Robust algorithm of control for a maneuver in the Martian atmosphere to insert a spacecraft into the planet’s satellite orbit

When inserting a satellite into an orbit around Mars with the use of aerodynamic drag, it is required to apply a robust algorithm which is capable of being adapted to the actual conditions of the planet’s atmosphere. We suggest a method of adaptation taking into account the specific features of the maneuver including descending and ascending legs of the trajectory. It is demonstrated that the algorithm is efficient when disturbances of the density of the Martian atmosphere increase by a factor of 2–3.     

Semianalytic estimations of boundaries of a corridor of spacecraft entry into the planetary atmosphere at considerable values of permissible maximum overload

Trajectories of spacecraft entry into the planetary atmosphere with a velocity essentially exceeding the first cosmic velocity are considered. An estimation of the minimum permissible value of the altitude of conditional pericenter (perigee in the case of the Earth), at which extreme permissible value of maximum overload is reached, is of the main interest. Semianalytic formulas including the cases of considerable values of the maximum overload are suggested.     

Statistical analysis of attitude motion of a light capsule entering the atmosphere

The laws of distribution of the space angle of attack are analyzed for a light descent capsule on the atmosphere’s conventional boundary and on the segment of motion in dense layers of the atmosphere until the moment of reaching the maximum velocity head. It is assumed that upon detachment from a base spacecraft the angular velocity components of the descent capsule represent independent random quantities distributed according to the normal law. The shape of the descent capsule is close to a body of revolution whose instantaneous aerodynamic characteristic has a sufficiently simple form (one stable and one unstable positions of static equilibrium). It is demonstrated that there is a possibility to approximate the distribution densities by well-known laws and by approximate functions constructed on the basis of simplified models. Evolution of the distribution laws at increasing mass-inertia asymmetry of the descent capsule is studied.     

Ballistics of a nonfragmenting meteor body with allowance made for mass outflow in the non-isothermal atmosphere. I

The paper is devoted to studying the motion of meteor bodies with mass outflow in a planet’s atmosphere, taking into account the non-isothermal character of the latter. Analytical solutions are obtained at the constant parameter of mass outflow in the model of a nonfragmenting meteoroid. A theoretical analysis of the derived regularities of the ballistics of such bodies is presented.     

Consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface

Possible consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface are described. The methodological basis of classification of consequences is the solution of meteor physics equations characterizing the trajectory of a body in the atmosphere, namely, the dependence of the body’s velocity and mass on the flight altitude. The solution depends on two dimensionless parameters characterizing the drag altitude and the role of mass loss by a meteoroid during its motion in the atmosphere. Depending on values of these parameters, the degree of effect on the planetary surface considerably changes. In particular, the conditions of cratering and meteorite fall on the planetary surface are obtained. The results are presented in a simple analytical form. They quite match to the real events considered in the paper. Recommendations are given on further investigations into the important problem of interaction of cosmic bodies with planetary atmospheres.     

Ballistics of a fragmenting meteor body with allowance made for ablation in the non-isothermal atmosphere. II

The second part of the work is devoted to studying the motion of fragmenting meteor bodies with ablation by fragments in a planet’s atmosphere, taking into account its non-isothermal character in altitude. The mechanical fragmentation of a meteoroid under the action of aerodynamic drag is considered in the context of statistical strength theory. An analytical solution for ballistics of a fragmenting body is obtained at a constant parameter of ablation. A theoretical analysis of the derived regularities is made and an example of their usage in the problem of a comet-asteroid hazard is presented.     

Transient flashes of electromagnetic radiation in the upper atmosphere

Experimental data related to electric discharges in the upper atmosphere are considered. These discharges occupy enormous volumes of the atmosphere (up to 1000 km³) and are accompanied by optical radiation (in the UV, optical, and IR ranges), and also by gamma-ray radiation. Possible physical processes responsible for the evolution of such discharges are also considered.     

Features of rotational motion of a spacecraft descending in the Martian atmosphere

Angular motion at atmospheric entry is studied in the paper for a spacecraft with a bi-harmonic moment characteristic. Special attention is given to the case when the spacecraft possesses two stable balanced positions, and, hence, it can oscillate in dense atmospheric layers in the ranges of small or large angles of attack. The averaged equations of spacecraft motion are derived, which allow one to increase the speed of calculations by several orders of magnitude. A real example is presented, which concerns a spacecraft specially designed for descending in the Martian atmosphere.     

