月球表面次级中子辐射环境仿真研究

由于缺少磁场和大气,宇宙线高能粒子轰击月壤可以形成月球特有的强中子辐射环境,并对航天员和电子设备造成潜在威胁。文章采用蒙特卡罗方法仿真研究宇宙线高能粒子辐射与月壤成分核反应产生的次级中子能谱特征,给出不同太阳活动、不同月壤深度下月球中子能谱特征和空间分布特征。仿真结果表明,宇宙线高能粒子导致的次级中子随着月壤深度的增加先增大后减小,大约在1 m深度达到最大值,深度越深银河宇宙线诱发的中子贡献越大。相关结果可为我国后续载人月球探测任务的辐射防护设计提供参考。     

Motion and transport of solar cosmic rays in heliospheric traps: The event on January 28–31, 2001

The results of studying the enhancement of solar cosmic ray fluxes on January 28?C31, 2001 in a wide energy range are presented using the ACE spacecraft data. A comparative analysis of temporal variations of the fluxes of charged particles and of the interplanetary medium parameters (interplanetary magnetic field and solar wind) has been performed on the basis of the ??reflection?? model of motion, accumulation, and modulation of cosmic rays. It is shown that a magnetic trap for solar cosmic rays was created by a plasma stream and flare ejection from an active region in the western part of the solar disk. Particles of low energies (<10 MeV) were captured inside the trap; the dispersion of distribution of particles with different energies inside the trap being determined by its complicated magnetic structure. The power-low dependence of the time of maximum for the flux of particles on their energy is found, and softer energy spectrum inside the trap is explained.     

Radiation protective structures on the base of a case study for a manned Mars mission

Plans for interplanetary manned space missions imply significant risks arising from human's exposure to the hostile space environment. Thus the design of reliable protection systems against the ionizing cosmic radiation becomes one of the most relevant issues. In this paper the composition and magnitude of the atmospheric radiation on the planetary surface and for typical interplanetary transfer configurations have been analyzed. The investigation based on prior NASA and ESA mission results, using a manned mission to planet Mars as a case study. According to this, the time-dependent character of the consistency of cosmic radiation has been taken into account, which is justified by the interdependence of the radiation magnitude to the solar cycle. With regard to this paper it implies even solar particle events. The results have been compared to the protective character of different materials potentially usable as a habitat's structural shell and for interplanetary spacecrafts. The investigation aimed on particle energy degradation rates and reduction of secondary particle production. In this regard the physical process of absorbing effectiveness against particle radiation has been examined by analytical calculation and given scientific results, depending on thickness and molecular composition of the materials. The most suitable materials have been used for shield design proposals using different configurations, evaluating the use of aluminium, water tanks and polyethylene bricks.     

Dynamics of Quasi-Biennal Variations of Cosmic Rays and Solar Activity

The quasi-biennial variations in the flux of galactic cosmic rays (GCRs) have been studied based on the data of stratospheric sensing and measurements by neutron monitors, as well as in various manifestations of solar activity and interplanetary medium parameters. It has been shown that quasi-biennial GCR variations are caused by variations with the same period in the mean magnetic field of the Sun that coincide with them over time and have been identified in the anti-phase, which respond to the sign of this field. The variations in the quasi-biennial cosmic ray are caused by quasi-biennial variations in the mean magnetic field of the Sun via the quasi-biennial variations in the interplanetary magnetic field.     

HZE particle effects in space

Among the various particulate components of ionizing radiation in space, heavy ions (the so-called HZE particles) have been of special concern to radiobiologists. To understand the ways by which HZE particles of cosmic radiation interact with biological systems, methods have been developed to precisely localize the trajectory of an HZE particle relative to the biological object and to correlate the physical data of the particle with the biological effects observed along its path. In a variety of test systems, injuries were traced back to the traversal of a single HZE particle, such as somatic mutations, and chromosomal aberrations in plant seeds, development disturbances and malformations in insect and salt shrimp embryos, or cell death in bacterial spores. In the latter case, a long-ranging killing effect around the particle's track was observed. Whereas, from spaceflight experiments, substantial infomation has been accumulated on single HZE particle effects in resting systems and in a few embryonic systems, there is a paucity of data on cosmic radiation effects in whole tissues or animals, especially mammalians.     

