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NASA NTRS1983

Sedimentary processes and crustal cycling on Venus

Sediment exists on the Venus surface. It is observed in Venera images between outcrops and boulders of sedimentary rocks. Sediment is produced by pyroclastic volcanism and chemical weathering. Chemical weathering is driven by an enhanced activity of water and an elevated surface temperature. Sediment is transported by wind action and lithified by cementration and diagenesis. Cementation may be by carbonate or silica cement; diagenesis may be products of chemical weathering acting as cement, or by compaction and recrystallization of sediment into a texture with interlocking grains. Sediment may be transported from the top of sialic continents (such as Ishtar) to the modal plains where it is deposited, lithified, and integrated into thy local crust. As new layers are added, the bottom of the crust melts and is, in part, returned to the mantle. A steady-state chemical exchange might exist by this mechanism of crustal cycling that links atmosphere, continents, modal plains, and mantle.

Warner, J. L.↗

NASA NTRS2005

Simulated Space Environment Effects on Tether Materials with Protective Coatings

Atomic oxygen (AO) erodes most organic materials. and ultraviolet radiation embrittles polymers. A previous study indicated untreated polymers such as ultra-high molecular weight polyethylene (UHMWPE) are severely degraded when exposed to AO. This test series was performed to determine the effect of AO and UV on the mechanical integrity of tether materials that were treated with AO-protective coatings. Three coating systems were evaluated for their ability to protect the underlying material from AO erosion. The first coating system is the Photosil surface modification process which incorporates silicon-containing functional groups into the top micron of an organic material. The Photosil process has had favorable results with polyurethane- and epoxy-based thermal control coatings . The second coating system is metallization, in this case nickel. The third coating system is silsesquioxane. The Marshall Space Flight Center Atomic Oxygen Beam Facility (AOBF) was used to simulate low Earth orbit AO of 5 eV energy. In addition, some tether samples were exposed to ultraviolet radiation then evaluated for any changes in mechanical strength. Tether missions, such as a momentum-exchange/electrodynamic reboost (MXER) tether, may benefit from this research.

Finckenor, Miria M.↗

NASA NTRS1989

The formation of weathering products on the LEW 85320 ordinary chondrite - Evidence from carbon and oxygen stable isotope compositions and implications for carbonates in SNC meteorites

Isotopic analysis of nesquehonite recovered from the surface of the LEW 85320 H5 ordinary chondrite shows that the delta C-13 and delta O-18 values of the two generations of bicarbonate (Antarctic and Texas) are different: delta C-13 = + 7.9 per mil and + 4.2 per mil; delta O-18 = + 17.9 per mil and + 12.1 per mil, respectively. Carbon isotopic compositions are consistent with equilibrium formation from atmospheric carbon dioxide at - 2 + or - 4 C (Antarctic) and + 16 + or - 4 C (Texas). Oxygen isotopic data imply that the water required for nesquehonite precipitation was derived from atmospheric water vapor or glacial meltwater which had locally exchanged with silicates, either in the meteorite or in underlying bedrock. Although carbonates with similar delta C-13 values have been identified in the SNC meteorites EETA 79001 and Nakhla, petrographic and temperature constraints argue against their simply being terrestrial weathering products.

Grady, Monica M.↗

NASA NTRS1993

Implementation of ADI: Schemes on MIMD parallel computers

In order to simulate the effects of the impingement of hot exhaust jets of High Performance Aircraft on landing surfaces a multi-disciplinary computation coupling flow dynamics to heat conduction in the runway needs to be carried out. Such simulations, which are essentially unsteady, require very large computational power in order to be completed within a reasonable time frame of the order of an hour. Such power can be furnished by the latest generation of massively parallel computers. These remove the bottleneck of ever more congested data paths to one or a few highly specialized central processing units (CPU's) by having many off-the-shelf CPU's work independently on their own data, and exchange information only when needed. During the past year the first phase of this project was completed, in which the optimal strategy for mapping an ADI-algorithm for the three dimensional unsteady heat equation to a MIMD parallel computer was identified. This was done by implementing and comparing three different domain decomposition techniques that define the tasks for the CPU's in the parallel machine. These implementations were done for a Cartesian grid and Dirichlet boundary conditions. The most promising technique was then used to implement the heat equation solver on a general curvilinear grid with a suite of nontrivial boundary conditions. Finally, this technique was also used to implement the Scalar Penta-diagonal (SP) benchmark, which was taken from the NAS Parallel Benchmarks report. All implementations were done in the programming language C on the Intel iPSC/860 computer.