火星大气来流模拟装置CFD仿真与试验

根据我国火星着陆巡视器工作过程,其着陆发动机需要在相对火星大气高速迎风运动中可靠点火。由于巡视器着陆时发动机喷管出口气流与火星稀薄气流方向相反,目前无法通过理论计算准确获得着陆过程的动态流场对发动机起动过程的影响量值。为验证火星着陆环境下发动机点火的适应性,需要建立发动机的火星大气来流试验环境模拟条件。为模拟发动机在火星大气条件下的相对运动,在真空舱内发动机保持固定,前端设置环形来流形成装置,该装置在发动机喷管周围形成一定速度的逆向来流包络。采用数值模拟技术结合试验验证方法,在火星着陆器巡视器主发动机性能考核试验中,针对来流的形成装置开展了设计研究工作。来流模拟试验测试数据表明:在确保贮箱供应压力稳定的条件下,来流模拟系统能够形成100~200 m/s速度的稳定来流,发动机在来流下能稳定启动工作,真空舱压力满足试验要求。     

Electrification of a rocket during its launch and motion in the atmosphere along active part of the trajectory

We studied the process of electrification of a rocket during launch and flight in the atmosphere at the active part of its trajectory. The values of charge, field strength, and rocket potential at the launch are estimated. Charging and discharging currents are determined for a rocket flying through clouds and precipitation, and solutions expressing the time variation of the rocket’s charge are found. The values of charge, field strength, and rocket potential are obtained as functions of time, together with the engine plume represented as a charged plasma structure. The rocket’s charge is shown to tend to an equilibrium state, and the time of reaching it is found. Mechanisms limiting the charge value are considered, and the conditions of origination of an electric breakdown (lightning) between the rocket and atmosphere are determined.     

Estimated corrections for the atmosphere in remote sensing problems

This paper makes an attempt to offer a unification of the procedure of atmosphere corrections in remote sensing problems, using a Monte Carlo method for the calculations.     

Ascending flows in the solar atmosphere and formation of the solar wind

Some morphological features of solar magnetic fields in the chromosphere and corona are considered based on studying various observational data. These data are compared to the results of observation of the solar wind and interplanetary magnetic field, as well as to the data on fluxes of solar cosmic rays. New specific features are found in the solar wind structure, and new additional indications of sources of the solar wind are obtained. The properties of the active regions and coronal holes are considered. A model of the ascending stream-like plasma flow is suggested. It flows around the discrete arched magnetic field tubes in the solar atmosphere and stretches them out into interplanetary space.     

Development of a complex prognostic model of the upper atmosphere and ionosphere

We consider possible stages of constructing complex models of the circumterrestrial plasma including both neutral and charged components in their interaction. At the initial stage it is suggested to use as a basis the empirical models of the upper atmosphere and ionosphere. These models have concentrated fundamental data about the near-Earth space (NES) accumulated for several decades of space exploration. The final goal is to construct a prognostic model which would allow one to calculate both long-periodic variations of the NES structure (they can occur over several decades of years and more) and short-period disturbances with a characteristic time of about a day. In order to predict the results of anthropogenic effects it is proposed to construct imitation mathematical models that should allow one to calculate NES variations which can proceed at various model scenarios of anthropogenic actions.     

Satellite orbit perturbations in a dusty Martian atmosphere

In this paper we calculate the effect of atmospheric dust on the orbital elements of a satellite. Dust storms that originate in the Martian surface may evolve into global storms in the atmosphere that can last for months can affect low orbiter and lander missions. We model the dust as a velocity-square depended drag force acting on a satellite and we derive an appropriate disturbing function that accounts for the effect of dust on the orbit, using a Lagrangean formulation. A first-order perturbation solution of Lagrange's planetary equations of motion indicates that for a local dust storm cloud that has a possible density of 8.323×10⁻¹⁰ kg m⁻³ at an altitude of 100 km affects the orbital semimajor axis of a 1000 kg satellite up −0.142 m day⁻¹. Regional dust storms of the same density may affect the semimajor axis up to of −0.418 m day⁻¹. Other orbital elements are also affected but to a lesser extent.     

