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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

The effects of simulated low Earth orbit environments on spacecraft thermal control coatings

Candidate Space Station Freedom radiator coatings including Z-93, YB-71, anodized aluminum and SiO(x) coated silvered Teflon have been characterized for optical properties degradation upon exposure to environments containing atomic oxygen, vacuum ultraviolet (VUV) radiation, and/or silicone contamination. YB-71 coating showed a blue-gray discoloration, which has not been observed in space, upon exposure in atomic oxygen facilities which also provide exaggerated VUV radiation. This is evidence that damage mechanisms occur in these ground laboratory facilities which are different from those which occur in space. Radiator coatings exposed to an electron cyclotron resonance (ECR) atomic oxygen source in the presence of silicone-containing samples showed severe darkening from the intense VUV radiation provided by the ECR and from silicone contamination. Samples exposed to atomic oxygen from the ECR source and to VUV lamps, simultaneously, with in situ reflectance measurement, showed that significantly greater degradation occurred when samples received line-of-site ECR beam exposure than when samples were exposed to atomic oxygen scattered off of quartz surfaces without line-of-site view of the ECR beam. For white paints, exposure to air following atomic oxygen/VUV exposure reversed the darkening due to VUV damage. This illustrates the importance of in situ reflectance measurement.

Dever, Joyce A.↗
NASA NTRS1993

Effects of long term space environment exposure on optical substrates and coatings (S0050-2)

Eastman Kodak Company included twelve substrate and coating samples on the Long Duration Exposure Facility (LDEF) structure. There were three Fused Silica and three Ultra Low Expansion (ULE) uncoated glass samples, two ULE samples with a high reflectance silver coating, two Fused Silica samples with an antireflectance coating, and two Fused silica samples with a solar rejection coating. A set of duplicate control samples was also manufactured and stored in a controlled environment for comparison purposes. Kodak's samples were included as a subset of the Georgia Institute of Technology tray, which was located on row 5-E, tray S0050-2. This placed the samples on the trailing edge of the structure, which protected them from the effects of atomic oxygen bombardment. An evaluation of the flight samples for effects from the 5 year mission showed that a contaminant was deposited on the samples, a micrometeoroid impact occurred on one of the samples, and the radiation darkening which was expected for the glass did not occur. The results are listed in more detail.

Harvey, Keith↗
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 NTRS1994

Thin CVD Coating Protects Titanium Aluminide Alloys

Feasibility of using very thin CVD coatings to provide both protection against oxidation and surfaces of low catalytic activity for thin metallic heat-shield materials demonstrated. Use of aluminum in compositions increases emittances of coatings and reduces transport of oxygen through coatings to substrates. Coatings light in weight and applied to foil-gauge materials with minimum weight penalties.

Clark, Ronald↗
NASA NTRS1993

Transparent conductive coatings in the far ultraviolet

In certain cases a space-borne optical instrument with a dielectric window requires a transparent conductive coating deposited on the window to remove the electrostatic charge collected due to the bombardment of ionized particles. Semiconductor and metal films are studied for use as transparent conductive coatings for the front window of far ultraviolet camera. Cr is found to be the best coating material. The theoretical search for the semiconductor and metal coating materials and experimental results for ITO and Cr films are reported.

Kim, Jongmin↗
NASA NTRS1991

Thick thermal barrier coatings for diesel components

An engineered thick thermal barrier coating consisting of multiple layers of zirconia and CoCrAlY with a zirconia top layer and having a system thermal conductance less than 410 w/m(exp 2)K exceeded the 100 hour engine durability goals set forth in this program. The thermal barrier coatings were intact at the test conclusion. Back to back single cylinder research engine tests were conducted with watercooled, metal hardware and oil-cooled, thermal barrier coating insulated hardware to determine apparent heat release and fuel economy. Apparent heat release data revealed that the insulated engine had a shorter ignition delay and a longer combustion duration than the metal engine. The insulated engine fuel economy was approximately two percent worse on average for this series of tests. There was no attempt to optimize engine efficiency of the insulated engine by modifying the engine timing, coating, or other techniques.

Yonushonis, T. M.↗
NASA NTRS1993

Atomic oxygen interaction at defect sights in protective coatings on polymers flown on LDEF

Although the Long Duration Exposure Facility (LDEF) has exposed materials with a fixed orientation relative to the ambient low-Earth-orbital environment, arrival of atomic oxygen is angularly distributed as a result of the atomic oxygen's high temperature Maxwellian velocity distribution and the LDEF's orbital inclination. Thus, atomic oxygen entering defects in protective coatings on polymeric surfaces can cause wider undercut cavities than the size of the defect in the protective coating. Because only a small fraction of atomic oxygen reacts upon first impact with most polymeric materials, secondary reactions with lower energy thermally accommodated atomic oxygen can occur. The secondary reactions of scattered and/or thermally accommodated atomic oxygen also contribute to widening the undercut cavity beneath the protective coating defect. As the undercut cavity enlarges, exposing more polymer, the probability of atomic oxygen reacting with underlying polymeric material increases because of multiple opportunities for reaction. Thus, the effective atomic oxygen erosion yield for atoms entering defects increases above that of the unprotected material. Based on the results of analytical modeling and computational modeling, aluminized Kapton multilayer insulation exposed to atomic oxygen on row 9 lost the entire externally exposed layer of polyimide Kapton, yet based on the results of this investigation, the bottom surface aluminum film must have remained in place, but crazed. Atomic oxygen undercutting at defect sites in protective coatings on graphite epoxy composites indicates that between 40 to 100 percent of the atomic oxygen thermally accommodates upon impact, and that the reaction probability of thermally accommodated atomic oxygen may range from 7.7 x 10(exp -6) to 2.1 x 10(exp -3), depending upon the degree of thermal accommodation upon each impact.

