Low Earth Orbital Atomic Oxygen Interactions with Materials

This paper discusses plans and initial results of efforts to characterize optical coatings, coating materials and optical substrates planned for use in the Space Based Laser (SBL) Integrated Flight Experiment (IPX) for their endurance in the low earth orbit (LEO) space environment. High energy laser (HEL) systems such as IPX place very challenging requirements on their constituent optics, and the degradation due to the natural LEO environment creates additional risk to system performance. The SBL program has chosen to mitigate this risk by use of ground and flight experiments. The flight experiment is participation in the collaborative experiment, Materials International Space Station Experiment (MISSE), a program funded by NASA and the U.S. Air Force Research Laboratory. The ground experiments are to use laboratory facilities to simulate the atomic oxygen exposure of the LEO environment. This paper begins with a discussion of the LEO environment and the potential effects on IPX optical components and materials. The next section gives an overview of the IPX and the optical components that make up each of the program elements. Next, an overview of the planned ground experimentation and participation in the MISSE collaboration is given. The final section gives an example of laboratory measurements madeon the samples with SBL legacy as a preview to the results expected from the flight experiment. The first flight of MISSE samples to Space Station Alpha is Summer 2001, with a return to Earth in June 2002. The Low Earth Orbit Environment and the Optics Challenge to IPX High energy laser (HEL) systems require extreme performance from their optics in order to meet system goals. Typically, HEL optics are stressing for high damage resistance, high reflectance, low absorptance, scatter and aberration along with predictable spatial uniformity. Producing such optics has been a main concern of the HEL community since the discovery of the laser. Usually, just building the optics is challenge enough. The space based laser (SBL) integrated flight experiment (IPX) program must make these optics and have them meet mission requirements in the challenging environs of low earth orbit (LEO). The LEO environment can be characterized by exposure to the neutral thermosphere (ambient atmosphere), charged plasma, the thermal environment (including diurnal cycles), exposure to solar radiation, debris/micrometeorites and ionizing radiation. The neutral thermosphere, is the atmospheric layer above an altitude of approximately 100 km. At an altitude of 80 kilometers or greater, solar ultra-violet (UV) bombardment of the tenuous atmosphere initiates chemical reactions and breaks down molecular species to their atomic components. In this region of the atmosphere, the concentration of individual species is essentially determined by weight segregation. At the expected altitude of IPX, ~480 km, the predominant species is atomic oxygen (AO). The abundance of neutral species at altitude is shown in Figure 1.

Low Earth orbit effects on indium tin oxide and polyester and comparison with laboratory simulations

Ablation of materials in the low-earth orbital environment

ABSTRACTAtomic oxygen, formed in Earth's thermosphere, interacts readily with many materials on spacecraft flying in low Earth orbit (LEO). All hydrocarbon based polymers and graphite are easily oxidized upon the impact of ∼4.5 eV atomic oxygen as the spacecraft ram into the residual atmosphere. The resulting interactions can change the morphology and reduce the thickness of these materials. Directed atomic oxygen erosion will result in the development of textured surfaces on all materials with volatile oxidation products. Examples from space flight samples are provided. As a result of the erosive properties of atomic oxygen on polymers and composites, protective coatings have been developed and are used to increase the functional life of polymer films and composites that are exposed to the LEO environment. The atomic oxygen erosion yields for actual and predicted LEO exposure of numerous materials are presented. Results of in-space exposure of vacuum deposited aluminum protective coatings on polyimide Kapton indicate high rates of degradation are associated with aluminum coatings on both surfaces of the Kapton. Computational modeling predictions indicate that less trapping of the atomic oxygen occurs, with less resulting damage, if only the space-exposed surface is coated with vapor deposited aluminum rather than having both surfaces coated.

Satellites in the Low Earth Orbit (LEO) environment face various hazards which threaten the long-term sustainability of the space economy. This article describes the potential dangers to satellites in LEO beyond commonly referenced orbital debris and satellite collisions, including hazards that arise from the LEO environment itself and from other anthropogenic sources such as laser interference and orbital light pollution. As the LEO economy surges in the coming decade, preventative policy such as that proposed in this article could address these risks before they become an issue and ensure that the LEO environment continues to grow sustainably.