Simulation of space cabin atmosphere

The Soyuz 22 space cabin atmosphere was studied for volatile organic trace contaminants. By gas chromatography the following constituents were identified: methane, ethane, heptane, methanol, ethanol, n-propanol, acetaldehyde, acetone, ethyl benzene. Except for acetone, concentrations of the above compounds were close to the values determined in the mock-up experiments.     

Determining total ozone content in the atmosphere using satellite measurements

In this paper a simple method is presented which is applicable for fast determination of total ozone content in the earth atmosphere by using IR radiation intensity data from satellite measurements. The method is based on the property that transmittance of inhomogeneous atmosphere in the 9.6 μm band can be well approximated by the transmittance of a homogeneous ozone slab characterized by its effective pressure and temperature. The effective pressure and temperature were determined as mean values weighted by the average ozone profile of each season. The transmission functions were computed from an empirical formula. Free parameters in the formula were determined by a multiple regression scheme, on the basis of the transmittance data either measured in the laboratory or evaluated by computations using a line by line integration procedure. The main advantage of the described method is an easy and fast computation procedure. According to comparison with direct ozone sounding the accuracy is good enough: the average relative error lies between 5 and 7%.     

Investigation of the Venus atmosphere and surface by the method of radiosounding using Venera-9 and 10 satellites

Using the Venera-9 and 10 satellites radio occultation measurements of the atmosphere and bistatic radar measurements of the surface of the planet Venus were realized from October 1975 to March 1976. The altitude dependence of the molecular number density, pressure and temperature on the night and day sides were derived.An analysis is made of the stratified structure and turbulence in the atmosphere of Venus. The results of pressure measurements on the surface by the method of bistatic radar are presented. The diagrams and the tables of the parameters of the atmosphere are given.     

Estimation of the Probability of Capture into a Resonance Mode of Motion for a Spacecraft during Its Descent in the Atmosphere

The estimation of the probability of capture into a resonance mode of motion is considered for a spacecraft with a small asymmetry during its entry into the atmosphere. It is assumed that the initial conditions of spacecraft motion are distributed uniformly in some sufficiently small domain. The problem is solved for the equations of spacecraft motion linear with respect to the angle of attack. An analytical estimate of the probability of the spacecraft capture into the resonance corresponding to an ascending branch of the velocity head is obtained. The emphasis in the analysis of the estimate is made on the effect of the spacecraft asymmetry type on the probability of capture. A comparison of the estimate with the results of numerical computation is carried out. A model problem concerning the construction of the domain of the spacecraft center of mass locations, most dangerous from the point of view of the realization of the stable resonant modes of motion, is solved.     

Structure of the Venusian atmosphere from surface up to 100 km

The goal of this paper is to summarize the experimental data on the atmosphere of Venus obtained after 1985, when the VIRA (Venus International Reference Atmosphere) or COSPAR model was published. Among the most important results that have appeared since then are the following: measurements of the vertical temperature profile by the VEGA spacecraft with high precision and high altitude resolution; measurements made with balloons of the VEGA spacecraft; radio occultation measurements of Magellan, Venera-15, and Venera-16; and temperature profiles derived from the data of infrared spectrometry obtained by Venera-15. The new result as compared to VIRA is the creation of a model of the atmosphere in the altitude range 55 to 100 km dependent on local time. This model is presented in our paper in tabulated form.     

Quantitative characteristics of long-term changes in parameters of the upper atmosphere of the earth over the 1966–1992 period

On the basis of the long series of mass-spectrometer measurements conducted in rocket experiments during 1966–1992 period, long-term changes in the structural parameters of the upper atmosphere within the 100–160 km height interval at equatorial, middle, and high latitudes of the Northern Hemisphere of the Earth are quantitatively estimated. At all latitudes statistically significant negative trends are revealed in the turbopause height, temperature of the neutral atmosphere, and atomic oxygen concentration. Since the contribution to the obtained quantitative estimates of the trends caused by long-term solar-induced factors does not exceed 15–20%, a conclusion is drawn on the anthropogenic nature of the changes having occurred in the upper atmosphere.