Dynamic surface imaging for the space shuttle experiments

In this article we discuss various techniques developed to estimate the position and velocity vector of the surface of an object subjected to various forces, both translational and rotational, during an analysis experiment to be performed on the U.S. Space Shuttle. This dynamical information will be used to understand the underlying dynamics of the overall system under investigation and develop an improved design. Here the emphasis is on the measurement sensor and the basic image processing required to achieve the goal of making this measurement. The scheme will be to provide a small cylindrical hole(s) in the mechanism under investigation, illuminate the surface through this “porthole,” and obtain a real-time image of the surface on a charged-coupled device (CCD) sensor array. The CCD array data will be compressed and transmitted to the ground tracking station as well as archived for future processing. Also, the design of an optimal tracker capable of providing both two-dimensional position and velocity estimates in real time is discussed. In this case, data synthesized from a dynamic simulation are processed demonstrating its capability and predicted performance. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol 9: 463–474, 1998     

Comparative analysis of projects for experiments in space to determine the gravitational constant

A comparative analysis is made of the most typical projects for experiments to measure the gravitational constant G and other gravitational interaction parameters utilizing artificial satellites, dating from 1967 and performed using state-of-the-art measurement technology. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 3–5, May 1996.     

传感器阵列的CO与H_2S混合气体检测系统设计与试验

采用气体传感器单敏感性和多敏感性相结合的交叉方法,基于传感器阵列和人工神经网络模式识别技术,设计了一种CO与H2S混合气体检测系统.该系统以AT89C51单片机芯片作为控制核心,优选MQ135,MQ136和TGS2602构成气体传感器阵列,通过RS232串行通信接口实现单片机与上位机通信连接,利用改进的BP神经网络算法进行模式识别,完成了CO和H2S混合气体浓度的检测试验.结果表明,BP神经网络训练误差均在0.01范围内,识别率达到95%,验证了检测系统设计的正确性和可行性,为气体检测传感器的进一步研究开发提供了基础.     

Fundamental experiments for the development of high-performance cold plates in a feasability study on space solar power system

To realize a concept of solar power satellite with high power generation, it is a promising method to transfer the power by laser beam using active mirror type amplifiers where cooling of the laser material accepting highly condensed sunray is inevitable. To remove high heat flux density from a large area, a structure of cold plate consisted of two parallel plates is devised and the effective liquid supply directly to the bottom of flattened bubbles due to nucleate boiling is realized by the auxiliary liquid feeder. The critical heat flux is increased by more than 1.5 times from that without the additional liquid supply. The technology can be applied not only to space but widely to the development of high-performance cold plates employed on ground.     

ISS experiments for the clarification of boiling and two-phase flow in microgravity and for the development of high-performance space cold plates

Inflow boiling, gravity effects on the distribution of both phases are observed in a heated tube and heat transfer coefficients due to two-phase forced convection is deteriorated in microgravity. In narrow channels between heated and unheated plates, the increase in subcooling enlarges a size of flattened bubble and reduces the frequency of detachment under microgravity conditions resulting the emphasis of heat transfer deterioration. To clarify reasons for the unknown behaviors of interfacial distribution and corresponding characteristics in heat transfer not easily be clarified through the experiments on ground, the opportunity on the experiments utilizing long-term microgravity duration realized in ISS is required. The experiments on microgravity boiling and two-phase flow are proposed by the collaboration of researchers in five countries. A common test loop is designed to conduct multiple experiments by the interchangeable structures of test sections; a transparent heated tube for the visualized flow boiling, a stainless tube for the measurement of CHF data, a copper surface for the heat transfer data of nucleate boiling with superimposed liquid flows in a duct, a glass heated plate with multiple array of small temperature sensors and transparent heaters for the clarification of mechanisms in nucleate boiling heat transfer, and one or two models of cold plates for practical applications. A direction of researches in the present discipline is proposed based on the existing experimental results and on the idea developed by the present authors.     

Thermal and neutron-physical features of the nuclear reactor for a power pulsation plant for space applications

We have explored the possibility of creating small-size reactors with a high power output with the provision of thermal stability and nuclear safety under standard operating conditions and in emergency situations. The neutron-physical features of such a reactor have been considered and variants of its designs preserving the main principles and approaches of nuclear rocket engine technology are presented.     

