PROTECTION OF MATERIALS AND STRUCTURES FROM SPACE ENVIRONMENT: Proceedings of the 9th International Conference: Protection of Materials and Structures From Space Environment
Spacecraft Materials in the Space Flight Environment: International Space Station—May 2002 to May 20081087(2009); http://dx.doi.org/10.1063/1.3076853View Description Hide Description
The performance of ISS spacecraft materials and systems on prolonged exposure to the low‐Earth orbit (LEO) space flight are reported in this paper. In‐flight data, flight crew observations, and the results of ground‐based test and analysis directly supporting programmatic and operational decision‐making are described. The space flight environments definitions (both natural and induced) used for ISS design, material selection, and verification testing are shown, in most cases, to be more severe than the actual flight environment accounting, in part, for the outstanding performance of ISS as a long mission duration spacecraft. No significant ISS material or system failures have been attributed to spacecraft‐environments interactions. Nonetheless, ISS materials and systems performance data is contributing to our understanding of spacecraft material interactions with the spaceflight environment so as to reduce cost and risk for future spaceflight projects and programs.
Study of Materials and Coatings on the Spacecraft Surfaces in the Salyut, MIR and ISS Orbital Stations: 1990‐20081087(2009); http://dx.doi.org/10.1063/1.3076844View Description Hide Description
The stability problem of operational characteristics of external materials in space vehicles is very important for spacecraft development with life span period of 20 years and more. Without the assessment of space factors’ effects on the properties of optical and thermo regulating covers, films and composite materials, special‐purpose fabrics and other materials used in long‐term missions, it is impossible to design adequately the satellites, interplanetary vehicles and orbital stations able to withstand such long‐term missions.
This paper is an attempt to review the results of materials’ tests carried on detachable cassettes and placed on Salyut, MIR and ISS orbital stations in the period 1990–2008. In all experiments, the samples underwent long‐term exposure in outer space.
The numerous material samples selected for investigations were installed on the external surfaces of the Space Stations Salyut and MIR and on the Russian segment of International Space Station as removable cassettes of FM‐110 FM‐111 and SKK types. The major properties of all samples including the thermo‐optical, mass, structural and other physical and chemical characteristics were evaluated before and after the space exposure. The test results of optical and thermo‐regulating covers and composite and film materials and other materials under long space exposure conditions (up to 1638 days) are presented in the report.
1087(2009); http://dx.doi.org/10.1063/1.3076865View Description Hide Description
The Materials International Space Station Experiment 2 (MISSE 2) Polymer Erosion and Contamination Experiment (PEACE) polymers were exposed to the environment of low Earth orbit (LEO) for 3.95 years from 2001 to 2005. There were forty‐one different PEACE polymers, which were flown on the exterior of the International Space Station (ISS) in order to determine their atomic oxygen erosion yields. In LEO, atomic oxygen is an environmental durability threat, particularly for long duration mission exposures. Although space flight experiments, such as the MISSE 2 PEACE experiment, are ideal for determining LEO environmental durability of spacecraft materials, ground‐laboratory testing is often relied upon for durability evaluation and prediction. Unfortunately, significant differences exist between LEO atomic oxygen exposure and atomic oxygen exposure in ground‐laboratory facilities. These differences include variations in species, energies, thermal exposures and radiation exposures, all of which may result in different reactions and erosion rates. In an effort to improve the accuracy of ground‐based durability testing, ground‐laboratory to in‐space atomic oxygen correlation experiments have been conducted. In these tests, the atomic oxygen erosion yields of the PEACE polymers were determined relative to Kapton H using a radio‐frequency (RF) plasma asher (operated on air). The asher erosion yields were compared to the MISSE 2 PEACE erosion yields to determine the correlation between erosion rates in the two environments. This paper provides a summary of the MISSE 2 PEACE experiment; it reviews the specific polymers tested as well as the techniques used to determine erosion yield in the asher, and it provides a correlation between the space and ground‐laboratory erosion yield values. Using the PEACE polymers’ asher to in‐space erosion yield ratios will allow more accurate in‐space materials performance predictions to be made based on plasma asher durability evaluation.