Cosmic ray impact on extrasolar earth-like planets in close-in habitable zones

Because of their different origins, cosmic rays can be subdivided into galactic cosmic rays and solar/stellar cosmic rays. The flux of cosmic rays to planetary surfaces is mainly determined by two planetary parameters: the atmospheric density and the strength of the internal magnetic moment. If a planet exhibits an extended magnetosphere, its surface will be protected from high-energy cosmic ray particles. We show that close-in extrasolar planets in the habitable zone of M stars are synchronously rotating with their host star because of the tidal interaction. For gravitationally locked planets the rotation period is equal to the orbital period, which is much longer than the rotation period expected for planets not subject to tidal locking. This results in a relatively small magnetic moment. We found that an Earth-like extrasolar planet, tidally locked in an orbit of 0.2 AU around an M star of 0.5 solar masses, has a rotation rate of 2% of that of the Earth. This results in a magnetic moment of less than 15% of the Earth's current magnetic moment. Therefore, close-in extrasolar planets seem not to be protected by extended Earth-like magnetospheres, and cosmic rays can reach almost the whole surface area of the upper atmosphere. Primary cosmic ray particles that interact with the atmosphere generate secondary energetic particles, a so-called cosmic ray shower. Some of the secondary particles can reach the surface of terrestrial planets when the surface pressure of the atmosphere is on the order of 1 bar or less. We propose that, depending on atmospheric pressure, biological systems on the surface of Earth-like extrasolar planets at close-in orbital distances can be strongly influenced by secondary cosmic rays.     

Instability of entropy waves in cosmic plasma

A dispersion equation is derived for small disturbances of the magnetohydrodynamic type in optically transparent plasma with cosmic abundance of elements. The electron heat conductivity along the magnetic field and proton heat conductivity across the field are taken into account. It is shown that entropy waves increase exponentially in wide ranges of temperatures and densities of the cosmic plasma. Manifestations of instability of the entropy waves in the cosmic plasma are discussed.     

Numerical Simulation of Geomagnetic Trapping of Anomalous Cosmic Ray Ions

A method for simulating the propagation processes for ions of the anomalous component of cosmic rays in the Earth's magnetic field is described with allowance made for a step-by-step stripping of the ions in the residual atmosphere and their trapping by the geomagnetic field. Numerical results are presented for the geomagnetic trapping of high-energy singly charged oxygen ions penetrating into the stripping region from interplanetary space.     

Specific features of solar cosmic ray fluxes and geomagnetic conditions on December 5–18, 2006

Results of the analysis of specific features of solar activity, dynamics of solar cosmic ray fluxes, and state of the interplanetary medium are presented for the period December 5–18, 2006. The data analysis is based on new model concepts on coronal and interplanetary propagation of solar cosmic rays: partial capture into the magnetic field traps and oscillations at reflections from magnetic mirrors. Some new hypotheses about possible relations of the features of the interplanetary medium with processes in the Earth’s magnetosphere are put forward: the influence of the discrete interplanetary medium on processes in the Earth’s magnetosphere does exist always and, in this sense, it is a fundamental phenomenon; the discreteness of the inter-planetary medium can be one of the causes of geomagnetic substorms.     

Toroidal magnetic fields for protecting astronauts from ionizing radiation in long duration deep space missions

Among the configurations of superconducting magnet structures proposed for protecting manned spaceships or manned deep space bases from ionizing radiation, toroidal ones are the most appealing for the efficient use of the magnetic field, being most of the incoming particle directions perpendicular to the induction lines of the field. The parameters of the toroid configuration essentially depend from the shape and volume of the habitat to be protected and the level of protection to be guaranteed. Two options are considered: (1) the magnetic system forming with the habitat a unique complex (compact toroid) to be launched as one piece; (2) the magnetic system to be launched separately from the habitat and assembled around it in space (large toroid).     

