摆动喷管与惯性器件超谐波耦合仿真研究

摆动喷管具有大惯量和强非线性特征,存在与惯性器件耦合的风险。建立了从指令输入到惯性器件响应输出的控制回路开环传递特性模型,用有限元方法模拟了摆动喷管非线性特征,发现了摆动喷管与惯性器件的超谐波共振耦合效应,同时讨论了几种改进措施的有效性和可行性,发现对作动器反馈信号进行幅值调制来降低耦合效应效果明显且易于应用实现。     

月球探测器着陆冲击试验及关键技术研究

中国正在开展月球探测活动,下一步将发射月球着陆器并实现月面软着陆。为确保着陆器在月面着陆时的稳定性和可靠性,发射前需在地球表面进行着陆冲击试验。对会影响月球着陆器着陆性能的月貌和月壤进行了详细的叙述,以便在试验过程中进行相应环境特征的模拟。用图表详尽阐述了三种月球重力场模拟器的原理和装置,并对各自的优缺点进行了评述。根据试验模型的不同,将月球着陆器着陆冲击试验分为原尺寸试验（模拟的月球重力场下）和1/6模型试验（地球重力场下）两类,分别介绍了两类模型的结构以及试验模型与着陆器原型机之间缩放关系。分别给出了原尺寸试验和1/6模型试验的试验平台和试验步骤,以及初始试验参数的给定方法。根据试验研究的需要以及月球探测器在月球表面着陆时的真实情况,给出了在地球上进行着陆模式模拟的方法。研究表明两种试验结果之间有良好的一致性,但是这两种试验的花费很高,且对试验场地有较高的要求。再者,由于在试验中对月壤没有太好的模拟方法,试验数据与真实着陆时数据存在一定差异。     

月球表面及月壤内温度分布特征的数值模拟

文章建立了月表辐射与月壤内二维非稳态导热的耦合传热模型,采用控制容积法数值模拟月壤内的温度分布,主要研究了月表、月壤内温度的分布和变化规律及探测器对局部月表温度的影响。计算结果表明一昼夜期间月壤内存在明显的温差:浅层月壤处的昼夜温差较大且受纬度的影响明显;随着深度的增加,月壤昼夜温差降低并趋于稳定,且受纬度的影响较小。探测器的存在遮挡了月表接受的太阳辐射,导致其阴影区域内月表温度发生突变,新的平衡温度接近探测器底面温度,且受探测器驻留时间的影响较小;当探测器移开,月表温度又迅速恢复到原有的变化规律。     

Some aspects of the application of the bunch of MPD engines

In the present work, the asymptotic dependence of the reservation multiplicity on the failure danger diminution coefficient in both cases of reservation replacement and continually acting reserver is investigated. The comparison of the method of reservation for different multiplicities with the method of diminution of the failure intensity, related to the mean performance time shows that the decrease of the failure intensity of the plazma engine is the most rational. Nevertheless, there is a value of the time flight for which even a simple duplication is better than arbitrarily large, though finite, failure intensity decrease of the engine. The reliability of coupled MOD-thrusters is verified experimentally. The specific character of the thruster V-I curves and, in particular, their increase in the pubricrcrisis region, yield normally working couples, conformly to many types of feed sources with weakly decreasing of constant V-I characteristics. The parallel connection of a second thruster is shown to double the customed current and, as a consequence the thruster intermediary regimes of the thruster and the dynamics of switching on and by breaking the electric line and stopping the propellant rate flow are investigated.     

