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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Contamination assessment and control in scientific satellites

Techniques for assessment and control of the contamination environment for both particulates and condensible vapors in the vicinity of spacecraft are developed. An analysis of the deposition rate on critical surfaces is made considering sources within the line of sight of the surface in question as well as those obscured from the line of sight. The amount of contamination returned by collision with the surrounding atmosphere is estimated. Scattering and absorption from the induced atmosphere of gases and particulates around the spacecraft are estimated. Finally, design techniques developed for Skylab to reduce the contamination environment to an acceptable level are discussed.

Naumann, R. J.↗
NASA NTRS1972

Contamination damage avoidance concepts for propulsion feed system components.

The potential gain in the reliability of reusable long-term mission vehicles through the minimization of component damage due to the ingestion of particulate contamination by feed system components has been recognized by the NASA-LeRC and MDAC, and a program to investigate these problems has been completed. This investigation covered the determination of the cycle life of a typical 2-in. poppet type of shutoff valve in an uncontaminated GH2 environment and then compared this component performance with simulated operation with GN2 and LN2 containing controlled amounts of AL2O2 contaminant particles. The original valve design was tested for contamination damage tolerance characteristics under full flow and cyclic operating conditions, redesigned to improve the damage tolerance to contaminants and then retested. A second method of approach to damage tolerance control was investigated through the evaluation of various types of particulate separation devices. The study included various types of dynamic separators but did not cover conventional filter assemblies.

Endicott, D. L.↗
NASA NTRS1973

Reactions of singlet oxygen with pine pollen.

A study was initiated to determine whether viable atmospheric particles such as plant pollens and fungal spores containing unsaturated lipids can interact with singlet oxygen to give oxygenated products that are potentially toxic. The results obtained confirm that surface and near surface components of common viable particulate matter in the atmosphere may be subject to rapid oxidation by singlet oxygen, leading to products which are probably allylic hydroperoxides. In connection with increasing atmospheric pollution, it is important to note that materials toxic to mammalian lung tissue may be oxidatively produced on the surfaces of viable particulate matter.

Dowty, B.↗
NASA NTRS1973

Ablation debris and primary micrometeoroids in the stratosphere.

Analysis of micrometer-sized stratospheric particulates suggests that the majority of extraterrestrial material in the atmosphere is the product of ablation of larger bodies. Ablation debris is of considerable interest because of the possibility that much of it may have originated from classes of easily fragmented meteoroids that are incapable of surviving atmospheric entry to become meteorites. Comparison is made between the elemental abundance patterns found in stratospheric particulates and that found in fusion crusts of primitive meteorite types. Also discussed are criteria for distinguishing ablation products from primary unablated micrometeoroids.

Brownlee, D. E.↗
NASA NTRS1972

Correcting airborne scanning infrared radiometer measurements for atmospheric effects

Two techniques were developed for determining atmospheric corrections from observations made by a scanning radiometer. Both techniques depend on knowing the radiometer's limb function. The limb function for an RS-18 scanning radiometer is derived from calculations made with a radiation model and used to demonstrate the techniques. One technique requires observations made over an isothermal water surface within the area being remotely sensed. The other technique does not depend on an isothermal water surface but requires a boat measurement of radiometric sea surface temperature within the area being remotely sensed. The radiation model used to derive the limb function does not account for the effects of atmospheric particulates on the correction. It is hypothesized that the effect of particulates on the limb function derived in this study is negligible, and therefore the technique essentially obtains the total correction. The techniques developed can be used over land provided that a section of isothermal land exists within the experiment area or that a radiometric measurement of surface temperature is made at the surface.

Boudreau, R. D.↗
NASA NTRS1973

Chemistry of the lower atmosphere

The presence of particulate matter in the lower atmosphere is considered, giving attention to the sources of particles in the troposphere, the composition of particles collected from the atmosphere, aspects of particle concentrations and size distributions, mechanisms of removal, residence times, and conditions in the lower stratosphere. The role of natural and anthropogenic pollutants in cloud and precipitation formation is discussed together with removal processes of gaseous and particulate pollutants, and the global sulfur cycle. Other topics examined include the chemical basis for climatic change and the carbon dioxide cycle. Individual items are announced in this issue.

