This paper presents the results of an experimental study of the ignition and slagging characteristics for combustion of boron-containing solid propellants with ammonium perchlorate as an oxidizer under conditions modeling the operation of the gas generator and afterburner of a rocket-rarnjet engine. It is shown that the introduction of fluorine-containing additives into the propellant reduces the content and adhesion capacity of primary condensed combustion products (slags). The dependences of the ignition delay on the radiant heat flux density in the range 20-180 W /cm2 are obtained for model solid propellants containing boron, carbon, boron carbide, and slag particles collected in the gas generator.