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Location of Hubble Space Telescope thermal control materials. In this figure, the flexible optical solar reflector (FOSR) is defined as metallized Teflon films used either as the top layer of MLI blankets or as tapes on radiator surfaces. MLI blankets were used on the entire light shield and most of the forward shell and equipment bays (equipment section). Tapes were used on the aperture door, a few locations on equipment bays, the entire aft shroud, and aft bulkhead (bottom of the telescope).
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During the Hubble Space Telescope (HST) second servicing mission (SM2), degradation of unsupported Teflon® FEP (fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and ret...
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... specimens; and perform simulated environmental exposures. This paper summarizes the results of the first two phases and draws overall conclusions about the failure mechanism. 2.1.1. Description. The Hubble Space Telescope uses several thermal control materials to passively control temperatures on-orbit. The two primary types are MLI blankets and radiator surfaces (figure 1). MLI blankets were used on over 80 per cent of the external surface area of HST. The top (space-exposed) layer of these blankets was 127 μ m ( 0 . 005 ) Teflon ® FEP with roughly 100 nm of vapour deposited aluminium (VDA) on the back (FEP/VDA). Next there were 15 layers of embossed 8.17 μ m ( 0 . 000 33 ) double-aluminized Kapton ® . The innermost layer was 24.5 μ m ( 0 . 001 ) single aluminized Kapton ® . The embossing pattern reduced layer- to-layer conduction, making spacers unnecessary. The blankets were closed out on all four sides with a taped cap section, and the layers were tied together intermittently throughout the blanket using spots of acrylic transfer adhesive film. Where the blankets were cut to fit around features (handrails, standoffs, etc) the blanket was closed out again by taping the cap section. In addition, the blankets were vented with ‘X’ cuts and the outer layer was reinforced using aluminized Kapton ® scrim tape. The entire blanket was attached to the spacecraft with Velcro ® stitched to the inner layer. The radiator surfaces were simply perforated silver Teflon ® tape bonded directly to the aluminium vehicle substrate. The space-exposed surface was 127 μ m (0 . 005 ) Teflon ® FEP with roughly 100 nm of vapour deposited silver (VDS) on the back (FEP/VDS). The silver side was coated with Inconel and finally with an acrylic adhesive. This material was purchased in rolls (4 width) with the adhesive already applied. The tape was applied in sections, and a Teflon ® wand was used to minimize air entrapment and ensure a good bond. Damaged tape was replaced as necessary as the telescope was ...
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Citations
... The rate of weight loss depends on the flux of the atomic oxygen. In general, the weight loss increases with increasing irradiation period [38][39][40][41][42]. ...
Polyimide (PI, PMDA-ODA, C22H11N2O5, Kapton-H), is a class of polymer, extensively used in microelectronics and space technology, due to its exceptional mechanical, dielectric, and chemical properties. In space, PI heat shield experiences a harsh environment of energetic electrons, ultra-violet radiation, and atomic oxygen, causing degradation and erosion. Radiation-assisted physicochemical surface modulations in PI, in view of understanding and reducing the degradation in laboratory-based systems, are discussed in the chapter. Strategies for the design and development of 2D, flat, and flexible electromechanical devices by swift heavy ion induced bulk modifications in PI are also described. Fabrication of a couple of such devices, including their performance analysis, is presented.
... 19,20 The metalized Teflon FEP has been used in various applications, including Hubble Space Telescope. 46 We charged a metalized Teflon FEP (thicknesses of the Al and the Teflon layers are 0.1 lm and 12.7 lm) from the Sheldahl by employing the corona discharge method, which is based on the projecting ions on the surface of an electret. Figure 2(b) depicts our corona discharge setup, which consists of a probe, a metal grid (removable) located between the probe and the sample, a grounded electrode, and a metal chamber. ...
