MON-1 were: parent or base metal, center weld, and heat affected zone. It was concluded that this chloride level in MON-1 does not affect the stress corrosion, crack growth properties of these alloys after 1000 hour exposure duration under high stresses.

Moran, C. M.↗
NASA NTRS1982

Contaminant characterization of five satellite materials

An extensive laboratory test program was performed to characterize outgassing of five satellite materials. The materials were Chemglaze Z-306 over 9922 primer, M-773 adhesive, multilayer insulation, polyurethane foam, and silverized Teflon. The souces were prepared to the specifications of a typical satellite program. Dynamic thermogravimetric mass loss characteristics of these five materials were obtained in vacuum with a beam microbalance. The temperature of the material was linearly raised from 25 C to over 650 C while monitoring the mass loss, rate of mass loss, temperature, and the composition of the outgassed material by residual gas analysis. Isothermal source emission/capture coefficients/reemission parameters were obtained with an array of quartz crystal microbalances (QCM). A detailed test matrix in which the temperatures of the QCMs (-160 C, - 100 C, -40 C, and +10 C) and the source material (125 C, and 90 C, and 50 C) were varied was performed. The array of QCMs was also used to measure the spatial distribution of the source emission. The effects of vacuum ultraviolet radiation on the deposition and reemission parameters was determined.

Muscari, J. A.↗
NASA NTRS1981

Columbia River volcanism - The question of mantle heterogeneity or crustal contamination

It is found that, although crystal fractionation played an important role in producing the chemical characteristics of Columbia River Province basalts displaying a wide range of chemical and isotopic compositions, the isotopic variability calls for the involvement of at least two isotopically distinct components. The major and trace element characteristics of the main volume of the basalts are not consistent with a metasomatized mantle source region, and the presence of a primordial mantel component is not supported by the chemical data. Models of simple binary mixing between a primary magma and Precambrian sialic crustal materials, while satisfying the observed Nd and Sr isotopic variations, fail to account for major trace element abundances. The combination of crustal assimilation and fractional crystalization is found to give a superior fit to the compositional data.

Carlson, R. W.↗
NASA NTRS1982

Thermocapillary flows and their stability: Effects of surface layers and contamination

The fluid mechanics and heat transfer of motions driven by surface tension gradients (Marangoni convection) were analyzed theoretically to obtain an understanding of the convection accompanying the process of growing high quality single crystals from the melt in a mu-g environment. The geometries considered include two dimensional liquid filled slots and axisymmetric float zone configurations.

Davis, S. H.↗
NASA NTRS1983

Test for contamination of MgF2 - coated mirrors

Graphs show preflight and postflight reflectivities in percent for exposed and covered mirrors carried on the OSS-1 payload pallet during STS-3. No changes greater than 1.8 sigma were observed except for a fingerprint. Weak evidence for degradation at 1216 A and 1600 A was found in several samples. There was no difference between flight mirrors and control mirrors. Covered samples suffered more than samples exposed to the Sun, but the differences are barely significant. The exposed side of the flight mirrors were somewhat dusty. No evidence was found for permanent solar-induced or shuttle-induced deterioration. There also was no evidence on oil-pumped vacuum versus oil-free vacuum during coating.

Bunner, A. N.↗
NASA NTRS1983

Shuttle measured contaminant environment and modeling for payloads. Preliminary assessment of the space telescope environment in the shuttle bay

A baseline gaseous and particulate environment of the Shuttle bay was developed based on the various measurements which were made during the first four flights of the Shuttle. The environment is described by the time dependent pressure, density, scattered molecular fluxes, the column densities and including the transient effects of water dumps, engine firings and opening and closing of the bay doors. The particulate conditions in the ambient and on surfaces were predicted as a function of the mission time based on the available data. This basic Shuttle environment when combined with the outgassing and the particulate contributions of the payloads, can provide a description of the environment of a payload in the Shuttle bay. As an example of this application, the environment of the Space Telescope in the bay, which may be representative of the environment of several payloads, was derived. Among the many findings obtained in the process of modeling the environment, one is that the payloads environment in the bay is not substantially different or more objectionable than the self-generated environment of a large payload or spacecraft. It is, however, more severe during ground facilities operations, the first 15 to 20 hours of the flight, during and for a short period after ater was dumped overboard, and the reaction control engines are being fired.