On the structure of the floating zone in melting

Floating zone melting is used in crystal growth and purification of high melting materials. The use of a reduced gravity environment will remove the constraint imposed on the length of the zone by the hydrostatic pressure. The equilibrium of the floating zone may involve, (1) Hydrostatic forces, when the zone rotates as a whole. (2) Convective driving forces, when the zone is stationary but fluid property gradients appear. (3) Hydrodynamic forces, when some parts of the zone are set into motion with respect to others. The last effects are considered in this paper. The flow pattern of a floating zone held between two discs in relative motion is complicated, and thence the solution of the problem is difficult even assuming a constant property-newtonian liquid. Nevertheless, when a small parameter appears in the problem, the complete flow field can be split into zones where simple solutions are found. To illustrate this approach, the spin-up from rest of an initially cylindrical floating zone is considered with detail. Here the small parameter is the time elapsed from the impulsive starting of motion. Since the problem which has been considered, as well as some others which can be tackled by use of similar methods, concern the viscous layer close to either plate, they can be simulated experimentally in the ground laboratory with short floating zones. Procedures to produce these zones are indicated.     

电子控制器PCB板电磁兼容性仿真与试验研究

随着航空发动机全权限数字控制系统的发展,电子控制器中PCB板电磁兼容性设计的重要性日益凸显.本文以某控制器PCB板为对象,在10MHz至1GHz频率范围内,对其电磁干扰使用Ansys公司的SIwave进行近场远场仿真研究,并使用容向公司EMSCAN电磁干扰扫描仅进行测试.通过测试与仿真结果的对比,验证了仿真的准确性.本文提出了一种基于仿真预测PCB板电磁干扰的实现途径,对于电子控制器PCB板的电磁兼容性设计具有参考价值.     

Evolution of the out-of-plane amplitude for quasi-periodic trajectories in the Earth–Moon system

The out-of-plane amplitude along quasi-periodic trajectories in the Earth–Moon system is highly sensitive to perturbations in position and/or velocity as underscored recently by the ARTEMIS spacecraft. Controlling the evolution of the out-of-plane amplitude is non-trivial, but can be critical to satisfying mission requirements. The sensitivity of the out-of-plane amplitude evolution to perturbations due to lunar eccentricity, solar gravity, and solar radiation pressure is explored and a strategy for designing low-cost deterministic maneuvers to control the amplitude history is also examined. The method is sufficiently general and is applied to the L₁ quasi-periodic orbit that serves as a baseline for the ARTEMIS P2 trajectory.     

试验条件对EPDM绝热层耐烧蚀性能的影响

通过烧蚀试验研究了烧蚀时间、燃气流量及烧蚀角度等因素对EPDM绝热层烧蚀性能的影响。结果表明，在不同烧蚀时间内，EPDM绝热层的烧蚀率表现出不同特征，EPDM绝热层烧蚀率与燃气流量成正比关系，燃气以一定角度侧向烧蚀绝热层时，炭化层极易脱落。     

基于码元同步环路的激光测距通信一体化算法优化研究

精密测距与高速通信一体化技术已发展成为星间激光链路的主要研究方向之一。为了探究基于空间激光通信系统的通信解调算法对测距性能的影响机理，根据现有的激光通信系统架构，分析了测距通信一体化系统的工作原理，搭建了基于码元同步的激光测距通信一体化系统模型，分析了基于Gardner同步环路信号跟踪系统的测距精度，并对鉴相算法进行了优化。理论和仿真证明，优化后的码元同步环能够同时实现码元同步判决和距离解算，并得到了4 dB的噪声容忍度提升，其测距方差主要与基带成型滤波参数、环路带宽、载噪比以及鉴相增益等因素有关。该算法简洁，不受载波相位影响，对高阶调制具有良好的兼容性，适用于空间激光链路系统，丰富了测距通信一体化理论，为后续一体化系统设计提供了仿真依据。     

Concept of a space telescope able to see the planets and even the satellites around the nearest stars

The Space Telescope will be launched in 1986 and will improve considerably our observational possibilities, but not the visibility of outer planetary systems.The solar system as seen from Alpha Centauri is presented, as well as the nearest stars and the main cameras of the Space Telescope.As a possible improvement the action of a distant and star-shaped screen is described; that screen is 100 to 800 meters and placed 10⁵ to 10⁶ km in front of the telescope; it allows one to avoid the dazzling effect of the stars and to look for planets such as Jupiter and Saturn up to 20 to 40 light-years. Such planets as Earth and Venus are a little less visible.The visibility of satellites such as the Moon is discussed; it remains at the limit of our technical possibilities.This conceptual paper does not consider in detail the technical difficulties involved.     

