Vol 57, No 4 (2019)

Results of experimental studies of the electron concentration and near-solar plasma velocity dependences on the heliocentric distance obtained in 1970–2012 by the method of radio transillumination by signals of spacecraft for the region of 3–50 solar radii are presented. A comparative analysis of different approximations of these dependences is given and it is shown that joint analysis of the data on the plasma velocity and concentration with allowance for independence of the plasma integral flux on the heliocentric distance makes it possible to find analytical expressions corresponding well to experimental data. Analytical approximations and graphs of dependences of the velocity, concentration, acceleration, force, and kinetic energy on the distance in the regions of solar wind acceleration for low and moderate solar activity are presented.

The paper theoretically studies the process of formation of volume charge in a spacecraft body under action of electron fluxes of Earth’s radiation belts and other cosmic particles, as well as the generation of induction currents caused by geomagnetic variations. The BLITS and BLITS-M satellites, which have a spherical configuration manufactured entirely of dielectric materials as well as the metal WESTPAC satellite, are considered. The relative simplicity of the form of a dielectric satellite allows one to obtain an analytical solution to the problem and calculate the distribution of fields and charges inside and on its surface. This solution shows that after the establishment of the stationary mode, charges accumulate mainly in a narrow layer near the satellite surface. According to the obtained estimates for low orbits, the electric field strength in this layer is below the threshold value corresponding to the breakdown of uniform dielectric in laboratory conditions. Nevertheless, one can expect the appearance of local electrical breakdowns and microdestructions in the dielectric during increasing solar activity accompanied by an increase in cosmic-ray fluxes. From this point of view, space experiments, in which dielectric destruction was observed during long-term exposure to radiation, can be interpreted as the result of accumulation of microdestructions similarly to fatigue destruction of materials under long-term load. For passive satellites similar to WESTPAC manufactured of conductive materials, the magnetic moment of induction currents in the spacecraft body is estimated. According to these estimates, the interaction of this moment with the geomagnetic field leading to the precession of the axis of the satellite’s rotation is most significant for Pc5 geomagnetic pulsations.

An approach based on the so-called K-means method has been used to analyze the approximation of gravitational potential of irregularly shaped celestial bodies as the potential of three gravitating balls. Relevant distributions have been constructed for asteroids Bacchus (2063), Kleopatra (216), and Eros (433). The proposed models have been compared with models that are based on alternative approaches [1–3].

The paper considers a method of the dose exposure decrease from the charged particles of Earth’s radiation belts (ERBs) affecting a reusable orbital transfer vehicle, which is launched from a low circular orbit into geostationary orbit using a nuclear electric propulsion system. The main idea of the method consists in numerical continuation of a solution of the minimum time problem with respect to an ionizing radiation dose accumulated at the end of a transfer. To do this, equations of motion of the orbital transfer vehicle are supplemented by an additional equation for the radiation dose, and the boundary condition for the dose at the right end is introduced. In calculating the dose, the AE8/AP8 MIN, AE8/AP8 MAX, and AE9/AP9 models of fluxes of charged particles of ERBs were used. By changing the insertion trajectory shape, it became possible to lower the radiation dose by 25–38% relative to the minimum time trajectory. At the same time, the transfer time increased no more than by 7% of the minimum time of launching into geostationary orbit, and the characteristic velocity expenses increased by 320–560 m/s.