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NASA NTRS2015

On Possible Arc Inception on Low Voltage Solar Array

Recent analysis of spacecraft failures during the period of 1990-2013 demonstrated clearly that electrostatic discharges caused more than 8 percent of all registered failures and anomalies, and comprised the most costly losses (25 percent) for operating companies and agencies. The electrostatic discharges on spacecraft surfaces are the results of differential charging above some critical (threshold) voltages. The mechanisms of differential charging are well known, and various methods have been developed to prevent a generation of significant electric fields in areas of triple junctions. For example, low bus voltages in Low Earth Orbit plasma environment and slightly conducting layer over cover-glass (ITO) in Geosynchronous Orbit surroundings are believed to be quite reliable measures to prevent discharges on respective surfaces. In most cases, the vulnerable elements of spacecraft (solar arrays, diode boards, etc.) go through comprehensive ground tests in vacuum chambers. However, tests articles contain the miniscule fragments of spacecraft components such as 10-30 solar cells of many thousands deployed on spacecraft in orbit. This is one reason why manufacturing defects may not be revealed in ground tests but expose themselves in arcing on array surface in space. The other reason for ineffectiveness of discharge preventive measures is aging of all materials in harsh orbital environments. The expected life time of modern spacecraft varies within the range of five-fifteen years, and thermal cycling, radiation damages, and mechanical stresses can result in surface erosion on conductive layers and microscopic cracks in cover-glass sheets and adhesive films. These possible damages may cause significant increases in local electric field strengths and subsequent discharges. The primary discharges may or may not be detrimental to spacecraft operation, but they can produce the necessary conditions for sustained arcs initiation. Multiple measures were developed to prevent sustained discharges between adjacent strings, and many ground tests were performed to determine threshold parameters (voltage and current) for sustained arcs. And again, manufacturing defects and aging in space environments may result in considerable decrease of critical threshold parameters. This paper is devoted to the analysis of possible reasons behind arcing on spacecraft with low bus voltages.

low voltage solar array↗

NASA NTRS1977

Chemical characterization of lunar core 60010

Twenty-eight major, minor, and trace-element abundances have been determined in nine fines fractions of core 60010 by instrumental thermal and 14 MeV neutron activation analysis. With the exception of the elements Fe, Co, and Ni, core section 60010 exhibits a much more uniform composition than the lower section (60009) of the double drive tube collected at the Apollo 16 LM site. The siderophilic meteorite indicator elements Fe, Co, and Ni are significantly enriched in subsample 40, which is located 3.0-4.5 cm below the lunar surface, and are highly variable throughout the 60010 core section. Microscopic examination of subsample 40 revealed the presence of numerous metallic fragments including an approximately 1-mm metal fragment exhibiting only Fe, Co, Ni, and Ir gamma-ray peaks and having a composition typical of a coarse octahedrite. Composition profiles of 60010 exhibit small variations in lithophilic element abundances which can be related to most of the seven stratigraphic units of Duke and Nagle (1976). Although the basal portion of 60010 has been described as texturally similar to the upper unit of 60009, the present chemical studies show a marked compositional difference at this interface.

Ali, M. Z.↗

NASA NTRS1998

Failure of Laminated Composites at Thickness Discontinuities: An Experimental and Analytical Study

Failure initiation of laminated composites at a thickness discontinuity is studied experimentally with the aid of an optical microscope under combined loading of tension, transverse shear and bending, making use of three- and four-point bending arrangements. Because transverse shear produced relatively small effects in failure initiation results are presented as tension-bending interactions. Two loading frames for three- and four-point bending were designed to apply moment and tension simultaneously to produce failure by generating a ply crack; this initiation was evaluated by finite element analysis using ABAQUS. For cross-plies bounding the interface at the base of the step it is found that a maximum strain criterion applied to the continuing (long) ply describes the failure initiation. Ultimate failure resulted at loads on the order of 25 to 35% higher than those at failure initiation.

