Titles:

• MISSE PEACE Polymers Atomic Oxygen Erosion Results  June 2006

• Ground-to-Space Effective Atomic Oxygen Fluence Correlation for DC 93-500 Silicone  March-April 2006

• Determination of Ground-Laboratory to In-Space Effective Atomic Oxygen Fluence for DC 93-500 Silicone  2006

• Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon Insulation  2006

• Osteoblast Attachment to a Textured Surface in the Absence of Exogenous Adhesion Proteins  December 2003

• Atomic Oxygen Effects on Spacecraft Materials  September 2003

• Use of Atomic Oxygen for the Determination of Document Alteration  September 2003

• Sputtering Erosion Measurement on Boron Nitride as a Hall Thruster Material  September 2002

• Fast Three-Dimensional Method of Modeling Atomic Oxygen Undercutting of Protected Polymers  May 2002
   
• The Development of Surface Roughness and Implications for Cellular Attachment in Biomedical Applications  November 2001
   
• The Dependence of Atomic Oxygen Undercutting of Protected Kapton® H Upon Defect Size  June 2000
   
• Effects of Ambient High Temperature Exposure on Alumina-Titania High Emittance Surfaces for Solar Dynamic Systems  November 1998
   
• Optical Property Enhancement and Durability Evaluation of Heat Receiver Aperture Shield Materials  January 1998
   
• Electric Arc and Electrochemical Surface Texturing Technologies  September 1997
   
• Performance and Durability of High Emittance Heat Receiver Surfaces for Solar Dynamic Power Systems  March 1994
   
• Modifying Surfaces with Ions and Arcs  December 1993

K. K. de Groh, B. A. Banks, C. E. McCarthy, R. N. Rucker, L. M. Roberts and L. A. Berger, “MISSE PEACE Polymers Atomic Oxygen Erosion Results” in the proceedings of the 2006 National Space & Missile Materials Symposium in conjunction with the 2006 MISSE Post-Retrieval Conference, Orlando, Florida, June 26 - 30, 2006; also NASA TM-2006-214482.

Forty-one different polymer samples, collectively called the Polymer Erosion and Contamination Experiment (PEACE) Polymers, have been exposed to the low Earth orbit (LEO) environment on the exterior of the International Space Station (ISS) for nearly four years as part of Materials International Space Station Experiment 2 (MISSE 2).  The objective of the PEACE Polymers experiment was to determine the atomic oxygen erosion yield of a wide variety of polymeric materials after long term exposure to the space environment.  The polymers range from those commonly used for spacecraft applications, such as Teflon FEP, to more recently developed polymers, such as high temperature polyimide PMR (polymerization of monomer reactants).  Additional polymers were included to explore erosion yield dependence upon chemical composition.  The MISSE PEACE Polymers experiment was flown in MISSE Passive Experiment Carrier 2 (PEC 2), tray 1, on the exterior of the ISS Quest Airlock and was exposed to atomic oxygen along with solar and charged particle radiation.  MISSE 2 was successfully retrieved during a space walk on July 30, 2005 during Discovery’s STS-114 Return to Flight mission.  Details on the specific polymers flown, flight sample fabrication, pre-flight and post-flight characterization techniques, and atomic oxygen fluence calculations are discussed along with a summary of the atomic oxygen erosion yield results.  The MISSE 2 PEACE Polymers experiment is unique because it has the widest variety of polymers flown in LEO for a long duration and provides extremely valuable erosion yield data for spacecraft design purposes.
 

K. K. de Groh, B. A. Banks and D. Ma, “Ground-to-Space Effective Atomic Oxygen Fluence Correlation for DC 93-500 Silicone,” (Special Section: Space Environmental Effects on Materials) Journal of Spacecraft and Rockets, Vol. 43, No. 2, March-April 2006, 414-420.