Rasool, S. I.↗
NASA NTRS1974

UCLA International Conference on Radiation and Remote Probing of the Atmosphere, University of California, Los Angeles, Calif., August 28-30, 1973, Proceedings

Approaches for solving multiple scattering problems in planetary atmospheres are considered along with the solution of the radiative transfer theory problems by the Monte Carlo method, the radiative transfer of visible radiation in turbid atmospheres, aspects of scattering and absorption from poly-dispersed aerosols, and multiple scattering in cloud layers. Other subjects discussed include particulate sizes from polarization measurements, lidar observations of atmospheric particulate content, methods of calculating infrared transfer, molecular absorption parameters in atmospheric modelling, and infrared remote sounding. The influence of the atmosphere on spectral radiance and contrasts of natural formations measured from space is investigated and analytical results for radiative transfer in thick atmospheres are presented. Individual items are announced in this issue.

Kuriyan, J. G.↗
NASA NTRS1974

Simultaneous Raman and laser velocimeter measurements

The feasibility of performing Raman and laser velocimeter measurements simultaneously is demonstrated, and it is shown that the background radiation associated with the Mie scattering and large particulate concentrations does not saturate or distort the relatively weak rotational Raman signals. Under stringent conditions of low static gas densities and large particulate concentrations, Raman density and temperature measurements agree to within plus or minus 5% of the calculated values.

Hillard, M. E., Jr.↗
NASA NTRS1974

Shuttle filter study. Volume 1: Characterization and optimization of filtration devices

A program to develop a new technology base for filtration equipment and comprehensive fluid particulate contamination management techniques was conducted. The study has application to the systems used in the space shuttle and space station projects. The scope of the program is as follows: (1) characterization and optimization of filtration devices, (2) characterization of contaminant generation and contaminant sensitivity at the component level, and (3) development of a comprehensive particulate contamination management plane for space shuttle fluid systems.

Source record↗
NASA NTRS1975

Effluent sampling of Titan 3 C vehicle exhaust

Downwind in situ ground-level measurements of the exhaust from a Titan 3 C launch vehicle were made during a normal launch. The measurement activity was conducted as part of an overall program to obtain field data for comparison with the multilayer dispersion model currently being used to predict the behavior of rocket vehicle exhaust clouds. All measurements were confined to land, ranging from the launch pad to approximately 2 kilometers downwind from the pad. Measurement systems included detectors for hydrogen chloride (HCl), carbon dioxide (CO2), and particulates (Al2O3). Airborne and ground-based optical systems were employed to monitor exhaust cloud rise, growth, and movement. These measurement systems, located along the ground track (45 deg azimuth from the launch pad) of the exhaust cloud, showed no effluents attributable to the launch. Some hydrogen chloride and aluminum oxide were detected in the surface wind direction (15 deg azimuth) from the pad. Comparisons with the model were made in three areas: (1) assumption of cloud geometry at stabilization; (2) prediction of cloud stabilization altitude; and (3) prediction of the path of cloud travel. In addition, the importance of elemental analyses of the particulate samples is illustrated.

Gregory, G. L.↗
NASA NTRS1975

An automated atmospheric sampling system operating on 747 airliners

An air sampling system that automatically measures the temporal and spatial distribution of selected particulate and gaseous constituents of the atmosphere has been installed on a number of commercial airliners and is collecting data on commercial air routes covering the world. Measurements of constituents related to aircraft engine emissions and other pollutants are made in the upper troposphere and lower stratosphere (6 to 12 km) in support of the Global Air Sampling Program (GASP). Aircraft operated by different airlines sample air at latitudes from the Arctic to Australia. This system includes specialized instrumentation for measuring carbon monoxide, ozone, water vapor, and particulates, a special air inlet probe for sampling outside air, a computerized automatic control, and a data acquisition system. Air constituents and related flight data are tape recorded in flight for later computer processing on the ground.

Perkins, P.↗
NASA NTRS1975

Results of examination of the nasal mucosa

The olfactory epithelium, but not the nasal respiratory epithelium, of the four pocket mice (Perognathus longimembris) that survived their flight on Apollo XVII showed both diffuse alterations and numerous disseminated focal lesions. The olfactory mucosa of the mouse that died during flight was also affected, but to a minor degree insofar as could be determined. All this was in contrast to the normal appearance of the olfactory mucosa of the numerous control animals. A number of possible causes were considered: systemic or regional infection; inhaled particulate material (seed dust); by-products from the KO2 bed in aerosol or particulate form; gas contaminants originating in the flight package; volatile substances from the dead mouse; weightlessness; and cosmic ray particle radiation. Where feasible, studies were conducted in an effort to rule in or rule out some of these potentially causative factors. No definitive conclusions were reached as to the cause of the lesions in the flight mice.

