He is an author of a number of results on charged particle acceleration in space including the theory of charged particle acceleration during reconnection of the magnetic field lines in plasmas. During the work on the problems of cosmic ray physics and radio astronomy, he was involved in the studies of the transport of ultrarelativistic charged particles in Galactic magnetic fields doing calculations on the electromagnetic radiation emitted by the cosmic ray electrons, and was developing cosmic ray acceleration theory during supernova explosions. The results of these studies are summarized in the monograph: “Astrophysics of Cosmic Rays”, which currently is a desktop book for experts in astro-particle physics and in high-energy astrophysics. S. V. Bulanov was involved in the studies of the magnetic confinement of thermonuclear plasmas and in the physics of the plasma pinch discharges. He pioneered the capillary discharge theory and computer simulations important in applications of capillary discharge plasmas for X-ray lasers, for guiding high intensity laser pulses, and for active lensing of charged particle beams. In studying the problems of relativistically intense laser radiation interaction with matter are distinctly seen the characteristic features of S. V. Bulanov’s scientific style which combine the methods of theoretical physics with extensive computer simulations in direct connection with the experiment. The ultrarelativistic limit of the laser wake-field accelerator has been thoroughly described. For the first time he brought into the scientific community attention the wake wave breaking as a mechanism of the charged particle injection into the acceleration phase, including the idea of the transverse wake wave breaking. Nowadays this is a commonly used injection mechanism in laser wake-field accelerators. The magnetic field line reconnection in relativistic laser plasmas has also been foreseen, which is the key importance result in “laboratory astrophysics”.