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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1921

The Effect of the Nature of Surfaces on Resistance as Tested on Struts

The chief concern was to measure the variations of resistance brought about by the nature of the surface of the struts. The struts were spanned with aviation linen, and then covered with one coat of varnish. The top surface was not perfectly smooth after this treatment, being slightly rough owing to the threads and raised fibers of the fabric. The results of the measurements of the surfaces are shown by the dotted lines of the curves plotted in several figures. The resistance is given in terms of the characteristic value. Next, the surface was altered by the removal of any roughness on it by means of filing with sandpaper. The measurements of surfaces thus treated gave values represented by extended lines. The increase of resistance with increasing characteristic value, more or less marked in the first series of measurements, was no longer observable. Resistance always decreases with the increase of characteristic value, excepting in the case of strut 7, which shows a slight tendency to rise again. The reasons for this phenomenon have not yet been fully explained.

Wieselsberger, Ing C↗
NASA NTRS1928

Corrosion Embrittlement of Duralumin IV : The Use of Protective Coatings

Although the corrosion resistance of sheet duralumin can be greatly improved by suitable heat treatment, protection of the surface is still necessary if long life under varied service conditions is to be insured. The coatings used for this purpose may be grouped into three classes: the varnish type of coating, the oxide type produced by a chemical treatment of the surface, and metallic coatings, of which aluminum appears to be the most promising. Since the necessary weather exposure tests are not complete, some of the conclusions regarding the value of various surface coatings are necessarily tentative.

Rawdon, Henry S↗
NASA NTRS1939

Physical Properties of Synthetic Resin Materials

A study was made to determine the physical properties of synthetic resins having paper, canvas, and linen reinforcements, and of laminated wood impregnated with a resin varnish. The results show that commercial resins have moduli of elasticity that are too low for structural considerations. Nevertheless, there do exist plastics that have favorable mechanical properties and, with further development, it should be possible to produce resin products that compare favorably with the light-metal alloys. The results obtained from tests on Compound 1840, resin-impregnated wood, show that this material can stand on its own merit by virtue of a compressive strength four times that of the natural wood. This increase in compressive strength was accomplished with an increase of density to a value slightly below three times the normal value and corrected one of the most serious defects of the natural product.

Fishbein, Meyer↗
NASA NTRS1927

The protection of duralumin from corrosion

Different types of coatings to protect duralumin from corrosion are discussed. Plating, etching, brushing, coloring, painting and varnishing are all investigated.

PROTECTIVE COATINGS - DURALUMIN↗
NASA NTRS1994

Atomic Oxygen Treatment for Non-Contact Removal of Organic Protective Coatings from Painting Surfaces

Current techniques for removal of varnish (lacquer) and other organic protective coatings from paintings involve contact with the surface. This contact can remove pigment, or alter the shape and location of paint on the canvas surface. A thermal energy atomic oxygen plasma, developed to simulate the space environment in low Earth orbit, easily removes these organic materials. Uniform removal of organic protective coatings from the surfaces of paintings is accomplished through chemical reaction. Atomic oxygen will not react with oxides so that most paint pigments will not be affected by the reaction. For paintings containing organic pigments, the exposure can be carefully timed so that the removal stops just short of the pigment. Color samples of Alizarin Crimson, Sap Green, and Zinc White coated with Damar lacquer were exposed to atomic oxygen. The lacquer was easily removed from all of the samples. Additionally, no noticeable change in appearance was observed after the lacquer was reapplied. The same observations were made on a painted canvas test sample obtained from the Cleveland Museum of Art. Scanning electron microscope photographs showed a slight microscopic texturing of the vehicle after exposure. However, there was no removal or disturbance of the paint pigment on the surface. It appears that noncontact cleaning using atomic oxygen may provide a viable alternative to other cleaning techniques. It is especially attractive in cases where the organic protective surface cannot be acceptably or safely removed by conventional techniques.