Vanderwijngaart, Rob F.↗

NASA NTRS1994

The chemical reactivity of the Martian soil and implications for future missions

Possible interpretations of the results of the Viking Biology Experiments suggest that greater than 1 ppm of a thermally labile oxidant, perhaps H2O2, and about 10 ppm of a thermally stable oxidant are present in the martian soil. We reexamine these results and discuss implications for future missions, the search for organics on Mars, and the possible health and engineering effects for human exploration. We conclude that further characterization of the reactivity of the martian regolith materials is warrented-although if our present understanding is correct the oxidant does not pose a hazard to humans. There are difficulties in explaining the reactivity of the Martian soil by oxidants. Most bulk phase compounds that are capable of oxidizing H2O to O2 per the Gas Exchange Experiment (GEx) are thermally labile or unstable against reduction by atmospheric CO2. Models invoking trapped O2 or peroxynitrates (NOO2(-)) require an unlikely geologic history for the Viking Lander 2 site. Most suggested oxidants, including H2O2, are expected to decompose rapidly under martian UV. Nonetheless, we conclude that the best model for the martian soil contains oxidants produced by heterogeneous chemical reactions with a photochemically produced atmospheric oxidant. The GEx results may be due to catalytic decomposition of an unstable oxidizing material by H2O. We show that interfacial reaction sites covering less than 1% of the available soil surfaces could explain the Viking Biology Experiments results.

Zent, Aaron P.↗

NASA NTRS1994

The global energy budget and satellite observations

During the last 30 years, space observations have provided new information about (a) the energy from our Sun, (b) the radiative exchange between our earth-atmosphere system and space, (c) required poleward energy transports by our atmosphere and oceans, (d) seasonal and interannual variations of (b) and (c), (e) the role of clouds in the global energy budget, and (f) preliminary information about the role of water vapor in the global energy budget. After a review of what we now know about these topics, the paper concludes with a discussion of major unknowns including the vertical variation of cloud forcing, the 'CO2 fingerprint,' the 'missing petawatt' of energy transport, and the role of non-cloud aerosols and surface features in the global budget.

Vonder Haar, Thomas H.↗

NASA NTRS1989

A study of oceanic surface heat fluxes in the Greenland, Norwegian, and Barents Seas

This study examines oceanic surface heat fluxes in the Norwegian, Greenland, and Barents seas using the gridded Navy Fleet Numerical Oceanography Central surface analysis and the First GARP Global Experiment (FGGE) IIc cloudiness data bases. Monthly and annual means of net and turbulent heat fluxes are computed for the FGGE year 1979. The FGGE IIb data base consisting of individual observations provides particularly good data coverage in this region for a comparison with the gridded Navy winds and air temperatures. The standard errors of estimate between the Navy and FGGE IIb winds and air temperatures are 3.6 m/s and 2.5 C, respectively. The computations for the latent and sensible heat fluxes are based on bulk formulas with the same constant heat exchange coefficient of 0.0015. The results show extremely strong wintertime heat fluxes in the northern Greenland Sea and especially in the Barents Sea in contrast to previous studies.

Hakkinen, Sirpa↗

NASA NTRS2004

Long Period Variations in Tidal and Librational Forcing of Europa

The gravitational field of Jupiter exerts a profound influence on the energy balance, thermal evolution, and stress regime of Europa. It widely appreciated that dissipation associated with the spheroidal tidal deformation is a major source of heat. Another possibly important source of dissipation is the toroidal deformation field associated with forced librations. Both tidal and librational deformations depend on the distance and direction Jupiter, as seen from Europa. These quantities vary with time as a result of the finite values of orbital eccentricity and spin pole obliquity, though the obliquity effects have been ignored in most previous studies. Variations in eccentricity and obliquity of the Galilean satellites occur on a very wide range of time scales, as angular momentum is exchanged among the orbital and rotational components of the coupled system. The orbital periods are only a few days in length, and the secular changes in orbital period associated with tidal and librational dissipation have characteristic time scales of 10-9 years or longer. On intermediate time scales, the satellites perturb each other, and the Sun and Saturn make additional contributions. The present values of satellite orbital inclinations and obliquities are not particularly representative their respective longer term variations. As a result, the tidal stress and dissipation regimes at present may not provide adequate explanation of the sources of surface features seen on the satellites.

