Low Earth Orbit Space Environment Research Articles

Effect of AO/UV/RD exposure on spaceborne diffusers: a comparative experiment.

The environmental measuring instrument (EMI) is a nadir-viewing wide-field imaging spectrometer, which adopts spaceborne diffusers in in-flight calibration systems, including an aluminum diffuser and a quartz volume diffuser. Spaceborne diffusers, are the key components of in-flight calibration systems, and are used to introduce sunlight into the EMI. Hemispheric reflectance and bidirectional reflectance distribution function were experimentally measured to analyze spaceborne diffuser performance. Radiation exposure experiments on atomic oxygen, UV, and radiation dose of the spaceborne diffusers were performed at ground level because the EMI works in low Earth orbit space environments. Effects of radiation exposure on spaceborne diffusers were discussed in detail. Protective methods were introduced to reduce the effects of the space environment, and an in-orbit monitoring method was also proposed.

LEO space environment exposure resistant behavior of Ag–Cu films

Ag–Cu films, deposited by arc ion plating and composed of face-centered cubic (fcc) Ag and AgCu alloy phases, had been exposed for 43.5h in low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard the China Shenzhou-7 manned spaceship. The structure, morphology, composition and tribological property of the Ag–Cu films after the space environment exposure (SEE) were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. After the SEE, the surface layer of Ag–Cu film was partially oxidized to Ag2O, in which the Ag2O content was decreased from the surface to inner and the Cu element was absent. Furthermore, the exposed Ag–Cu film surface became color and exhibited lots of fine particle-like protuberances, but cracking and flaking phenomena that were common for the exposed Ag film, were not observed. Overall, the influence of space exposure on Ag–Cu film was slight compared to the pure Ag film. Sliding friction tests revealed that for the exposed Ag–Cu film, the friction coefficient was stable and the mean value was almost equivalent to one of the non-exposed Ag–Cu film.

Changes in the composition, structure and friction property of sputtered MoS2 films by LEO environment exposure

Radio frequency-sputtered MoS2 films had been exposed for 43.5h in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard China Shenzhou-7 manned spaceship. The composition, morphology, phase structure and friction property of the exposed films were investigated using X-ray photoelectron spectroscope (XPS), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray energy-dispersive spectroscopy (EDS) and ball-on-disk tribometer. XRD and EDS results revealed that the as-deposited MoS2 films were characterized by a MoSxOy phase structure, in which x and y values were determined to be ∼0.65 and 1.24, respectively. XPS analysis revealed that due to space atomic oxygen attack, the film surface was oxidized to MoO3 and MoSxOy with higher O concentration, while the partial S was lost. However, the affected depth was restricted within the surface layer because of protective function of the oxidation layer. As a result, the friction coefficient only exhibited a slight increase at initial stage of sliding friction.

Changes in the structure and tribological property of Ag film by LEO space environment exposure

Ag films, deposited by arc ion plating, had been exposed for 43.5h in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard the China Shenzhou-7 manned spaceship. The structure, morphology, composition and tribological property of the Ag films after the space environment exposure (SEE) were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. Depth XPS and XRD analysis revealed that after the SEE, the surface layer of Ag films was partially oxidized to Ag2O, the cracking and flaking phenomena could be observed from the film surface by FESEM, and so the Ag films lose its metallic shine and became gray. As a result, the tribological performance was deteriorated and the high/unstable friction was obtained.