Rutledge, Sharon K.↗
NASA NTRS1994

Opportunity to sample something different: The dark, unweathered, mafic sands of Cerberus and the Pathfinder 1997 Mars landing

A very important surface component, typically described as 'dark gray material', was not seen at the Viking lander sites, but is common to all low-albedo regions on Mars. Dark material probably includes unaltered mafic volcanic and/or crustal rock and soil not coated by dust, weathering rinds, or varnish. A Pathfinder landing in Cerberus (9 deg N - 16 deg N, 194 deg W - 215 deg W) will guarantee examination of materials that are distinctly different from the two Viking lander sites. In situ study of dark material will provide vital ground truth for orbiter-based observations like those anticipated from Mars '94/'96 and Mars Global Surveyor.

Edgett, Kenneth S.↗
NASA NTRS1993

The US Geological Survey, digital spectral reflectance library: version 1: 0.2 to 3.0 microns

We have developed a digital reflectance spectral library, with management and spectral analysis software. The library includes 500 spectra of 447 samples (some samples include a series of grain sizes) measured from approximately 0.2 to 3.0 microns. The spectral resolution (Full Width Half Maximum) of the reflectance data is less than or equal to 4 nm in the visible (0.2-0.8 microns) and less than or equal 10 nm in the NIR (0.8-2.35 microns). All spectra were corrected to absolute reflectance using an NBS Halon standard. Library management software lets users search on parameters (e.g. chemical formulae, chemical analyses, purity of samples, mineral groups, etc.) as well as spectral features. Minerals from sulfide, oxide, hydroxide, halide, carbonate, nitrate, borate, phosphate, and silicate groups are represented. X-ray and chemical analyses are tabulated for many of the entries, and all samples have been evaluated for spectral purity. The library also contains end and intermediate members for the olivine, garnet, scapolite, montmorillonite, muscovite, jarosite, and alunite solid-solution series. We have included representative spectra of H2O ice, kerogen, ammonium-bearing minerals, rare-earth oxides, desert varnish coatings, kaolinite crystallinity series, kaolinite-smectite series, zeolite series, and an extensive evaporite series. Because of the importance of vegetation to climate-change studies we have include 17 spectra of tree leaves, bushes, and grasses.

Clark, Roger N.↗
NASA NTRS1996

Definition of exobiology experiments for future Mars missions

During the past year we have concentrated on two objectives. The first objective is ongoing and is to define the experimental parameters that are necessary to conduct autonomously a mineralogical analysis of the Martian surface in situ using differential thermal analysis coupled with gas chromatography (DTA/GC). The rationale in support of this objective is that proper interpretation of the mineralogical data from the DTA/GC can be used to better describe the present and past environments of Mars, leading to a better assessment of the probability of life evolving on Mars. To meet these objectives we have analyzed a number of samples collected from nature using the DTA/GC. One of the more significant findings was that in samples of desert varnish we detected magnetite and maghemite that may serve as potential biomarkers applicable to DTA/GC analyses of Martian surface material during landed missions. The second objective follows from the first and is to better understand microbe-environment interactions by determining the response of microbes to changes in their environment, including extreme desiccation and solar UV-radiation. The rationale behind this is to develop hypotheses regarding what may have happened to life that may have arose on Mars, and microbial life that may get to the surface of Mars via spacecraft, or meteors from Earth. To accomplish this objective we have exposed microbes, collected from NaCl and gypsum-halite crystals, to the space environment aboard the ESA-German Biopan facility for 15 days. The most significant finding was that these microbes survived the exposure better than others.

Mancinelli, Rocco L.↗
NASA NTRS1998

Atomic Oxygen Treatment as a Method of Recovering Smoke Damaged Paintings

Smoke damage, as a result of a fire, can be difficult to remove from some types of painting media without causing swelling, leaching or pigment movement or removal. A non-contact technique has been developed which can remove soot from the surface of a painting by use of a gently flowing gas containing atomic oxygen. The atomic oxygen chemically reacts with the soot on the surface creating gasses such as carbon monoxide and carbon dioxide which can be removed through the use of an exhaust system. The reaction is limited to the surface so that the process can be timed to stop when the paint layer is reached. Atomic oxygen is a primary component of the low Earth orbital environment, but can be generated on Earth through various methods. This paper will discuss the results of atomic oxygen treatment of soot exposed acrylic gesso, ink on paper, and a varnished oil painting. Reflectance measurements were used to characterize the surfaces before and after treatment.