The objective of this research was to calibrate the ground-to-space effective atomic oxygen fluence for DC 93-500 silicone in a thermal energy electron cyclotron resonance (ECR) oxygen plasma facility. A technique has been developed at NASA Glenn Research Center to determine the equivalent amount of atomic oxygen exposure in an ECR ground-test facility to produce the same degree of atomic oxygen damage as in space. The approach used was to compare changes in the surface hardness of ground test (ECR)-exposed DC 93-500 silicone with DC 93-500 exposed to low Earth orbit (LEO) atomic oxygen as part of a shuttle flight experiment. The ground-to-space effective atomic oxygen fluence correlation was determined based on the fluence in the ECR source that produced the same hardness for the fluence in space. A nanomechanical measurement system operated in conjunction with an atomic force microscope (AFM) was used to determine the surface hardness of the silicones. Hardness vs contact depth measurements were obtained for five ECR-exposed DC 93-500 samples (ECR exposed for 18 to 40 h, corresponding to Kapton effective fluences of 4.2×1020 to 9.4×1020 atoms/cm2, respectively) and for space-exposed DC 93-500 from the Evaluation of Oxygen Interactions with Materials III (EOIM III) shuttle flight experiment, exposed to LEO atomic oxygen (2.3×1020atoms/cm2). Pristine controls for the ECR tests and for the EOIM III flight sample were also evaluated. A ground-to-space correlation value was determined based on correlation values for four contact depths (150, 200, 250, and 300 nm), which represent the near-surface depth data. The results indicate that the Kapton effective atomic oxygen fluence in the ECR facility needs to be 2.64 times higher than in LEO to replicate equivalent exposure damage in the ground test silicone as occurred in the space exposed silicone.

K. K. de Groh, B. A. Banks and D. Ma, “Determination of Ground-Laboratory to In-Space Effective Atomic Oxygen Fluence for DC 93-500 Silicone,” in Space Technology Proceedings, Protection of Materials and Structures from the Space Environment, Proceedings of the 7th International Space Conference, ICPMSE-7, Ed. J. I. Kleiman, Kluwer Academic Publishers, 2006.

The objective of this research was to calibrate the ground-to-space effective atomic oxygen fluence for DC 93-500 silicone in a thermal energy electron cyclotron resonance (ECR) oxygen plasma facility.  Silicones, a commonly used spacecraft material, do not chemically erode with atomic oxygen attack like other organic materials.  Silicones react with atomic oxygen and form an oxidized hardened silicate surface layer. Therefore, the effective atomic oxygen fluence in a ground test facility should not be determined based on mass loss measurements, as they are with organic polymers, such as Kapton, a polyimide.  A technique has been developed at the Glenn Research Center to determine the equivalent amount of atomic oxygen exposure in an ECR ground test facility to produce the same degree of atomic oxygen damage as in space.  The approach used was to compare changes in the surface hardness of ground test (ECR) exposed DC 93-500 silicone with DC 93-500 exposed to low Earth orbit (LEO) atomic oxygen as part of a shuttle flight experiment.  The ground to in-space effective atomic oxygen fluence correlation was deter¬mined based on the fluence in the ECR source that produced the same hardness for the fluence in-space.  Because microhardness measurements need to be obtained on the very surface layer of a rubber substrate (with primarily elastic deformation) traditional techniques for microhardness that apply large forces and indenta¬tions based on plastic deforma¬tion, could not be used.  Therefore, a nanomechanical measurement system operated in conjunction with an atomic force microscope (AFM) was used to determine the surface hardness of the silicones.  The nanomechanical system can provide ultra light load indentations and can continuously measure force and displacement as an indent is made.  Hardness versus contact depth measurements were obtained for five ECR exposed DC 93-500 samples (ECR exposed for 18 hrs to 40 hrs, corresponding to Kapton effective fluences of 4.2 x 1020 to 9.4 x 1020 atoms/cm2, respectively) and for a space exposed DC 93-500 from the Evaluation of Oxygen Interactions with Materials III (EOIM III) shuttle flight experiment, exposed to LEO atomic oxygen for 2.3 x 1020 atoms/cm2.  Pristine controls for the ECR tests and for the EOIM III flight sample were also evaluated.  A ground-to-space correlation value was determined based on correlation values for four contact depths (150, 200, 250 & 300 nm), which represent the near surface depth data.  The results indicate that the Kapton effective atomic oxygen fluence in the ECR facility needs to be 2.64 times higher than in LEO to replicate equivalent exposure damage in the ground test silicone as occurred in the space exposed silicone.

K. K. de Groh, J. A. Dever, A. Snyder, S. Kaminski, C. E. McCarthy, A.L. Rapoport and R. N. Rucker, "Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon Insulation," in “Materials in Extreme Environments,” edited by C. Mailhiot, P.B. Saganti, D. Ila (Mater. Res. Soc. Symp. Proc. 929, Warrendale, PA, 2006), 0929-II05-08.