航天器火工冲击环境分析预示方法研究综述

航天器火工冲击力学环境问题是一个宽频、瞬态和强非线性的冲击动力学问题。火工冲击响应的预示涵盖结构动力学、冲击动力学、爆炸力学、高应变率材料力学行为等多学科理论。目前,工程上尚无统一、有效的预示方法。在航天工程中,航天器及其组件冲击环境条件设计以及系统级和单机缓冲设计,都迫切需要能够准确预示航天器的火工冲击响应。文章对国内外航天器火工冲击响应机理进行综合理论分析,并在系统调研分析预示方法的基础上提出了航天器火工冲击响应预示研究的重点和难点。     

Halo orbits in the vicinity of the L 2 libration point in the Sun-Earth system

Methods are proposed for constructing the orbits of spacecraft remaining for long periods of time in the vicinity of the L ₂ libration point in the Sun-Earth system (so-called halo orbits), and the trajectories of uncontrolled flights from low near-Earth orbits to halo orbits. Halo orbits and flight trajectories are constructed in two stages: A suitable solution to a circular restricted three-body problem is first constructed and then transformed into the solution for a restricted four-body problem in view of the real motions of the Sun, Earth, and Moon. For a halo orbit, its prototype in the first stage is a combination of a periodic Lyapunov solution in the vicinity of the L ₂ point and lying in the plane of large-body motion, with the solution for the linear second-order system describing small deviations of the spacecraft from this plane along the periodic solution. The desired orbit is found as the solution to the three-body problem best approximating the prototype in the mean square. The constructed orbit serves as a similar prototype in the second stage. In both stages, the approximating solution is constructed by continuation along a parameter that is the length of the approximation interval. Flight trajectories are constructed in a similar manner. The prototype orbit in the first stage is a combination of a solution lying in the plane of large-body motion and a solution for a linear second-order system describing small deviations of the spacecraft from this plane. The planar solution begins near the Earth and over time tends toward the Lyapunov solution existing in the vicinity of the L ₂ point. The initial conditions of both prototypes and the approximating solutions correspond to the spacecraft’s departure from a low near-Earth orbit at a given distance, perigee, and inclination.     

Role of the astronaut in operating the Advanced Fluid Physics Module

The role of man in space is investigated in the operation of the Advanced Fluid Physics Module (AFPM), a scientific instrument dedicated to fluid physics research in a microgravity environment and flown on the Spacelab D2 mission. The astronaut involvement is addressed by applying the criteria of the THURIS study, conducted by NASA for the optimization of future manned space flights. Outcomes of the THURIS study are first summarized. The AFPM characteristics and interfaces are briefly presented. The five experiments performed on board Spacelab D2 are introduced and the involvement of the astronaut is described. Finally, THURIS criteria are applied to an AFPM experiment scenario. Results show that, of all the activities involved in the AFPM nominal operation, two thirds are related to hardware manipulation and to procedure following, while the last third uses the unique astronaut intellectual capabilities, making his presence in orbit mandatory for successful experiment completion.     

表面缺陷对原子氧掏蚀效应影响的数值模拟研究

Kapton作为基底的热控涂层被广泛应用于航天器的外表层设计中,表面保护层中缺陷处所发生的掏蚀效应是近地轨道空间飞行时原子氧对此类热控材料作用的一种主要方式.文章通过蒙特卡洛方法研究了这些尺寸参数与原子氧效应之间的关系.结果表明,保护层缺陷的宽度直接影响进入缺陷内的原子氧的数量,空腔的"颈部"宽度与空腔最大宽度之比随着缺陷宽度增加,掏蚀深度的增加速度则随着缺陷的加宽而变小;保护层厚度主要对初次入射原子氧的入射过程有影响,加厚保护层可以减小原子氧的掏蚀深度和掏蚀空腔的宽度.这些结果可为原子氧防护层的设计提供参考依据.     

