Application of a modified generalized sail model on a solar sail with wrinkles

In this paper, we present an analysis of effect of wrinkles on the solar sail performance. We describe different analytical, semi-analytical and numerical approaches to the calculation of general large-scale curvature of a solar sail as well as parameters of so-called wrinkled domains, and introduce the impact of such wrinkles on the thrust and torque of the solar sail. Finally, we present a model of an optically-orthotropic surface for such non-ideal sail, providing a connection with the Generalized Sail Model, and other solar sail thrust models.     

Non-stationarity and cross-correlation effects in the MHD solar activity

The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously.     

Investigating the Coronal Mass Ejections associated with DH type-II radio bursts and solar flares during the ascending phase of the solar cycle 24

We studied a set of 74 CMEs, with shedding the light on the halo-CMEs (HCMEs), that are associated with decametric – hectometric (DH) type-II radio bursts (1–16?MHz) and solar flares during the period 2008–2014. The events were classified into 3 groups (disk, intermediate, and limb events) based on their longitudinal distribution.We found that the events are mostly distributed around 15.32° and 15.97° at the northern and southern solar hemispheres, respectively. We found that there is a clear dependence between the longitude and the CME’s width, speed, acceleration, mass, and kinetic energy. For the CMEs’ widths, most of the events were HCMEs (～62%), while the partial HCMEs comprised ～35% and the rest of events were CMEs with widths less than 120°. For the CMEs’ speeds, masses, and kinetic energies, the mean values showed a direct proportionality with the longitude, in which the limb events had the highest speeds, the largest masses, and the highest kinetic energies. The mean peak flux of the solar flares for different longitudes was comparable, but the disk flares were more energetic. The intermediate flares were considered as gradual flares since they tended to last longer, while the limb flares were considered as impulsive flares since they tended to last shorter.A weak correlation (R?=?0.32) between the kinetic energy of the CMEs and the duration of the associated flares has been noticed, while there was a good correlation (R?=?0.76) between the kinetic energy of the CMEs and the peak flux of the associated flares. We found a fair correlation (R?=?0.58) between the kinetic energy of the CMEs and the duration of the associated DH type-II radio bursts.     

Latitudinal distribution of solar coronal active regions

We studied the cyclic evolution of the latitudinal distribution of solar coronal active regions based on daily images from SOHO EIT for the period 1995–2017. Fully automated software was used, which included the following steps: initial preparation of images in the data series, normalization of histograms and correction of limb brightening, segmentation of images using threshold intensity values obtained from their histograms, scanning of segmented images in heliographic coordinates and obtaining profiles of latitudinal distribution of coronal active regions for each image of the data series. From the output data, we obtained a temporary change in the latitudinal distribution profiles and the migration of activity centers on the solar disk. From the period of minimum activity to the next minimum in both hemispheres, activity centers begin to migrate from high latitudes towards the equator. At the same time, the general center of activity repeatedly changes the direction of migration. The latitudinal distribution of the so-called presence factor of coronal active regions closely resembles the magnetic butterfly diagram, which proves their direct causal relationships. Variations in the presence factor of coronal active regions are correlated with cyclic variations in the sunspot daily numbers.     

Plasma polarization electric field derived from radio sounding of solar wind acceleration region with spacecraft signals

Presented is the analytical approximation of averaged solar wind velocity radial dependence in the solar wind acceleration region at heliolatitudes below 60° under low and moderate solar activity. This empirical approximation is based on the data of radio sounding of the solar corona with radio signals from various spacecraft. Deduced is an equation connecting the solar wind velocity radial dependence and the radial dependence of solar wind plasma polarization electric field intensity. This allows constructing a semi-empirical radial dependence of plasma polarization electric field corresponding to the empirical radial dependence of solar wind velocity. Main properties of the semi-empirical dependence, which is based on radio sounding data, are described.     

Solar sailing in realistic mode,based on a locally-optimal control laws

Ballistic design of solar sailing missions in the solar system is composed of defining the design parameters, the control programs, and the trajectories that provide performance goals of a flight. The use of a solar sail spacecraft imposes specific restrictions on mission parameters that include the degradation limit on the flight duration, the maximum temperature of solar sail's surface, the minimum distance from the Sun, the maximum angular velocity of the spacecraft's rotation and others.Many authors considered the impact of these restrictions on the design of the mission separately, but they used a sophisticated method of finding the exact optimal motion control or applied the most straightforward laws of motion control. This paper uses local-optimal control laws at the complete mathematical models of motion and functioning of solar sail spacecraft to describe a technique of designing interplanetary missions. The described method avoids the need to obtain an accurate optimal solution to the control problem and does not cause significant computational difficulties.     