Banks, Bruce A.↗
NASA NTRS1994

The tribology of PS212 coatings and PM212 composites for the lubrication of titanium 6Al-4V components of a Stirling engine space power system

The Stirling space power machine incorporates a linear alternator to generate electrical power. The alternator is a reciprocating device that is driven by a solar or nuclear-powered Stirling engine. The power piston and cylinder are made of titanium 6Al-4V (Ti6-4) alloy, and are designed to be lubricated by a hydrodynamically-generated gas film. Rubbing occurs during starts and stops and there is the possibility of an occasional high speed rub. Since titanium is known to have a severe galling tendency in sliding contacts, a 'back-up', self-lubricating coating on the cylinder and/or the piston is needed. This report describes the results of a research program to study the lubrication of Ti6-4 with the following chromium carbide based materials: plasma-sprayed PS212 coatings and sintered PM212 counterfaces. Program objectives are to achieve adherent coatings on Ti6-4 and to measure the friction and wear characteristics of the following sliding combinations under conditions simulative of the Stirling-driven space power linear alternator: Ti6-4/Ti6-4 baseline, Ti6-4/PS212-coated Ti6-4, and PS212-coated Ti6-4/PM212.

Sliney, Harold E.↗
NASA NTRS1994

Probability of detection of defects in coatings with electronic shearography

The goal of this research was to utilize statistical methods to evaluate the probability of detection (POD) of defects in coatings using electronic shearography. The coating system utilized in the POD studies was to be the paint system currently utilized on the external casings of the NASA Space Transportation System (STS) Revised Solid Rocket Motor (RSRM) boosters. The population of samples was to be large enough to determine the minimum defect size for 90 percent probability of detection of 95 percent confidence POD on these coatings. Also, the best methods to excite coatings on aerospace components to induce deformations for measurement by electronic shearography were to be determined.

Maddux, Gary A.↗
NASA NTRS1994

New Trends in Coatings Developments for Turbine Blades: Materials Processing and Repair

Turbine engines for aeronautic applications now have to face strenuous requirements concerning not only operating performances but also reliability and repairability. This evolution of the specifications induces important consequences regarding the choice and the design of turbine blade protective coatings. This paper presents several key features concerning the deposition techniques and the real-life behavior of such coatings: (1) complex aluminides well suited to the protection against high temperature oxidation and hot corrosion of directionally solidified nickel-base superalloy turbine blades; (2) ceramic coatings used as thermal barriers - they have to exhibit both high resistance to thermomechanical fatigue and adequate smoothness; (3) processing techniques for thermal barriers, including plasma spraying, electron beam physical vapor deposition and plasma enhanced chemical vapor deposition; and (4) blades and coatings repair techniques.

S Alpérine↗
NASA NTRS1995

Evaluation of Thermal Barrier and PS-200 Self-Lubricating Coatings in an Air-Cooled Rotary Engine

This project provides an evaluation of the feasibility and desirability of applying a thermal barrier coating overlaid with a wear coating on the internal surfaces of the combustion area of rotary engines. Many experiments were conducted with different combinations of coatings applied to engine components of aluminum, iron and titanium, and the engines were run on a well-instrumented test stand. Significant improvements in specific fuel consumption were achieved and the wear coating, PS-200, which was invented at NASA's Lewis Research Center, held up well under severe test conditions.

Moller, Paul S.↗
NASA NTRS1995

Effects of long term space environment exposure on optical substrates and coatings

At the time of our Second LDEF Post-Retrieval Symposium report, we had completed cleaning and measuring the post flight spectral performance of all of the samples except for the fused silica substrate with an antireflection (SiO2/TiO2) coating. As was documented in that report, after cleaning, all of the samples returned to their original pre-flight performance, with the exception of the fused silica anti-reflectance coated sample, which had significant degraded performance. All normal methods of removing the contaminant from the surface of this sample failed except for oxygen plasma etch. At the time of the previous report, we had only exposed the sample to three hours of plasma etch. We have since continued the plasma etch for a total of 32 hours, after which time, the transmission of the sample almost reached its pre-flight values. The peak areas of the transmission curves remained shifted approximately 150 nm. Of interest is the fact that the control samples, which hadn't flown, did not exhibit any spectral shifting. In summary, after the 6 yr exposure to the space environment, all of the coatings and substrates returned to their pre-flight performance after cleaning, with the exception of the antireflection coated fused silica sample. On this sample, the spectral transmission curves shifted approximately 150 nm.