Protective effect of nanocomposite film from the low earth orbit environment

The various hazards in the low earth orbit space cause damage mostly on the exposed surfaces of polymer-based materials. Neutral particles, especially atomic oxygen, erode the exposed surface, and cyclic temperature variation produces microcracks that degrade mechanical performance. To protect substrate materials from the harmful environments, this research investigated the protective effect of nanocomposite film under a simulated low earth orbit space environment involving 4 × 10−4 torr high vacuum, 200 nm ultraviolet radiation, 14 thermal cycles ranging from −70℃ to 100℃, and atomic oxygen flux of 2.07 × 1014 atoms/cm2s. The protective films of multi-walled carbon nanotubes or nano-silica dispersed in epoxy matrix were fabricated using a comma roll casting machine. The physical and mechanical changes of the film-protected specimens under the simulated low earth orbit environment were compared to those of no-film-protected specimens. The amount of specimen erosion during the low earth orbit simulation test was analyzed through mass change. Furthermore, the tensile performance before and after exposure to the simulated low earth orbit environment was evaluated. Since the uniformly dispersed nano-silica blocked the attack of atomic oxygen and ultraviolet radiation, and internal multi-walled carbon nanotubes impeded crack propagation due to the bridging effect, the specimens protected by nanocomposite film showed less damage on the exposed surfaces and smallest in degradation of tensile strength after exposure to the simulated low earth orbit environment.

A near edge X-ray absorption fine structure study of oxidized single crystal and polycrystalline diamond surfaces

The influence of oxidizing environments on single crystal diamond and polycrystalline chemical vapor deposited CVD diamond films was studied using the near edge X-ray absorption fine structure (NEXAFS) pre-edge region in both bulk and surface sensitive modes. The NEXAFS of (100) oriented single crystal diamond was measured following (i) exposure to a microwave (MW) hydrogen plasma, (ii) annealing to 1000 °C, (iii) exposure of the as annealed surface to H2O, and (iv) exposure of the as annealed surface to O2. From these measurements particular surface bonding configurations have been assigned to features in the pre-edge structure. The NEXAFS of microcrystalline CVD diamond films was studied following different oxidative treatments using (i) a thermal atomic oxygen (AO) environment, (ii) a hyperthermal (5 eV) AO source, and (iii) an RF oxygen plasma exposure. The nature of the surface layer was found to be different for differently oxidized surfaces. These treatments were carried out as part of a study of CVD diamond durability in the low Earth orbit space environment.

The Organism/Organic Exposure to Orbital Stresses (O/OREOS) Satellite: Radiation Exposure in Low-Earth Orbit and Supporting Laboratory Studies of Iron Tetraphenylporphyrin Chloride

We report results from the exposure of the metalloporphyrin iron tetraphenylporphyrin chloride (FeTPPCl) to the outer space environment, measured in situ aboard the Organism/Organic Exposure to Orbital Stresses nanosatellite. FeTPPCl was exposed for a period of 17 months (3700 h of direct solar exposure), which included broad-spectrum solar radiation (∼122 nm to the near infrared). Motivated by the potential role of metalloporphyrins as molecular biomarkers, the exposure of thin-film samples of FeTPPCl to the space environment in low-Earth orbit was monitored in situ via ultraviolet/visible spectroscopy and reported telemetrically. The space data were complemented by laboratory exposure experiments that used a high-fidelity solar simulator covering the spectral range of the spaceflight measurements. We found that thin-film samples of FeTPPCl that were in contact with a humid headspace gas (0.8-2.3% relative humidity) were particularly susceptible to destruction upon irradiation, degrading up to 10 times faster than identical thin films in contact with dry headspace gases; this degradation may also be related to the presence of oxides of nitrogen in those cells. In the companion terrestrial experiments, simulated solar exposure of FeTPPCl films in contact with either Ar or CO2:O2:Ar (10:0.01:1000) headspace gas resulted in growth of a band in the films' infrared spectra at 1961 cm(-1). We concluded that the most likely carriers of this band are allene (C3H4) and chloropropadiene (C3H3Cl), putative molecular fragments of the destruction of the porphyrin ring. The thin films studied in space and in solar simulator-based experiments show qualitatively similar spectral evolution as a function of contacting gaseous species but display significant differences in the time dependence of those changes. The relevance of our findings to planetary science, biomarker research, and the photostability of organic materials in astrobiologically relevant environments is discussed.

