Unloading law for a LEO spacecraft with two-gimbals solar array

The purpose of this paper is to present a modified cross-product unloading law that can be used to provide an open-loop compensation control design to counteract the predominant effects of the gravity gradient torque. The modified cross-product unloading law, is successfully applied to a three-axis stabilized, nadir-pointed LEO spacecraft with two-gimbals solar array. The variation of the two solar array orientations can significantly change the spacecraft's moment of inertia during the nominal operation mode, which can produce significant momentum accumulation in the roll–yaw body plane and cause large yaw pointing error. A rigorous study of momentum management performance capability has been conducted by using a high-fidelity performance simulation software that contains models of four environmental disturbance torque (gravity gradient, aerodynamic, solar, and magnetic). The simulation results show that the proposed momentum unloading control law has enabled a substantial reduction in the maximum accumulated roll momentum, which results in improving the pointing accuracy of the LEO spacecraft enormously.     

A new type of magnetic gimballed momentum wheel and its application to attitude control in space

A new type of magnetically suspended gimbal momentum wheel utilizing permanent magnets is described. The bearing was composed of four independent thrust actuators which control the rotor thrust position and gimbal angles cooperatively, so that the bearing comes to have a simple mechanism with high reliability and light weight. The high speed instability problem due to the internal damping was easily overcome by introducing anisotropic radial stiffness. A momentum flywheel with the 3-axis controlled magnetic bearing displays good performance for attitude control of satellite with biased momentum.     

Fluid-electrolyte changes in physically conditioned subjects after hypokinesia and chronic hyperhydration

The aim of this study was to determine whether fluid-electrolyte changes, which are developed during prolonged hypokinesia (decreased number of km per day), can be prevented or minimized with the use of a daily intake of fluid and salt supplementation (FSS). The experiments on hypokinesia (HK) were performed for 364 days on 18 endurance-trained male volunteers in the age range of 21-23 years, with an average maximum oxygen uptake of 67 ml kg-1. All volunteers were divided into three equal groups: six volunteers were placed on a continuous regime of exercise of 14.0 km day-1 and served as control subjects. Six volunteers were subjected to continuous HK without FSS and were considered as the unsupplemented hypokinetic subjects (UHS). The remaining volunteers were under continuous HK and FSS and were considered as the supplemented hypokinetic subjects (SHS). For the simulation of the hypokinetic effect, the UHS and SHS groups were kept continuously under an average of 2.7 km day-1 for the duration of the experiment. Prior to exposure to HK, all volunteers were on the same exercise regime as the controls. During the pre-experimental period of 60 days and during the post-experimental period, urinary excretion of electrolytes and concentrations of sodium, potassium, calcium and magnesium in serum as well as serum osmolality were determined. An increased renal excretion of fluid and electrolytes and a decreased serum electrolyte concentration were observed in the SHS, while a decreased renal excretion of fluid and electrolytes and an increased serum electrolyte concentration were observed in the UHS, during the initial stages of the post-hypokinetic period. By day 30 of the post-hypokinetic period these changes were reverted back to the control levels. We concluded that chronic hyperhydration may be used to attenuate urinary and serum electrolyte changes in endurance-trained volunteers after exposure to prolonged HK.     

Element exchange in a water- and gas-closed biological Life Support System.

Liquid human wastes and household water used for nutrition of wheat made possible to realize 24% closure for the mineral exchange in an experiment with a 2-component version of "Bios-3" life support system (LSS) Input-output balances of revealed, that elements (primarily trace elements) within the system. The structural materials (steel, titanium), expanded clay aggregate, and catalytic furnace catalysts. By the end of experiment, the permanent nutrient solution, plants, and the human diet gradually built up Ni, Cr, Al, Fe, V, Zn, Cu, and Mo. Thorough selection and pretreatment of materials can substantially reduce this accumulation. To enhance closure of the mineral exchange involves processing of human-metabolic wastes and inedible biomes inside LSS. An efficient method to oxidize wastes by hydrogen peroxide icon a quartz reactor at the temperature of 80 degrees C controlled electromagnetic field is proposed.     

Interaction of physical-chemical and biological regeneration processes in ecological Life Support Systems.

Catalytic combustion of inedible biomass of plants in ecological Life Support Systems (LSS) gives rise to gaseous oxides (CO2, NO2, SO2, etc.). Some of them are toxic for plants suppressing their photosynthesis and productivity. Experiments with "Bios-3" experimental LSS demonstrate that a decrease of photosynthetic productivity in a system with straw incineration can jeopardize its steady operation. Analysis of the situation by a mathematical model taking into account absorption parameters of the system in terms of toxic elements makes it possible to formulate requirements for the structure and operation of LSS to provide for its stability. Avenues for further investigation of the problem of toxic stability of LSS are proposed.     

Gravitational unloading effects on muscle fiber size, phenotype and myonuclear number.