矩形波导宽边纵向裂缝的分析

利用缝隙口面切向磁场连续的条件建立关于未知电场的联立积分方程,将波导内外部的互耦、波导壁厚及波导内高次模的影响全部考虑进去,然后运用矩量法求解得到一端短路和两端开路时的波导单缝中的电场分布。该结果与文献结果和HFSS仿真结果作比较,两者吻合良好,证明理论推导和编程计算的正确性。根据缝隙等效导纳和反射系数的关系计算波导一端短路时不同偏距纵缝的谐振长度,进行矩形端头与半圆端头的等效转化并给出了与仿真结果的比较。单个缝隙参数的确定为采用HFSS软件仿真法、等效电路法或场分析法进行波导裂缝阵列天线的分析和设计奠定了基础。     

小长径比复杂零件磁粉检测工装设计

介绍了采用的磁场、磁路、磁阻以及磁场分布理论,给出了用于小长径比零件磁粉检测专用工装的设计规范,利用该工装可明显提高发动机机架零件磁粉检测的灵敏度。该项技术已应用于发动机无损检测之中。     

一种不借助零磁线圈的星载磁强计校准方法

文章介绍一种星载磁强计校准装置及方法。首先,将高精度地面磁强计的三分量磁传感器置于标准磁场发生装置形成的磁场环境内,通过后端数据处理装置采集得到第一磁场数据,并进行不同量程下螺线管线圈常数C_i的标定;然后,将星载磁强计置于上述标准磁场环境内,并以高精度地面磁强计不同量程下获得的C_i作为基准,通过后端数据处理装置采集得到第二磁场数据;最后,对第一磁场数据和第二磁场数据进行比对,得到星载磁强计的量程、分辨率及稳定性校准值。上述校准项目所有参数的校准结果不确定度为u=0.12%（k=2）。本方法已成功应用于多种军民型号星载磁强计校准。     

X波段波导端头裂缝的互耦分析

用矩量法(MOM)导出求解X波段波导端头裂缝单元间互耦等效磁流的模型。在此基础上给出了等效磁流在激励和未激励单元内部产生的场、反射系数、驻波系数和两单元间耦合系数等的计算公式。分别在共E、H面条件下分析了两X波段波导端头裂缝互耦的影响,并对单元间不同相对距离和工作频率时的互耦影响规律进行了讨论。研究结果表明,该算法简单,计算值与测试结果吻合较好。     

The Use of Quaternions in the Optimal Control Problems of Motion of the Center of Mass of a Spacecraft in a Newtonian Gravitational Field: III

The results of numerical solution of the problem of a rendezvous in the central Newtonian gravitational field of a controlled spacecraft with an uncontrollable spacecraft moving along an elliptic Keplerian orbit are presented. Two variants of the equations of motion for the spacecraft center of mass are used, written in rotating coordinate systems and using quaternion variables to describe the orientations of these coordinate systems. The problem of a rendezvous of two spacecraft is formulated [1, 2] as a problem of optimal control by the motion of the center of mass of a controlled spacecraft with a movable right end of the trajectory, and it is solved on the basis of Pontryagin's maximum principle. The paper is a continuation of papers [1, 2], where the problem of a rendezvous of two spacecraft has been considered theoretically using the two above variants of the equations of motion for the center of mass of the controlled spacecraft.     

Further analyses of the slide lander and of drop delivery systems for improved lunar surface access

The paper discusses two methods for lunar surface access. One method is characterized by very little propellant consumption for landing (lunar slide lander, LSL); the other (drop delivery method, DDM) avoids release of propellant gases at the lunar surface. The LSL is of particular promise and importance. Its analysis and development introduces a new field of cosmic dynamics—harenodynamics, the science and technology of interaction of surfaces with dust and sand at near-orbital speeds down to low velocities. Although the data base is small so far and needs to be enlarged, analyses of the LSL so far indicate promise as to feasibility. Its realization will revolutionize present conventional concepts of lunar development. The DDM offers cost-effective alternatives to conventional lunar landing by retrothrust, but on a more selective basis, because propellant-savings are secondary to avoiding gas releases into the lunar high-vacuum environment. It was found that stationary energy absorption systems (EAS) are required, because vehicle-attached absorption systems are entirely inadequate. This requires large structures which can be built on the lunar surface only after a somewhat higher degree of industrial capability has been established. However, they can be built entirely of lunar materials. Altogether, the LSL is the more significant of the two both in terms of economy and of operational scope.     

