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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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NASA NTRS1985

CU in space: The University of Colorado get away special payload G-285

The University of Colorado's first Get Away Special was conceived by a dozen science and engineering students in the spring of 1984. Since that time, the project has grown to include over 100 undergraduate and graduate students who have 'provided the experimental objectives, design, construction, integration, testing and management of the payload. Faculty and staff of the university and its affiliated laboratories as well as engineers from local industries have provided many useful suggestions at all stages of development. The principal motivation for developing this payload is to provide university students with the opportunity to participate in space science and engineering beginning at the ground level. At the same time, they are contributing their results from new science and technological discoveries to several disciplines. There are four separate experiments integrated into the /'single payload of G-285 which are supported by internal payload !power, thermal environment control, command land data handling [ facilities and structural subsystems. The four experiments contained in this payload are: a single spectrometer performing i two experiments- one to study night time shuttle glow phenomena in the ultraviolet and the other to observe NO2 concentrations over / equatorial latitudes in the day; a fluids management experiment ' using centrifugation for particle/liquid/vapor separation; and an experiment using Phycomyces fungi to study the gravireceptor mechanism theory. The experiments are supported by a microprocessor, data storage devices, power and thermal control subsystems. All these are located within a sealed aluminum container. The container, a refitted sounding rocket casing, has a top and bottom which bolt to the main body of the rocket section. The top section holds a five inch diameter quartz window through which light enters the spectrometer. A rotating mirror assembly and one of two battery boxes are mounted on the outside of the top section below the interface plane of the MDA. A second battery box is attached to the bottom section of the sealed container. All payload items except the battery boxes and mirror assembly are located inside the sealed rocket section to insure containment and to prevent outgassing of materials. The container will be sealed prior to launch and purged with one atmosphere of argon.

Kent Tobiska↗
NASA NTRS1985

Measurements of concentrations of chlorofluoromethanes (CFMs) carbon dioxide and carbon isotope ratio in stratospheric and tropospheric air by grab-sampling systems

Measurements of concentrations of chlorofluoromethanes (CFMs), carbon dioxide and carbon isotope ratio in stratospheric and tropospheric air by grab-sampling systems are reported. The balloon-borne grab-sampling system has been launched from Sanriku Balloon Center three times since 1981. It consists of: (1) six sampling cylinders, (2) eight motor driven values, (3) control and monitor circuits, and (4) pressurized housing. Particular consideration is paid to the problem of contamination. Strict requirements are placed on the choice of materials and components, construction methods, cleaning techniques, vacuum integrity, and sampling procedures. An aluminum pressurized housing and a 4-m long inlet line are employed to prevent the sampling air from contamination by outgassing of sampling and control devices. The sampling is performed during the descent of the system. Vertical profiles of mixing ratios of CF2Cl2, CFCl3 and CH4 are given. Mixing ratios of CF2Cl2 and CFCl3 in the stratosphere do not show the discernible effect of the increase of those in the ground level background, and decrease with altitude. Decreasing rate of CFCl3 is larger than that of CF2Cl2. CH4 mixing ratio, on the other hand, shows diffusive equilibrium, as the photodissociation cross section of CH4 is small and concentrations of OH radical and 0(sup I D) are low.

Itoh, T.↗
NASA NTRS1986

The composition of lunar noble gases traped 2.5 AE and 3.5 AE ago

The times when the soils 74001 and 73261 were exposed on the lunar surface were determined by the U-235 - Xe-136 dating method. The isotopic composition of the trapped noble gases in these two soils is compared with that of the surface correlated noble gases in the young soils 12001 and in the present day solar wind. The surface correlated trapped gases are a mixture of implanted solar wind particles and retrapped lunar atmospheric gases. The observed changes are interpreted as a result of decreasing outgassing of radiogenic Ar-40 and perhaps He-4 and of fissiogenic Xe from the lunar crust. The old soils probably also contain surface correlated Kr-80 and Kr-82 produced by secondary cosmic ray neutron capture of adsorbed or retrapped bromine. To some extent the isotopic composition of the trapped gases in old lunar soil may also have been altered due to diffusion loss from material of low retentivity.

