Patent ID: 8281568

Claim:
A solid fuel rocket motor comprising: a cylindrical housing having an inside surface; a plurality of propellant cartridges disposed within the housing; an igniter disposed to ignite propellant material within the propellant cartridges; and a nozzle disposed to exhaust combustion gases out of the housing, wherein at least some of the propellant cartridges are castellated propellant cartridges; wherein the propellant cartridges are annular propellant cartridges each having an annular first cartridge end and an annular second cartridge end, with each of the annular cartridge ends bordered by a cylindrical inner surface of the propellant cartridge, and a cylindrical outer surface of the propellant cartridge; wherein the castellated propellant cartridges each have castellations at one or both of the first cartridge end and the second cartridge end; wherein the castellations each extend from the cylindrical inner surface to the cylindrical outer surface; and wherein most of the flow from combustion of the propellant is from combustion along the inner surfaces of the propellant cartridges, which goes longitudinally past the inner surfaces of the cartridges, and through the nozzle; wherein each propellant cartridge comprises an open-ended essentially cylindrical case having an outer surface, an inner surface, a first end, and a second end; and an annular cylinder of propellant material having an outside surface and a longitudinal cavity, the outside surface proximate to the inside surface of the case; and wherein a total cross-sectional area of the castellations of the plurality of propellant cartridges is sufficient to reduce a maximum pressure differential between a pressure within the longitudinal cavity and a pressure within interstitial spaces between the outside surfaces of the propellant cartridges and the inside surface of the housing to less than a predetermined maximum pressure value; wherein the castellations reduce the maximum pressure differential to 400 psi or less.