scholarly journals On the Utility of Coated POSS-Polyimides for Vehicles in Very Low Earth Orbit (VLEO)

2021 ◽  
Author(s):  
Timothy Minton ◽  
Thomas Schwartzentruber ◽  
Chenbiao Xu
Keyword(s):  
Molecular Nitrogen ◽  
Molecular Beams ◽  
Thermal Control ◽  
Low Earth Orbit ◽  
Surface Scattering ◽  
Earth Orbit ◽  
Space Vehicles ◽  
Inorganic Polymers ◽  
Coating Materials ◽  
Silicon Oxide Layer

The environment encountered by space vehicles in very low Earth orbit (VLEO, 180 – 350 km altitude) contains predominantly atomic oxygen (AO) and molecular nitrogen (N2), which collide with ram surfaces at relative velocities of ~7.5 km s-1. Structural, thermal-control, and coating materials containing organic polymers are particularly susceptible to AO attack at these high velocities, resulting in erosion, roughening, and degradation of function. Copolymerization or blending of a polymer with polyhedral oligomeric silsesquioxane (POSS) yields a material that can resist AO attack through the formation of a passivating silicon-oxide layer. Still, these hybrid organic/inorganic polymers become rough through AO reactions as the passivating layer is forming. Surface roughness may enhance satellite drag because it promotes energy transfer and scattering angle randomization during gas-surface collisions. As potential low-drag and AO-resistant materials, we have investigated POSS-containing films of clear and Kapton-like polyimides that have an atomically smooth AO-resistant coating of Al2O3 that is grown by atomic layer deposition (ALD). Coated and uncoated films were exposed to hyperthermal molecular beams containing atomic and molecular oxygen to investigate their AO resistance, and molecular beam-surface scattering studies were conducted to characterize the gas-surface scattering dynamics on pristine and AO-exposed surfaces to inform drag predictions. The AO erosion yield of Al2O3 ALD-coated films is essentially zero. Simulations of drag on a representative satellite structure that are based on the observed scattering dynamics suggest that the use of the Al2O3 ALD-coated POSS-polyimides on external satellite surfaces have the potential to reduce drag to less than half that predicted for diffuse scattering surfaces. These smooth and AO-resistant polymer films thus show promise for use in the extreme oxidizing and high-drag environment in VLEO.

Degradation modeling of satellite thermal control coatings in a low earth orbit environment

Solar Energy ◽  
2016 ◽  
Vol 139 ◽  
pp. 467-474 ◽  
Author(s):  
Tianyu Liu ◽  
Quan Sun ◽  
Jieru Meng ◽  
Zhengqiang Pan ◽  
Yanzhen Tang
Keyword(s):  
Thermal Control ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Degradation Modeling ◽  
Thermal Control Coatings

scholarly journals Combustion Synthesis Technology for a Sustainable Settlement Overnight

2018 ◽  
Vol 20 (1) ◽  
pp. 3
Author(s):  
Osamu Odawara
Keyword(s):  
Combustion Synthesis ◽  
Resource Utilization ◽  
High Vacuum ◽  
Thermal Control ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
The Moon ◽  
The Earth

Space technology has been developed for frontier exploration not only in low-earth orbit environment but also beyond the earth orbit to the Moon and Mars, where material resources might be strongly restricted and almost impossible to be resupplied from the earth for distant and long-term missions performance toward “long-stays of humans in space”. For performing such long-term space explorations, none would be enough to develop technologies with resources only from the earth; it should be required to utilize resources on other places with different nature of the earth, i.e., in-situ resource utilization. One of important challenges of lunar in-situ resource utilization is thermal control of spacecraft on lunar surface for long-lunar durations. Such thermal control under “long-term field operation” would be solved by “thermal wadis” studied as a part of sustainable researches on overnight survivals such as lunar-night. The resources such as metal oxides that exist on planets or satellites could be refined, and utilized as a supply of heat energy, where combustion synthesis can stand as a hopeful technology for such requirements. The combustion synthesis technology is mainly characterized with generation of high-temperature, spontaneous propagation of reaction, rapid synthesis and high operability under various influences with centrifugal-force, low-gravity and high vacuum. These concepts, technologies and hardware would be applicable to both the Moon and Mars, and these capabilities might achieve the maximum benefits of in-situ resource utilization with the aid of combustion synthesis applications. The present paper mainly concerns the combustion synthesis technologies for sustainable lunar overnight survivals by focusing on “potential precursor synthesis and formation”, “in-situ resource utilization in extreme environments” and “exergy loss minimization with efficient energy conversion”.

scholarly journals Property changes in materials due to atomic oxygen in the low Earth orbit

