水星近日点的进动

计算绕太阳运行的航天器轨道的长期进动需要考虑广义相对论。然而,作者发现爱因斯坦
用他的广义相对论解释行星近日点进动的文章有误,他的计算行星近日点进动的公式是建立
一系列错误上的杜撰。本文详细分析了爱因斯坦的失误,尤其是他的积分错误,并用计算机
的数值积分直接验证了他的失误。     

全太阳系深空探测轨迹全局优化(英文)

针对太阳系中全部的248997颗行星的探测问题,给出了一种关于探测飞行器的深空探测全局四维轨迹(t,x,y,z)优化方案,即飞行器从地球发射进入太阳系并采用小推力控制,优化方案的性能指标为飞行器与太阳系中全部行星中相遇和交会的星的数量最多并且燃料消耗最少。本方案给出了四维飞行轨迹进行全局优化的一套算法,该算法由搜索算法和四维轨迹优化算法组成。此搜索算法从太阳系的248997颗行星中寻找获得尽可能多的经过近地球3维走廊内的行星;而四维轨迹优化算法由改进的动态规划算法、基于最优控制理论的共轭梯度算法和静态参数优化算法组成,其中静态参数优化算法用于搜索最优发射时间窗口。基于该组合算法,通过长时间的大规模的飞行数字仿真,最终计算出探测器的四维最优飞行轨迹,在一年内路过了太阳系中全部行星中的12颗行星。     

锥体目标空间进动特性分析及其参数提取

空间进动是弹道导弹中段飞行过程中锥体目标特有的运动特性，本文首先建立了锥体目标空间进动数学模型，给出了姿态角与空间进动参数的关系式，并利用进动参数获取了反映目标质量分布特性的惯量比。然后通过对目标RCS回波数据进行多项式拟合，估计进动参数，以此为雷达目标识别提供新的技术思路。仿真实验结果表明本文提出的算法能够有效估计出目标的进动角。     

对天体的近星点进动的二阶后牛顿效应（后—后牛顿效应）的估计

本文利用在ＰＰＮ近似中给出的天体的近黑点进支的理论式对于对行星、卫星和双星的近星点进点进行的二阶后牛顿效应做了数值估计，估计的结果已在表１－４中给出了。对于四种天体，其中以双星的效应值为最大。     

基于一维距离像序列的空间弹道目标微动特征提取

弹道导弹的空间微动特性是中段空间弹道目标识别的重要依据之一.以一维距离像序列为研究对象,首先利用距离像散射中心位置加权、纵向积累估计空间锥体进动目标的进动周期,然后基于广义Radon变换提取空间锥体目标散射中心位置变化曲线,并根据获得的曲线参数估计得到空间进动角,最后给出了基于广义Radon变换的散射中心位置估计新方法.仿真实验验证了所提算法的有效性.     

弹道目标进动特性的微多普勒研究与特征分析

从两个不同方面建立弹道导弹进动的数学模型,然后用时频分析方法给出微多普勒的分析结果,证明这两种建立弹道导弹进动数学模型的方法是等价的、正确的.根据不同微运动微多普勒时频分布的差异以及不同微运动微多普勒变化周期的不同,可以识别出真弹头和诱饵.这为弹道导弹防御中段弹头和其他轻重诱饵的识别提供了一个新的可靠的方法.     

基于PID控制的主动磁轴承-飞轮转子系统运动稳定性研究

磁悬浮支承应用于控制力矩陀螺具有很多优点,但是飞轮转子在高转速下表现出的陀螺效应是影响系统稳定性的主要因素。现研究了由于陀螺效应产生的章动和进动造成系统失稳的根本原因,并对控制系统提出改进方案。为研究方便,提出了相位分析的方法进行PID控制系统分析。研究结果表明,章动失稳的主要原因是系统的相位滞后引起,进动失稳主要因为积分控制项对系统负阻尼作用引起,同时,研究表明积分控制对系统章动稳定性影响很小。     

曲轴连杆轴颈行星磨削算法及编程

以曲轴连杆轴颈行星磨削为研究对象,通过对坐标轴移动指令值与移动速度的计算以及对自变量的分析,给出了曲轴连轴颈行星磨削的算法.介绍了砂轮进给方式,给出了FANUC系统编制的加工用户宏程序,并进行了精度分析.     