Corrigendum to “Enhanced durability of silanized multi-walled carbon nanotube/epoxy nanocomposites under simulated low earth orbit space environment” [Compos. Sci. Technol. 87 (2013) 224–231

Corrigendum to “Enhanced durability of silanized multi-walled carbon nanotube/epoxy nanocomposites under simulated low earth orbit space environment” [Compos. Sci. Technol. 87 (2013) 224–231

Microstructure evolution of 2024 and 7A09 aluminium alloys subjected to thermal cycling in simulated LEO space environment

The microstructures and properties of 2024 and 7A09 aeronautical aluminium alloys subjected to thermal cycling have been investigated in simulated low earth orbit (LEO) space environment using microhardness tests, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The microhardness tests revealed that the hardness decrease first and then increase, but finally decrease with the cycle times. The results of XRD and TEM show that, in 2024 aluminium alloy, the precipitate evolution with the cycling time is the small needle-like S′ phases transforming to the rod-like equilibrium S phases. In 7A09 aluminium alloys, needle-like η′ phases and short rod-like η equilibrium phases transform to rod-like η equilibrium phases and large size of Guinier–Preston zones in the process of thermal cycling. Furthermore, many cavities around the precipitated phase appear after 500 cycles in both 2024 and 7A09 aluminium alloys. The relationship between microstructural evolution and thermal fatigue in LEO space environment was discussed.

Stability of Silk and Collagen Protein Materials in Space

Collagen and silk materials, in neat forms and as silica composites, were flown for 18 months on the International Space Station [Materials International Space Station Experiment (MISSE)-6] to assess the impact of space radiation on structure and function. As natural biomaterials, the impact of the space environment on films of these proteins was investigated to understand fundamental changes in structure and function related to the future utility in materials and medicine in space environments. About 15% of the film surfaces were etched by heavy ionizing particles such as atomic oxygen, the major component of the low-Earth orbit space environment. Unexpectedly, more than 80% of the silk and collagen materials were chemically crosslinked by space radiation. These findings are critical for designing next-generation biocompatible materials for contact with living systems in space environments, where the effects of heavy ionizing particles and other cosmic radiation need to be considered.

Microstructure Evolution of 2024 Aluminum Alloys Subjected to Thermal Cycling in Simulated LEO Space Environment

The microstructures and properties of 2024 aeronautical aluminum alloy subjected to thermal cycling were investigated in simulated Low Earth Orbit space environment. The experimental results demonstrate that the microhardness of aluminum alloys changed with the increasing of thermal cycles. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that the property changes of the 2024 aluminum alloys during the thermal cycling period are closely related to the microstructural evolution. The relationship between the microstructural evolution and the thermal fatigue was also discussed.

Enhanced durability of silanized multi-walled carbon nanotube/epoxy nanocomposites under simulated low earth orbit space environment

Silane treated carbon nanotube filled polymer nanocomposites are suggested as a new alternative to reduce the degradation of polymer matrix composites (PMCs) exposed to the low earth orbit (LEO) environment. The silanization of multiwalled carbon nanotubes (MWCNTs) is conducted using 3-aminopropyltriethoxysilane (APTES). Nanocomposites filled with MWCNTs with and without silanization were prepared by the solution mixing method using mechanical/physical approaches to homogeneously disperse the MWCNTs into the polymer matrix. The samples were exposed to an accelerated low earth orbit simulated space environment for 20 h. The synergistic environmental factors used in the ground simulation systems were high vacuum, atomic oxygen (AO), ultraviolet (UV) radiation and thermal cycling. The material properties for nanocomposites reinforced with MWCNTs with and without silanization before and after exposure to the low earth orbit space environment were evaluated by total mass loss (TML), tensile test, thermo-gravimetric analysis (TGA), thermo-mechanical analysis (TMA), and thermo-optical analysis. Surface morphologies of the exposed samples were characterized through scanning electron microscopy (SEM). The results indicated that improvement of the interfacial bonding between the nanotubes and the matrix by the silanization of MWCNTs can considerably reduce the degradation rate and enhance the thermal stability, without sacrificing the thermo-mechanical properties of nanocomposites with very low MWCNT content under LEO space environmental conditions.