Vallimont, John↗
NASA NTRS1995

Weightless Environment Training Facility (WETF) Materials Coating Evaluation, Volume 1

The Weightless Environment Training Facility Material Coating Evaluation project has included preparing, coating, testing, and evaluating 800 test panels of three differing substrates. Ten selected coating systems were evaluated in six separate exposure environments and subject to three tests for physical properties. Substrate materials were identified, the manner of surface preparation described, and exposure environments defined. Exposure environments included immersion exposure, cyclic exposure, and field exposure. Cyclic exposures, specifically QUV-Weatherometer and the KTA Envirotest were found to be the most agressive of the environments included in the study when all three evaluation criteria are considered. This was found to result primarily from chalking of the coatings under ultraviolet (UV) light exposure. Volumes 2 and 3 hold the 5 appendices to this report.

Source record↗
NASA NTRS1995

Weightless Environment Training Facility (WETF) materials coating evaluation, volume 2

This volume consists of Appendices A and B to the report on the Weightless Environment Training Facility Materials Coating Evaluation project. The project selected 10 coating systems to be evaluated in six separate exposure environments, and subject to three tests for physical properties. Appendix A holds the coating system, surface preparation, and application data. Appendix B holds the coating material infrared spectra.

Source record↗
NASA NTRS1995

A simulation technique for predicting thickness of thermal sprayed coatings

The complexity of many of the components being coated today using the thermal spray process makes the trial and error approach traditionally followed in depositing a uniform coating inadequate, thereby necessitating a more analytical approach to developing robotic trajectories. A two dimensional finite difference simulation model has been developed to predict the thickness of coatings deposited using the thermal spray process. The model couples robotic and component trajectories and thermal spraying parameters to predict coating thickness. Simulations and experimental verification were performed on a rotating disk to evaluate the predictive capabilities of the approach.

Goedjen, John G.↗
NASA NTRS1995

Probability of detection of defects in coatings with electronic shearography

The goal of this research was to utilize statistical methods to evaluate the probability of detection (POD) of defects in coatings using electronic shearography. The coating system utilized in the POD studies was to be the paint system currently utilized on the external casings of the NASA space transportation system reusable solid rocket motor boosters. The population of samples was to be large enough to determine the minimum defect size for 90-percent POD of 95-percent confidence POD on these coatings. Also, the best methods to excite coatings on aerospace components to induce deformations for measurement by electronic shearography were to be determined.

Russell, S. S.↗
NASA NTRS1995

Replacement of corrosion protection chromate primers and paints used in cryogenic applications on the Space Shuttle with wire arc sprayed aluminum coatings

With the advent of new environmental laws restricting volatile organic compounds and hexavalent chrome emissions, 'environmentally safe' thermal spray coatings are being developed to replace the traditional corrosion protection chromate primers. A wire arc sprayed aluminum coating is being developed for corrosion protection of low pressure liquid hydrogen carrying ducts on the Space Shuttle Main Engine. Currently, this hardware utilizes a chromate primer to provide protection against corrosion pitting and stress corrosion cracking induced by the cryogenic operating environment. The wire are sprayed aluminum coating has been found to have good potential to provide corrosion protection for flight hardware in cryogenic applications. The coating development, adhesion test, corrosion test and cryogenic flexibility test results will be presented.

Daniel, R. L.↗
NASA NTRS1995

Environmentally regulated aerospace coatings

Aerospace coatings represent a complex technology which must meet stringent performance requirements in the protection of aerospace vehicles. Topcoats and primers are used, primarily, to protect the structural elements of the air vehicle from exposure to and subsequent degradation by environmental elements. There are also many coatings which perform special functions, i.e., chafing resistance, rain erosion resistance, radiation and electric effects, fuel tank coatings, maskants, wire and fastener coatings. The scheduled promulgation of federal environmental regulations for aerospace manufacture and rework materials and processes will regulate the emissions of photochemically reactive precursors to smog and air toxics. Aerospace organizations will be required to identify, qualify and implement less polluting materials. The elimination of ozone depleting chemicals (ODC's) and implementation of pollution prevention requirements are added constraints which must be addressed concurrently. The broad categories of operations affected are the manufacture, operation, maintenance, and repair of military, commercial, general aviation, and space vehicles. The federal aerospace regulations were developed around the precept that technology had to be available to support the reduction of organic and air toxic emissions, i.e., the regulations cannot be technology forcing. In many cases, the regulations which are currently in effect in the South Coast Air Quality Management District (SCAQMD), located in Southern California, were used as the baseline for the federal regulations. This paper addresses strategies used by Southern California aerospace organizations to cope with these regulatory impacts on aerospace productions programs. All of these regulatory changes are scheduled for implementation in 1993 and 1994, with varying compliance dates established.

Morris, Virginia L.↗