1087(2009); http://dx.doi.org/10.1063/1.3076885View Description Hide Description
Space mirrors in Low Earth Orbit (LEO) encounter a degradation problem caused by the impact of atomic oxygen (ATOX) in the space environment. This paper presents an experiment of the atomic oxygen impact degradation and UV synergic effects on ground simulation. The experiment was carried out in a dedicated ATOX simulation vacuum chamber. As target materials, a polished CVD Beta‐silicon carbide (SiC) coating was investigated. The selection of silicon carbide is due to its high potential candidate as a mirror layer substrate material for its good reflectance at UV wavelengths and excellent thermal diffusivity. It has highly desirable mechanical and thermal properties and can achieve an excellent surface finish. The deposition of the coatings were on carbon‐based material substrate; i.e., silicon impregnated carbon fiber composite (C/SiC). Mechanical and thermal properties of the coatings such as hardness and Coefficient of Thermal Expansion (CTE) were achieved. Several atomic oxygen impact angles were studied tilting the target samples respect to the flux direction. The various impact angles permitted to analyze the different erosion rates and typologies which the mirrors would encounter in LEO environment. The degradation was analyzed in various aspects. Macroscopic mass loss per unit area, surface roughness and morphology change were basically analyzed. The exposed surfaces of the materials were observed through a Scanning Electron Microscope (SEM). Secondly, optical diagnostic of the surfaces were performed in order to investigate their variation in optical properties as the evaluation of reflectance degradation. The presence of micro‐cracks caused by shrinkage, grinding, polishing or thermal cycling and the porosity in the coatings, could have led to the undercutting phenomenon. Observation of uprising of undercutting was also conducted. Remarks are given regarding capabilities in short‐term mission exposures to the LEO environment of this coating.
1087(2009); http://dx.doi.org/10.1063/1.3076888View Description Hide Description
Effects of atomic oxygen (AO) on mechanical properties of polyimide films were investigated using surface topography observations and tensile tests. The ITO‐coated polyimide films, which are expected to have a high durability against AO attacks, were also evaluated. Surfaces of polyimide films irradiated by AO were deeply eroded, exhibiting a rough texture. The roughness developed as the AO fluence increased. Tensile strength and elongation of the polyimide films degraded after AO irradiation tests. In addition, that degradation became marked concomitantly with increased AO fluence. These results indicate that development of surface roughness can degrade mechanical properties of polyimide films. In contrast, surfaces of ITO‐coated polyimide films remained flat and were hardly affected by AO irradiation. Nevertheless, the tensile strength and elongation of ITO‐coated polyimide films were decreased by AO irradiation. Such degradation resulted from undercut cavities formed by AO erosion at the defects sites of ITO coating.
1087(2009); http://dx.doi.org/10.1063/1.3076889View Description Hide Description
Atomic oxygen (AO) is among the predominant factors in Low Earth Orbit (LEO) space environment. Ground‐based laboratory AO exposure testing was performed to investigate interaction between atomic oxygen and materials that were intended for use in future missions on LEO spacecraft. Two types of adhesive materials, i.e., E‐32 epoxy and GS414 silicone were tested in Atomic Oxygen Test Facility at the Beijing Institute of Spacecraft Environment Engineering (BISEE). The effective atomic oxygen fluence in the conducted tests was approximately which is close to the fluence of a two‐year exposure in LEO orbit. Significant mass losses of epoxy adhesive materials were detected after the exposure to atomic oxygen, but relatively small mass changes were found in silicone samples. The erosion yields of epoxy samples were from to Surface bleaching by atomic oxygen was found in epoxy samples. The surface on silicone sample remained glossy after AO exposure. Both materials were analyzed using Scanning Electron Microscopy (SEM) and X‐ray Photoelectron Spectroscopy (XPS) to study the changes of material surfaces. A number of interesting results concerning the surface changes in the exposed materials have been found after a comparison study between unexposed and exposed samples.
