At laser intensities over 1016‒1018 W/cm2, relativistic effects must be taken into account, since the energy of electrons oscillating in the laser radiation field is comparable to relativistic energies. The distribution function of fast particles can be obtained by solving the Fokker–Planck equation. Since the distribution function of the plasma particles of the laser plume is close to Maxwellian, the Rosenbluth-Trubnikov potentials are used to describe the diffusion and friction coefficients in the Fokker–Planck equation. The problem is posed and solved in relation to new types of propulsion engines in the aerospace industry.