可再充填启动篮表面张力推进剂管理装置设计及试验研究

对启动篮表面张力推进剂管理装置工作原理进行了说明,建立了可再充填启动篮再充填过程仿真模型,根据仿真结果对影响启动篮再充填的各种因素进行了分析.加工原理性试验件进行了静态充填试验和动态充填试验,试验结果和仿真结果基本一致,验证了计算模型的正确性.初步掌握了可再充填启动篮表面张力推进剂管理装置设计、加工和地面试验技术.     

一种推进剂剩余量在轨测量方法研究

对我国某卫星平台气体注入压力激励推进剂剩余量测量方法进行了研究,建立了剩余量计算模型,开发了计算软件,开展了地面试验,结果表明,测量误差在-0.68%~0.66%范围内,达到了较高的测量精度。     

聚醚推进剂吸湿特性研究

以聚醚推进剂为研究对象,进行了常温、不同相对湿度条件下的吸湿试验,得到了聚醚推进剂吸湿的规律,建立了以平衡含湿率作为表征聚醚推进剂吸湿特性特征参数的数学模型。结果表明,配方、工艺固定后,聚醚推进剂平衡含湿率与推进剂的初始含湿率无关,是材料自身的吸湿特性参数,主要取决于环境相对湿度。初始含湿率高可导致聚醚推进剂力学性能下降。同时,利用平衡含湿率参数,研究了常温下水分在聚醚推进剂中的扩散,得到了扩散系数的修正模型,发现依据平衡含湿率参数计算的扩散系数是与相对湿度无关的常数。     

固体火箭发动机预固化技术及其应用

依据HTPB复合推进剂界面特性 ,提出改变固化反应温度与时间来调节交联程度 ,使系统的官能团逐步进行化学反应 ,形成化学键和氢键 ,改善了生成物的力学性能。论述了预固化技术和粘接模型。将其应用于固体发动机推进剂 衬层界面粘接、发动机装药成型和推进剂药柱修补技术 ,经地面热试车和飞行考核 ,以及试件的十年储存试验考核 ,性能可靠 ,满足设计要求     

低温推进剂液位监测系统设计

以液体火箭发动机地面试验用低温推进剂为研究对象,建立了以电容式液位传感器和C-V线性电容变送仪为主体的低温推进剂液位测量系统。经某型号氢氧发动机真实试车过程中的搭载试验证明,该系统能准确、快速的跟踪并实时显示低温容器中的液位值,具有精度高、重复性好、操作简单及安全可靠等质量特性,很好的解决了试验过程中低温推进剂液位实时监测显示的技术难题,具备了应用地面试车试验的条件。     

贫氧推进剂一次燃烧产物的热力计算

贫氧推进剂一次燃烧的物理和化学动力学因素决定了其一次燃烧为非平衡燃烧。说明了非平衡燃烧的特点，提出了计算贫氧推进剂一次燃烧的理论模型。以参与化学反应的推进剂组分为基础，把燃烧剩余物和燃烧产物分开，建立了燃烧产物的质量和化学平衡方程以及体系的能量平衡方程，采用布林克莱法解决了贫氧推进剂非平衡燃烧产物的热力计算。     

固体火箭发动机撞击变形及装药内部热点形成数值分析

以热粘弹理论和动力有限元法为基础,结合机械撞击载荷下固体推进剂裂纹摩擦热点细观模型,分析计算了发动机壳体和装药结构撞击变形及装药内部热点形成,确定了产生高温热点撞击临界速度。计算模型中考虑了推进剂初始弥散细观裂纹离散、裂纹扩展对推进剂宏观力学性能影响、基体粘性加热对热点形成影响等问题。通过与高能炸药Steven撞击试验结果进行对比分析,证明了理论模型及计算方法的有效性。计算了某小型发动机撞击试验临界速度。     

