Patent ID: 8601790

Claim:
An apparatus for providing an exhaust, comprising: a fuel grain comprising: a solid fuel body; a solid fuel core; an entry disposed along one end of the fuel grain and having an entry gas flow; an exit disposed along another end of the fuel grain and having an exit gas flow for passing a gas through the fuel grain between the entry and the exit; at least one initial burn channel having side walls disposed through the fuel grain and extending between the entry and exit of the fuel grain, the solid fuel core at least partially defining the initial burn channel side walls; and at least one buried channel disposed in the fuel grain and including a first end and a second end, the first end separated from the initial burn channel side walls by a portion of the solid fuel core, the second end opening into the initial burn channel, the solid fuel core at least partially defining the at least one buried channel between the second end and the first end, wherein flowing the gas into the entry burns the sidewalls which burns away the portion of the solid fuel core separating the first end from the initial burn channel side walls, thereby opening the first end into the initial burn channel and allowing the gas to flow into the first end, through the at least one buried channel, and out the second end.