Abstract: A bi-propellant rocket motor having controlled thermal management is disclosed. The rocket motor produces thrust using a solid or gel-phase primary propellant that can be either fuel- or oxidizer-rich, with a complementary self-pressurizing secondary propellant selected to balance the primary propellant in terms of the equivalence ratio. The motor houses multiple propellant grains arranged in such a configuration that each chamber containing a primary grain serves as both propellant storage and the main combustion chamber for that propellant grain as it burns with the secondary propellant. The secondary propellant is stored separately, and the flow routed past the primary propellant chamber to provide cooling for adjacent primary propellant chambers limiting the temperature rise in the motor structure.