结构参数对火星探测用伞开伞性能的影响

文章以"火星探路者"所用伞为基础,对其结构作相应改变后进行充气过程仿真计算,研究结构参数对降落伞充气性能的影响。计算结果表明,盘缝带伞的阻力系数随着带宽和缝宽的增加而减小;但超声速开伞时,降落伞充气过程中伞衣的喘振现象随着带宽的增加而减弱,投影面积的波动随带宽增长变得缓和,这对盘缝带伞的开伞安全性和可靠性有利。     

小型空间有效载荷回收系统

文中介绍瑞典空间公司研制的200kg空间有效载荷(如:导弹弹头、再入飞行器头部等)的回收系统。该回收系统中降落伞采用高强度、轻重量凯夫拉材料制作,重量(不包括伞舱)不到7kg。采用这种回收系统后,有效载荷的着地速度不超过8m/s。文中介绍了两种回收方案。一种是常规方案,采用锥形带条稳定减速伞和轻型十字形主伞的二级降落伞回收系统;另一种是改进方案,采用具有高阻力系数的旋转伞作稳定伞和主伞的二级降落伞回收系统。第二种方案较为先进,可大大减少降落伞的重量和体积,不过还处在试验阶段。     

小型空间有效载荷回收系统

文中介绍瑞典空间公司研制的２００ｋｇ空间有效载荷（如：导弹弹头，再入飞行器头部等）的回收系统，该回收系统中降落伞采用高强度，轻重量凯夫拉材料制作，重量（不包括伞舱）不到７ｋｇ，采用这种回收系统后，有效载葆的着地速度不超过８ｍ／ｓ。文中介绍了两种回收方案，一种是常规方案，采用锥形带条稳定减速伞和轻型十字形主伞的二级降落伞回收系统，另一种是改进方案，采用具有高阻力系数的旋转伞作稳定伞和主伞的二级降落伞     

静电对降落伞开伞的影响

文章介绍了降落伞常用尼龙、聚酯类和芳纶等材料，在开伞过程中由于摩擦产生静电并具有保持静电的能力，分析和计算了静电对降落伞开伞的影响。     

带牵顶伞的大面积环帆伞充气性能分析

采用流固耦合的计算方法对带牵顶伞的主伞的充气过程进行了数值模拟,得到了主伞伞衣充气过程外形变化情况,并与试验结果进行了对比;对牵顶伞阻力系数的变化进行了分析,给出了适合工程估算的牵顶伞阻力系数公式。     

静电对降落伞开伞的影响

文章介绍了降落伞常用尼龙、聚酯类和芳纶等材料,在开伞过程中由于摩擦产生静电并具有保持静电的能力,分析和计算了静电对降落伞开伞的影响。     

低密度大气中降落伞开伞动载的研究

文章根据建立的降落伞充气过程中轴向和径向动量方程，研究了低密度大气中降落伞的开伞动载。通过计算并与高密度大气中开伞动载的比较，得出了低密度大气中开伞动载的特点。     

低密度大气中降落伞开伞动载的研究

文章根据建立的降落伞充气过程中轴向和径向动量方程,研究了低密度大气中降落伞的开伞动载。通过计算并与高密度大气中开伞动载的比较,得出了低密度大气中开伞动载的特点。     

超声速透气降落伞系统的气动干扰数值模拟研究

盘–缝–带伞是目前主流的火星用超声速降落伞,然而由于其阻力性能的限制,新一代的火星探测任务已经开始考虑采用环帆伞来获得足够的阻力性能。同时,在超声速条件下,由于稳定性的需要,透气性对降落伞系统减速性能的影响研究日益受到重视。文章基于计算流体力学方法对不同孔隙率的降落伞系统模型进行数值模拟,旨在分析开缝位置及孔隙率对环帆伞气动性能的影响机理。结果表明:在马赫数为2的大拖拽距离比条件下,无缝环帆伞系统流场与盘–缝–带伞有较大区别,主要表现在伞前激波的形成过程及前体尾流和伞前激波的作用阶段上。此外,开缝产生的孔隙率对环帆伞的减速性能有较大影响。开缝伞形的阻力性能劣于无缝伞形,但稳定性能显著高于无缝伞形。而前缝伞形的稳定性能及阻力性能均优于后缝伞形。该结果对超声速降落伞的伞型结构透气性参数设计有一定的参考价值。     