Lee, Sangwook↗

NASA NTRS2003

Automated Rock Identification for Future Mars Exploration Missions

A key task for human or robotic explorers on the surface of Mars is choosing which particular rock or mineral samples should be selected for more intensive study. The usual challenges of such a task are compounded by the lack of sensory input available to a suited astronaut or the limited downlink bandwidth available to a rover. Additional challenges facing a human mission include limited surface time and the similarities in appearance of important minerals (e.g. carbonates, silicates, salts). Yet the choice of which sample to collect is critical. To address this challenge we are developing science analysis algorithms to interface with a Geologist's Field Assistant (GFA) device that will allow robotic or human remote explorers to better sense and explore their surroundings during limited surface excursions. We aim for our algorithms to interpret spectral and imaging data obtained by various sensors. The algorithms, for example, will identify key minerals, rocks, and sediments from mid-IR, Raman, and visible/near-IR spectra as well as from high resolution and microscopic images to help interpret data and to provide high-level advice to the remote explorer. A top-level system will consider multiple inputs from raw sensor data output by imagers and spectrometers (visible/near-IR, mid-IR, and Raman) as well as human opinion to identify rock and mineral samples.

Gulick, V. C.↗

NASA NTRS1977

Relation of morphology of electrodeposited zinc to ion concentration profile

The morphology of electrodeposited zinc was studied with special attention to the ion concentration profile. The initial concentrations were 9M hydroxide ion and 1.21M zincate. Current densities were 6.4 to 64 mA/sq cm. Experiments were run with a horizontal cathode which was observed in situ using a microscope. The morphology of the zinc deposit was found to be a function of time as well as current density; roughly, the log of the transition time from mossy to large crystalline type deposit is inversely proportional to current density. Probe electrodes indicated that the electrolyte in the cathode chamber was mixed by self inducted convection. However, relatively large concentration gradients of the involved species existed across the boundary layer of the cathode. Analysis of the data suggests that the morphology converts from mossy to large crystalline when the hydroxide activity on the cathode surface exceeds about 12 M. Other experiments show that the pulse discharge technique had no effect on the morphology in the system where the bulk concentration of the electrolyte was kept homogeneous via self induced convection.

May, C. E.↗

NASA NTRS1982

The mechanisms of fine particle generation and electrification during Mount St. Helens volcanic eruption

Microscopical investigation of volcanic ash collected from ground stations during Mount St. Helens eruptions reveal a distinctive bimodel size distribution with high concentrations of particle ranges at (1) 200-100 microns and (2) 20-0.1 microns. Close examination of individual particles shows that most larger ones are solidified magma particles of porous pumice with numerous gas bubbles in the interior and the smaller ones are all glassy fragments without any detectable gas bubbles. Elemental analysis demonstrates that the fine fragments all have a composition similar to that of the larger pumice particles. Laboratory experiments suggest that the formation of the fine fragments is by bursting of glassy bubbles from a partially solidified surface of a crystallizing molten magma particle. The production of gas bubbles is due to the release of absorbed gases in molten magma particles when solubility decreases during phase transition. Diffusion cloud chamber experiments strongly indicate that sub-micron volcanic fragments are highly hygroscopic and extremely active as cloud condensation nuclei. Ice crystals also are evidently formed on those fragments in a supercooled (-20 C) cloud chamber. It has been reported that charge generation from ocean volcanic eruptions is due to contact of molten lava with sea water. This seems to be insufficient to explain the observed rapid and intense lightning activities over Mount St. Helens eruptions. Therefore, a hypothesis is presented here that highly electrically charged fine solid fragments are ejected by bursting of gas bubbles from the surface of a crystallizing molten magma particles.

Cheng, R. J.↗

NASA NTRS2001

Surface Analysis Evaluation of Handwipe Cleaning for the Space Shuttle RSRM

In this paper we discuss the role of surface-sensitive spectroscopy (electron spectroscopy for chemical analysis, or ESCA) in the selection of solvents to replace 1,1,1-trichloroethane in handwipe cleaning of bonding surfaces on NASA's Space Shuttle Reusable Solid Rocket Motor (RSRM). Removal of common process soils from a wide variety of metallic and polymeric substrates was characterized. The cleaning efficiency was usually more dependent on the type of substrate being cleaned and the specific process soil than on the solvent used. A few substrates that are microscopically rough or porous proved to be difficult to clean with any cleaner, and some soils were very tenacious and difficult to remove from any substrate below detection limits. Overall, the work showed that a wide variety of solvents will perform at least as well as 1,1,1-trichloroethane.