This study demonstrates an energy harvester that combines a piezoelectric nanogenerator and an electret-based electrostatic generator. The device consists of an in-house fabricated nanocomposite (polydimethylsiloxane/barium titanate/carbon nanotube) as a piezoelectric layer and a monocharged Teflon fluorinated ethylene propylene as an electret electrostatic layer. The mechanical impedance of the structure can be altered easily by changing the nanocomposite monomer/cross-linker ratio and optimizing various mechanical energy sources. The energy harvester’s performance was characterized by performing measurements with different frequencies (5–20Hz) under applied dynamic loading. A total volumetric power density of 8.8 lW cm3 and a total stored energy of 50.2 lJ min1 were obtained. These findings indicate that this versatile, lightweight, and low-cost energy harvester can be employed as a power supply source for microelectronics in applications, such as wearables.
... Less is known about the influence of thermal cycling on thermo-optical, mechanical and electrical properties of flexible OSRs as a whole, as well as other metal-polymer composites for similar applications. In low earth orbit (LEO), temperatures typically range between ± 100°C [8,9] with 16 thermal cycles per day [10]. In flexible electronics thermal cycling also occurs, caused by current induced heating and on/off switching of domains. ...
... The values of normal and hemispherical emittance ε N and ε H for pristine Ag/ Inconel-coated 50 μm FEP substrate are ≥0.60 [39]. As the thickness of FEP does not change within the applied cycle number also the emittance will likely remain unaffected, as has previously been reported [8][9][10]. The results of the performed reflectivity measurements, including absolute and relative values for ρ T, ρ D and ρ S are summarized in Table 1 and Fig. 10. ...
... The impact of decreased reflectivity after thermal cycling is similar to that of increased solar absorptance observed in space-retrieved FEP foils due to degradation of the external FEP layer upon space-exposure [9]. The emittance, dominated by the dielectric behavior of the polymer substrate, is likely to remain unaffected [8][9][10]. The extent of total heat accumulation depends on several factors including the specific space environment, the heat flux from inside the spacecraft and also the view factor to external heat sources. ...
Multilayer thin film systems on flexible polymer substrates are used as flexible optical solar reflectors or thermal insulation of satellites and spacecraft. During one year of operation, a satellite in low earth orbit typically encounters 6000 thermal cycles of ±100 °C. Due to the different coefficients of thermal expansion between the individual layers and the substrate it is important to investigate the thermo-mechanical stability of the multilayers as a function of the cyclic heat load. Scanning electron microscopy and focused ion beam cross-sectioning revealed that Inconel-Ag bilayers on fluorinated ethylene propylene (FEP) substrate severely degrade during thermal cycling of ±150 °C in a gaseous N2 atmosphere. After only 100 cycles through thickness cracks and subsurface voids in the Ag layer form as a result of equi-biaxial thermal stresses caused by the large difference in thermal expansion between film and substrate. Transmission Kikuchi Diffraction (TKD) before and after thermal cycling also revealed grain growth and twin widening in the Ag layer. Cracking and void formation are detrimental to application relevant material properties including corrosion protection (Inconel) and reflectivity (Ag). Reflectance measurements revealed that the amount of reflected energy as well as the reflection mode (specular vs. diffuse) significantly change during the first 100 cycles. Saturation of reflection characteristics was observed after 25 cycles, which correlates to a turning point in the evolution of Ag voids. Results of this study indicate that special focus should be directed towards thermal stress control (Δα) and tailoring of the metal-polymer interface to improve resistance of versatile metal-polymer systems against thermal cycling.
... Other influencing factors of the space environment like, thermal cycling, high vacuum, electromagnetic irradiation or further types of charged particle irradiation [9,21] have not been investigated in this work. The influence of mixed irradiation is discussed elsewhere [1][2][3]5,6,8]. ...
... Polymer foils used in spacecrafts, e.g., as thermal control foils, are usually exposed to multiple types of radiation and severe thermal cyclic loading [1][2][3]. The influence of irradiation on the mechanical properties of polymer foil materials has already been studied widely, mainly via testing macroscopic tensile specimens [1,[4][5][6][7][8][9][10]. Existing experiments on the macro scale cannot, however, resolve local variations in mechanical properties, e.g., caused by degradation due to inhomogeneous irradiation conditions. ...