우주파편 충돌분석을 위한 CSM 궤도데이터 분석

우주파편은 1957년 인류가 우주에 위성을 보내기 시작하면서 그 숫자가 급격하게 증가하고 있으며, 현재 미합동우주전략사령부(JSpOC, Joint Space Operations Center)에 의하면 지름 10cm 이상의 우주파편이 22,000개 이상이라고 알려지고 있다. 최근에는 중국이 자국의 위성을 미사일로 요격시킨 사건과 Iridium 33 및 Cosmos 2251 위성이 우주상공에서 서로 충돌한 사건이 발생함에 따라 아리랑 2호가 운영 중인 저궤도의 우주환경이 급격히 악화되고 있다. 미합동우주전략사령부는 15,000개 이상의 우주파편의 궤도정보를 이용하여 운영위성과의 충돌분석을 수행하고 있으며, 충돌 위험이 발생할 경우 해당 위성의 운영자에게 CSM(Conjunction Summary Message)이란 형식의 메시지를 제공하여 충돌분석 시 활용할 수 있도록 지원하고 있다. 본 논문은 JSpOC에서 제공하는 CSM의 아리랑2호 궤도데이터와 항우연이 관리하는 아리랑 2호의 정밀궤도 데이터와 비교하였으며, 아리랑 2호와 우주파편과의 충돌분석 결과를 도시하였다. Since plenty of spacecrafts were launched in space after 1957, the number of space debris has been increased. According to the JSpOC, the number of space debris which diameter is bigger than 10 cm are more than 22,000. Recently there were two critical events. Which one is that China shot down their satellite using missile and the other is that two satellite, Iridium and Cosmos 2251, collied. Space environment in low-earth orbit has been severe. JSpOC analyzes the collision risk between 15,000 space debris and all operation satellites and then they send CSM to the satellite operator to utilize its orbital information if collision risk might be occurred. This paper analyzes the CSM orbit data by comparing with KOMPSAT-2 precise orbit data and shows conjunction assessment results.

Space Flight Validation of Design and Engineering of the ZDPS-1A Pico-satellite

The ZDPS-1A pico-satellites are the first satellites in China within the 1-10 kg mass range that are successfully operated on orbit. Unlike common pico-satellites, they are designed to be “larger but stronger” with more powerful platforms and unique payloads so as to bear a better promise for real applications. Through their space flight mission, the functionality and performance of the two flight models are tested on orbit and validated to be mostly normal and in consistency with design and ground tests with only several inconforming occasions. Moreover, they have worked properly on orbit for one year so far, well exceeding their life expectancy of three months. Therefore, the space flight mission has reached all its goals, and verified that the design concept and the engineering process of the pico-satellites are sufficient in allowing them the desired functionality and performance in, and the adaption to the launch procedure and the low-Earth orbit space environment. In the foreseeable future, the platform together with the design concept and the engineering process of the pico-satellites are expected to be applied to more complicated real space applications.

Charge-Enhanced Contamination and Environmental Degradation of MISSE-6 SUSpECS Materials

The effects of prolonged exposure to the low Earth orbit space environment and charge-enhanced contamination on optical, thermal, and electron emission and transport properties of common spacecraft materials have been investigated by comparing pre- and postflight characterization measurements. The State of Utah Space Environment and Contamination Study (SUSpECS), deployed in March 2008 on board the Materials International Space Station Experiment (MISSE-6) payload, was exposed for ~18 months on the exterior of the International Space Station (ISS) and was retrieved in September 2009. A total of 165 samples was mounted on three separate SUSpECS panels on the ram and wake sides on the ISS. Some samples, particularly those exposed to atomic oxygen in the ram direction, showed pronounced effects due to exposure. Biased samples for the charge-enhanced contamination study showed subtle variations in visible and infrared reflectivity.

Comparison of Macro and Microtribological Property of Molybdenum Disulfide Film Exposed to LEO Space Environment

Macro- and microtribological properties of the MoS2 film exposed to atomic oxygen, ultraviolet rays and radiation both in low earth orbit (LEO) and in ground-based facility were evaluated relevance to micro/nano satellites. MoS2 samples are exposed to LEO space environment by the space environment exposure device experiment on international space station. Laser-detonation atomic oxygen beam source was used for atomic oxygen simulation on the ground. X-ray photoelectron spectroscopy and energy dispersive spectroscopy measurements suggested that electron beam and ultraviolet exposure did not affect chemical structure of MoS2 surfaces. However, atomic oxygen-exposed and flight samples showed surface oxidation. It was found that the macroscopic friction coefficient of the flight sample was similar to that of the control sample. In contrast, remarkable increase in friction coefficient in microscopic properties was observed.