Eugster, O.↗
NASA NTRS1985

Hidden carbon dioxide on Mars

A recent proposal that much of the outgassed CO2 on Mars is tied up in the planet's crust in the form of carbonate mineral is discussed. According to this hypothesis, carbonate formation on Mars continued after open bodies of liquid water became unstable. A consequence of the hypothesis is that, in the absence of a recycling mechanism for CO2, the surface pressure on Mars will monotonically decrease until it reaches the minimum atmospheric overburden pressure required for liquid water to form. The theory explains Mars' low surface pressure, and also implies that the climate of Mars has evolved linearly over geologic time, rather than cyclically.

Haberle, R. M.↗
NASA NTRS1985

Radiation thresholds for synthetic elastomers

Synthetic elastomeric materials, when used in systems that must operate in radiation fields, frequently comprise the weakest link for materials. The results of a comprehensive tabulation of mechanical response data are summarized in graphical form useful to designers. General information on elastomers is given along with electrical, outgassing and thermal response data.

Bouquet, F. L.↗
NASA NTRS1986

Effects of the law for nongravitational forces on the precession model of comet Encke

The precession model for P/Encke formulated by Whipple and Sekanina (1979) is reexamined in the light of the recent measurements of the OH and H production rates. An optimized precession solution derived using the production law of A'Hearn et al. (1985) is shown to require unacceptably small nucleus dimensions and to offer an inferior fit to observed variations in the orientation of the comet's perihelion fan-shaped coma. Observed changes in the emission fan suggest that both the thrust on the nucleus exerted by unit mass of sublimating ice and the average lag in outgassing are substantially greater before than after perihelion. It is concluded that at this time the Whipple-Sekanina model remains the best available precession solution for this comet.

Sekanina, Z.↗
NASA NTRS1986

Improvements in the Goddard balloon-borne lidar

The Goddard balloon-borne lidar system for the measurement of stratospheric ozone and the hydroxyl radical has made three additional flights since the last laser radar conference. On September 27, 1984, a flight was made from Palestine, Texas obtaining a measurement of hydroxyl diurnal variation at 36 km. These data are presented on the plot which shows hydroxyl concentration as a function of GMT for the range cell closest to the instrument. Local noon corresponds to 18 hours on the plot. The rapid drop in concentration after noon is not predicted by models of stratospheric chemistry. It may represent the effects of contamination of the sample volume by hydrocarbons outgassed from the balloon. The more recent flights on June 30, 1985, and December 6, 1985, focussed on measurements of concentration in the lower stratosphere (less than 30 km). The June flight succeeded in obtaining an average concentration measurement (1.8 + or - 0.0000018 molecules/cubic cm) over the altitude range 21 to 26 km. The December flight obtained measurements down to 24 km with a better signal-to-noise ratio than that obtained in June. Prospects for further improvement in sensitivity and absolute calibration will be discussed.

Heaps, W. S.↗
NASA NTRS1986

Cometary dynamics

In order to provide observers with accurate cometary ephemerides, up-to-date astrometric positions must be used to update the existing orbit and ephemeris for each object. In addition, nongravitational forces must be taken into account; these forces are assumed due to the rocket effect of outgassing cometary ices. Once successfully modeled, the cometary nucleus spin direction, spin axis evolution, and the volatility of the nucleus ices can be inferred. The predicted ephemerides also become far more accurate.

Yeomans, D. K.↗
NASA NTRS1986

Space ultra-vacuum facility and method of operation

A wake shield facility providing an ultrahigh vacuum level for space processing is described. The facility is in the shape of a truncated, hollow hemispherical section, one side of the shield convex and the other concave. The shield surface is preferably made of material that has low out-gassing characteristics such as stainless steel. A material sample supporting fixture in the form of a carousel is disposed on the convex side of the shield at its apex. Movable arms, also on the convex side, are connected by the shield in proximity to the carousel, the arms supporting processing fixtures, and providing for movement of the fixtures to predetermined locations required for producing interations with material samples. For MBE processes a vapor jet projects a stream of vaporized material onto a sample surface. The fixtures are oriented to face the surface of the sample being processed when in their extended position, and when not in use they are retractable to a storage position. The concave side of the shield has a support structure including metal struts connected to the shield, extending radially inward. The struts are joined to an end plate disposed parallel to the outer edge of the shield. This system eliminates outgassing contamination.