Bills, Bruce G.↗

NASA NTRSDate not supplied

A Blockchain Case Study for Urban Air Mobility Operational Intent

The next generation of aerial passenger and cargo transportation may leverage the concept of Urban Air Mobility (UAM). UAM is a concept that proposes to develop short-range, point-to-point transportation systems in metropolitan areas using vertical takeoff and landing (VTOL) or short takeoff and landing (STOL) aircraft to overcome increasing surface congestion [1]. The UAM concept leverages a decentralized service-based architecture for airspace solutions. Within the environment, UAM operators work collaboratively to manage aerial vehicles in the urban environment. Providers of Services for UAM (PSU), UAM operators, and Supplemental Data Service Providers (SDSP) provide services to support flight operations within the UAM environment. Also, various views of UAM flight information are provided to the public and public safety entities [2]. The Federal Aviation Administration (FAA) can coordinate flight information between the FAA controlled National Airspace System (NAS) and the UAM environments through the FAA-Industry Data Exchange Protocol (FIDXP). To realize the potential of UAM, an assurance of cybersecurity is critical for public acceptance. Cybersecurity has come to the forefront highlighting the need to protect these networks and systems from cyberattacks. The growth in the development of UAM systems, and the associated data exchange and service interactions will be at risk due to numerous types of cybersecurity attacks. As these threats evolve, the UAM cybersecurity capabilities must adapt to these changes as well [3]. This research focuses on the secure data exchange and storage of this decentralized UAM environment to address these challenges. This research intends to leverage a permissioned blockchain approach to address cybersecurity threats that may impact a UAM environment. Blockchain technologies can be used for tracking transactions and verifying negotiated agreements between stakeholders in the NAS environment. For example, the record of the submitted flight plan and the approved flight plan could be verified using the Blockchain-based immutable ledger.

UAM↗

NASA NTRS1992

Factors controlling sulfur gas exchange in Sphagnum-dominated wetlands

Atmosphere-peatland exchange of reduced sulfur gases was determined seasonally in fen in NH, and in an artificially-acidified fen at the Experimental Lakes Area (ELA) in Canada. Dimethyl sulfide (DMS) dominated gas fluxes at rates as high as 400 nmol/m(sup -2)hr(sup -1). DMS fluxes measured using enclosures were much higher than those calculated using a stagnant-film model, suggesting that Sphagnum regulated efflux. Temperature controlled diel and seasonal variability in DMS emissions. Use of differing enclosure techniques indicated that vegetated peatlands consume atmospheric carbonyl sulfide. Sulfate amendments caused DMS and methane thiol concentrations in near-surface pore waters to increase rapidly, but fluxes of these gases to the atmosphere were not affected. However, emission data from sites experiencing large differences in rates of sulfate deposition from the atmosphere suggested that chronic elevated sulfate inputs enhance DMS emissions from northern wetlands.

Demello, William Zamboni↗

NASA NTRS2007

Effect of PdO on TiO(sub2) Loading on Chemochromic Detection of Hydrogen

Safety is always a concern in all applications that utilize hydrogen (H(sub2)) in one form or the other. Hydrogen leaks are invisible and odorless. In addition, blending odorants or additives into hydrogen in a manner similar to natural gas is generally undesirable for certain applications including proton exchange membrane fuel cells. To facilitate detection of the location of hydrogen leaks, a special chemochromic H(sub2) sensing material that employs titania (Ti0(sub2)) supported palladium oxide (PdO) pigments encapsulated within a special silicone matrix has been developed at the Florida Solar Energy Center (FSEC). Several batches of PdO H(sub2) sensing pigments were synthesized using various Ti0(sub2) supports and their hydrogen detection activity determined. TEM and Particle size distribution analysis showed that smaller particles with hemispherical crystalline structure produced faster coloration kinetics when exposed to H(sub2) gas. However, uniformly distributed PdO particles on the Ti0(sub2) surface displayed greater color contrast, quantified by delta epsilon measurements. XRD analysis indicated that the crystalline phase of Ti0(sub2) had no effect on the chemochromic performance of the pigments in laboratory environment.