Scialdone, J. J.↗
NASA NTRS1984

Contamination control and cleanliness level integrity for the Space Shuttle Orbiter PLB, payloads and facilities at KSC

The PLB, its cargo, and payload canister must satisfy the cleanliness requirements of visual clean (VC) level 1, 2, 3, or special as stated in NASA document SN-C-0005A. The specific level of cleanliness is chosen by the payload bay customer for their mission. During orbiter turnaround processing at KSC, the payload bay is exposed to the environments of the Orbiter Processing Facility (OPF) and the Payload Changeout Room (PCR). In supportive response to the orbiter payload bay/facility interface, it is necessary that the facility environment be controlled and monitored to protect the cleanliness/environmental integrity of the payload bay and its cargo. Techniques used to meet environmental requirements during orbiter processing are introduced.

Bartelson, D.↗
NASA NTRS1983

Wing contamination - Threat to safe flight

Attention is given to the initial results of systematic investigations of the potentially hazardous effect of heavy rain, ice, and frost accretion on aircraft wings. In the laminar region of an airfoil, roughness interferes with smooth flow and tends to encourage transition from laminar to turbulent flow upstream of its normal point of occurrence. In the airfoil's turbulent region, roughness considerably worsens the turbulent friction coefficient, thereby increasing the drag coefficient. Consequent dramatic decreases of maximum lift coefficient at high angles of attack lead to premature stall. Such decreases in stall angle destroy the safety margin of an aircraft approaching stall. An assessment is given to the state of knowledge in this field of research.

Luers, J. K.↗
NASA NTRS1984

The effect of surface contamination on thermocapillary flow in a two-dimensional slot

In an analysis of the effect of insoluble surfactants on the steady capillary flow in a shallow slot, the problem is formulated as a two-dimensional channel heated differentially from the side, with a free surface on which an insoluble surface species is adsorbed. The vertical boundaries are considered to be isothermal and impenetrable and the lower horizontal boundary to be insulated and impenetrable. Lubrication theory and matched asymptotic expansions are used to reduce the problem to a single nonlinear integral-algebraic equation. For small elasticity E, the surface velocity is nearly constant, with the result that, for small Pe, the surface concentration is nearly uniform while, for large Pe, it develops a boundary layer near the stagnation point at the cold wall, resulting in high local surface concentrations. Condensed surfactant layers will form only with E much less than one and Pe much greater than one.

Homsy, G. M.↗
NASA NTRS1983

Induced environment contamination monitor (IECM) cascade impactor

The Cascade Impactor on the IECM is an aerosol sampling instrument which employs three cascade impaction-type nozzles of progressively smaller diameter. The considered approach makes it possible to achieve particle size discrimination involving three ranges (5 microns and larger, 1 to 5 microns, and 0.3 to 1 micron). In addition to the particulate measuring cascade stages, a fourth quartz crystal microbalance measures the cumulative airborne molecular nonvolatile residue (NVR) at ambient temperature. The cascade measurements provide a temporal record of the payload bay's particulate environment during ascent, descent, and immediate postlanding periods. The NVR stage functions throughout the mission. Particulates of a size greater than five microns in diameter were below 10 micrograms per cu m throughout the mission.

Duncan, B. J.↗
NASA NTRS1984

A method for measuring skin friction drag on a flat plate in contaminated gas flows

A technique for measuring friction drag in turbulent gas and gas/particle flows over flat plates is presented, and preliminary results are reported. A 0.25-in.-thick 72 x 6-in. Al plate is suspended by six horizontal support air bearings and four vertical alignment air bearings between fixed dummy plates and leading-edge and trailing-edge fairings in the 32-in.-high 48-in.-wide 11-ft-long test section of a closed-circuit atmospheric wind tunnel operating at 50-150 ft/sec. Particles of Fe and Al oxides of diameter 20-150 microns and density up to 0.3 lb particles per lb air are injected via a 6 x 0.167-in. nozzle; turbulence is induced by a roughened section of the leading-edge fairing; and friction drag is measured using a load-cell pressure transducer. Sample results are shown in a graph, demonstrating good agreement with theoretical drag calculations.

Oetting, R. B.↗

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