Numerical Simulation of Atomic Oxygen Flux and Fluence Distribution on Spacecraft Surfaces in LEO Environment1087(2009); http://dx.doi.org/10.1063/1.3076890View Description Hide Description
A mathematical model has been developed for solving the atomic oxygen flux and fluence distribution on spacecraft surfaces in low Earth orbit space environment (LEO), based on Monte Carlo ray tracing and domain decomposition methods (MCRT‐DD). The geometry of the spacecraft, the number density and molecular thermal motion of atomic oxygen, the spacecraft velocity affected by atmosphere co‐rotation and orbit propagation parameters are considered in the model. Flux is calculated directly by integrating a differential equation and fluence is integrated by flux with orbit propagation. The results had shown that incidence angle plays an important role in affecting flux and fluence distribution. Maximum and minimum values are occurring in upwind and lee‐wind direction separately. Calculated error is in agreement with the Long Duration Exposure Facility of National Aeronautics and Space Administration (LDEF‐NASA) flight experiment data as well.
1087(2009); http://dx.doi.org/10.1063/1.3076891View Description Hide Description
Irradiation damage effects of the epoxy resin 648 and epoxy nano‐composites were studied by exposing them to vacuum ultraviolet irradiation (VUV) with wavelength varying from 5 nm to 200 nm. Experimental results obtained from mass loss, Scanning Electron Microscopy (SEM) and X‐ray Photoelectron Spectroscopy (XPS) show that nano‐ particles provide better resistance performance. Epoxy nano‐composite was found to be more advantageous over epoxy resin due to significant lower mass loss, lower flexural strength variation and the lower outgassing, with less gas component varieties after irradiation. In addition, now new carbon peaks were found and the principle components of the O ls peak did not change.
1087(2009); http://dx.doi.org/10.1063/1.3076826View Description Hide Description
Silicon impregnation and glass fabric coatings were used to increase the resistance of polymeric threads to the impact by atomic oxygen. The protected samples were exposed to atomic oxygen with fluencies of up to and the results of these studies are presented. For unprotected materials a sharp fall in mechanical properties and a deterioration of optical characteristics were observed. The application of protective coatings is shown to reduce this degradation.
1087(2009); http://dx.doi.org/10.1063/1.3076827View Description Hide Description
Spacecraft often rely heavily on passive thermal control to maintain operating temperature. An important parameter in the spacecraft heat balance equation is the emittance of thermal control coatings as a function of coating temperature. One method for determining the emittance of spacecraft thermal control from elevated temperature to cryogenic temperatures relies on a calorimetric technique. The fundamental equation governing this test method can be found in numerous places in the literature and although it generally provides reasonable results, its formulation is based on a conceptual flaw that only becomes apparent when the sample temperature approaches the wall temperature during testing. This paper investigates the cause for this error and develops the correct formulation for calorimetric emittance testing. Experimental data will also be presented that illustrates the difference between the two formulations and the resulting difference in the calculated emittance.
1087(2009); http://dx.doi.org/10.1063/1.3076828View Description Hide Description
To clarify the effects of space environment on mechanical properties of polymer, exposure experiments were conducted utilizing the International Space Station Russian Service Module. Poly‐ether‐ether‐ketone (PEEK) films under tensile stress were exposed to low Earth orbit (LEO) environment, and reference samples were irradiated with atomic oxygen (AO), electron beam (EB), and ultraviolet light (UV) in ground facilities. By comparing the results of flight and ground tests, the degradation behavior and the influential factors in LEO were investigated. The following results were obtained. (1) UV was found to be the harshest factor in LEO on tensile properties, since it decreased elongation to 15% of pristine sample after 46‐months exposure. (2) AO in LEO eroded the specimen surface with a cone‐like morphology and reduced the thickness; however, it had no significant effect on tensile properties. (3) EB irradiation in LEO had no measurable effects on the material properties.
Comparison Study of Combined and Single Space Environmental Degradation Effects on Thermal Control Materials1087(2009); http://dx.doi.org/10.1063/1.3076829View Description Hide Description
This paper presents a comparison study of single and combined space environmental effects by electrons, protons and near ultraviolet (NUV) radiation on thermal control coatings. The space environment includes many hazardous factors. Because of synergistic effects among different environmental factors and the expensive nature of the open space experiments, ground‐based combined environmental test methods are necessary to simulate orbital environmental effects. In many cases, the combined environmental effect from two or more factors is not equal to the sum of single environmental effects. By studying the effects from single environmental factors, a better knowledge of their influence on the degradation of materials could be acquired. Space environmental degradation of thermal control coatings of S781 white paint, SR107‐ZK white paint, silvered FEP, and OSR used on the outer satellite surfaces was simulated by exposing them to combined irradiation with electrons, protons and NUV. In addition, irradiation with single factors with the same parameters was performed for comparison studies. Low energy proton irradiation has been found to affect the thermal control coatings the most. The effects from combined irradiation were found to be lower than from the sum of single environmental factors.
