The effects of contamination from silicones and a modified-tefzel insulation on critical surfaces of the international space station

Babel, H. W.; Hasegawa, Mark M.; Jones, Cherie; Fussell, John

doi:10.1016/s0094-5765(97)00104-5

Cited by 5 publications

(2 citation statements)

References 1 publication

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“…Whereas the temperature of a spacecraft surface facing away from the sun can fall below -20 • C, outgassed deposits have a high probability of sticking. To prevent this contamination, materials for use in space are screened in accordance with established standards [9], [10] and simulation tools that emulate both outgassing and deposition kinetics to assess the amount of contaminant deposition in orbit [11], [12]. The QCM sensor is widely used to assess the deposition/desorption amounts of contaminants in a vacuum chamber, which simulates conditions in space such as extreme temperatures [3].…”

Section: Introductionmentioning

confidence: 99%

Twin-CQCM and Twin-TQCM Sensors With Wide Operating Temperature Range for Outgassing and Atomic Oxygen Measurement

et al. 2021

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In this paper, we propose a new Quartz Crystal Microbalance (QCM) sensor with temperature control, which can assess outgassing properties during spacecraft development. It will be referred to as the "Twin-QCM sensor." There are two types. The Twin-Cryogenic QCM (Twin-CQCM) sensor is warmed by a built-in heater with an operating temperature of -190 to +125 • C, and the Twin-Thermoelectric QCM (Twin-TQCM) sensor is warmed and cooled by a builtin Peltier module that can control the temperature within -80 to +125 • C. Using a temperature compensation technique, the temperature-dependent drift of the frequency was found to be less than ±10 ppm over all operating temperatures. An RTD temperature sensor was mounted on the quartz crystal to improve the accuracy of temperature measurement. To confirm the accuracy, an additional temperature sensor installed at the center of the crystal. The sensor output temperature value was compared to that of the additional sensor, with the difference between both temperature sensors being +0.4 to +2.6 • C in the temperature range from -130 to +100 • C. Through the measurement of the sensor's dynamic range, it was found that the deposited contaminant film in a vacuum increasingly changed such physical properties as viscoelasticity as the temperature increases.

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Section: Introductionmentioning

confidence: 99%

Twin-CQCM and Twin-TQCM Sensors With Wide Operating Temperature Range for Outgassing and Atomic Oxygen Measurement

et al. 2021

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“…Modeling the material's thermo-optical properties, absorptance (α) and emittance (ε), is complex due to these effects. Ultraviolet (UV) darkening or photochemical darkening of thermal control materials and that of contaminant layers has been documented in numerous on-orbit experiments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] and under simulated conditions [18][19][20][21][22][23][24][25] . The collection of data suggests that ceramic (inorganic)-based coatings/paints (Z-93, AZ93, YB-71) that have not been heavily contaminated have performed well in the space and simulated environment.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the optical performance of AZ93 with a fluoropolymer overcoat under ultraviolet exposure

Huang

Schmidl

Soares

2008

Optical System Contamination: Effects, Measurements, and Control 2008

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AZ93 with a fluoropolymer overcoat is an option to simplify ground handling of space hardware. The overcoat applied on some on-orbit International Space Station (ISS) hardware provides contamination protection for optically sensitive ceramic thermal control coatings. However, if the fluoropolymer is not eroded on-orbit by atomic oxygen (AO), then it will darken. This will increase the solar absorptance resulting in possible thermal performance degradation. If the fluoropolymer overcoat was not present, optical performance would be significantly improved. To characterize the optical performance of the AZ93 with the fluoropolymer overcoat for modeling the UV degradation, laboratory testing of the coating was performed at Marshall Space Flight Center (MSFC). Sample coupons prepared by AZ Technology were exposed under vacuum to ultraviolet radiation. At periodic intervals, the samples were removed from the testing chamber to acquire images and to measure the solar absorptance. The images showed visible differences between AZ93 with the overcoat and without the overcoat as vacuum ultraviolet (VUV) exposure increased. Darkening is more pronounced in the samples with the fluoropolymer overcoat. This was also evident in the solar absorptance measurements. Optical properties of AZ93 with the fluoropolymer overcoat significantly degraded in comparison to those without the overcoat. A short period of little change followed by an exponential rise in solar absorptance was observed. The optical degradation of the fluoropolymer overcoat is described in terms of surface reaction chemistry and kinetics and is found to follow a pseudo first order reaction rate.

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Polydimethylsiloxane–cristobalite composite adhesive system for aerospace applications

Ansari¹,

Varghese²,

Dayas³

2008

Polymers for Advanced Techs

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The effect of phase‐pure cristobalite (a high temperature crystalline polymorph of silica) on the adhesive characteristics of hydroxyl terminated polydimethylsiloxane (PDMS) was studied. The potential advantages of PDMS/cristobalite composite system as an adhesive for aerospace applications are also discussed. A PDMS/cristobalite composite adhesive system containing different filler contents (0–46 volume percentage, vol%) was prepared. The filler material, phase‐pure cristobalite, was synthesized by the pyrolysis of fused silica at 1400°C. The mechanical, rheological, and thermal characteristics of the composites were studied. A high yield stress (0.151 Pa), shear‐thinning index (1.051), and fast recovery rate were observed for ∼34 vol% cristobalite loading, which indicate that PDMS retains its excellent adhesive and flow characteristics even at high filler loading with enhanced mechanical characteristics. Thermal analysis shows the onset of degradation of PDMS shifts to higher temperatures, 372–438°C and 317–417°C in nitrogen and air atmosphere respectively, which shows excellent thermal stability. The residual component yields after thermal degradation of PDMS/cristobalite composite system in nitrogen and air atmosphere show different degradation mechanisms. Copyright © 2008 John Wiley & Sons, Ltd.

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The effects of contamination from silicones and a modified-tefzel insulation on critical surfaces of the international space station

Cited by 5 publications

References 1 publication

Twin-CQCM and Twin-TQCM Sensors With Wide Operating Temperature Range for Outgassing and Atomic Oxygen Measurement

Twin-CQCM and Twin-TQCM Sensors With Wide Operating Temperature Range for Outgassing and Atomic Oxygen Measurement

Characterizing the optical performance of AZ93 with a fluoropolymer overcoat under ultraviolet exposure

Polydimethylsiloxane–cristobalite composite adhesive system for aerospace applications

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