Lesley, Michael W.↗

NASA NTRS1972

Lunar sample analysis

A simple and convenient method of making quantitative magnetic separations of the lunar fines is described. The fractions obtained form groups containing distinctively different particle types; thus it appears that magnetic separation in itself may be a useful way of characterizing lunar fines. Mossbauer studies of fines 10084 show that the metal can not contain more than about 1.5% Ni implying that by far the bulk of it results from reduction rather than being a direct meteoritic addition. Mossbauer data also places an upper limit on the magnetite content of the fines at least an order of magnitude below that required to account for the characteristic ferromagnetic resonance observed. Microscopic examination of magnetic separates from the 15101 fines suggests that reduction of Fe accompanies every major impact event on the moon and also suggests that the bulk of the material at the collection site has at one time been in an impact plume.

Housley, R. M.↗

NASA NTRS1979

Fourier emission infrared microspectrophotometer for surface analysis. I - Application to lubrication problems

A far-infrared interferometer was converted into an emission microspectrophotometer for surface analysis. To cover the mid-infrared as well as the far-infrared the Mylar beamsplitter was made replaceable by a germanium-coated salt plate, and the Moire fringe counting system used to locate the moveable Michelson mirror was improved to read 0.5 micron of mirror displacement. Digital electronics and a dedicated minicomputer were installed for data collection and processing. The most critical element for the recording of weak emission spectra from small areas was, however, a reflecting microscope objective and phase-locked signal detection with simultaneous referencing to a blackbody source. An application of the technique to lubrication problems is shown.

Lauer, J. L.↗

NASA NTRS1972

Ion and laser microprobes applied to the measurement of corrosion produced hydrogen on a microscopic scale.

Use of an ion microprobe and a laser microprobe to measure concentrations of corrosion-produced hydrogen on a microscopic scale. Hydrogen concentrations of several thousand ppm were measured by both analytical techniques below corroded and fracture surfaces of hot salt stress corroded titanium alloy specimens. This extremely high concentration compares with only about 100 ppm hydrogen determined by standard vacuum fusion chemical analyses of bulk samples. Both the ion and laser microprobes were used to measure hydrogen concentration profiles in stepped intervals to substantial depths below the original corroded and fracture surfaces. For the ion microprobe, the area of local analysis was 22 microns in diameter and for the laser microprobe, the area of local analysis was about 300 microns in diameter. The segregation of hydrogen below fracture surfaces supports a previously proposed theory that corrosion-produced hydrogen is responsible for hot salt stress corrosion embrittlement and cracking of titanium alloys. These advanced analytical techniques suggest great potential for many areas of stress corrosion and hydrogen embrittlement research, quality control, and field inspection of corrosion problems. For example, it appears possible that a contour map of hydrogen distribution at notch roots and crack tips could be quantitatively determined. Such information would be useful in substantiating current theories of stress corrosion and hydrogen embrittlement.

Gray, H. R.↗

NASA NTRS1987

Melting of troilite at high pressure in a diamond cell by laser heating

A system for measuring melting temperatures at high pressures is described. The sample is heated with radiation from a YAG laser. The beam is reflected downward through a microscope objective, through the upper diamond anvil, and focused onto the sample. Hense, intense heating is produced only at the sample and not within the diamond anvils. A vidicon system is used to observe the sample during heating. Incandescent light from the heated sample passes back through the objective lens into a grating spectrometer. The spectrum of the incandescent light is received by the photodiode array and stored in the multichannel analyzer. These data can then be transferred to floppy disk for analysis. A curve fitting program is used to compare the spectra with standard blackbody curves and to determine the temperature. Pressure is measured by the ruby fluorescence method. The system was used to study the melting behavior of natural troilite (FeS).

Bassett, William A.↗

NASA NTRS1998

The Effect of Solution Parameters on Lysozyme Nucleation Rates and Crystal Quality

In the pursuit of strongly diffracting high quality macromolecule crystals of suitable volume, this study investigates how the formation of macromolecules in solution and their growth characteristics effect crystal volume and diffracting quality. We systematically investigated the effect of solution conditions on lysozyme nucleation rates and the volume of crystals produced. Batch crystallization plates were used in combination with a video microscope system to measure nucleation rates and crystal volume. As expected from classical nucleation theory, crystal numbers were found to increase with increases in temperature and supersaturation. Small changes in solution pH, at constant supersaturation values were found, however, to dramatically effect the number of crystals nucleated in the wells varying from 1000s to 10s in the pH range 4.0 to 5.2. Having optimized the conditions required to produce an appropriate number of crystals of a suitable volume for X-ray analysis, a large number of uniform crystals were produced under exactly the same conditions. In the X-ray analysis of more than 50 such crystals there was found a wide variation in crystal lattice parameters and data quality. The variation in X-ray quality crystal samples is thought to be related to the growth rate variation caused by growth rate dispersion seen in lysozyme crystal growth experiments.