近空间高超声速飞行器惯性导航系统Simulink仿真研究

近空间高超声速飞行器具有高动态性特点,能实现精确打击,要保证其高精度,导航系统是关键。惯性导航技术具有可靠性好、输出连续的优点,是近空间巡航飞行器的核心导航系统。本文利用Simulink与M语言结合完成对近空间高超声速飞行器惯性导航系统的仿真研究。构建了近空间高超声速飞行器惯性导航系统的Simulink仿真模型,通过对静基座下的惯导导航误差进行分析,验证了仿真系统的正确性。对近空间高超声速飞行器的航迹进行了仿真,分析了飞行速度对向心加速度及哥氏加速度的影响,对开展近空间高超声速飞行器惯性导航系统的研究具有良好的参考意义。     

弹道导弹主动段扰动引力的一种逼近算法

弹道导弹扰动引力的计算量非常大,目前的弹载计算机因计算速度限制,是不可能实现计算的,必须采用快速的扰动引力逼近算法。针对地面司托克斯积分方法等方法计算扰动引力的不足,提出了利用重力线求解重力的一种方法,并用该方法计算标准弹道附近的扰动引力,作为实际弹道扰动引力的逼近准备数据。给出了弹道主动段扰动引力的BP-神经网络逼近算法,并通过算例证明扰动引力的神经网络逼近是可行的。     

航天运载器的电气系统数字化研制技术

针对运载器电气系统的数字化,给出研制过程中层次的划分、研制的关键环节及相互关系,并对运载器电气系统的数字样机技术和产品全生命周期管理技术进行扼要的分析,最后给出完整的应用系统框架结构。为运载器的数字化研制作了重要的补充。     

Determination of the Quasistatic Component of Microaccelerations at the MirStation

We describe the determination of the quasistatic component of microaccelerations, as it was done during the space experiments with the instruments DACON and ALICE-2. This component was calculated using the telemetric information related to the motion of the station with respect to its center of mass. The information consists of the values of the station angular velocity vector and the quaternion which specifies its orientation, determined at discrete instants of time. The quaternion is determined with a step of about 1 min, the angular velocity with a step of about 10 s. The information is used in the following manner. At first, the quaternion components corresponding to some time interval are smoothed by splines. Then, employing the obtained splines and kinematic equations, the angular velocity and acceleration of the station are calculated on this interval. Finally, the microacceleration is calculated as a function of time at the point of the location of the instrument. The data of measurements of the angular velocity are used for the purpose of control. As a rule, the available telemetric information allows one to find the quasi-static component for the entire time interval of carrying out the experiment. Examples of determination of this component for some experiments are presented. A comparison with the results of calculating the microacceleration quasistatic component by other methods is made.     

太阳、地球、卫星相关模拟墓准源

本文主要讨论用于自旋静止气象卫星大回路成像试验的太阳、地球、卫星相关模拟基准源。本基准源是用于测量自旋静止气象卫星星上同步控制系统的性能，检查云图传输系统的同步控制精度，并作为地面测试卫星云图传输性能的基准设备。本文论述了其基本原量，介绍了用数字信号处理器（ＤＳＰ）集成电路ＴＭＳ３２０Ｃ２５实现的方法，并分析了成像精度。     

高校财务人员全新理念的确立

当前，高校所面临的客观形势发生着日新月异的变化，高校财务人员的管理理念不能与时俱进，制约着财务管理水平的提高，影响着高校的发展。高校财务人员应确立全新理念，提高财务管理水平，促进高校发展。