Abstract: A solid propellant grain for a rocket is encased in and bonded to an elastomeric insulation sheath. Stresses that would occur between the propellant grain and the rocket case as a result of differential expansion and contraction if the grain were bonded to the case are eliminated by an expandible bearing sleeve that is bonded to the elastomeric sheath. The bearing sleeve is made of noncombustible material and comprises a series of overlapping segments that permit longitudinal motion of the propellant grain relative to the rocket case. The segments may be formed either by separate hoops or by a tape that is wound in a helical pattern on the elastomeric sheath. Since the segments of the sleeve overlap, the rocket case is always protected from hot gases. Hence, the sleeve also functions as a part of the insulation for the rocket case.