... Polymer foils used in spacecrafts, e.g., as thermal control foils, are usually exposed to multiple types of radiation and severe thermal cyclic loading [1][2][3]. The influence of irradiation on the mechanical properties of polymer foil materials has already been studied widely, mainly via testing macroscopic tensile specimens [1,[4][5][6][7][8][9][10]. Existing experiments on the macro scale cannot, however, resolve local variations in mechanical properties, e.g., caused by degradation due to inhomogeneous irradiation conditions. ...
The influence of irradiation on mechanical properties of polymer foils used in spacecraft applications has widely been studied via macroscopic tensile samples. An increase in the local resolution of this investigation can be achieved by reducing the sample’s dimensions. A femtosecond laser enables a fast fabrication of micro-samples with dimensions from tens of
μ
m to the mm range, with ideally no influence on the material. Tensile experiments using such micro-tensile samples were conducted on FEP, Upilex-S and PET foils. The influence of the laser processing on the polymer foils was evaluated. Additionally an investigation of degradation due to electron irradiation was performed. Furthermore an outlook to extend this technique to depth-resolved measurements by preparing samples from locally thinned foils is presented. The study demonstrates the feasibility of femtosecond laser processing for rapid fabrication of micro-samples, enabling insights into the effect of electron irradiation on local mechanical properties of polymers.
... A multilayer insulation material (MLI) is a type of high-performance insulator for satellites and spacecraft which uses multiple radiationheat transfer barriers to retard the flow of energy. Individual radiation barriers usually are thin polymer foils with vapour-deposited metal on one or both sides [1][2][3][4]. Aluminium (Al) on Polyimide (PI) is a frequently used material combination for MLI systems because of its lightweight and high temperature resistance [5,6]. In low earth orbit (LEO) a spacecraft typically encounters 6000 thermal cycles of ± 100°C during one year in operation [7]. ...
The stability of metal-polymer interfaces after extreme thermal cycling is essential for high-performance thermal insulation of satellites. The Aluminium-Polyimide (Al-PI) system investigated here is used as a multilayer insulator for satellites currently in low earth orbit. Its interfacial adhesion should be resistant to thermal loading caused by the sun during orbit. In this study, transmission electron microscopy (TEM) is combined with X-ray photoelectron spectroscopy (XPS) to relate the interface structure and chemistry to the mechanical strength of the Al-PI interface as a function of thermal cycling. Results show that the interfacial properties of Al-PI remain unaffected by thermal cycling of ±. 150. °C in gaseous nitrogen up to 200 thermal cycles. TEM cross-sections were used to examine the interface structure and revealed a 3.6. nm, amorphous interlayer between Al and PI for as deposited and cycled samples. XPS survey scans and relevant high resolution core levels were recorded on both sides of the interface to identify and understand relevant interfacial bonding as well as to distinguish between adhesive failure at the interface and cohesive failure in the polyimide substrate. The Al-PI system presented in this study can serve as a model for strong and thermally resistant metal-polymer interfaces. The combination of interface strength, structure and chemistry allows for an improved understanding of how thermal treatments can influence interfacial behaviour between metals and polymers and will help improve design and reliability of materials used in space as well as terrestrial applications.
... Another area of use is multilayer insulation systems (MLI), which are key components for today's and future space missions. To ensure optimal operational conditions for the very sensitive scientific equipment on board of a satellite, MLIs are used to decouple the interior of the spacecraft from the thermal conditions outside with temperatures ranging from −70 and +125°C, depending on the specific purpose and position of the spacecraft in relation to the sun [3,4]. Typically a Low Earth Orbit (LEO) spacecraft encounters 16 thermal cycles a day leading to about 6000 thermal cycles during one year of operation [5]. ...