A section of the retrieved Hubble Space Telescope (HST) solar array drive arm (SADA) multilayer insulation (MLI), which experienced 8.25 years of space exposure, was analyzed for environmental durability of the top layer of silver-Teflon fluorinated ethylene propylene (Ag-FEP).  Because the SADA MLI had solar and anti-solar facing surfaces and was exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on the environmental degradation of Ag-FEP, a commonly used spacecraft thermal control material.  Data obtained included tensile properties, solar absorptance, surface morphology and chemistry.  The solar facing surface was found to be extremely embrittled and contained numerous through-thickness cracks.  Tensile testing indicated that the solar facing surface lost 60% of its mechanical strength and 90% of its elasticity while the anti-solar facing surface had ductility similar to pristine FEP.  The solar absorptance of both the solar facing surface (0.155  0.032) and the anti-solar facing surface (0.208  0.012) were found to be greater than pristine Ag-FEP (0.074).  Solar facing and anti-solar facing surfaces were microscopically textured, and locations of isolated contamination were present on the anti-solar surface resulting in increased localized texturing.  Yet, the overall texture was significantly more pronounced on the solar facing surface indicating a synergistic effect of combined solar exposure and increased heating with atomic oxygen erosion.  The results indicate a very strong dependence of degradation, particularly embrittlement, upon solar exposure with orbital thermal cycling having a significant effect.

dMata, A., Su, X., Fleischman, A., Banks, B., Miller, S., and Midura, R., "Osteoblast Attachment to a Textured Surface in the Absence of Exogenous Adhesion Proteins,” IEEE Transactions on Nanobioscience, Vol. 2, No. 4, December 2003.

The present study investigated whether osteoblasts could attach to a culture substratum through a surface texture-dependent mechanism. Four test groups were used: untextured (A), and three texture groups with maximum feature sizes of <0.5 µm (B), 2 µm (C), and 4 µm (D), respectively. All surfaces were coated with the non-adhesive protein bovine serum albumin (BSA). Osteoblasts were allowed to adhere in serum-free medium for either 1 or 4 hours (h), at which time non-adherent cells were removed. At 4 h, un-textured surface A exhibited no cell attachment, while textured surfaces B, C, and D exhibited 9%, 32% and 16% cell adhesion, respectively. At 16 h of incubation, adherent osteoblasts on textured surface C exhibited focal adhesion contacts and microfilament stress-fiber bundles. These results indicate that micro-textured surfaces in the absence of exogenous adhesive proteins can facilitate osteoblast adhesion. 


Banks, B., Miller, S., de Groh, K., and Demko, R., “Atomic Oxygen Effects on Spacecraft Materials,” NASA TM-2003-212484, Paper presented at the 9th International Symposium on Materials in a Space Environment, Noordwijk, The Netherlands, June 16-20, 2003; or "Scattered Atomic Oxygen Effects on Spacecraft Materials," Proceedings of the 9th International Symposium on Materials in a Space Environment, Noordwijk, The Netherlands, 16-20 June 2003 (ESA SP-540, September 2003)

Low Earth orbital (LEO) atomic oxygen cannot only erode the external surfaces of polymers on spacecraft, but can cause degradation of surfaces internal to components on the spacecraft where openings to the space environment exist. Although atomic oxygen attack on internal or interior surfaces may not have direct exposure to the LEO atomic oxygen flux, scattered impingement can have can have serious degradation effects where sensitive interior surfaces are present. The effects of atomic oxygen erosion of polymers interior to an aperture on a spacecraft is simulated using Monte Carlo computational techniques. A 2-dimensional model is used to provide quantitative indications of the attenuation of atomic oxygen flux as a function of distance into a parallel walled cavity. The degree of erosion relative is compared between the various interior locations and the external surface of an LEO spacecraft.

Banks, B. and Klubnik, L. "Use of Atomic Oxygen for the Determination of Document Alteration," NASA TM-2003-212519, Paper presented at the 34th Annual Education Seminar sponsored by the Independent Association of Questioned Document Examiners, Inc., Earth City, MO, September 24-27, 2003.

Atomic oxygen, which normally is found only the near Earth space environment, causes oxidation and erosion of polymers on spacecraft. The development of technology to prevent this degradation has required NASA to develop ground laboratory facilities that generate atomic oxygen.  Atomic oxygen has also been found to be able to oxidize most types of ink from a variety of types of pens.  The use of atomic oxygen to identify alteration of documents has been investigated and is reported. Results of testing indicates that for many types of ink, pen, and paper, identification of document alteration of pen and ink numbers and evidence of alteration can be made visible by exposing the questionable writing to atomic oxygen.  Atomic oxygen provides discrimination because different inks may oxidize at different rates, the amount of time between delayed alterations, may add to ink thickness at crossings, and the end of pen strokes tend to have much thicker ink deposits than the rest of the character.  Examples and techniques of using atomic oxygen to identify document alteration indicate that the technology can, in many but not all cases, provide discrimination between original and altered documents.