Rutledge, Sharon K.↗
NASA NTRS2002

Polyesters by Photochemical Cyclopolymerization

The polyesters of this invention are derived from a Diels-Alder cyclopolymerization of a photochemically generated bisdiene with dienophiles, such as di(acrylates), tri (acrylates), di(methacrylates), tri(methacrylates) and mixtures thereof with mono(methacrylates) or mono(acrylate) end-caps. Irradiation of one or more diketones produces two distinct hydroxy o-quinodimethane (photoenol) intermediates. These intermediates are trapped via a Diels-Alder cycloaddition with appropriate dienophiles, e.g., di(acrylates) to give the corresponding in polyesters quantitative yields. When di(acrylates), tri(acrylates) and di and tri(methacrylates) or mixtures thereof with monoacrylate end-caps are used as the dienophile, the resulting polyesters have glass transition temperatures (Tg) as high as 200 C. Polyesters films can be prepared by ultraviolet irradiation of high solids content varnishes of the monomers in a small amount of solvent, e.g., cyclohexanone, dimethyl formamide, N-methylpyrollidone and the like. These polyesters, i.e. polyesters are characterized as having high glass transition temperatures, good mechanical properties and improved processing in the manufacture of composites, adhesives, electronic materials and films.

Michael A Meador↗
NASA NTRS2003

Polyimides by Photochemical Cyclopolymerization

The polyimides of this invention are derived from a Diels-Alder cyclopolymerization of a photochemically generated bisdiene with dienophiles, such as bismaleimides, trismaleimides and mixtures thereof with maleimide end-caps. Irradiation of one or more diketones produces two distinct hydroxy o-quinodimethane (photoenol) intermediates. These intermediates are trapped via a Diels-Alder cycloaddition with appropriate dienophiles, e.g., bismaleimide and/or trismaleimides to give the corresponding polyimides in quantitative yields. When bismaleimides, trismaleimides or mixtures thereof with maleimide end-caps are used as the dienophile, the resulting polyimides have glass transition temperatures (Tg) as high as 300 C. Polyimide films can be prepared by ultraviolet irradiation of high solids content varnishes of the monomers in a small amount of solvent, e.g., cyclohexanone, dimethyl formamide, N-methylpyrollidone and the like. These polyimides are characterized as having high glass transition temperatures, good mechanical properties and improved processing in the manufacture of adhesives, electronic materials and films.

Michael A Meador↗
NASA NTRS2003

Mars Hematite Site: Potential for Preservation of Microfossils

Defining locations where conditions may have been favorable for life is a key objective for the exploration of Mars. Of prime importance are sites where conditions may have been favorable for the preservation of evidence of pre-biotic or biotic processes. Areas displaying significant concentrations of the mineral hematite (alpha-Fe2O3) have been identified from orbit by thermal emission spectrometry. The largest such deposit, in Sinus Meridiani, is a strong candidate landing site for one of the twin Mars Exploration Rovers, scheduled to launch in 2003. The Martian hematite site may have significance in the search for evidence of extraterrestrial life. Since iron oxides can form as aqueous mineral precipitates, the potential exists for preserving microscopic evidence of life in ecosystems that deposit iron oxides. Terrestrial hematite deposits proposed as possible analogs for the hematite sites on Mars include massive (banded) iron formations, iron oxide hydrothermal deposits, iron-rich laterites and ferricrete soils, and rock varnish. We are engaged in a systematic effort to document the evidence of life preserved in iron oxide deposits from each of these environments.

Allen, Carlton C.↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Mars: Surface Coatings, Mineralogy, and Surface Properties

The session "Mars: Surface Coatings, Mineralogy, and Surface Properties" contained the following reports:High-Silica Rock Coatings: TES Surface-Type 2 and Chemical Weathering on Mars; Old Desert Varnish-like Coatings and Young Breccias at the Mars Pathfinder Landing Site; Analyses of IR-Stealthy and Coated Surface Materials: A Comparison of LIBS and Reflectance Spectra and Their Application to Mars Surface Exploration; Contrasting Interpretations of TES Spectra of the 2003 Rover:Opportunity-Landing Site: Hematite Coatings and Gray Hematite; A New Hematite Formation Mechanism for Mars; Geomorphic and Diagenetic Analogs to Hematite Regions on Mars: Examples from Jurassic Sandstones of Southern Utah, USA; The Geologic Record of Early Mars: A Layered, Cratered, and "Valley-"ed: Volume; A Simple Approach to Estimating Surface Emissivity with THEMIS; A Large Scale Topographic Correction for THEMIS Data; Thermophysical Properties of Meridiani Planum, Mars; Thermophysical and Spectral Properties of Gusev, the MER-Spirit Landing Site on Mars; Determining Water Content of Geologic Materials Using Reflectance Spectroscopy; and Global Mapping of Martian Bound Water at 6.1 Microns Based on TES Data: Seasonal Hydration.