火星盘缝带伞超声速风洞试验结果分析

为了研究盘缝带(DGB)伞在超声速条件下的阻力特性、摆动角以及伞绳载荷分布的不均匀性，在FD 12风洞中开展了盘缝带伞的阻力特性风洞试验，并通过安装柔性传感器测量了伞绳所受载荷。试验结果表明，在Ma1.50到Ma2.50来流条件下，盘缝带伞的阻力系数随着马赫数的增大先增加后减小，在Ma1.75时达到最大，为0.60，而最大摆动角则是先减小后增大，在Ma2.00时摆动角最小，为7.4°，传感器的安装对降落伞风洞试验结果影响很小。通过柔性传感器的标定和误差分析，获取了伞绳载荷数据，结果显示不同伞绳所受拉力的比值可达到1.98。且传感器数据与风洞天平的测量降落伞总载荷结果吻合，进一步验证了柔性传感器结果的正确性。     

对伞包拉绳断裂故障的分析

文中针对某型号降落伞系统空投试验,第一架次试验中出现的伞包拉绳断裂的故障,建立了简单的求解伞包拉绳载荷的模型,通过计算分析表明:造成伞包拉绳断裂的主要原因是其强度设计不足。     

大型降落伞开伞过程中的“抽鞭”现象

＂抽鞭＂现象是在大型降落伞开伞过程中可能的顶部甩动现象,它可能造成伞衣破损、不对称充气、伞衣翻转、鞭打等后果,严重时可能造成回收任务完全失败。该文对美国回收系统降落伞开伞过程中出现的＂抽鞭＂现象及其后果进行了综述,并介绍了避免＂抽鞭＂现象的途径。目前对这一现象的机理还缺乏深入研究,有必要从理论和设计上对其进行分析。     

圆形降落伞顶孔的孔口圈新技术

文章介绍了美国近年来研究的降落伞中的一项新技术—圆形降落伞顶孔的孔口圈技术。该项技术去掉顶孔绳 ,代之以高强编织带孔口圈。在X— 38计划的减速伞和超音速引导伞、在SDW减速稳定伞和主伞以及PLER伞上应用 ,均获得成功。     

深空探测用低温推进剂贮箱热力排气系统研究

Cryogenic propellant usually experiences long term on orbit storage. The pressure increase in cryogenic storage tank is faced by most of space missions. The thermodynamic vent system (TVS) is treated as the promising method to control the increase of the tank pressure by scholars both at home and abroad. Based on the investigation conducted by different research agencies, literature review and management are conducted to reflect the recent research statue on TVS. The development profile of the experimental research on the pressure control performance of TVS is specially summarized. The condition setting and performance difference of TVS conducted by different agencies are compared and analyzed. The key technique and related conclusion are refined during the operation of TVS. Finally, based on the requirement of the large scale using of cryogenic propellant in deep space exploration in China, the development plan is proposed on the aspect of TVS pressure control on cryogenic storage tanks.     

Tethered propellant resupply technique for space stations

Interim results of a study on use of the tethered propellant resupply technique on the space station are summarized. The acceleration produced by a gravity-gradient-stabilized tether can predictably settle propellants and thereby simplify propellant resupply of vehicles when compared to zero-g techniques. Separation of the gas and liquid phases by settling enables performance of liquid acquisition and gas venting without special hardware in the propellant tanks and without special procedures. The primary requirement for propellant transfer is control of liquid sloshing to maintain liquid over the supply tank outlet and gas over the receiver tank vent. Ultimately, the decision to use this technique on the space station may depend upon the capability to adjust depot logistic operations to a tether.     