Britton, M., Waters, D., Messer, R., Sechkar, E. and Banks, B., “Sputtering Erosion Measurement on Boron Nitride as a Hall Thruster Material,” NASA TM-2002-211837, September 2002.

The durability of a high-powered Hall thruster may be limited by the sputter erosion resistance of its components.  During normal operation, a small fraction of the accelerated ions will impact the interior of the main discharge channel, causing its gradual erosion.   A laboratory experiment was conducted to simulate the sputter erosion of a Hall thruster.  Tests of sputter etch rate were carried out using 300 to 1000 eV Xenon ions impinging on boron nitride substrates with angles of attack ranging from 30 to 75 degrees from horizontal.  The erosion rates varied from 3.41 to 14.37 Angstroms/[sec•(mA/cm2)] and were found to depend on the ion energy and angle of attack, which is consistent with the behavior of other materials.

Snyder, A., Banks, B. A., “Fast Three-Dimensional Method of Modeling Atomic Oxygen Undercutting of Protected Polymers,” presented at the Sixth International Conference on Protection of Materials and Structures from the Space Environment, NASA TM-2002-211578, Toronto, Canada, May 1-3, 2002.

A method is presented to model atomic oxygen erosion of protected polymers in low Earth orbit (LEO). Undercutting of protected polymers by atomic oxygen occurs in LEO due to the presence of scratch, crack or pin-window defects in the protective coatings. As a means of providing a better understanding of undercutting processes, a fast method of modeling atomic-oxygen undercutting of protected polymers has been developed. Current simulation methods often rely on computationally expensive ray-tracing procedures to track the surface-to-surface movement of individual “atoms”. The method introduced in this paper replaces slow individual particle approaches by substituting a model that utilizes both a geometric configuration-factor technique, which governs the diffuse transport of atoms between surfaces, and an efficient telescoping series algorithm, which rapidly integrates the cumulative effects stemming from the numerous atomic oxygen events occurring at the surfaces of an undercut cavity. This new method facilitates the systematic study of three-dimensional undercutting by allowing rapid simulations to be made over a wide range of erosion parameters.
 

The application of a microscopic surface texture produced by ion beam sputter texturing to the surfaces of polymer implants has been shown to result in significant increases in cellular attachment compared to smooth surface implants in animal studies. A collaborative program between NASA Glenn Research Center and the Cleveland Clinic Foundation has been established to evaluate the potential for improving osteoblast attachment to surfaces that have been microscopically roughened by atomic oxygen texturing. The range of surface textures that is feasible depends upon both the texturing process and the duration of treatment. To determine whether surface texture saturates or continues to increase with treatment duration, an effort was conducted to examine the development of surface textures produced by various physical and chemical erosion processes. Both experimental tests and computational modeling were performed to explore the growth of surface texture with treatment time. Surface texturing by means of abrasive grit blasting of glass, stainless steel and polymethylmethacrylate surfaces was examined to measure the growth in roughness with grit blasting duration by surface profilometry measurements. Laboratory tests and computational modeling was also conducted to examine the development of texture on Aclar® (chlorotrifluoroethylene) and Kapton® polyimide, respectively. For the atomic oxygen texturing tests of Aclar®, atomic force microscopy was used to measure the development of texture with atomic oxygen fluence. The results of all the testing and computational modeling support the premise that development of surface roughness obeys Poisson statistics. The results indicate that surface roughness does not saturate but increases as the square root of the treatment time.

Understanding the behavior of polymeric materials when exposed to the low-Earth-orbit (LEO) environment is important in predicting performance characteristics such as in-space durability. Atomic oxygen (AO) present in LEO is known to be the principle agent in causing undercutting erosion of SiOx protected polyimide Kapton® H film, which serves as a mechanically stable blanket material in solar arrays. The rate of undercutting is dependent on the rate of arrival, directionality and energy of the AO with respect to the film surface. The erosion rate also depends on the distribution of the size of defects existing in the protective coating. This paper presents results of experimental ground testing using low energy, isotropic AO flux together with numerical modeling to determine the dependence of undercutting erosion upon defect size.

de Groh, K. K., Smith, D. C., Wheeler, D. R., and MacLachlan, B. J., "Effects of Ambient High Temperature Exposure on Alumina-Titania High Emittance Surfaces for Solar Dynamic Systems", prepared for the Space Technology and Applications International Forum, 1999, AIP CP 458, pp. 627-635, NASA TM-1998-208813.