Tribological characteristics of bonded film exposed to AO, UV and real LEO environment in SM/SEED experiment1087(2009); http://dx.doi.org/10.1063/1.3076830View Description Hide Description
Influence of a ground‐simulated space environment on a solid lubricant was compared to that of the real space environment. The tested lubricant that has been used for space applications was a bonded film with organic binder. The film was irradiated individually with atomic oxygen (AO), ultraviolet rays (UV), and electron beam (EB). The fluencies of these space environment factors corresponded to exposure to the LEO environment around the International Space Station (ISS) in the Space Environment Exposure Device (SEED) experiment to about 1,2, and 3 years. Friction tests in vacuum and surface analyses were carried out for the samples. Tribological behavior of the different samples was measured using a classical reciprocating pin‐on‐flat friction test. Furthermore, XPS analysis of the film surface and the rubbing tracks was performed on the samples. Results show that due to AO irradiation, the friction coefficient decreased at an early stage of the tests that was similar to the results obtained on film exposed to the real LEO environment. However, no significant difference was observed with difference in AO fluence, whereas the friction coefficient of flight samples decreased concomitantly with the duration of exposure to the LEO environment.
Studies of the Individual and Combined Effects of VUV Radiation and Hyperthermal O or Ar Atoms on FEP Teflon® and PMMA Surfaces1087(2009); http://dx.doi.org/10.1063/1.3076831View Description Hide Description
Atomic oxygen and molecular nitrogen are the major constituents in the residual atmosphere at low Earth orbital altitudes, and they collide with spacecraft surfaces at relative velocities of The energy associated with these hyperthermal collisions is in excess of many bond dissociation energies and may help promote materials degradation by allowing barriers to reaction or to collision‐induced dissociation (CID) to be overcome. Spacecraft in low Earth orbit (LEO) are also exposed to high fluxes of vacuum ultraviolet (VUV) radiation, which may degrade materials through various photochemical mechanisms. Fluorinated ethylene‐propylene copolymer (FEP Teflon®) is commonly used on spacecraft. Many researchers have studied the individual and/or combined effects of atomic oxygen, VUV light, and CID on FEP Teflon®, yet the detailed degradation mechanisms of FEP Teflon® in LEO are still a subject of debate. Although not as ubiquitous as a spacecraft material, polymethylmethacrylate (PMMA) has been studied as a model and control polymer because of its well known propensity to “unzip” upon exposure to VUV radiation. A combination of beam‐surface scattering, quartz crystal microbalance (QCM), and surface‐recession experiments were conducted to study the effects of various combinations of O atoms (in the ground state), Ar atoms, and VUV light on FEP Teflon® and PMMA. A laser‐breakdown source was used to create hyperthermal beams containing O and or argon. A deuterium lamp provided a source of VUV light. O atoms with 4 eV of translational energy or less did not react with a pristine FEP Teflon® surface. Volatile O‐containing reaction products were observed when the O‐atom energy was higher than 4.5 eV, and the signal increased with O‐atom energy. Significant FEP Teflon erosion ( of Kapton® H) was observed when it was exposed to the hyperthermal beam with an average O‐atom energy of 5.4 eV. FEP Teflon® and PMMA that were exposed to VUV light alone yielded volatile products and mass loss. Similarly, CID by Ar also yielded volatile products and mass loss, when the Ar energy was higher than 8 eV. However, the erosion caused by VUV light and/or CID is not significant compared to that caused by There were no observed synergistic effects of VUV light and exposure.