固体火箭发动机模态分析中的推进剂建模研究

应用有限元软件Marc建立了某固体发动机有限元计算模型，对其中难以用有限元模型准确描述的推进剂，采用了两种简化建模方法。一种是仅仅考虑推进剂质量，忽略其刚度等属性，将推进剂简化为均匀附加在发动机壳体有限元模型节点上的集中质量；另一种是将推进剂作为几何实体，考虑其质量和刚度，建立推进剂实体模型。模态计算结果与试验比较表明：推进剂的壳体节点集中质量模型，能较好地模拟发动机的弯曲特性，由于忽略了推进剂刚度，对于呼吸振动特性的模拟不太理想；相比之下，推进剂的实体模型，由于同时考虑质量和刚度，对弯曲和呼吸振动特性的模拟较好一些。计算还表明，要逼近高阶振型，需要将推进剂弹性模量修正得更高一些。     

低温推进剂地面加注系统冷量利用方案分析

为了降低低温推进剂损耗,提高利用效率,降低发射成本,提出了4套运载火箭低温推进剂地面加注系统的冷量利用方案。基于热力学原理,建立了非稳态数学模型,并以能量品质高低作为衡量方案优劣的标准,通过实例计算对比分析了各个冷量利用方案的可行性。研究得出4套冷量利用方案从热力学角度出发都是可行的,其中方案A和方案D最优,方案A可应用在目前现有低温推进剂地面加注系统中,而方案D则可应用于未来重型运载火箭低温推进剂地面加注系统之中。     

N2O微推力器性能及喷管热结构分析

针对采用氧化亚氮推进剂的单组元微推力器开展了比冲性能影响因素的分析,分析结果显示微推力器比冲与氧化亚氮分解效率及喷管扩张比有着密切关系。利用有限元分析法对高空及地面试验两种工况下氧化亚氮单组元微推力器喷管的结构温度场开展了数值仿真计算,并在结构温度场仿真计算的基础上进一步对地面试验用喷管的结构应力场进行了分析。初步试验表明,所设计的微喷管在地面工况下工作良好。     

感应电动机寿命预测的加速退化试验方法研究

感应电动机正常使用时一般具有长寿命高可靠性,为在较短时间内预测感应电动机的寿命,提出了一种简单易行的感应电动机加速退化试验方法:在电动机转轴上偏心安装圆孔叶片模拟电动机负载工作时承受的不平衡载荷,并且通过改变叶片偏心安装孔的位置模拟增大不平衡载荷。进行了3种应力形式的试验研究,以试验中测得的电动机轴心轨迹面积值表征电动机的性能退化指标,建立了轴心轨迹面积相对变化的漂移Brown运动和幂律加速退化模型,利用无偏估计法和最小二乘法得到模型参数的估计,外推获得叶片无偏心安装状态下的不平衡重力矩,以该值作为电动机正常工作时承受的不平衡载荷,预测和分析了电动机正常工作寿命和可靠性,验证了加速退化试验方法的可行性和高效性。     

并联贮箱不平衡输出及其解决途径

分析了空间飞行器推进剂贮箱并联设置时产生的不平衡输出问题，从工程角度估计了不平衡输出的程度。对于不允许测量贮箱压降的金属膜片贮箱，在其出口设置气蚀文都利管是解决并联贮箱不平衡输出的简单而又有效的方案。     

一种对基于耗尽关机多级固体火箭概念设计的改进方法

由于维护简单和发射快速,弹道导弹多用固体火箭发动机,但繁杂的推力终止装置使各级装药不能耗尽并让结构增重。提出了一种对基于耗尽关机多级固体火箭概念设计的改进方法,此方法满足导弹系统主要的战技要求。为解决无推力终止装置的末速不准问题。可在末级发动机采用姿态调整装置,对射角进行调整,配合末速以满足射程要求。本方法还可抑制敌方反导探测。     