Mohajeri, Nahid↗

NASA NTRS2015

A Formal Messaging Notation for Alaskan Aviation Data

Data exchange is an increasingly important aspect of the National Airspace System. While many data communication channels have become more capable of sending and receiving data at higher throughput rates, there is still a need to use communication channels efficiently with limited throughput. The limitation can be based on technological issues, financial considerations, or both. This paper provides a complete description of several important aviation weather data in Abstract Syntax Notation format. By doing so, data providers can take advantage of Abstract Syntax Notation's ability to encode data in a highly compressed format. When data such as pilot weather reports, surface weather observations, and various weather predictions are compressed in such a manner, it allows for the efficient use of throughput-limited communication channels. This paper provides details on the Abstract Syntax Notation One (ASN.1) implementation for Alaskan aviation data, and demonstrates its use on real-world aviation weather data samples as Alaska has sparse terrestrial data infrastructure and data are often sent via relatively costly satellite channels.

communications↗

NASA NTRS2016

CubeSat Constellation Cloud Winds(C3Winds) A New Wind Observing System to Study Mesoscale Cloud Dynamics and Processes

The CubeSat Constellation Cloud Winds (C3Winds) is a NASA Earth Venture Instrument (EV-I) concept with the primary objective to better understand mesoscale dynamics and their structures in severe weather systems. With potential catastrophic damage and loss of life, strong extratropical and tropical cyclones (ETCs and TCs) have profound three-dimensional impacts on the atmospheric dynamic and thermodynamic structures, producing complex cloud precipitation patterns, strong low-level winds, extensive tropopause folds, and intense stratosphere-troposphere exchange. Employing a compact, stereo IR-visible imaging technique from two formation-flying CubeSats, C3Winds seeks to measure and map high-resolution (2 km) cloud motion vectors (CMVs) and cloud geometric height (CGH) accurately by tracking cloud features within 5-15 min. Complementary to lidar wind observations from space, the high-resolution wind fields from C3Winds will allow detailed investigations on strong low-level wind formation in an occluded ETC development, structural variations of TC inner-core rotation, and impacts of tropopause folding events on tropospheric ozone and air quality. Together with scatterometer ocean surface winds, C3Winds will provide a more comprehensive depiction of atmosphere-boundary-layer dynamics and interactive processes. Built upon mature imaging technologies and long history of stereoscopic remote sensing, C3Winds provides an innovative, cost-effective solution to global wind observations with potential of increased diurnal sampling via CubeSat constellation.

mesoscale dynamics↗

NASA NTRS1979

Low-cost, high-efficiency silicon by heat exchanger method and fixed abrasive slicing technique

The paper describes the heat exchanger method (HEM) for growing silicon crystals. The problem of ingot cracking was solved by using a graded structure silica crucible, and vacuum processing eliminated expensive high-purity argon. Solar cells fabricated from HEM silicon demonstrated conversion efficiencies up to 15% (AM1) at low cost, using square cross-section, single crystal silicon. A modified multiblade slurry machine was adapted for multiwire fixed abrasive slicing of silicon which uses a diamond attached to wires; this method provides a conversion ratio of 1.08 sq m of wafer per kg of silicon ingot, and produces wafers free of edge chipping with a surface damage of 3-5 microns.