基于磁流变悬置的动力装置垂向隔振控制与试验研究

悬置阻尼宽频可控对动力装置实现积极隔振具有重要意义。分析了基于挤压模式的磁流变半主动悬置工作原理和阻尼特性,在建立动力装置垂向隔振模型的基础上,设计出模糊自适应隔振控制器,用量化、比例因子自调整算法降低不同工况下动力装置垂向激励力的传递;给出了一种改进的天棚控制算法,通过抑制动力装置振动来降低能量传递。设计出动力装置隔振台架试验系统,在不同工况下进行了隔振对比试验。结果表明,在动力装置处于中低转速时,可控磁流变悬置能在宽频范围内把力绝对传递率抑制到25%内,隔振效果优于橡胶悬置;而磁流变悬置垂向隔振方法中,兼顾振动传递率和激励频率的模糊自适应控制,优于通过抑制动力装置自身振动来隔振的天棚控制。     

Microcalorimeter Instruments for the Spectrum-R(X)G and NeXT Missions

X-ray spectrometers utilizing a microcalorimeter array are presently under study for the Russian Spectrum R-G (or Spectrum-X-Gamma) mission, which is to be launched in 2011, and for the Japanese NeXT (New X-ray Telescope or Non-thermal energy eXploration Telescope) mission, whose launch is expected to be in 2012 to 2015. The primary instrument of Spectrum R-G is eROSITA, which will make an all sky survey in the 0.1–10 keV range using an array of seven telescopes and X-ray CCD cameras. The mission also carries smaller instruments, a wide-field monitor (Lobster) and a hard X-ray telescope (ART). We are proposing SXC—the Spectrum-X Calorimeter—to obtain spatially-resolved precision spectra of a number of nearby massive clusters of galaxies during an initial 6-month pointed phase, and to obtain a detailed spectral map of the soft X-ray diffuse background during the 4-year survey phase. The NeXT mission is a combination of wide band X-ray spectroscopy provided by multi-layer coating, focusing X-ray mirrors and pixel detectors, and high resolution soft X-ray spectroscopy by microcalorimeter instrument, SXS—the Soft X-ray Spectrometer. The effective area of the SXS is about 20 times larger than that of SXC at the iron K line energy (6.7 keV) while the solid angle of the field of view is by a factor of 15 smaller. One of the major scientific objectives of SXS is to determine turbulent and/or macroscopic velocities in the hot gas of distant clusters of galaxies. Both of the instruments will use 6×6 microcalorimeter array similar to the one launched on Suzaku, while both will adopt a ³He Joule Thomson cooler and two-stage Stirling cycle in the cryogenic systems. The ³He Joule Thomson cooler provides a thermal guard to liquid He but it can also work as a 1.8 K heat bath for the adiabatic demagnetization refrigerator.      

The chemistry of micrometeoroid and space debris remnants captured on hubble space telescope solar cells

Prior to the retrieval in 1993 from low Earth orbit (LEO), the “—V2” Solar Array wing of the Hubble Space Telescope was exposed to hypervelocity impacts (micrometre to millimetre scale) from both micrometeoroids and space debris. The initial survey of the damage (100–3500μm diameter sized craters) identified that micrometeoroid remnants dominated the flux in the 100–1000μm size regime, with debris dominating>1000μm. These residues were composed of remnants of silicate minerals, calcite, metal sulfides and metals that often appeared as complex poly-mineralic melts within melt pits. A further survey of 10–100μm diameter craters identified that the most common chemistry was space debris with the crossover from meteoroids to debris being at around 30μm D_CO. Residues include remnants of specialised steels and paint fragments but the dominant type is aluminium and aluminium oxide, which are almost certainly remnants of solid rocket motor operations. It is found that the relative contribution of debris as a function of size, agrees remarkably with a prediction derived using flux data from Long Duration Exposure Facility and a meteoroid model.     