链路状态感知的低轨卫星网络路由机制

低轨卫星的空间组网能够突破地形限制,实现全天候、高带宽、低时延、广覆盖的数据通信,弥补地面通信系统的不足,使通信服务全球化成为可能。但是,卫星节点的快速移动和能量受限使得空间链路面临高动态、不可靠、间歇性等问题。同时接入用户的分布不均容易导致卫星网络出现重载节点和局部拥塞的情况,这对空间组网和数据传输提出了新的挑战。传统的静态卫星组网模式可靠性差,可伸缩性低,难以适应空间动态组网的需求。针对低轨卫星网络拓扑变化快的特点,提出链路状态感知的路由机制,在降低卫星能耗的同时减轻网络的局部拥塞,使用树莓派搭建半实物仿真平台,并在该平台上进行实验,验证了该机制的有效性。     

Generation of experimental plasma parameter maps around the baffle aperture of a Kaufman (UK-25) ion thruster

The plasma produced by a Kaufman (UK-25) ion thruster possesses four distinct regions. The interaction of two of these regions, the coupling and discharge plasmas, is important for thruster design and efficiency, since it controls the production of the primary electrons responsible for most of the ionisation in the thruster. This paper details the measurement and analysis techniques used to obtain two-dimensional experimental plasma parameter maps across a plasma double layer in the baffle aperture region of this type of ion thruster. This plasma-interaction region was mapped experimentally using Langmuir probes.The Langmuir probe data were collected and analysed to produce maps of plasma potential, Maxwellian and primary electron energy and number density. Detailed static magnetic field measurements using Hall-effect probes were also obtained. A number of derived plasma parameter maps were then made possible, such as electron pressure. The application of the analysis techniques used here allowed ion thruster plasma property maps to be constructed of a spatial extent and resolution previously unseen. Two-dimensional maps of the spatial location of primary electrons are presented, as effected by applied magnetic field changes, along with the detection of regions showing depletion of primary electron energies.     

High-resolution simulations of the final assembly of Earth-like planets. 2. Water delivery and planetary habitability

The water content and habitability of terrestrial planets are determined during their final assembly, from perhaps 100 1,000-km "planetary embryos " and a swarm of billions of 1-10-km "planetesimals. " During this process, we assume that water-rich material is accreted by terrestrial planets via impacts of water-rich bodies that originate in the outer asteroid region. We present analysis of water delivery and planetary habitability in five high-resolution simulations containing about 10 times more particles than in previous simulations. These simulations formed 15 terrestrial planets from 0.4 to 2.6 Earth masses, including five planets in the habitable zone. Every planet from each simulation accreted at least the Earth's current water budget; most accreted several times that amount (assuming no impact depletion). Each planet accreted at least five water-rich embryos and planetesimals from the past 2.5 astronomical units; most accreted 10-20 water-rich bodies. We present a new model for water delivery to terrestrial planets in dynamically calm systems, with low-eccentricity or low-mass giant planets-such systems may be very common in the Galaxy. We suggest that water is accreted in comparable amounts from a few planetary embryos in a " hit or miss " way and from millions of planetesimals in a statistically robust process. Variations in water content are likely to be caused by fluctuations in the number of water-rich embryos accreted, as well as from systematic effects, such as planetary mass and location, and giant planet properties.     

Astrophysical ionizing radiation and Earth: a brief review and census of intermittent intense sources