Judge, R. A.↗

NASA NTRS2000

Effects of JP-8 Jet Fuel on Homeostasis of Clone 9 Rat Liver Cells

Chronic exposure to JP-8 and other kerosene-based petroleum distillates has been associated with hepatic, renal, neurologic, pulmonary, and immune toxicity. However, the effects of kerosene-type jet fuels on cellular homeostasis hitherto have not been reported. Fluorescence imaging using a Meridian Ultima laser scanning fluorescence microscope was used to evaluate the effect of JP-8 jet fuel on a communication competent rat liver cell line. Several endpoints of cellular function were measured including gap junctional intercellular communication (GJIC), mitochondrial and plasma membrane potential (MMP and PMP, respectively), intracellular glutathione (GSH) concentration, glutathione-S-transferase (GST) activity, and reactive oxygen species (ROS) generation. Cells were treated with JP-8 (0.01 to 2% in ethanol (EtOH)) for the following time points: 1 h, 24 h, 48 h, and analysis immediately after addition of jet fuel. GJIC analyzed directly after addition of 1% JP-8 was reduced 4.9-fold relative to EtOH-dosed control groups and further reduction (12.6-fold) was observed in cells treated for 1 h. Moreover, GJIC was not recoverable in cells treated with 1% JP-8 for 1 h and subsequently washed and incubated in fresh medium for 1 h. Significant changes in GSH content and GST activity were observed in cells analyzed directly after addition of 1% JP-8. GSH content increased in cells treated for 1 h with less than 2% JP-8 whereas treatment with 2% JP-8 for 1 h resulted in a 50% reduction in intracellular GSH relative to EtOH-dosed controls. Cells treated with 1% JP-8 for 48 h exhibited changes in GSH levels. However, higher JP-8 concentrations exhibited more pronounced changes in GSH and GST, which led to suppression of GSH synthesis. ROS increased in a dose-responsive fashion at JP-8 concentrations up to 1%, but decreased to 80% of control values at 2% and 3% JP-8. A 25% reduction in PMP was observed in cells treated for 1 h with 1% JP-8. In contrast, cells treated for 48 h with 2% JP-8 exhibited a 25% increase when compared to control. No significant changes were noted in the 0.01 and 1% treatment groups. Moreover, no significant changes were observed in MMP or intracellular calcium concentrations in cells treated with 0.01 to 2% JP-8 for up to 48 h. In summary, the most significant effects observed in the present study which may contribute to the toxicity of JP-8 jet fuel in cultured rat liver cells include effects on GJIC, ROS production, and GSH depletion at high (i.e., greater than 2%) JP-8 concentrations.

Wilson, C. L.↗

NASA NTRSDate not supplied

SHERLOC: Results of the first 350 sols of operations

On February 18th 2021, the Perseverance rover landed in Jezero crater, Mars. This site was chosen because orbiter data analysis provides evidence that the crater hosted a stream-fed lake during the Martian Noachian period. The Octavia Butler landing site is located ~1.9 km east of the remnants of a river delta. Deltaic and lacustrine sediments can preserve biosignatures, making Jezero crater a prime target for Mars sample return science. One of the seven instruments on Perseverance’s science payload is SHERLOC –Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals. SHERLOC combines fluorescence and Raman spectroscopy with microscopic imaging to analyze surface material to better understand the history of the aqueous environments recorded in the rocks of Jezero crater and to search for potential biosignatures. SHERLOC imaging obtains high spatial resolution images of geological targets to identify grain-scale structure and texture. SHERLOC spectroscopy enables high-sensitivity detection, characterization, and spatially resolved correlation of trace organic materials. Native fluorescence emissions from aromatic organic species allow for detection and classification of aromatic organic molecules, whereas Raman scattered photons from molecules allow identification of functional groups of organics, chemicals, and minerals. In the first 300 sols, SHERLOC has analyzed 3 natural surfaces, and 5 abraded rock patches created during the Crater Floor Campaign within Jezero crater. SHERLOC has been able to identify phosphates, amorphous/microcrystalline silicate (AMS), olivine, sulfates, and carbonates in abraded patches in the green zone campaign within Jezero Crater Máaz and Séítah formations. Within these detections we have begun to tell the story of what this crater was like when it was full of liquid water over 3 billion years ago. In each of these samples we have identified fluorescence features that are likely aromatic organics native to the rock interiors. We have identified multiple unique fluorescence signatures, within each of the abraded patches. The organic signatures have either been widely distributed over an extended area, which is probably due to planetary wide dust, or have spatially resolved locations that are collocated with different mineral signatures. Note: Additional information available on attachment.