Naumann, Robert J.↗
NASA NTRS1986

Controlling and monitoring the space-station plasma interaction: A baseline for performing plasma experiments and using advanced technology

The size, complexity, and motion of space station through the Earth's environmental plasma means that there will be a large, complicated interaction region, involving a sheath, wake, charging of surfaces, induced electric fields, secondary emission, outgassing with ionization, etc. This interaction will necessarily be a factor in carrying out and interpreting plasma experiments and in the use of certain technologies. Attention should be given ahead of time to: (1) monitoring this interaction so that it is well described; (2) implifying the interaction by appropriate design and construction of the spacecraft and by appropriate planning of technology use; and (3) controlling the interaction by both active and passive means. Plasma emitters for modifying and controlling the spacecraft charge should be placed in several locations. Portable electrostatic shields could be deployed around noisy sections of the spacecraft in order to carry out sensitive experiments. A particle umbrella could be raised to deflect the ram ions and neutrals in order to provide a controlled environment. These interactions are briefly discussed.

Whipple, Elden C.↗
NASA NTRS1987

Fully redundant mechanical release actuator

A system is described for performing a mechanical release function exhibiting low shock. This system includes two pyrotechnic detents fixed mounted in opposing axial alignment within a cylindrical housing having two mechanical bellows. Two mechanical bellow assemblies, each having one end hermetically bonded to the housing and the other to the respective actuator pin extending from either end of the housing, ensure that all outgassing and contamination from the operation of the pyrotechnic devices will be contained within the housing and bellows. The pin on one end of the assembly is fixed mounted and supported, via a bolt or ball-and-socket joint so that when the charge corresponding to that pin ignites, the entire assembly will exhibit rectilinear movement, including the opposing pin providing the unlatching motion. The release detent pin is supported by a linear bearing and when its corresponding pyrotechnic charge ignites the pin is retracted within the housing producing the same unlatching motion without movement of the entire assembly, thus providing complete mechanical, electrical and pyrotechnic redundancy for the unlatching pin.

Lucy, Melvin H.↗
NASA NTRS1986

HCN production from Comet Halley

Observations of the HCN J=1-0 rotational transition at 3.4 mm wavelength in comet P/Halley with a 14m antenna were obtained during 56 individual observing sessions between Nov. 1985 and May 1986. The HCN production rate is well correlated with the total visual magnitude of the comet, indicating that HCN follows the overall gas and dust production. However, comparison of HCN production to the total gas production of the comet indicates that it is a relatively minor consitiuent with 0.1% of the abundance of H2O. Spectra obtained by binning the HCN data with heliocentric distance show that the HCN line width, and thus the parent outflow velocity, increases with decreasing heliocentric distance, and that there is a tendency for the lines to be blue shifted as expected from the observed anisotropic outgassing from the nucleus. There is evidence of day-to-day time variability in the total HCN emission and variations in the HCN hyperfine ratios from their LTE values.

Schloerb, F. Peter↗
NASA NTRS1986

OH radio observations of Comet Halley

Results of OH observations of P/Halley obtained with the NRAO 43 m antenna between July 1985 and May 1986 are presented. Using Radio Model 1986a, the OH production rate derived from these data follows an rh(-2) law for heliocentric distances in the range 0.6 to 2.1 AU. Comparison of radio OH production rates to those estimated by UV techniques continues to show that the radio technique finds systematically lower production rates. Observations of the OH line shape show that the line width increases as the comet approaches perihelion, and that the broader line widths persist after perihelion out to at least rh = 1AU. Modeling of the profiles suggest that this may be accounted for through an increase in the velocity of the OH parent. The mean velocity of the OH emission (after correction for the OH Greenstein effect) is slightly blue shifted compared to the nucleus velocity and suggests that the outgassing from the nucleus is largely directed sunward.