Thin metal films on polymer substrates are key components for a variety of terrestrial and space applications such as flexible microelectronics or multilayer insulation systems. Although these applications seem to be quite different, there is a similarity in terms of thermal stress. In both cases the material undergoes a considerable amount of thermal cycling of ± hundreds of degree Celsius during its lifetime. Due to the composite nature of the material it is important to investigate interfacial properties as a function of this thermal cycling. This work investigates interface strength and electro-mechanical behaviour as a function of thermal cycling for vapour deposited Aluminum (Al) films (150 nm) on 25 μm Polyimide (PI). The material is subjected to various numbers of thermal cycles of ± 150 °C in a gaseous N2 atmosphere. Tensile induced delamination with in-situ resistance measurements is used to measure adhesion values as well as the electro-mechanical failure behaviour. It was found that although the adhesion of Al-PI is unaffected by the applied thermal load, a strong decrease in the electro-mechanical properties of the system was observed. Since good electro-mechanical properties are crucial for flexible electronic applications the resistance against thermal cycling needs to be taken into account when assessing the suitability of a material for flexible applications.
... Polymers, such as aluminized-Teflon fluorinated ethylene propylene (Al-FEP), are often used on the exterior of spacecraft for passive thermal control because they are light weight, flexible and have excellent optical and thermal. But, as witnessed on the Hubble Space Telescope, Teflon FEP insulation becomes extremely embrittled in the space environment.[1][2][3][4][5]In an effort to better understand the effect of space exposure on the degradation of Teflon insulation, Teflon samples for tensile testing were exposed for 1.5 years to the space environment on the exterior of the International Space Station (ISS). ...
Materials on the exterior of spacecraft in low Earth orbit are subject to extremely harsh environmental conditions, including exposure to various forms of radiation, temperature extremes and thermal cycling, and atomic oxygen. These environmental exposures can result in erosion, and optical and mechanical property degradation of susceptible materials, threatening spacecraft performance and durability. In an effort to better understand the effect of space exposure on the mechanical property degradation of Teflon insulation, 19 tensile samples were exposed to the space environment for 1.5 years on the exterior of the International Space Station. The samples were flown in ram, wake, zenith, or nadir orientations as part of three Materials International Space Station Experiment 7 mission experiments. This paper provides an overview of the flight mission, an introduction to the experiments, and compares the Teflon property degradation in the various orientations. The reduction in ductility of the samples correlates with the amount of solar radiation. Samples with high solar exposure (zenith orientation) experienced a 76% reduction in elongation relative to controls, while samples in the shadowed nadir orientation only experienced a 4% reduction. Additionally, thickness loss measurements show that erosion is significant in the ram orientation, but negligible in other orientations.
... On HST, the length of cracks induced in the Teflon insulation has been observed to be up to on the order of meters, as shown in Figure 2. The cracking of FEP on HST has been attributed to radiation induced embrittlement that is further enhanced with thermal exposure. [1] Curling of cracked insulation through environmentally induced surface strain of the Teflon has allowed the underlying components to be directly exposed to the space environment; hence in those areas the insulation is no longer functioning properly for thermal control. ...
... This tendency to curl indicates that if an FEP/VDA blanket is held flat by its perimeter that a tensile stress will build up on the space exposed surface until cracks are initiated. Once the cracks become large, then the FEP/VDA torn pieces will tend to roll up exposing the underlying materials to increased temperatures due to a lack of emissive surfaces as has occurred on the Hubble Space Telescope light shield [1]. ...
Experiments have been conducted in low Earth orbit (LEO) on the Long Duration Exposure Facility (LDEF) and the Materials International Space Station Experiment 2 (MISSE 2) that involved slightly stretched polymers held at their perimeters. In several instances, tearing occurred at the polymers’ perimeters. A possible cause for such material failure may be polymer shrinkage as a result of LEO exposure, causing the stress level to gradually increase until the polymers tear. The potential for tearing may be increased by radiation induced surface embrittlement of the polymer. An active experiment, called the Polymer Strain Experiment (PSE), was designed and installed on MISSE 6B to measure the strain in 6 one-end free standing polymers as a function of time. It was thought that radiation or other environmental factors may possibly induce shrinkage in some polymers developing a tensile stress when held in place. Post-flight testing was conducted on the six flight samples including dehydration shrinkage, thermal vacuum strain, scanning electron microscopy and mandrel bend testing.