Synergistic effect of EUV from the laser‐sustained detonation plasma in a ground‐based atomic oxygen simulation on fluorinated polymers1087(2009); http://dx.doi.org/10.1063/1.3076832View Description Hide Description
The contribution of extreme ultraviolet (EUV) from a laser‐sustained plasma on the mass loss phenomenon of fluorinated polymer in a ground‐based laser‐detonation atomic oxygen beam source was evaluated. The atomic oxygen beam and EUV from the oxygen plasma were separated by the high‐speed chopper wheel installed in the beam source. The mass changes of the fluorinated polymer and polyimide were measured from the frequency shift of the quartz crystal microbalance during the beam exposures. It has been made clear that the fluorinated polymer erodes by EUV exposure alone. In contrast, no erosion was detected for polyimide by EUV alone. The atomic oxygen‐induced erosion was measured for both materials even without EUV exposure. However, no strong synergistic effect was observed for a fluorinated polymer even under the simultaneous exposure condition of atomic oxygen and EUV. Similar results were observed even in simultaneous exposure of atomic oxygen (without EUV) and 172 nm vacuum ultraviolet (VUV) from an excimer lamp. These experiments suggest that the primary origin of the accelerated erosion of fluorinated polymer observed in a laser detonation atomic oxygen source is not the EUV from the laser‐sustained plasma.
1087(2009); http://dx.doi.org/10.1063/1.3076833View Description Hide Description
Deposition of outgassed products of a polymeric composite on model material surfaces being irradiated by electrons and protons with initial energies of and respectively was studied. It was shown that deposition of volatile products on model material surfaces being under ionizing radiations results in increase of organic film growth rate.
1087(2009); http://dx.doi.org/10.1063/1.3076834View Description Hide Description
The Materials Exposure and Degradation Experiment (MEDET) was recently launched to the ISS on Space Shuttle Flight IE, as part of the EuTEF payload on the external payload facility of ESA’s Columbus module. The experiment will operate in‐orbit for at least 1.5 years, and has the overall objectives of evaluating the effects of the complex low Earth orbit space environment on material properties, investigating material degradation due to contamination, characterising the local ISS environment and measuring the local micro‐particle flux. This paper gives a brief overview of the experiment function and the material samples which are being exposed, before presenting some of the early flight data. In this phase of the mission, all of the instruments are operating successfully, and continuously acquiring data. The preliminary results mainly concern the environmental sensors, which are operating at relatively high acquisition rates (e.g. one reading every few seconds). It has been shown that the docking of the Space Shuttle to the ISS has a significant effect on the local pressure environment. The more complex degradation experiments are acquiring at much slower rates (e.g. one reading per day) and several more months of space exposure will be required before sufficient data is generated to reach conclusions about the behaviour of the materials. However, preliminary data is presented.
1087(2009); http://dx.doi.org/10.1063/1.3076835View Description Hide Description
A space materials exposure experiment was condcuted on the exterior of the Russian Service Module (SM) of the International Space Station (ISS) using the Micro‐Particles Capturer and Space Environment Exposure Device (MPAC&SEED) of the Japan Aerospace Exploration Agency (JAXA). Results reveal artificial environment effects such as sample contamination, attitude change effects on AO fluence, and shading effects of UV on ISS. The sample contamination was coming from ISS components. The particles attributed to micrometeoroids and/or debris captured by MPAC might originate from the ISS solar array. Another MPAC&SEED will be aboard the Exposure Facility of the Japanese Experiment Module, KIBO Exposure Facility (EF) on ISS. The JEM/MPAC&SEED is attached to the Space Environment Data Acquisition Equipment‐Attached Payload (SEDA‐AP) and is exposed to space. Actually, SEDA‐AP is a payload on EF to be launched by Space Shuttle flight 2J/A. In fact, SEDA‐AP has space environment monitors such as a high‐energy particle monitor, atomic oxygen monitor, and plasma monitor to measure in‐situ natural space environment data during JEM/MPAC&SEED exposure. Some exposure samples for JEM/MPAC&SEED are identical to SM/MPAC&SEED samples. Consequently, effects on identical materials at different positions and operation periods of ISS will be evaluated. This report summarizes results from space environment monitoring samples for atomic oxygen analysis on SM/MPAC&SEED, along with experimental plans for JEM/MPAC&SEED.
Analysis of the ISS Russian Segment Outer Surface Materials Installed on the CKK Detachable Cassette1087(2009); http://dx.doi.org/10.1063/1.3076836View Description Hide Description
This report presents an analysis of the effects caused by space environmental factors (SEF) and the International Space Station’s (ISS) outer environment on operational parameters of the outer surface materials of the ISS Russian Segment (RS). The tests were performed using detachable container cassettes (CKK) that serve as a part of the ISS RS contamination control system.