Kraft, L. M.↗
NASA NTRS1975

Computed atmospheric corrections for satellite data

The corrections are presented for the visible and near infrared spectrum. The specifications of earth-atmosphere models are given. Herman's and Dave's methods of computing the four Stokes parameters are presented. The relative differences between the two sets of values are one percent. The absolute accuracy of the computations can be established only by comparisons with measured data. Suitable observations do not yet exist. Nevertheless, comparisons are made between computed and aircraft and satellite measured radiances. Particulates are the principal atmospheric variable in the window bands. They have a large effect on the radiances when the surface reflectivity is low. When the surface reflectivity exceeds 0.1, only absorbing particulates have a large effect on the reflectivity, unless the atmospheric turbidity is high. The ranges of the Multispectral Scanner responses to atmospheric effects are computed.

Fraser, R. S.↗
NASA NTRS1975

Spacecraft recontamination

A computer simulation program to model the redistribution of particulate contaminants on a spacecraft after launch was developed. The component models for particulate adhesion, meteoroid impact, and electrostatic forces are described and intermediate results are presented. The results of a sample calculation show that the recontamination process is important.

Barengoltz, J.↗
NASA NTRS1976

Method and apparatus for fluffing, separating, and cleaning fibers

A perforated tube is housed in a chamber in which vacuum is drawn. An air jet is directed into one end of the tube and fiber bundles are fed into the jet which separates and dispenses individual fibers from the bundle, fluffs them, cleanses them of any particulate material, and carries them into the tube. The tube retains the fibers while fiber fragments, undesirably short fibers and particulate matter are drawn by the vacuum and resultant air flow out of the tube through its perforations to a suitable discharge.

Padilla, D.↗
NASA NTRS1976

Laser Doppler systems in pollution monitoring

The paper reports on a program undertaken to determine the feasibility of using a laser Doppler velocimeter (LDV) to measure smoke-stack gas exit velocity, particulate concentration, and mass flow. Measurements made with a CO2 laser Doppler radar system at a coal-burning power plant are compared with in-stack measurements made by a pitot tube. The operational principles of a LDV are briefly described along with the system employed in the present study. Data discussed include typical Doppler spectra from smoke-stack effluents at various laser elevation angles, the measured velocity profile across the stack exit, and the LDV-measured exit velocity as a function of the exit velocity measured by the in-stack instrument. The in-stack velocity is found to be about 14% higher than the LDV velocity, but this discrepancy is regarded as a systematic error. In general, linear relationships are observed between the laser data, the exit velocity, and the particulate concentration. It is concluded that an LDV has the capability of determining both the mass concentration and the mass flow from a power-plant smoke stack.

Miller, C. R.↗
NASA NTRS1976

Satellite measurement of mass of Sahara dust in the atmosphere

Landsat 1 measurements of nadir radiance are used to obtain the mass of particulates in a vertical column of dust from the Sahara Desert. A radiative transfer model, constructed with knowledge of a few values of optical parameters measured from a ship, is developed to account for the measured radiance values. Measurement and model accuracies are discussed. It is found that the mass of particulates with smaller than a 10 micron radius in a vertical column is 1.6 g/sq m.

Fraser, R. S.↗
NASA NTRS1977

Development of a microbalance suitable for space application

The tapered element oscillating microbalance (TEOM), an ultrasensitive mass measurement device which is suitable for both particulate and vapor deposition measurements is described. The device can be used in contamination measurements, surface reaction studies, particulate monitoring systems or any microweighing activity where either laboratory or field monitoring capability is desired. The active element of the TEOM consists of a tube or reed constructed of a material with high mechanical quality factor and having a special taper. The element is firmly mounted at the wide end while the other end supports a substrate surface which can be composed of virtually any material. The tapered element with the substrate at the free (narrow) end is set into oscillation in a clamped free mode. A feedback system maintains the oscillation whose natural frequency will change in relation to the mass deposited on the substrate.

Patashnick, H.↗