Schloerb, F. Peter↗
NASA NTRS1986

Elemental, isotopic and molecular abundances in comets

The chemical composition of comet nuclei and the factors affecting it are discussed, summarizing the results of recent theoretical, experimental, and observational investigations. Consideration is given to the evidence supporting the view that the nucleus is radially differentiation (except for a thin outer layer), surface differentiation by heat processing and outgassing, and mantle buildup on an undifferentiated core. The nature of the refractory and volatile components is examined, and the elemental and isotopic compositions are given in tables and characterized. The uncertain (except for H2O) molecular composition of the volatile fraction is considered, and it is suggested that some oxides or aldehydes (such as CO, CO2, and H2CO), but no large amounts of fully hydrogenated compounds (such as CH4 and NH3) are included.

Delsemme, A. H.↗
NASA NTRS1986

Diatoms in comets

The fossil record of the microscopic algae classified as diatoms suggests they were injected to earth at the Cretaceous boundary. Not only could diatoms remain viable in the cometary environment, but also many species might replicate in illuminated surface layers or early interior layers of cometary ice. Presumably they reached the solar system on an interstellar comet as an already-evolved assemblage of organisms. Diatoms might cause color changes to comet nuclei while their outgassing decays and revives around highly elliptical orbits. Just as for interstellar absorption, high-resolution IR observations are capable of distinguishing whether the 10-micron feature arises from siliceous diatom material or mineral silicates. The 10-30-micron band and the UV 220-nm region can also provide evidence of biological material.

Hoover, R.↗
NASA NTRS1985

Cometary kilometric radio waves and plasma waves correlated with ion pick-up effect at Comet Halley

Bow-shock movements at Comet Halley are inferred from the discrete spectra of the cometary kilometric radiation (30-195 kHz); the observed emissions can be interpreted as being generated and propagating from the moving shock. The shock motion is possibly associated with the time variation of the solar wind and cometary outgassing. It is concluded that these plasma wave phenomena are manifestations of ion pick-up processes, which occur even in a remote region 7 million to 10 million km from the cometary nucleus.

Oya, H.↗
NASA NTRS1987

A more perfect vacuum

Design and operational features, problems and benefits of a Space Ultravacuum Research Facility (SURF), a wake shield, are discussed. SURF is primarily targeted at providing vacuums exceeding 10 to the -14th torr for performing materials processing experiments and, eventually, commercial-scale production. The materials to be processed would be at the apex of a convex shield, with the quality of vacuum limited mainly by the backscattering toward the wake surface of atmospheric molecules which have collided with molecules leaving the SURF surface. A stainless steel skin on the SURF, cured in orbit, is proposed as a means to minimize the molecules outgassed from the surface. Applications of SURF could include coating mirrors or other optical equipment, containerless melting and solidification of materials, and ultrapurification processing.

Naumann, Robert J.↗
NASA NTRS1987

Volatile degassing of basaltic achondrite parent bodies Evidence from alkali elements and phosphorus

The Na, K, Rb, Cs, and P abundances in eucrites, diogenites, basaltic clasts from polymict eucrite, howardites, and mesosiderites are examined, and compared with an average of highly incompatible refractory (AHIR) elements normalized to cosmic abundances. It is observed that basaltic eucrites and basaltic clasts show a positive correlation between K, Rb, and Cs, and alkali element/AHIR ratios; the volatile loss of the alkali elements from the basalt affects the parent body inventory of volatile elements. The data reveal that for diogenites, the alkali /AHIR ratios are 1.4-2 times greater than in basaltic eucrites and are more variable; and the negative relation between K, Rb, Cs, and the alkali/AHIR ratio correlate with progressive alkali loss through volatile outgassing during crystallization of one or more magmas resulting in a greater than 90 percent loss of the volatile element inventory from the parent body. It is also detected that P displays volatile loss from the basaltic eucrites and elevated P/AHIR ratios in diogenites.

Mittlefehldt, David W.↗