Cosmic radiation backgrounds are a constraint on life, and their distribution will affect the Galactic Habitable Zone. Life on Earth has developed in the context of these backgrounds, and characterizing event rates will elaborate the important influences. This in turn can be a base for comparison with other potential life-bearing planets. In this review, we estimate the intensities and rates of occurrence of many kinds of strong radiation bursts by astrophysical entities, ranging from gamma-ray bursts at cosmological distances to the Sun itself. Many of these present potential hazards to the biosphere; on timescales long compared with human history, the probability of an event intense enough to disrupt life on the land surface or in the oceans becomes large. Both photons (e.g., X-rays) and high-energy protons and other nuclei (often called "cosmic rays") constitute hazards. For either species, one of the mechanisms that comes into play even at moderate intensities is the ionization of Earth's atmosphere, which leads through chemical changes (specifically, depletion of stratospheric ozone) to increased ultraviolet B flux from the Sun reaching the surface. UVB is extremely hazardous to most life due to its strong absorption by the genetic material DNA and subsequent breaking of chemical bonds. This often leads to mutation or cell death. It is easily lethal to the microorganisms that lie at the base of the food chain in the ocean. We enumerate the known sources of radiation and characterize their intensities at Earth and rates or upper limits on these quantities. When possible, we estimate a "lethal interval," our best estimate of how often a major extinction-level event is probable given the current state of knowledge; we base these estimates on computed or expected depletion of stratospheric ozone. In general, moderate-level events are dominated by the Sun, but the far more severe infrequent events are probably dominated by gamma-ray bursts and supernovae. We note for the first time that so-called "short-hard" gamma-ray bursts are a substantial threat, comparable in magnitude to supernovae and greater than that of the higher-luminosity long bursts considered in most past work. Given their precursors, short bursts may come with little or no warning.     

Iron-scytonemin complexes: DFT calculations on new UV protectants for terrestrial cyanobacteria and astrobiological implications

Cyanobacterial colonies produce the radiation-protectant biomolecule scytonemin as part of their response strategy for survival in environmentally stressed conditions in hot and cold deserts. These colonies frequently use sandstone rocks as host matrices for subsurface colonization, which is accompanied by a zone of depletion of iron and transportation of iron compounds to the mineral surface. It is suggested that an iron-scytonemin complex could feature in this survival strategy and facilitate the movement of iron through the rock. Calculations were carried out on several hypothetical iron-scytonemin complexes to evaluate the most stable structure energetically and examine the effect of the complexation of the biomolecule upon the electronic absorption characteristics of the radiation-protectant species. The implications for extraterrestrial planetary detection and analytical monitoring of an iron-scytonemin complex are assessed.     

The effect of a strong stellar flare on the atmospheric chemistry of an earth-like planet orbiting an M dwarf

Main sequence M stars pose an interesting problem for astrobiology: their abundance in our galaxy makes them likely targets in the hunt for habitable planets, but their strong chromospheric activity produces high-energy radiation and charged particles that may be detrimental to life. We studied the impact of the 1985 April 12 flare from the M dwarf AD Leonis (AD Leo), simulating the effects from both UV radiation and protons on the atmospheric chemistry of a hypothetical, Earth-like planet located within its habitable zone. Based on observations of solar proton events and the Neupert effect, we estimated a proton flux associated with the flare of 5.9?×?10? protons cm?2 sr?1 s?1 for particles with energies >10?MeV. Then we calculated the abundance of nitrogen oxides produced by the flare by scaling the production of these compounds during a large solar proton event called the Carrington event. The simulations were performed with a 1-D photochemical model coupled to a 1-D radiative/convective model. Our results indicate that the UV radiation emitted during the flare does not produce a significant change in the ozone column depth of the planet. When the action of protons is included, the ozone depletion reaches a maximum of 94% two years after the flare for a planet with no magnetic field. At the peak of the flare, the calculated UV fluxes that reach the surface, in the wavelength ranges that are damaging for life, exceed those received on Earth during less than 100?s. Therefore, flares may not present a direct hazard for life on the surface of an orbiting habitable planet. Given that AD Leo is one of the most magnetically active M dwarfs known, this conclusion should apply to planets around other M dwarfs with lower levels of chromospheric activity.     

释放SF_6气体改变电离层电子密度的实验研究

电离层受到自然或人工扰动后产生的电子密度变化会影响无线电的传播。实验模拟了人工释放SF_6气体扰动电离层,通过对SF_6气体在电离层中的扩散过程和相应的离子化学反应的分析,并结合实验测量,研究了电离层电子密度随SF_6气体释放量的变化规律。实验结果表明:SF_6气体在电离层高度释放后,电子密度显著减少,且减少量与气体释放量在一定范围内呈负指数关系。研究可为今后提高卫星通信保密性和实施通信干扰等应用提供理论依据。