论广义相对论以太--关于准物性物质、存在的参考证明(三)

本文就爱因斯坦对以太的陈述和作者提出的宇宙空间存在准物性物质DM 概念相比对,认为两个概念原本就是同一客体——广义相对论以太。进一步分析广义相对论以太,得出结论:宇宙间所有物质,因它们均浮游于DM之中,故其运动速度必然存在上限——“光速C_0”。而且从中看到,V/C_0有资格作为主要成员参与对运动物质与DM之间相互作用的度量。同时,也可想象出V/C_0=1,运动物质的质量为无穷大的物理机制。     

星敏感器杂光抑制分析

介绍了用蒙特卡洛法进行星敏感器杂光分析的基本思想、数学模型以及表面热辐射概率模型 ,对典型卫星星敏感器的杂光传递进行了模拟。在复杂的杂光环境下 ,建立杂光传递模型 ,获得了星敏感器杂光环境的定量杂光贡献 ,并对大衰减比遮光罩及光学系统内的杂光传递进行了跟踪 ,给出了遮光罩的消杂光能力     

On the Precession of Saturn

The precession of Saturn under the effect of the gravity of the Sun, Jupiter and planet’s satellites has been investigated. Saturn is considered to be an axisymmetric (A = B) solid body close to the dynamically spherical one. The orbits of Saturn and Jupiter are considered to be Keplerian ellipses in the inertial coordinate system. It has been shown that the entire set of small parameters of the problem can be reduced to two independent parameters. The averaged Hamiltonian function of the problem and the integrals of evolutionary equations are obtained disregarding the effect of satellites. Using the small parameter method, the expressions for the precession frequency and the nutation angle of the planet’s axis of rotation caused by the gravity of the Sun and Jupiter are obtained. Considering the planet with satellites as a whole preceding around the normal to the unmovable plane of Saturn’s orbit, the satellites effect on the Saturn rotation is taken into account via the corrections in the formula for the undisturbed precession frequency. The satellites are shown to have no effect on the nutation angle (in the framework of the accepted model), and the disturbances from Jupiter to make the main contribution to the nutation angle evolution. The effect of Jupiter on the nutation angle and the precession period is described with regard to the attraction of satellites.     

A Celestial Mechanics Model of Oscillations of the Poles of a Deformable Earth

The problem of Chandler motion of the Earth's poles is studied in the context of the model of a viscoelastic body. The Earth-Moon system is considered as a binary planet rotating around their barycenter. Numerical values of the period and amplitudes of oscillations of the poles are obtained by estimating the elastic deformation of the Earth and the variation of its inertia tensor, and they agree well with observational data. An evolution model of the Earth-Moon-Sun system is constructed by taking into account tidal forces of dissipation character. By means of the method of averaging, the qualitative properties of motion on asymptotically large intervals of time (comparable and essentially longer than the period of precession of the Earth's axis) are established and commented on.     

振动时效在消除铸铝合金框架变形中的应用

铸铝合金异型件在加工过程中的变形问题广泛存在,而残余应力是引起变形的关键因素。本文从框架类产品的设计结构入手,分析残余应力与产品变形间的关系,结合振动时效工艺机理,重点详述了利用振动时效消除铸铝合金框架类产品变形工艺。试验表明,振动时效可显著消除铸铝合金框架件变形。     

Vegetation's red edge: a possible spectroscopic biosignature of extraterrestrial plants

Earth's deciduous plants have a sharp order-of-magnitude increase in leaf reflectance between approximately 700 and 750 nm wavelength. This strong reflectance of Earth's vegetation suggests that surface biosignatures with sharp spectral features might be detectable in the spectrum of scattered light from a spatially unresolved extrasolar terrestrial planet. We assess the potential of Earth's step-function-like spectroscopic feature, referred to as the "red edge," as a tool for astrobiology. We review the basic characteristics and physical origin of the red edge and summarize its use in astronomy: early spectroscopic efforts to search for vegetation on Mars and recent reports of detection of the red edge in the spectrum of Earthshine (i.e., the spatially integrated scattered light spectrum of Earth). We present Earthshine observations from Apache Point Observatory (New Mexico) to emphasize that time variability is key to detecting weak surface biosignatures such as the vegetation red edge. We briefly discuss the evolutionary advantages of vegetation's red edge reflectance, and speculate that while extraterrestrial "light-harvesting organisms" have no compelling reason to display the exact same red edge feature as terrestrial vegetation, they might have similar spectroscopic features at different wavelengths than terrestrial vegetation. This implies that future terrestrial-planet-characterizing space missions should obtain data that allow time-varying, sharp spectral features at unknown wavelengths to be identified. We caution that some mineral reflectance edges are similar in slope and strength to vegetation's red edge (albeit at different wavelengths); if an extrasolar planet reflectance edge is detected care must be taken with its interpretation.     

