Abstract: Stresses induced by differential expansion and contraction of the solid propellant grain and the rocket motor case to which it is conventionally bonded are obviated by bonding a special sheath to the propellant grain and attaching it to the rocket motor case only at its forward and aft ends. A thin layer of Teflon is confined intermediately between the sheath and the rocket motor case. The sheath is extended beyond the propellant grain and bonded to the case so that an unbonded section thereof extends between the zone at which it is bonded to the case and the propellant grain. The propellant grain joins the sheath by a surface fillet to relieve surface stresses at this juncture. A gastight seal is provided in the thrust nozzle of the rocket motor for pressurizing of the combustion chamber to inhibit radial shrinkage of the propellant.