The effects of gravitational unloading with or without intact neural activity and/or tension development on myosin heavy chain (MHC) composition, cross-sectional area (CSA), number of myonuclei, and myonuclear domain (cytoplasmic volume per myonucleus ratio) in single fibers of both slow and fast muscles of rat hindlimbs are reviewed briefly. The atrophic response to unloading is generally graded as follows: slow extensors > fast extensors > fast flexors. Reduction of CSA is usually greater in the most predominant fiber type of that muscle. The percentage of fibers expressing fast MHC isoforms increases in unloaded slow but not fast muscles. Myonuclear number per mm of fiber length and myonuclear domain is decreased in the fibers of the unloaded predominantly slow soleus muscle, but not in the predominantly fast plantaris. Decreases in myonuclear number and domain, however, are observed in plantaris fibers when tenotomy, denervation, or both are combined with hindlimb unloading. All of these results are consistent with the view that a major factor for fiber atrophy is an inhibition or reduction of loading of the hindlimbs. These data also indicate that predominantly slow muscles are more responsive to unloading than predominantly fast muscles.     

Enzyme activities and membrane lipids in Artemia cysts after a long duration space flight

In the Free Flyer Biostack Experiment (L.D.E.F. mission) investigations have shown that biological objects in a resting state can survive more than 5.5 years of exposure to the space factors in particular microgravity and cosmic rays. We have measured enzyme activities involved in metabolic pathways of sugar and lipid degradation and determined phospholipid composition. Pyruvate kinase and glucose-6-phosphate dehydrogenase activities in space-exposed cysts were higher than in earth controls after 1 hour incubation. In controls, total phospholipids remained unchanged, on the contrary they increased significantly in space-exposed cysts. The rate of metabolism of various phospholipid components was unchanged in controls allowing the development while the level of most of them decreased in space-exposed cysts except for phosphatidylcholine. Enzyme activities (acetylhydrolase, phospholipase A₂ and lyso phospholipase) involved in phospholipid degradation increased; however, activities were much higher in space-exposed cysts. In conclusion, the long duration space flight resulted in an increase of the metabolic activity correlated with a faster development within the first 20 hours of post flight incubation.     

Solar orbiter, a high-resolution mission to the sun and inner heliosphere

The scientific rationale of the Solar Orbiter is to provide, at high spatial (35 km pixel size) and temporal resolution, observations of the solar atmosphere and unexplored inner heliosphere. Novel observations will be made in the almost heliosynchronous segments of the orbits at heliocentric distances near 45 R and out of the ecliptic plane at the highest heliographic latitudes of 30° – 38°. The Solar Orbiter will achieve its wide-ranging aims with a suite of sophisticated instruments through an innovative design of the orbit. The first near-Sun interplanetary measurements together with concurrent remote observations of the Sun will permit us to determine and understand, through correlative studies, the characteristics of the solar wind and energetic particles in close linkage with the plasma and radiation conditions in their source regions on the Sun. Over extended periods the Solar Orbiter will deliver the first images of the polar regions and the side of the Sun invisible from the Earth.     

Two energy release processes for CMEs: MHD catastrophe and magnetic reconnection

It remains an open question how magnetic energy is rapidly released in the solar corona so as to create solar explosions such as solar flares and coronal mass ejections (CMEs). Recent studies have confirmed that a system consisting of a flux rope embedded in a background field exhibits a catastrophic behavior, and the energy threshold at the catastrophic point may exceed the associated open field energy. The accumulated free energy in the corona is abruptly released when the catastrophe takes place, and it probably serves as the main means of energy release for CMEs at least in the initial phase. Such a release proceeds via an ideal MHD process in contrast with nonideal ones such as magnetic reconnection. The catastrophe results in a sudden formation of electric current sheets, which naturally provide proper sites for fast magnetic reconnection. The reconnection may be identified with a solar flare associated with the CME on one hand, and produces a further acceleration of the CME on the other. On this basis, several preliminary suggestions are made for future observational investigations, especially with the proposed Kuafa satellites, on the roles of the MHD catastrophe and magnetic reconnection in the magnetic energy release associated with CMEs and flares.     

三维曲面部分匹配的算法研究

将基于曲率分析的曲面片形状划分方法和几何哈希相结合，提出一种通用的空间曲面匹配算法。对待匹配的三维曲面模型，计算其网格顶点的主曲率和法矢；由主曲率和该点所在的曲面片类型来构造其无向脚标，有向脚标为该点的法矢。按照多重筛选标准生成数量少却有效的匹配点对，建立候选点对列表。由候选点对所生成的三维空间变换组成哈希表，运用双层哈希投票机制得出使模型能够正确匹配的三维坐标变换矩阵。实验表明，该算法适用于具有部分重叠的曲面模型的匹配，并能保证较好的匹配精度和速度。