Solar dynamic (SD) space power systems require durable, high emittance surfaces on a number of critical components, such as heat receiver interior surfaces and parasitic load radiator (PLR) elements. To enhance surface characteristics, an alumina-titania coating has been applied to 500 heat receiver thermal energy containment canisters and the PLR of NASA Glenn Research Center's (GRC) 2kW SD ground test demonstrator (GTD). The alumina-titania coating was chosen because it had been found to maintain its high emittance under vacuum at high temperatures for an extended period. However, preflight verification of SD system components, such as the PLR, require operation at ambient pressure and high temperatures. Therefore, the purpose of this research was to evaluate the durability of he alumina-titania coating at high temperature in air. Fifteen of sixteen alumina-titania coated Incoloy samples were exposed to high temperatures for various durations (2 to 32 hours). Samples were characterized prior to, and after, heat treatment for reflectance, solar absorptance, room temperature emittance, and emittance at 1200° F. Samples were also examined to detect physical defects and to determine surface chemistry using optical microscopy, scanning electron microscopy, operated with an energy dispersive spectroscopy (EDS) system, and x-ray photoelectron spectroscopy (XPS). Visual examination of the heat-treated samples showed a whitening of samples exposed to temperatures of 1000° F and above. Correspondingly, the optical properties of these samples degraded. A sample exposed to 1500° F for 24 hours had whitened and the thermal emittance at 1200° F had decreased from the non-heat treated value of 0.94 to 0.62. The coating on this sample had become embrittled, with spalling off the substrate noticeable at several locations. Based on this research it is recommended that preflight testing of SD components with alumina-titania coatings be restricted to temperatures no greater than 600° F in air to avoid optical degradation. Moreover, components with the alumina-titania coating are likely to experience optical property degradation with direct atomic oxygen exposure in space.

de Groh, K. K., Jaworske, D. A., and Smith, D. C., "Optical Property Enhancement and Durability Evaluation of Heat Receiver Aperture Shield Materials", prepared for the 36th Aerospace Sciences Meeting and Exhibit sponsored by the American Institute of Aeronautics and Astronautics, Reno, Nevada, January 12-15, 1998.

Solar Dynamic (SD) power systems have been investigated by the National Aeronautics and Space Administration (NASA) for electrical power generation in space. As part of the International Space Station (ISS) program, NASA Glenn Research Center (GRC) teamed with the Russian Space Agency (RSA) to build a SD system to be flown on the Russian Space Station MIR. Under the US/Russian SD Flight Demonstration (SDFD) program, GRC worked with AlliedSignal Aerospace, the heat receiver contractor, on the development, characterization, and durability testing of materials to obtain appropriate optical and thermal properties for the SDFD heat receiver aperture shield. The aperture shield is composed of refractory metal multi-foil insulation (MFI) attached to an aperture back plate. Because of anticipated off-pointing periods, the aperture shield was designed to withstand the extreme temperatures that 80 W/cm² would produce. To minimize the temperature that the aperture shield will reach during off-pointing, it was desired for the aperture shield exterior layer to have a solar absorptance (a _s) to thermal emittance (e ) ratio as small as possible. In addition, a very low specular reflectance (r _s < 0.1) was also necessary, because reflected concentrated sunlight could cause overheating of the concentrator which is undesirable. Testing was conducted at GRC to evaluate pristine and optical property enhanced molybdenum and tungsten foils and screen covered foils. Molybdenum and tungsten foils were grit-blasted using silicon carbide or alumina grit under various grit-blasting conditions for optical property enhancement. Black rhenium coated tungsten foil was also evaluated. Tungsten, black rhenium-coated tungsten, and grit-blasted tungsten screens of various mesh sizes were placed over the pristine and grit-blasted foils for optical property characterization. Grit-blasting was found to be effective in decreasing the specular reflectance and absorptance/emittance ratio of the refractory foils. The placement of a screen further enhanced these optical properties, with a grit-blasted screen over a grit-blasted foil producing the best results. Based on the optical property enhancement results, samples were tested for atomic oxygen (AO) and vacuum heat treatment (VHT) durability. Grit-blasted (Al₂O₃ grit) 2 mil tungsten foil was chosen for the exterior layer of the SDFD heat receiver shield. A 0.007 in. diameter, 20x20 mesh tungsten screen was chosen to cover the tungsten foil. Based on these test results, a heat receiver aperture shield test unit has been built by Aerospace Design and Development (A.D.D.) with the screen covered grit-blast tungsten foil exterior layers. The aperture shield was tested in GRC's Solar Dynamic Ground Test Demonstration (SDGTD) system to verify the thermal and structural durability of the outer foil layers during an off-pointing period.