全模颤振双索悬挂系统刚体模态频率研究

研究绳系结构和绳索预紧力对全模颤振双索悬挂系统刚体模态频率的影响。首先，基于绳索并联机构理论，对双索悬挂系统进行静力学建模，引入加权矩阵，推导了双索悬挂系统静刚度模型；其次，建立双索悬挂系统无阻尼振荡方程，分析双索悬挂系统刚体模态频率变化规律；进而，搭建了双索悬挂系统地面样机，开展系统模态频率测试试验，研究系统刚体模态频率的影响因素及其变化规律；最后，参考试验结果修正所建数学模型。结果表明，随着绳索预紧力的增加，系统刚体模态频率呈上升趋势，但各阶刚体模态的固有频率上升速率不同，平动模态的固有频率受绳索预紧力影响比转动模态小得多；在转动模态方面，滚转模态的固有频率最大且上升快；在平动模态方面，升沉模态的固有频率大于横侧滑模态的固有频率；双索经过的机身前后滑轮与飞机模型质心之间的相对位置变化会不同程度地影响支撑系统俯仰模态、偏航模态的固有频率，但几乎不影响其滚转模态的固有频率。研究发现，通过控制悬挂绳索预紧力的大小，合理设计机身上的滑轮安装位置，能够有效降低双索悬挂系统刚体模态频率。研究结果对于优化设计全模颤振双索悬挂系统具有指导意义。     

Solar sails for perturbation relief: Application to asteroids

A major cause of spacecraft orbital variation comes from natural perturbations, which, in close proximity of a body, are dominated by its non-spherical nature. For small bodies, such as asteroids, these effects can be considerable, given their uneven (and uncertain) mass distribution. Solar sail technology is proposed to reduce or eliminate the net secular effects of the irregular gravity field on the orbit. Initially, a sensitivity analysis will be carried out on the system which will show high sensitivity to changes in initial conditions. This presents a challenge for optimisation methods which require an initial guess of the solution. As such, the Genetic Algorithm (GA) is proposed as the preferred optimisation method as this requires no initial guess from the user. A multi-objective optimisation is performed which aims to achieve a periodic orbit whilst also minimising the effort required by the sail to do so. Given the system sensitivity, the control law for one orbit is not necessarily applicable for any subsequent orbit. Therefore, a new method of updating the control law for subsequent orbits is presented, based on linearisation and use of a Control Transition Matrix (CTM). The techniques will later find application in a multiple asteroid rendezvous mission with a solar sail as the primary propulsion system.     

某飞行器推力矢量试验测力装置研制

为满足某飞行器推力矢量试验的测试要求,采用两台六分量应变天平和一个空气桥组成测力装置来实现飞机全机气动力和喷管推进特性同时分别测量。基于有限元软件,对天平的应变及空气桥对天平的干扰进行了分析。结果表明:空气桥对天平力分量的干扰值优于5%,对力矩(滚转力矩除外)分量的干扰值优于15%,达到了设计指标。通过校准获得了单独天平、天平带空气桥(充压、不充压)状态下的校准公式,校准结果表明:两台天平各分量的综合加载误差均优于0.3%,天平带空气桥(充压、不充压)状态下各分量的综合加载误差优于0.5%,空气桥对天平的干扰量值与有限元分析结果一致。理论分析与实测结果证明:研制的天平及空气桥达到了预定目标,它的测量精准度高,满足推力矢量风洞试验需求。     

TEC differences for the mid-latitude ionosphere in both sides of the longitudes with zero declination

Based on measurements of ground-based GPS station network, differences of the mid-latitude ionospheric TEC in the east and west sides of North America, South America and Oceania have been analyzed in this paper. Results show that for nearly all seasons from 2001 to 2010 and in both sides of the longitudes with zero declination, there exist systematic differences for the mid-latitude ionospheric TEC in the regions mentioned above and the features of these differences markedly depend upon the local time but less depend upon seasons and the level of solar activity. Theory analysis shows that the longitude variations of both declination and zonal thermospheric winds are one of important factors to cause differences of the mid-latitude ionospheric TEC in both sides of the longitudes with zero declination.