We examine the use of the interplanetary substance as a possible fuel for spacecraft's plasma thrusters for interplanetary flights. The solar radiation is considered as an energy source for the ionization and the acceleration of particles of captured space environment that is used as drop weight. The method of capturing the space environment, which is dependent on its density, the velocity of the spacecraft, and the power of solar radiation, defines the technical feasibility of this scheme. Both pulsed and continuous operations of the plasma accelerator are possible under some conditions as shown in the estimates.