Durable and impact-resistant thermoset polymers for the extreme environment of low Earth orbit

Different materials were considered for high-frequency circuit applications requiring exposure to low Earth orbit (LEO) space environment. The potential candidates were TMM3 which is a ceramic thermoset polymer composite, and RO4003 which is a glass reinforced hydrocarbon/ceramic laminate, both manufactured by Rogers Corporation (USA). Various constituents of the space environment can affect these materials’ properties. Atomic oxygen is considered the most hazardous component since it may cause degradation of these materials by etching and/or changing the chemical composition. The candidate materials were tested by exposure to different equivalent atomic oxygen (ATOX) fluences of up to 1.9 × 1021 atoms cm−2. The effects of the atomic oxygen exposures were studied by means of scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), atomic force microscopy (AFM) and mass loss measurements. Both materials were degraded under ATOX exposure, resulting in intensive mass loss as well as changes in surface morphology and chemistry. In order to protect these materials in the LEO environment several protective coatings were evaluated for TMM3. The protective coatings tested were SiO2, CV1144-0 (a clear silicone coating) and SG120FD (a white silicone paint). SG120FD was found to provide the best protection against ATOX irradiation attack, while CV1144-0 provided a sufficient, though somewhat inferior protection.

Radiation damage behavior of carbon/carbon composite in Low Earth Orbit environment

Investigation of degradation mechanisms in mechanical properties of polyimide films exposed to a low earth orbit environment

To study the effects of low earth orbit (LEO) environment on film surface structure and resistance characteristics, reduced graphene oxide paper (rGOP) was irradiated by atomic oxygen (AO) in ground‐based simulation facility. A rough pits surface, chemical oxidation, and change in lamina thickness were found after AO exposure. The erosion yield under AO attack changed from 3.56 × 10 −25 to 4.04 × 10 −25 cm 3 /atom. The resistance data exhibited a linear relationship between R 0 /R and AO fluence, and the maximum AO detect fluence reached to 5 × 10 19 atom/cm 3 when rGOP thickness was 0.8 μm, which implies that greater thickness is expected to improve space service life of rGOP.

The effect of atomic oxygen flux and impact energy on the damage of spacecraft metals

Advances in atomic oxygen resistant polyimide composite films

The relatively poor atomic-oxygen (AO) resistance of the standard polyimide (PI) films greatly limits the wide applications in low earth orbit (LEO) environments. The introduction of polyhedral oligomeric silsesquioxane (POSS) units into the molecular structures of the PI films has been proven to be an effective procedure for enhancing the AO resistance of the PI films. In the current work, a series of POSS-substituted poly (pyromellitic anhydride-4,4′-oxydianiline) (PMDA-ODA) films (POSS-PI) with different POSS contents were synthesized via a POSS-containing diamine, N-[(heptaisobutyl-POSS)propyl]-3,5-diaminobenzamide (DABA-POSS). Subsequently, the effects of the molecular structures on the thermal, tensile, optical, and especially the AO-erosion behaviors of the POSS-PI films were investigated. The incorporation of the latent POSS substituents decreased the thermal stability and the high-temperature dimensional stability of the pristine PI-0 (PMDA-ODA) film. For instance, the PI-30 film with the DABA-POSS content of 30 wt% in the film exhibited a 5% weight loss temperature (T5%) of 512 °C and a coefficient of linear thermal expansion (CTE) of 54.6 × 10−6/K in the temperature range of 50–250 °C, respectively, which were all inferior to those of the PI-0 film (T5% = 574 °C; CTE = 28.9 × 10−6/K). In addition, the tensile properties of the POSS-containing PI films were also deteriorated, to some extent, due to the incorporation of the DABA-POSS components. The tensile strength (TS) of the POSS-PI films decreased with the order of PI-0 > PI-10 > PI-15 > PI-20 > PI-25 > PI-30, and so did the tensile modulus (TM) and the elongations at break (Eb). PI-30 showed the TS, TM, and Eb values of 75.0 MPa, 1.55 GPa, and 16.1%, respectively, which were all lower than those of the PI-0 film (TS = 131.0 MPa, TM = 1.88 GPa, Eb = 73.2%). Nevertheless, the incorporation of POSS components obviously increased the AO resistance of the PI films. All of the POSS-PI films survived from the AO exposure with the total fluence of 2.16 × 1021 atoms/cm2, while PI-0 was totally eroded under the same circumstance. The PI-30 film showed an AO erosion yield (Es) of 1.1 × 10−25 cm3/atom, which was approximately 3.67% of the PI-0 film (Es = 3.0 × 10−24 cm3/atom). Inert silica or silicate passivation layers were detected on the surface of the POSS-PI films after AO exposure, which efficiently prevented the further erosion of the under-layer materials.