The Use of Quaternions in the Optimal Control Problems of Motion of the Center of Mass of a Spacecraft in a Newtonian Gravitational Field: I

The problem of optimal control is considered for the motion of the center of mass of a spacecraft in a central Newtonian gravitational field. For solving the problem, two variants of the equations of motion for the spacecraft center of mass are used, written in rotating coordinate systems. Both the variants have a quaternion variable among the phase variables. In the first variant this variable characterizes the orientation of an instantaneous orbit of the spacecraft and (simultaneously) the spacecraft location in this orbit, while in the second variant only the instantaneous orbit orientation is specified by it. The suggested equations are convenient in the respect that they allow the general three-dimensional problem of optimal control by the motion of the spacecraft center of mass to be considered as a composition of two interrelated problems. In the first variant these problems are (1) the problem of control of the shape and size of the spacecraft orbit and (2) the problem of control of the orientation of a spacecraft orbit and the spacecraft location in this orbit. The second variant treats (1) the problem of control of the shape and size of the spacecraft orbit and the orbit location of the spacecraft and (2) the problem of control of the orientation of the spacecraft orbit. The use of quaternion variables makes this consideration most efficient. The problem of optimal control is solved on the basis of the maximum principle. Several first integrals of the systems of equations of the boundary value problems of the maximum principle are found. Transformations are suggested that reduce the dimensions of the systems of differential equations of boundary value problems (without complicating them). Geometrical interpretations are given to the transformations and first integrals. The relation of the vectorial first integral of one of the derived systems of equations (which is an analog of the well-known vectorial first integral of the studied problem of optimal control) with the found quaternion first integral is considered. In this paper, which is the first part of the work, we consider the models of motion of the spacecraft center of mass that employ quaternion variables. The problem of optimal control by the motion of the spacecraft center of mass is investigated on the basis of the first variant of equations of motion. An example of a numerical solution of the problem is given.     

基于全张量磁场梯度的磁偶极子定位及误差分析

为了对磁偶极子进行高精度的磁性定位,文章从磁偶极子模型出发,推导出磁偶极子的空间坐标与其产生的磁场及磁场梯度之间的关系式;针对模型及关系式,设计了一种全张量磁场梯度传感器,能够一次测量出精确定位所需的9个磁场梯度值和3个磁场强度值;对比仿真结果和实验结果,发现二者具有较好的一致性,证明了该理论模型的有效性。对于磁偶极子,用半径为0.05 m的梯度传感器对磁矩为2 A·m~2的磁偶极子进行定位测量,在0.5~1 m距离内定位误差不大于10%。文章还对定位测量误差的原因进行了分析,包括梯度测量基线距离及传感器半径对定位误差的影响。     

Simulation of rocket plume and lunar dust using DSMC method

When lunar modules land on the Moon, dust impingement on the lunar module components and deposition on the thermal and optical surfaces would cause many serious problems. The emphasis of this research is on simulating the interaction of rocket plume and lunar dust using the direct simulation Monte Carlo (DSMC) method. The method is extended to model the movement and collision stages of rarefied plume gas and dust particles, including three collisional mechanisms: molecule–molecule, molecule–particle and particle–particle collisions. The reflection of gas molecules on the particle surface is computed by an indirect approach based on the coordinate transformation. Neighboring-cell contact detection scheme is applied to check for contacts between all possible particle pairs. The simulation results show that the acceleration of dust particle is mostly determined by the parameters of plume field. In the computational regions with larger gas density and velocity the particles can be accelerated to larger velocity and convected to higher temperature.     

Features of whistling electromagnetic wave propagation descending from above upon the night ionosphere

The results of numerical solution of the wave equations for the oblique incidence of whistling electromagnetic waves upon the night ionosphere from above have been obtained and analyzed. In the studied region of altitudes, within the wavelength scale, charged particle concentration varies drastically, and damping caused by collisions between the charged and neutral particles decreases considerably. Below, the sharp lower boundary of the ionosphere, the refractive index of the whistler wave approaches unity, and plasma turbulence transform into atmospheric electromagnetic waves. The dependences of the whistler reflection factor are found in terms of energy and horizontal magnetic component of the electromagnetic wave near the Earth’s surface on the frequency and the wave vector transverse component for the plain-layered medium model at two values of latitude. Strong dependences have been found on the wave angle of incidence and frequency. At rather small angles of incidence, the wave disturbances reach the Earth’s surface, and the module of reflection coefficient logarithm is in the range of 0.4–1. At large angles of incidence, the reflection coefficient module varies over a wide range depending on specific conditions. The obtained results explain the absence of oscillation modes of plasma magnetosphere maser in the night magnetosphere.