Effects of Atomic Oxygen Irradiation on PDMS/POSS Hybrid Films in Low Earth Orbit Environment

In order to improve the atomic oxygen (AO) erosion resistance of polyimide films in low earth orbit space environment, a type PDMS/POSS hybrid coating on polyimide substrate was prepared based on a silanol terminated polydimethylsiloxane (PDMS-OH) and Octakis(trimethylsiloxy)octaprismosilsesquioxane (Q8[Si(CH3)3]8) by copolymerizing process in DMAc solution. The atomic oxygen exposure tests were carried out using a ground-based atomic oxygen simulation facility. The mass loss, surface morphology and surface chemical compositions of PDMS/POSS hybrid films before and after exposure to incremental AO flux were investigated by using microbalance and field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The data indicated that a silica-rich layer was formed on the surface of the hybrid coating when the coating is exposed to AO flux, which could provide a protective barrier on the surface preventing further degradation of the polymer during extended exposure to AO and obviously improved the AO resistance of polyimide films.

Low Earth Orbit Space Environment Testing of Extreme Temperature 6H-SiC JFETs on the International Space Station

This paper reports long-term electrical results from two 6H-SiC junction field effect transistors (JFETs) presently being tested in Low Earth Orbit (LEO) space environment on the outside of the International Space Station (ISS). The JFETs have demonstrated excellent functionality and stability through 4600 hours of LEO space deployment. Observed changes in measured device characteristics tracked changes in measured temperature, consistent with well-known JFET temperature-dependent device physics.

Improvement of tensile properties of CFRP composites under LEO space environment by applying MWNTs and thin-ply

Multi-wall carbon nanotube (MWNT) added carbon fiber reinforced plastics (CFRP) and thin-ply composites are suggested as solutions to improve resistance against low earth orbit (LEO) environment and mechanical properties. Accelerated ground simulation experiments were performed for CFRP, MWNT reinforced CFRP, thin-ply CFRP and MWNT reinforced thin-ply CFRP. The used ground simulation facility can simulate high vacuum, atomic oxygen, ultraviolet (UV) light and thermal cycling simultaneously. The aging experiment was performed for 20 h. After the aging experiment, total mass loss (TML) and tensile properties were measured. As a result, by applying thin-ply thickness and MWNT fillers, the tensile strength was improved at ground conditions. Under an LEO space environment, while thin-ply composites cannot relieve the degradation rate, the composites with MWNT can do so. Highly improved tensile strength was observed by simultaneously applying the thin-ply techniques and MWNT under both LEO aged and LEO non-aged conditions.

Development of Flexible LEO-Resistant PI Films for Space Applications Using a Self-Healing Mechanism by Surface-Directed Phase Separation of Block Copolymers

Polimide-block-polydimethylsiloxane (PI-b-PDMS) block copolymers have been synthesized from commercially available amino-terminated polysiloxanes with different molecular weights, for use as polymeric materials resistant to the low earth orbit (LEO) space environment. A structural optimization with respect to maximum environmental protection has been performed by varying the PDMS block length as well as the architecture of the block copolymers spanning from multiblock to triblock and star-shaped morphologies. The synthesized polymers and casted films show good mechanical and thermal performance. For block copolymers with a load of 2% PDMS (in the case of the multiblock copolymers), a complete surface coverage of the PDMS has been found. It has been shown that the transfer of the surface enriched PDMS layer into a thin silica layer after atomic oxygen (AO) exposure results in a drastic decrease in AO erosion rate. The silica layer protects the underlying material from oxygen initiated erosion resulting in a drastic decrease of surface roughness. This phenomena is observable for loads as small as 6 wt % PDMS.