One-step synthesis,characterization and oxidative desulfurization of 12-tungstophosphoric heteropolyanions immobilized on amino functionalized SBA-15

Keggin-type 12-tungstophosphoric [PW₁₂O₄₀]^3? heteropolyanions were successfully immobilized onto mesoporous material surface of SBA-15 functionalized using the (3-aminopropyl)triethoxysilane (APTES) synthesized by one-pot co-condensation method, also called one-step synthesis. The synthesized PW^?-NH₃⁺-SBA-15 catalyst was characterized by XRD, N₂ adsorption–desorption, FT-IR, TGA, SEM, TEM, EDS, XPS methods. The results indicated that ordered hexagonal mesostructure for SBA-15 support was still maintained after being functionalized with amine groups, while the specific surface area of SBA-15 was decreased. The active species of phosphotungstic acid H₃PW₁₂O₄₀ (HPW) retained its Keggin structure of the heteropolyanions on the amine-modified SBA-15. The PW^?–⁺H₃N–SBA–15 catalyst exhibited a high catalytic activity for oxidative desulfurization process of sulfur-containing model fuel. The dibenzothiophene (DBT) conversion of almost 100% was achieved with reaction conditions of 40?mg of catalyst dosage, 2?mL of hydrogen peroxide, 90?°C of reaction temperature, and 120?min of reaction time.     

RGD peptide immobilized on TiO2 nanotubes for increased bone marrow stromal cells adhesion and osteogenic gene expression

Recently, TiO₂ nanotube layers are widely used in orthopedics and dental applications because of their good promotion effect on bone cells. Furthermore, peptide sequences such as arginine–glycine–aspartic acid are used to modify Ti implant for binding to cell surface integrins through motif. In this study, a cellular adhesive peptide of arginine–glycine–aspartic acid–cysteine (RGDC) was immobilized onto anodized TiO₂ nanotubes on Ti to examine its in vitro responses on rat bone marrow stromal cells (BMSCs). Materials were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy techniques. High-resolution C1s scans suggested the presence of RGDC on the surface and SEM images confirmed the nanotubes were not destroyed after modification. BMSCs adhesion and osteogenic gene expression were detected in TiO₂ nanotube layers with and without RGDC modification by fluorescence microscopy, confocal laser scanning microscopy, SEM, and realtime polymerase chain reaction (Real-time PCR). Results showed that the TiO₂ nanotube layers immobilized with RGDC increased BMSCs adhesion compared to nonfunctionalized nanotubes after 4 h of cultivation. Furthermore, the osteogenic gene expression of BMSCs was dramatically enhanced on the TiO₂ nanotube layers immobilized with RGDC (10 mM) compared to the TiO₂ nanotube layers immobilized with RGDC (1 mM) and non-functionalized anodized Ti. Our results from in vitro study provided evidence that Ti anodized to possess nanotubes and then further functionalized with RGDC should be further studied for the design of better biomedical implant surfaces.     

Residual stress in CIGS thin film solar cells on polyimide: simulation and experiments

Sputtering technique is used to prepare Cu(In,Ga)Se₂ (CIGS) thin film solar cells on a UPILEX-S 50S polyimide substrate in order to investigate the residual stress in the Mo back contact and CIGS absorber layer after selenized annealing with various the thickness ratios of the Mo contact, R_Mo. A comparison between the results of numerical simulation and those obtained from X-ray diffractometry, indicate the existence of compressive residual stress in both the Mo contact and the CIGS absorber layer. The residual stress in the Mo contact was inversely proportional to the residual stress in the CIGS absorber layer. Residual stress decreased with an increase in the thickness ratio of the Mo contact. The empirical formulae for the residual stresses as a function of R_Mo in the Mo and CIGS films were deduced, from the results of this study.     

Magnetic circuit design for the squeeze mode experiments on magnetorheological fluids

Magnetorheological (MR) fluid is a manageable fluid that exhibits drastic changes in rheological properties and interchangeable depending on the applied magnetic field strength. The fluid is potentially advantageous to be employed in many applications. This paper presents the design of test equipment for the performance of compression and tension tests. Finite element method magnetics (FEMM) was used to analyze the magnetic field distribution through the MR fluid. The test equipment was constructed and modified according to the operational principles, conditions and simulation results. The tests were performed in a vertical direction to the DC magnetic field generated by a coil. Experimental results showed that the compressive/tensile stresses of MR fluids increased as the applied current increased. The test equipment was utilized to investigate the performance of the MR fluid in squeeze mode.     