Novel orbits of Mercury,Venus and Mars enabled using low-thrust propulsion

Exploration of the inner planets of the Solar System is vital to significantly enhance the understanding of the formulation of the Earth and other planets. This paper therefore considers the development of novel orbits of Mars, Mercury and Venus to enhance the opportunities for remote sensing of these planets. Continuous acceleration is used to extend the critical inclination of highly elliptical orbits at each planet and is shown to require modest thrust magnitudes. This paper also presents the extension of existing sun-synchronous orbits around Mars. However, unlike Earth and Mars, natural sun-synchronous orbits do not exist at Mercury or Venus. This research therefore also uses continuous acceleration to enable circular and elliptical sun-synchronous orbits, by ensuring that the orbit's nodal precession rate matches the planets mean orbital rate around the Sun, such that the lighting along the ground-track remains approximately constant over the mission duration. This property is useful both in terms of spacecraft design, due to the constant thermal conditions, and for comparison of images. Considerably high thrust levels are however required to enable these orbits, which are prohibitively high for orbits with inclinations around 90°. These orbits therefore require some development in electric propulsion systems before becoming feasible.     

Pervasive orbital eccentricities dictate the habitability of extrasolar earths

The long-term habitability of Earth-like planets requires low orbital eccentricities. A secular perturbation from a distant stellar companion is a very important mechanism in exciting planetary eccentricities, as many of the extrasolar planetary systems are associated with stellar companions. Although the orbital evolution of an Earth-like planet in a stellar binary system is well understood, the effect of a binary perturbation on a more realistic system containing additional gas-giant planets has been very little studied. Here, we provide analytic criteria confirmed by a large ensemble of numerical integrations that identify the initial orbital parameters leading to eccentric orbits. We show that an extrasolar earth is likely to experience a broad range of orbital evolution dictated by the location of a gas-giant planet, which necessitates more focused studies on the effect of eccentricity on the potential for life.     

Circumstellar habitable zones: an overview

We review aspects of circumstellar habitable zones based on results reported at the First International Conference on Circumstellar Habitable Zones (held in 1994 at NASA Ames Research Center). Recent advances in atmospheric radiative transfer modeling have shown that circumstellar habitable zones are wider than previously thought. New considerations may allow a much shorter time scale both for the origin as well as the evolution of biological forms. The most abundant M dwarf stars, contrary to previous views, appear to be able to support the necessary conditions for a habitable zone around them. New planet formation models indicate that at least one planet should form within the circumstellar habitable zone of single dwarf stars regardless of mass. Biogenic materials also appear to be widespread and delivery to terrestrial planets via cometary impacts may be a viable mechanism. Finally, biology will modify a planet and provide positive feedback, in general, to increase the habitability of a planet. Overall, new astronomical, planetary, and biological considerations each seem to indicate that habitable zones around other stars may be both more widespread and more stable than previous research had indicated.     

Tides and the evolution of planetary habitability

Tides raised on a planet by the gravity of its host star can reduce the planet's orbital semi-major axis and eccentricity. This effect is only relevant for planets orbiting very close to their host stars. The habitable zones of low-mass stars are also close in, and tides can alter the orbits of planets in these locations. We calculate the tidal evolution of hypothetical terrestrial planets around low-mass stars and show that tides can evolve planets past the inner edge of the habitable zone, sometimes in less than 1 billion years. This migration requires large eccentricities (>0.5) and low-mass stars ( less or similar to 0.35 M(circle)). Such migration may have important implications for the evolution of the atmosphere, internal heating, and the Gaia hypothesis. Similarly, a planet that is detected interior to the habitable zone could have been habitable in the past. We consider the past habitability of the recently discovered, approximately 5 M(circle) planet, Gliese 581 c. We find that it could have been habitable for reasonable choices of orbital and physical properties as recently as 2 Gyr ago. However, when constraints derived from the additional companions are included, most parameter choices that indicate past habitability require the two inner planets of the system to have crossed their mutual 3:1 mean motion resonance. As this crossing would likely have resulted in resonance capture, which is not observed, we conclude that Gl 581 c was probably never habitable.     

Hypothetical flora and fauna of Venus

Hypothetical habitability of some of extrasolar planets is a fundamental question of science. Some of exoplanets possess physical conditions close to those of Venus. Therefore, the planet Venus, with its dense and hot (735 K) oxygen-free atmosphere of CO₂, having a high pressure of 9.2 MPa at the surface, can be a natural laboratory for this kind of studies. The only existing data on the planet׳s surface are still the results obtained by the Soviet VENERA landers in the 1970s and 1980s. The TV experiments of Venera-9 and 10 (October, 1975) and Venera-13 and 14 (March, 1982) delivered 41 panoramas of Venus surface (or their fragments). There have not been any similar missions to Venus in the subsequent 39 and 32 years. In the absence of new landing missions to Venus, the VENERA panoramas have been re-processed. The results of these missions are studied anew. A dozen of relatively large objects, from a decimeter to half a meter in size, with an unusual morphology have been found which moved very slowly or changed slightly their shape. Their emergence by chance could hardly be explained by noise. Certain unusual findings that have similar structure were found in different areas of the planet. This paper presents the last results obtained of a search for hypothetical flora and fauna of Venus.