Source record↗
NASA NTRS2004

Signs of Life in Meridiani Planum: What Might Opportunity See (Or Miss)?

The Meridiani Planum hematite deposit has been designated as the prime landing site for Opportunity, one of the two Mars Exploration Rover (MER) spacecraft. Iron oxide and hydroxide minerals, including hematite, can mineralize and preserve microfossils and physical biomarkers. Previous research by ourselves and others, summarized below, has demonstrated such mineralization in a variety of terrestrial hematite deposits. Our most recent study has focused on the mineralization of microorganisms in rock varnish, the iron- and manganese-rich layers that coat rocks in many arid environments.

Allen, C. C.↗
NASA NTRS2001

Importance of a martian hematite site for astrobiology

Defining locations where conditions may have been favorable for life is a key objective for the exploration of Mars. Of prime importance are sites where conditions may have been favorable for the preservation of evidence of prebiotic or biotic processes. Areas displaying significant concentrations of the mineral hematite (alpha-Fe2O3), recently identified by thermal emission spectrometry, may have significance in the search for evidence of extraterrestrial life. Since iron oxides can form as aqueous mineral precipitates, the potential exists to preserve microscopic evidence of life in iron oxide-depositing ecosystems. Terrestrial hematite deposits proposed as possible analogs for hematite deposits on Mars include massive (banded) iron formations, iron oxide hydrothermal deposits, iron-rich laterites and ferricrete soils, and rock varnish. We report the potential for long-term preservation of microfossils by iron oxide mineralization in specimens of the approximately 2,100-Ma banded iron deposit of the Gunflint Formation, Canada. Scanning and analytical electron microscopy reveals micrometer-scale rods, spheres, and filaments consisting predominantly of iron and oxygen with minor carbon. We interpret these objects as microbial cells permineralized by an iron oxide, presumably hematite. The confirmation of ancient martian microbial life in hematite deposits will require the return of samples to terrestrial laboratories. A hematite-rich deposit composed of aqueous iron oxide precipitates may thus prove to be a prime site for future sample return.

Exobiology/methods↗
NASA NTRS2005

Atomic Oxygen Treatment and Its Effect on a Variety of Artist's Media

Atomic oxygen treatment has been investigated as an unconventional option for art restoration where conventional methods have not been effective. Exposure of surfaces to atomic oxygen was first performed to investigate the durability of materials in the low Earth orbit environment of space. The use of the ground based environmental simulation chambers, developed for atomic oxygen exposure testing, has been investigated in collaboration with conservators at a variety of institutions, as a method to clean the surfaces of works of art. The atomic oxygen treatment technique has been evaluated as a method to remove soot and char from the surface of oil paint (both varnished and unvarnished), watercolors, acrylic paint, and fabric as well as the removal of graffiti and other marks from surfaces which are too porous to lend themselves to conventional solvent removal techniques. This paper will discuss the treatment of these surfaces giving an example of each and a discussion of the treatment results.

Miller, Sharon K. R.↗
NASA NTRS2005

Iron-tolerant Cyanobacteria as a Tool to Study Terrestrial and Extraterrestrial Iron Deposition

We are investigating biological mechanisms of terrestrial iron deposition as analogs for Martian hematite recently confirmed by. Possible terrestrial analogs include iron oxide hydrothermal deposits, rock varnish, iron-rich laterites, ferricrete soils, moki balls, and banded iron formations (BIFs). With the discovery of recent volcanic activity in the summit craters of five Martian volcanoes, renewed interest in the iron dynamics of terrestrial hydrothermal environments and associated microorganisms is warranted. In this study we describe a new genus and species of CB exhibiting elevated dissolved iron tolerance and the ability to precipitate hematite on the surface of their exopolymeric sheathes.

Brown, I. I.↗