低温推进剂集成管理技术的发展与启示

低温推进剂集成管理技术(IVF)是实现上面级等航天器长期在轨的新技术思路。通过将液氢液氧长期在轨产生的蒸汽与内燃机技术结合,实现贮箱增压、排气、姿控、沉底、发电功能一体化,减小航天器系统质量,增强任务灵活性。回顾了IVF模块设计的发展过程,探讨了IVF的技术优势,与燃料电池技术、蒸发量控制技术对比分析了IVF技术的使用范围及不足,提出了研究气氢气氧内燃机技术、IVF模块方案设计、系统仿真等关键技术的建议,并展望了其应用前景。     

轴对称降落伞稳定下降阶段的流场特性

文章根据降落伞的特点,通过3点假设(伞衣的薄膜假设、降落伞的轴对称假设和流场的定常 假设),将三维复杂流动问题,转化成二维轴对称问题,以节约计算时间。然后,建立轴对称降落伞的流体力 学计算模型,利用数值模拟手段,求解RNG(Renormalization Group)k-epsilon湍流模型下的N—S方程组,获 得与有关单位试验相吻合的计算结果。分析发现带顶孔的轴对称降落伞绕流和亚临界状态下带中心孔的 圆球绕流,在尾流区拓扑结构上几乎完全一致。结果表明建立的轴对称降落伞模型,能够揭示降落伞流场 的本质特性,为进一步研究降落伞流场的流动机理和流固耦合问题打下基础。     

Controller development of photo bioreactor for closed-loop regulation of O2 production based on ANN model reference control and computer simulation

When Bioregenerative Life Support System (BLSS) is used for long-term deep space exploration in the future, it is possible to perform closed-loop control on growth of microalgae to effectively regulate O₂ production process in emergencies. However, designing controller of microalgae cultivating device (MCD) by means of traditional methods is very difficult or even impossible due to its highly nonlinearity and large operation scope. In our research, the Artificial Neural Network Model Reference Control (ANN-MRC) method was therefore utilized for model identification and controller design for O₂ production process of a specific MCD prototype—photo bioreactor (PBR), based on actual experiment and computer simulation. The results demonstrated that the ANN-MRC servo controller could robustly and self-adaptively control and regulate the light intensity of PBR to make O₂ concentrations in vent pipe be in line with step reference concentrations with prescribed dynamic response performance.     

Nitrogen reduction under hydrothermal vent conditions: implications for the prebiotic synthesis of C-H-O-N compounds

Dinitrogen is reduced in dilute hydrogen sulfide (H2S) solutions to ammonium at 120 degrees C. Experiments with dissolved dinitrogen (partial pressure 50 bar) in a 12 x 10(-3) mol/L H2S(aq) solution yield approximately 10(-5) mol/L NH4+ within 2-7 days. These yields are consistent with the equilibrium NH4+ concentration for the N-S-H system under these conditions. The formation of ammonium is catalyzed by the presence of freshly precipitated iron monosulfide. These results indicate that dinitrogen can be reduced at moderate temperatures in hydrothermal vent systems. Abiotic nitrogen reduction could have taken place within primordial hydrothermal vents, supplying some ammonia for the synthesis of C-H-O-N compounds via abiotic processes. The yield of ammonia via dinitrogen reduction by hydrogen sulfide, however, is so low that it is doubtful this process could have produced enough ammonia to sustain prebiotic hydrothermal synthesis of C-H-O-N compounds in or around vent systems.     

Microbial diversity of Indian Ocean hydrothermal vent plumes: microbes tolerant of desiccation, peroxide exposure, and ultraviolet and gamma-irradiation

The microbial diversity of Kali chimney plumes, part of a hydrothermal vent field in the Rodriguez Triple Junction, Indian Ocean (depth approximately 2,240 m), was examined in an attempt to discover "extremotolerant" microorganisms that have evolved unique resistance capabilities to this harsh environment. Water and sediment samples were collected from the vent and from sediments located at various distances (2-20 m) away from and surrounding the chimney. Samples were screened for hypertolerant microbes that are able to withstand multiple stresses. A total of 46 isolates were selected for exposure to a number of perturbations, such as heat shock, desiccation, H(2)O(2), and ultraviolet (UV) and gamma-irradiation. The survival of Psychrobacter sp. L0S3S-03b following exposure to >1,000 J/m(2) UV(254) radiation was particularly intriguing amid a background of varying levels of resistance. Vegetative cells of this non-spore-forming microbe not only survived all of the treatments, but also exhibited a 90% lethal dose of 30 s when exposed to simulated martian UV radiation and a 100% lethal dose of 2 min when exposed to full spectrum UV, which is comparable to findings for bacterial endospores.