As part of the Materials on The International Space Station Experiment (MISSE), aromatic polymers containing phenylphosphine oxide groups were exposed to low Earth orbit for ∼4 years. All of the aromatic polymers containing phenylphosphine oxide groups survived the exposure despite the high fluence of atomic oxygen that completely eroded other polymer films such as Kapton® and Mylar® of comparable or greater thickness. The samples were characterized for changes in physical properties, thermal/optical properties surface chemistry, and surface topography. The data from the polymer samples on MISSE were compared to samples from the same batch of material stored under ambient conditions on Earth. In addition, comparisons were made between the MISSE samples and those subjected to shorter term space flight exposures. The results of these analyses will be presented.
Research Containing: Material science
Space Environment Exposure Results from the MISSE 5 Polymer Film Thermal Control Experiment on the International Space Station
It is known that polymer films can degrade in space due to exposure to the environment, but the magnitude of the mechanical property degradation and the degree to which the different environmental factors play a role in it is not well understood. This paper describes the results of an experiment flown on the Materials International Space Station Experiment (MISSE) 5 to determine the change in tensile strength and % elongation of some typical polymer films exposed in a nadir facing environment on the International Space Station and where possible compare to similar ram and wake facing experiments flown on MISSE 1 to get a better indication of the role the different environments play in mechanical property change.
The Polymer Film Tensile Experiment (PFTE) was flown as part of Materials International Space Station Experiment 6 (MISSE 6). The purpose of the experiment was to expose a variety of polymer films to the low Earth orbital environment under both relaxed and tension conditions. The polymers selected are those commonly used for spacecraft thermal control and those under consideration for use in spacecraft applications such as sunshields, solar sails, and inflatable and deployable structures. The dog-bone shaped samples of polymers that were flown were exposed on both the side of the MISSE 6 Passive Experiment Container (PEC) that was facing into the ram direction (receiving atomic oxygen, ultraviolet (UV) radiation, ionizing radiation, and thermal cycling) and the wake facing side (which was supposed to have experienced predominantly the same environmental effects except for atomic oxygen which was present due to reorientation of the International Space Station). A few of the tensile samples were coated with vapor deposited aluminum on the back and wired to determine the point in the flight when the tensile sample broke as recorded by a change in voltage that was stored on battery powered data loggers for post flight retrieval and analysis. The data returned on the data loggers was not usable. However, post retrieval observation and analysis of the samples was performed. This paper describes the preliminary analysis and observations of the polymers exposed on the MISSE 6 PFTE.
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.
Black Kapton XC polyimide was flown as part of the Polymer Film Tensile Experiment (PFTE) on Materials International Space Station Experiment 6 (MISSE 6). The purpose of the experiment was to expose a variety of polymer films, typical of those used for thermal control blankets or supporting membranes on Earth orbiting spacecraft, to the low Earth orbital (LEO) environment under both relaxed and tension conditions. Black Kapton XC under tensile stress experienced a higher erosion rate during exposure in LEO than the same material that was flown in a relaxed condition. Testing conducted to determine the magnitude of the stress and erosion dependence using a ground-based thermal energy atomic oxygen plasma showed a slight dependence of erosion yield on stress for Kapton HN and Black Kapton XC, but not to the extent observed on MISSE 6. More testing is needed to isolate the factors present in LEO that cause stress dependent erosion.
In this paper, we report on the SHS reaction 3NiO + 5Al → 3NiAl + Al2O3 carried out aboard International Space Station (Flight Mission 18) with special emphasis on the effect of the composition of reaction products on the composition of coatings formed on a Ti substrate.
Specific coating processes and materials were investigated in the quest to develop multilayer coatings with greater tolerance to space radiation exposure. Ultraviolet reflection (UVR) and wide-band antireflection (AR) multilayer coatings were deposited on solar cell covers and test substrates and subsequently exposed to simulated space environments and also flown on the Materials International Space Station Experiment-7 (MISSE-7) to determine their space environment stability. Functional solar cells integrated with these coatings underwent simulated UV and MISSE-7 low earth orbit flight exposure. The effects of UV, proton, and atomic oxygen exposure on coatings and on assembled solar cells as related to the implemented deposition processes and material compositions were small. The UVR/AR coatings protected flexible polymer substrate materials that are intended for future flexible multijunction cell arrays to be deployed from rolls. Progress was made toward developing stable and protective coatings for extended space-mission applications. Test results are presented.
It is known that polymer films can degrade as a result of space environmental exposure, but the magnitude of the mechanical property degradation and the degree to which the difference environmental factors play a role is not well understood. An experiment was flown on the Materials International Space Station Experiment 5 to determine the change in tensile strength and recent elongation of some typical polymer films exposed in a nadir-facing environment on the International Space Station and, where possible, compare with similar ram-and wake-facing experiment flown on the Materials Internationals Space Station Experiment 1 to get a better indication of the role the difference environments play in mechanical property change. It was found that the majority of the polymers tested experienced some loss in tensile/yield strength and percent elongation with polytetrafluroethylene Teflon having the greatest change. Where comparisons could be made with the Materials International Space Station Experiment 1, it appears that the loss in percent elongation is dependent on the radiation level while the loss of tensile strength is not as sensitive to the level of radiation.
The Materials on International Space Station Experiment (MISSE): First Results from MSFC Investigations
Hundreds of material samples were passively exposed to the space environment for nearly four years as part of the Materials on International Space Station Experiment (MISSE). The experiment was planned for one year of exposure, but its return was delayed by the Columbia accident and subsequent grounding of the Space Shuttle fleet. The experiment was attached externally to the Quest Airlock. Atomic oxygen fluence and ultraviolet radiation dose varied across the experiment because of shadowing and space station orientation. Over a hundred meteoroid/space debris impacts were found. Many polymer film samples were completely eroded by atomic oxygen. Some particulate contamination was noted, but black light inspection and the transmission measurements of magnesium fluoride windows indicated that molecular contaminant deposition was limited. Optical property changes in thermal control materials are discussed.
Six samples of pristine and dust-abraded outer layer spacesuit fabrics were included in the Materials International Space Station Experiment-7, in which they were exposed to the wake-side low Earth orbit environment on the International Space Station (ISS) for 18 months in order to determine whether abrasion by lunar dust increases radiation degradation. The fabric samples were characterized using optical microscopy, optical spectroscopy, field emission scanning electron microscopy, atomic force microscopy, and tensile testing before and after exposure on the ISS. Comparison of pre- and post-flight characterizations showed that the environment darkened and reddened all six fabrics, increasing their integrated solar absorptance by 7 to 38 percent. There was a decrease in the ultimate tensile strength and elongation to failure of lunar dust abraded Apollo spacesuit fibers by a factor of four and an increase in the elastic modulus by a factor of two.