L. W. Beegle↗

NASA NTRSDate not supplied

Use of an Internal Mercury-Argon Lamp for the Calibration of Raman Frequency in Large Raman Images of Astromaterials

Raman imaging is an emerging tool for the analysis of meteorites, as it is capable of describing the mineralogy and organics within a petrographic context. Adequately examining the heterogeneous composition of a meteorite often requires the collection of large Raman images with long collection times on the time-scale of days. However, the frequency calibration of the Raman instrument/spectrometer drifts on long timescales resulting in low frequency precision for the Raman spectra comprising a large Raman image. Here we utilize a Hg-Ar calibration lamp integrated into our Raman microscope to calibrate the Raman spectra within a Raman image. We characterize this method of calibration in detail.

Ryan S. Jakubek↗

NASA NTRS1999

Unusual Contact-Line Dynamics of Thick Films and Drops

We report several novel phenomena In contact-line and fingering dynamics of macroscopic spinning drops and gravity-driven films with dimensions larger than the capillary length. It is shown through experimental and theoretical analysis that such macroscopic films can exhibit various interfacial shapes, including multi valued ones, near the contact line due to a balance between the external body forces with capillarity. This rich variety of front shapes couples with the usual capillary, viscous, and intermolecular forces at the contact line to produce a rich and unexpected spectrum of contact-line dynamics. A single finger develops when part of the front becomes multivalued on a partially wetting macroscopic spinning drop in contrast to a different mechanism for microscopic drops of completely wetting fluids. Contrary to general expectation, we observe that, at high viscosity and low frequencies of rotation, the speed of a glycerine finger increases with increasing viscosity. Completely wetting Dow Corning 200 Fluid spreads faster over a dry inclined plane than a prewetted one. The presence of a thin prewetted film suppresses fingering both for gravity-driven flow and for spin coating. We analyze some of these unique phenomena in detail and offer qualitative physical explanations for the others.

Veretennikov, Igor↗

NASA NTRS2005

Automated Counting of Particles To Quantify Cleanliness

A machine vision system, similar to systems used in microbiological laboratories to count cultured microbes, has been proposed for quantifying the cleanliness of nominally precisely cleaned hardware by counting residual contaminant particles. The system would include a microscope equipped with an electronic camera and circuitry to digitize the camera output, a personal computer programmed with machine-vision and interface software, and digital storage media. A filter pad, through which had been aspirated solvent from rinsing the hardware in question, would be placed on the microscope stage. A high-resolution image of the filter pad would be recorded. The computer would analyze the image and present a histogram of sizes of particles on the filter. On the basis of the histogram and a measure of the desired level of cleanliness, the hardware would be accepted or rejected. If the hardware were accepted, the image would be saved, along with other information, as a quality record. If the hardware were rejected, the histogram and ancillary information would be recorded for analysis of trends. The software would perceive particles that are too large or too numerous to meet a specified particle-distribution profile. Anomalous particles or fibrous material would be flagged for inspection.

Rhode, James↗

NASA NTRS1992

Glass sample preparation and performance investigations

This final report details the work performed under this delivery order from April 1991 through April 1992. The currently available capabilities for integrated optical performance modeling at MSFC for large and complex systems such as AXAF were investigated. The Integrated Structural Modeling (ISM) program developed by Boeing for the U.S. Air Force was obtained and installed on two DECstations 5000 at MSFC. The structural, thermal and optical analysis programs available in ISM were evaluated. As part of the optomechanical engineering activities, technical support was provided in the design of support structure, mirror assembly, filter wheel assembly and material selection for the Solar X-ray Imager (SXI) program. As part of the fabrication activities, a large number of zerodur glass samples were prepared in different sizes and shapes for acid etching, coating and polishing experiments to characterize the subsurface damage and stresses produced by the grinding and polishing operations. Various optical components for AXAF video microscope and the x-ray test facility were also fabricated. A number of glass fabrication and test instruments such as a scatter plate interferometer, a gravity feed saw and some phenolic cutting blades were fabricated, integrated and tested.

Johnson, R. Barry↗