Living cells of Staphylococcus aureus immobilized onto the capillary surface in electrochromatography: a tool for screening of biofilms

Microorganisms attach to nonliving surfaces in many natural, industrial, and medical environments, enveloped within extracellular polymeric substances. The result is a biofilm. Biofilms are reported to exist in 65-80% of bacterial infections refractory to host defenses and antibiotics therapy and are regarded as a central problem in present-day medical microbiology. Understanding of the parameters governing the interaction of antimicrobials with biofilms is thus of great interest in any attempt to increase biocide efficacy. In this work, study was made of the feasibility of using open tubular capillary electrochromatography (CEC) in bacterial biofilm studies with living cells. Staphylococcus aureus was selected as model bacterium. First, S. aureus was shown, under various conditions, to form a biofilm on the inner wall of a fused-silica capillary coated with poly(L-lysine). Optimal conditions for biofilm formation, such as bacterial concentration, growing time, and the stability of the ensemble, were preliminarily defined with conventional 96-microtiter well plates. Continuous flushing of the capillary with fresh cells meant that no growth medium was needed. The presence of biofilm in the capillary was confirmed by atomic force microscopy. Interactions between S. aureus biofilms and different antibiomicrobial agents were studied by capillary electrochromatography. The effect of five antibiotics (penicillin G, oxacillin, fusidic acid, rifampicin, vancomycin) on biofilms was examined in terms of retention factors and reduced mobilities of the antibiotics. The antibiotic susceptibility profile for S. aureus is similar as the result of minimal inhibitory concentrations registered on the 96-microtiter well plates for both planktonic and biofilm cells. The results show, for the first time, that bacterial biofilms can be studied by CEC. The technique allows highly efficient and easy characterization of interactions between S. aureus biofilms and potentially active antimicrobial compounds under different conditions. Reagent and cell consumption are minimal.     

空间环境复合材料的性能研究与表征

采用质损率、FTIR、DSC、动态热力学（DMA）及力学性能等作为评价指标,选择了一种耐高温复合材料的环氧树脂体系,以该树脂体系为基体制备了用于模拟空间环境的复合材料真空附舱,通过测试其常温及高温状态下的结构稳定性、漏气率和出气率等指标进行了应用评估。结果表明:该真空附舱在150℃高真空环境下结构稳定,高温性能达到国际领先水平,透波性能优于已报道的同类产品,可满足空间环境使用。      

Hypervelocity impacts on solar cells — observations, experiments, and empirical scaling laws

The recent retrieval of the EURECA satellite and one solar array from the Hubble Space Telescope initiated meteoroid and debris impact investigations on these surfaces. This paper gives an overview of observations of impact sites found on retrieved spacecraft surfaces, hypervelocity test programs performed as part of the European Space Agency (ESA) post-flight investigation programs (PFIP), and develops empirical scaling laws for various geometric parameters. These empirical scaling laws are intended to relate particle parameters to crater dimensions to support the modeling of the microparticle environment in near-Earth space.     

Evidence for nonsingular vorticity in the Helsinki experiments on rotating3He-A

A theory for the satellite peak in the NMR spectrum of rotating superfluid³He-A is presented. Absorption at the frequency of the satellite is produced by spin waves localized on vortex lines. The peak frequency and total intensity of the satellite are calculated for both singular and nonsingular vortices; a comparison with the Helsinki NMR data strongly suggests that nonsingular vorticity was actually observed in the experiments.     

Characterization and corrosion behavior of duplex-chromized steel for the sulfur container in NaS cells

A chromium-rich diffusion coating was developed for low carbon steels used in the containment of molten sulfur and sodium polysulfides. The coating, which was obtained by pack-chromizing methods, promises to meet the corrosion, conductivity and cost requirements for the high temperature NaS battery. This paper presents information on the preparation, structure and behavior of this new coating/substrate system.