Acknowledgements. Introduction. Organizing Committee. Section A: AO/VUV Effects, Evaluation and Modeling. 1. Monte Carlo Computational Modeling of the Energy Dependence of Atomic Oxygen Undercutting of Protected Polymers B.A. Banks, et al. 2. Dynamics of Atomic-Oxygen-Induced Degradation of Materials T.K. Minton, et al. 3. Generalization of the Predictive Model of Erosion of Carbon-Based Materials by Atomic Oxygen J.I. Kleiman, et al. 4. Spectroscopic Ellipsometry Characterization of Polymers Modified by Atomic Oxygen and Ultraviolet Radiation C.L. Bungay, et al. 5. Effect of Atomic Oxygen Exposures on the Tribological Properties of Molybdenum Disulfide Lubricants M. Tagawa, et al. 6. Influence of Shielding Upon the Structure and Properties of Polymer Composite Materials, Exposed on the Surface of the Mir Orbital Complex O.V. Startsev, et al. 7. Cleanliness Support of Vehicle Fairings for Spacecraft V. Sitalo, V. Tikhiy. 8. In situ XPS Studies of Kapton Exposed to 5 eV Atomic Oxygen E. Grossman, et al. Section B: Instrumentation, Sensors, New Technologies. 9. A Low Cost, Lightweight Reusable Sensor for Atomic Oxygen Detection J.J. Osborne, et al. 10. Large-Scale ECR-CVD Preparation of Integrated Thin-Film Structures for Space Applications R.V. Kruzelecky, et al. 11. Non-Silicone Inorganic Polymer-Based Coatings for Atomic Oxygen Protection in LEO - Part 2 E. Poire, et al. 12. Research Aspects of Scaling Up the Implantox Technology for Protection of Polymers in Space Z.A. Iskanderova, et al. Section C: ThermalControl in LEO. 13. A Comparison of Space and Ground-Based Facility Environmental Effects for FEP Teflon S.K. Rutledge, et al. 14. Evaluation of Low Earth Orbit Environmental Effects on International Space Station Thermal Control Materials J.A. Dever, et al. 15. Some Aspects of the Degradation of FEP Teflon Material Under the Action of VUV, the Sun and Ground Test VUV Facilities A. Milintchouk, M. Van Eesbeek. 16. Evaluation of COF MDPS Chromic Acid Anodization in LEO Environment C. Acket, et al. 17. A Database for the Selection of Surfaces and Materials for Space and Ground-based Applications S.H. McCall, et al. 18. Thermal Control Materials and Coatings Currently Being Developed in France for Use in Low Earth Orbit F. Guerard, J.C. Guillaumon. 19. Modification of Thermal Control Paints by Photosil (TM) Technology J.I. Kleiman, et al. Section D: Charged Particles/Soft X-Rays/Meteoroids/Thermal Cycling. 20. Simulated Solar Flare X-Ray and Thermal Cycling Durability Evaluation of HST Thermal Control Candidate Replacement Materials K.K. de Groh, et al. 21. Radiation-Induced Effects in SiO2 Protective Coatings on Polymeric Spacecraft Materials C. Coia, et al. 22. Influence of Electron and Proton Fluxes on Optical Properties of Protective Enamel S.N. Skovorod'ko, et al. 23. Meteoroid Hazard in the LEO Space Environment Y.S. Yatskiv, et al. 24. Characterizing the Annual Meteoroid Streams M. Beech. 25. Oxidation Kinetics of VB Group Metals by Atomic and Molecular Oxygen A.G. Gusakov, et al. 26.

Forty-one different polymers are being exposed to the low Earth orbit (LEO) environment on the exterior of the International Space Station (ISS) for one year as part of MISSE (Materials International Space Station Experiment). MISSE is a materials flight experiment sponsored by the Air Force Research Lab/Materials Lab and the National Aeronautics and Space Administration (NASA). A second set of the same polymers is planned to be flown as part of PEACE (Polymer Erosion And Contamination Experiment), a short duration shuttle flight experiment, and therefore these forty-one polymers on ISS are collectively called the MISSE PEACE Polymers. The objective of the MISSE PEACE Polymers experiment is to accurately determine the atomic oxygen (AO) erosion yield of a wide variety of polymeric materials. 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. Details on the specific polymers being flown, flight sample fabrication, and pre-flight characterization techniques will be discussed. The MISSE PEACE Polymers experiment was placed on the exterior of ISS during a spacewalk on August 16, 2001 and is planned to be retrieved in the fall of 2002. The erosion yield data obtained from this experiment will be compared with data from the future short duration experiment PEACE and with predicted results from models developed by a Canadian group that predicts the AO erosion yield of organic materials based on their chemical structure. Having flight data, and comparing flight data with the predictive model results, will be valuable for spacecraft design purposes.