Khattak, C. P.↗

NASA NTRS2014

Dust Tolerant Commodity Transfer Interface Mechanisms for Planetary Surfaces

Regolith is present on most planetary surfaces such as Earth's moon, Mars, and Asteroids. If human crews and robotic machinery are to operate on these regolith covered surfaces, they must face the consequences of interacting with regolith fines which consist of particles below 100 microns in diameter down to as small as submicron scale particles. Such fine dust will intrude into mechanisms and interfaces causing a variety of problems such as contamination of clean fluid lines, jamming of mechanisms and damaging connector seals and couplings. Since multiple elements must be assembled in space for system level functionality, it will be inevitable that interfaces will be necessary for structural connections, and to pass commodities such as cryogenic liquid propellants, purge and buffer gases, water, breathing air, pressurizing gases, heat exchange fluids, power and data. When fine regolith dust is present in the environment it can be lofted into interfaces where it can compromise the utility of the interface by preventing the connections from being successfully mated, or by inducing fluid leaks or degradation of power and data transmission. A dust tolerant, hand held "quick-disconnect" cryogenic fluids connector housing has been developed at NASA KSC which can be used by astronaut crews to connect flex lines that will transfer propellants and other useful fluids to the end user. In addition, a dust tolerant, automated, cryogenic fluid, multiple connector, power and data interface mechanism prototype has been developed, fabricated and demonstrated by NASA at Kennedy Space Center (KSC). The design and operation of these prototypes are explained and discussed.

Dust Tolerant↗

NASA NTRSDate not supplied

Performance of a Regenerative Fuel Cell System for the Lunar Surface

Regenerative fuel cells (RFCs) are an attractive energy storage solution for lunar missions as a technology capable of providing a higher specific energy (i.e., W∙h/kg) than state-of-the-art packaged Li-ion battery systems. An RFC consists of the (1 & 2) electrochemical stacks (chemical to electrical energy conversion to supply electricity to an external load, i.e. the fuel cell reaction, and electrical to chemical energy conversion of supplied electrical power to dissociate water into hydrogen and oxygen gases, i.e. water electrolysis), (3) fluidic conditioning, (4) reactant storage, (5) avionics, (6) power management and distribution (PMAD), and (7) thermal management. NASA’s Glenn Research Center has designed, assembled, and tested a breadboard RFC sys-tem capable of operating autonomously for multiple simulated lunar day/night cycles in a laboratory environment. The system is comprised of a non-flow through proton exchange membrane (PEM) fuel cell stack and a liquid-anode feed PEM electrolyzer (EZ) stack designed to electrochemically compress the reactants at balanced pressures up to 12.4 MPa (1800 psia). The fluidic conditioning, avionics, PMAD, and thermal management sub-systems are largely comprised of commercial-off-the-shelf components for this system-level development effort. The hardware is controlled by a CubeSat space processor running an operational program based on core flight architecture that can control the RFC hardware autonomously through a state machine with fault monitoring. The testing results highlighted here were completed with the system in an open-loop configuration such that reactants generated through water electrolysis were vented while gas cylinders supplied fuel cell operation. The breadboard operated autonomously, but there were five unplanned transitions to a safe state that required a manual restart after reviewing the data, determining a root cause, and implementing a solution. Four of the transitions were caused by the thermal management subsystem and the fifth was caused by a water management control issue in the EZ sub-system. The RFC system operated for over 550 hours with the final cycle being slightly abbreviated due to reasons unrelated to system performance.

Kerrigan Cain↗

NASA NTRSDate not supplied

Performance of a Regenerative Fuel Cell System for the Lunar Surface

Kerrigan Cain↗

NASA NTRS1990

The influence of gas velocity on surface heat pumping for the orifice pulse tube refrigerator

The basic pulse tube refrigerator produces cooling by a mechanism known as surface heat pumping. Cyclical compression and expansion of a gas within an enclosed tube produces large temperature gradients. The purpose of the tube is to act as 'nodal regenerator'. Heat is stored at node positions along the tube wall and is transported between nodes by moving gas parcels. This process gives rise to refrigeration, with hot temperatures at the closed end and cold temperatures at the open end. Unfortunately, much of the available refrigeration is not realized because the closed end of the basic pulse tube restricts gas movement - gas at the extreme temperatures does not come in contact with the heat exchangers. The orifice pulse tube overcomes this limitation by using a valve and surge volume assembly at the warm, closed end. This allows for a residual gas velocity to remain present during the heat transfer process, thereby permitting more gas to exchange heat at the heat exchangers. This paper describes the pulse tube as a nodal regenerator and the effect residual gas velocity has on the heat transfer mechanism of the orifice pulse tube.

Lee, J. M.↗