## 2 Analysis of Astrophysical Data
The observations in [17; 20; 22] indicate that approximately 25,000 to 45,000 tons of interplanetary dust settles on Earth each year, corresponding to a mass flow rate of \(J_{d}=0.79\div 1.42\) kg/s. For our analysis, let us consider \(J_{d}=1.11\) kg/s a characteristic value for the mass of the dust flow reaching the Earth's surface. On the other hand, this dust flux can also be estimated as a function of the cross-sectional area of Earth's orbit around the Sun and the density of interplanetary dust  
\[J_{d}=\mu_{d}n_{d}US_{E}, \tag{1}\]  
where \(\mu_{d}\) is the mass of a dust particle, \(n_{d}\) is the dust density, \(U\) is the speed of the dust flow relative to the Earth, and \(S_{E}\) is an effective cross-section of the Earth through which the dust flow enters the Earth's atmosphere. To determine the value of \(n_{d}\) near Earth, we shall proceed from the point that \(U\) coincides with the speed of the Earth's rotation around the Sun, \(v_{Et}=30\) km/s. This assumption considers the dust to be stationary, and the effective cross-section is considered to be a circle with a radius \(R_{ef}=R_{Et}+h\), where \(R_{Et}\approx 6371\) km is the radius of the Earth and \(h\approx 1000\) km is the height of the atmosphere, above which there are no collisions with particles. Using these astrophysical data and setting \(\mu_{d}\equiv\mu_{\Sigma}\), from Equation (1), we find \(n_{d}\approx 36\) cm\({}^{-3}\). Note that this result coincides in its order of magnitude with the experimental values in [15; 18; 19] in which the density \(n_{d}=10\) cm\({}^{-3}\) was observed in near-Earth space. Therefore, based on this information, we can estimate the dust density in the near-Earth space to be \(10\leq n_{d}\leq 36\) cm\({}^{-3}\). According to experimental data [11; 19; 22], the density of neutral gas in the solar system is much smaller than the density of the solar wind and dust. Therefore, as fuel for plasma thrusters, one may consider only the solar wind and interplanetary dust as a fuel medium. As can be seen from our estimations, in the near-Earth space (at a distance of about 1 \(A.U.\)), these components of the interplanetary medium provide the maximum density, \(n_{\Sigma}=n_{sw}+n_{d}\cong 12\div 41\) cm\({}^{-3}\). However, in order to use this value of density, we must consider the magnitude and direction of the solar wind flow relative to the ship. To simplify our estimations, we shall consider only a stationary, immobile interplanetary medium with a low density of \(n_{\Sigma}=10\) cm\({}^{-3}\). As a result, we shall obtain a rough assessment of the process under study, as shown below. To determine the possibility of using solar radiation for ionizing neutral atoms and their subsequent acceleration we must take the solar radiation power distribution \(W_{C}\) as a function of the distance from the Sun. As a characteristic temperature of the Sun, we take \(T_{S}=6000\) K at a distance of \(R_{S}=6.9\cdot 10^{8}\) m [11; 16; 23]. Then, using the Stephan-Boltzmann law, we find  
\[W=\frac{\sigma T_{S}^{4}}{(r/R_{S})^{2}}, \tag{2}\]  
where \(\sigma\) is the Stefan-Boltzmann constant. This dependence is sketched in Figure 2, and for the convenience of perception, the distances from the Sun to the planets that fall inside a sphere of radius \(R_{C}\) are labeled, where \(R_{C}\) is the distance from the Sun to the edge of the asteroid belt since there is no dust beyond this boundary. In the present case, the value \(R_{C}\) is the natural boundary of the area in which the proposed scheme can be used. The results presented in Figure 2 coincide with the experimental data [19; 20]. So, it is possible to use Equation (2) in order to make rude estimates in the near-Earth region. Again, we would like to emphasize that all values presented in this section must be considered from the point of view of the rude estimate below, which only shows the physical and technical feasibility of the present idea in principle.