2021 ◽  
Author(s):  
Aki Goto ◽  
Kaori Umeda ◽  
Kazuki Yukumatsu ◽  
Yugo Kimoto
Keyword(s):  
Photoelectron Spectroscopy ◽  
Atomic Oxygen ◽  
Surface Reactions ◽  
Ccd Camera ◽  
Polymeric Materials ◽  
Thermal Control ◽  
Polyimide Film ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Exposure Experiment

AbstractWe expect satellites at altitude below 300 km, very low Earth orbit (VLEO), making observations of the Earth at optical wavelength with increasingly higher resolution. The density of atomic oxygen (AO) at VLEO is significantly higher than that at LEO; severe degradation of spacecraft materials (polymers) due to the high-flux AO is a serious concern. To clarify VLEO environmental effects on spacecraft materials, we designed the Material Degradation Monitor (MDM) and MDM2 missions. The MDM is a material exposure experiment onboard the Super Low-Altitude Test Satellite (SLATS). It aims to understand reactions and degradation of polymeric materials depending on AO fluence in VLEO. In the MDM, samples of spacecraft material were exposed at altitude of 160–560 km; their degradation behaviors were observed optically by a CCD camera for 1.8 years. The MDM2 is a material exposure experiment onboard the International Space Station (ISS) and aims to correctly understand surface reactions and degradation of the same samples used in the MDM at a given AO fluence. In the MDM2, the samples were exposed at altitude of 400 km for 1 year and then returned to Earth for analysis. Based on the results from both missions, we will help in the molecular design of more-durable materials, and establish design standards for future VLEO satellites. This study aims to quantitatively understand the surface reactions and degradation of the 11 types of thermal control materials exposed on the ISS in the MDM2. Five types of multilayer insulation (MLI) films (three types of Si-containing AO protective materials (a silsesquioxane-(SQ-) containing coated polyimide film, two types of polysiloxane-block polyimide (BSF-30) films), an ITO-coated polyimide film, and a Beta Cloth), and flexible optical solar reflectors (flexible OSRs) were found to have a high durability against erosion by AO. This was determined by measuring their loss of mass and thermo-optical properties. The Ag/Inconel layer’s discoloration and peeling were observed for three types of FEP/Ag films as determined by the Ag layer’s oxidation by AO. Also, X-ray photoelectron spectroscopy (XPS) showed that reactions of the Si-containing materials, the SQ-coated polyimide film and the BSF-30 film, form a layer of silica that protects against AO. Even though the concentration of Si in the SQ-coating is the same or greater than in the BSF-30 film, the amount of the SQ-coating that reacted was larger than that of the BSF-30 film under the same AO fluence. Moreover, the effective ability of the UV-shielding coating, composed of ITO and CeO2 coated onto one of the BSF-30 films, was demonstrated by UV–Vis spectrometry. Its sufficient AO protection was confirmed by mass measurements, XPS analyses, and FE-SEM observations.

scholarly journals Experimental Arrangement for Testing the Effectiveness of Lead Glass for Shielding Against Ionizing Radiation in Low Earth Orbit for Future Space Vehicles

2021 ◽  
Vol 9 (10) ◽  
pp. 94-98
Author(s):  
Anurag Chapagain
Keyword(s):  
Ionizing Radiation ◽  
Structural Engineering ◽  
Low Earth Orbit ◽  
Radiation Shielding ◽  
Experimental Arrangement ◽  
Earth Orbit ◽  
Space Vehicles ◽  
Lead Glass ◽  
Future Space ◽  
The Future

Abstract: The present times are exhilarating, full of possibilities, which humans, just a century ago, would deem impossible. One of them is space travel: an effort to step one foot in the vast cosmic ocean. Through this experimental arrangement, we want to make the journey a little bit affordable, easier, and most importantly, more enjoyable. The future of transportation is in space. The future space vehicle needs a material that is transparent, cheap, and safe by blocking ionizing radiation. Lead glass which is abundantly found on earth and is cheap is proved to be effective in shielding ionizing radiation. The problem is that it is tested in the earth’s environment for less energy radiation. Our experiment arrangement is designed to test the effectiveness of lead glass and if effective, the thickness of lead glass required for effective shielding of skin cells and microdrive. The experiment is designed as such to accommodate the whole setup in a cube of 3cm*3cm*3cm, so that experiment will be portable enough and easy to transport in low earth orbit This paper, however, doesn’t address the structural engineering solutions regarding implementation of lead glass as the material for space vehicles. Keywords: Ionizing radiation, radiation shielding, lead glass, low earth orbit, future space vehicles

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