Banks, B. A., Rutledge, S. K., and Snyder, S. A., "Electric Arc and Electrochemical Surface Texturing Technologies", prepared for the 11th International Conference on Surface Modification Technologies sponsored by the Society of Metallurgy and Materials, Paris, France, September 8-10, 1997.

Surface texturing of conductive materials can readily be accomplished by means of a moving electric arc which produces a plasma from the environmental gases as well as form the vaporized substrate and arc electrode materials. As the arc is forced to move across the substrate surface, a condensate from the plasma redeposits an extremely rough surface which is intimately mixed and attached to the substrate material. The arc textured surfaces produce greatly enhanced thermal emittance and hold potential for use as high temperature radiator surfaces in space, as well as in systems which use radiative heat dissipation such as computer assisted tomography (CAT) scan systems. Electrochemical texturing of titanium alloys can be accomplished by using sodium chloride solutions along with ultrasonic agitation to produce a random distribution of craters on the surface. The crater size and density can be controlled to produce surface craters appropriately sized for direct bone in-growth of orthopedic implants. Electric arc texturing and electrochemical texturing techniques, surface properties, and potential applications will be presented.
 

Haynes 188, a cobalt-based super-alloy, will be used to make thermal energy storage (TES) containment canisters for a 2 kW solar dynamic ground test demonstrator (SDGTD). Haynes 188 containment canisters with a high thermal emittance (e ) are desired for radiating heat away from local hot spots, improving the heat distribution, which will in turn improve canister service life. In addition to needing a high emittance, the surface needs to be durable in an elevated temperature, high vacuum (» 830° C, <10-7 torr) environment for an extended time period. Thirty-five Haynes 188 samples were exposed to 14 different types of surface modification techniques for emittance and vacuum heat treatment (VHT) durability enhancement. Optical properties were obtained for the modified surfaces. Emittance enhanced samples were exposed to VHT for up to 2692 hours at 827° C and <10-6 torr with integral thermal cycling. Optical properties were taken intermittently during exposure, and after final VHT exposure. The various surface modification treatments increased the emittance of pristine Haynes 188 from 0.11 to 0.86. Seven different surface modification techniques were found to provide surfaces which met the SDGTD receiver VHT durability requirement (e ³ 0.70 after 1000 hours). Of the 7 surface treatments, 2 were found to display excellent VHT durability: alumina-titania (AlTi) coatings (e = 0.85 after 2695 VHT hours) and zirconia-titania-yttria coatings (e = 0.86 after 2024.3 VHT hours). The AlTi coating was chosen for the e enhancement surface modification technique for the SDGTD receiver. Details of the alumina-titania coating and other Haynes 188 emittance surface modification techniques are discussed. Technology from this program will lead to successful demonstration of solar dynamic power for space applications, and has potential for applications in other systems requiring high emittance.
 

NASA originally conducted research in the field of electron bombardment because the technology involves generation of high-velocity ions, which have the potential to produce much higher propellant exhaust velocities for spacecraft than chemical propulsion. As a consequence, considerable data were collected about the effects of ion beams on a wide range of materials. Based on this information, researchers designed specialized surface modification techniques such as ion beam sputter texturing, etching, and simultaneous deposition and etching. Arc-texturing technology was developed as a result of research on high-thermal-emittance radiators. In this process, an electric arc is formed between a carbon or silicone-carbide electrode and a moving metal surface, resulting in durable, microscopically rough surfaces that emit heat more efficiently than coated materials. Atomic-oxygen texturing is a by-product of studies about the effects of atomic oxygen on the surfaces of spacecraft. The purpose of the original research was to find coatings that could withstand atomic-oxygen attack, but it evolved into deliberate bombardment of polymeric materials to increase thermal emittance or reduce coefficient of friction.
 

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