... In addition to materials spaceflight experiments, hardware from the Solar Max Mission (SSM) spacecraft, and materials retrieved from the Hubble Space Telescope (HST) during its five servicing missions, have provided important information on spacecraft materials durability in the space environment. For example, the metallized Teflon fluorinated ethylene propylene (FEP) outer layer of multilayer insulation (MLI) on the HST has become extremely embrittled on-orbit resulting in severe through-thickness cracking (Townsend et al., 1999). Teflon FEP insulation retrieved during HST's servicing missions have been analyzed and tested to determine the cause of degradation of this very commonly used thermal control material (Townsend et al., 1998;de Groh et al., 2000de Groh et al., , 2001. ...
... Teflon FEP insulation retrieved during HST's servicing missions have been analyzed and tested to determine the cause of degradation of this very commonly used thermal control material (Townsend et al., 1998;de Groh et al., 2000de Groh et al., , 2001. The results indicate that radiation in space causes FEP embrittlement, and that thermal cycling further contributes to degradation with the maximum on-orbit temperature playing a crucial role (Townsend et al., 1999). Data from materials spaceflight experiments have been used for micrometeoroid and orbital debris (MMOD) model verification and/or modification, and for atomic oxygen erosion predictive model development. ...
Space environmental effects on spacecraft materials can be severe due to individual and synergistic interactions of orbital environments such as solar ultraviolet radiation, charged particle radiation, temperature extremes and thermal cycling, impacts from micrometeoroids and orbital debris, environment induced contamination, and low Earth orbital atomic oxygen. Space environmental threats vary greatly based on spacecraft materials, thicknesses and stress levels, and the mission environment and duration. Materials spaceflight experiments have been conducted since the early 1970s to help understand the effects of the space environment on spacecraft materials, components and devices. Materials experiments have been flown on Skylab, Salyut and Mir, the space shuttle, and the International Space Station. In addition, there have been free-flyer experiments such as the Long Duration Exposure Facility. In addition to being critical for understanding the engineering performance of materials exposed to specific space environments, data from spaceflight experiments can be used to determine correlations between exposures in ground-test facilities and space, thus allowing more accurate in-space materials performance predictions to be made based on ground-facility testing. This chapter reviews most major materials spaceflight experiments along with some of the lessons learned from the experiments, and how the results have influenced materials use and selection.
... The main requirement, especially in the case of high sensitivity devices, is high transparency under low intensity and ambient conditions combined with opacity under high intensity radiation conditions. Polymeric materials-based OPL filters can experience degradation in optical, nonlinear optical and mechanical properties when exposed to the space environment for long periods of time [2]. Damaging space environment effects include solar ultraviolet radiation, solar flare x-rays, electron and proton radiation, atomic oxygen in low Earth orbits, and temperature cycle effects. ...
Optical limiters are nonlinear optical devices that limit the amount of power or energy transmitted. They function through either optically-induced nonlinear absorption or refraction or a combination of the two. At low incident optical power or pulse energy, the transmission of the system is high enough to allow nominal operation of the system. At high incident optical power or pulse energy, the transmission decreases to protect sensitive components such as optical receivers or transmitters. The interest in optical power limiters (OPL) for use in the space environment is due to the increasingly large number of space based missions and applications that require laser protection. Temperature and space radiation-induced effects in optical and electronic materials are well known and they can cause disruption in OPL functions, or in the worst case, failure of the sensor. Therefore, designing materials that can withstand the space environment has been an area of intense exploration in recent years. Some of the best-performing optical limiters are materials containing chromophores that work via reverse saturable absorption, multiphoton absorption or nonlinear scattering mechanisms; however, such materials are difficult to prepare and have problems with long-term stability. In this paper, a novel type of polymeric OPL materials based on a multi-chromophore approach is described. The origin of the OPL properties in these materials and preliminary results of their effects of radiation on the OPL properties are discussed.
