Abstract: Methods and systems for mixing propellant formulations are disclosed herein. In one embodiment, a method of mixing a solid propellant formulation includes placing a first component (e.g., a polymer or fuel) and a second component (e.g., an oxidizer of suitable particle size) in a mix vessel. The method further includes mixing the first and second components together by rotating the mix vessel about a first axis and, during at least a portion of the vessel rotation, revolving the vessel about a second axis spaced apart from the first axis. In one embodiment, the first axis can be a vessel spin axis, and the second axis can be spaced apart from the first axis so that the vessel revolves about the second axis in a planetary manner. In another embodiment, the vessel can rotate about the first axis in a first direction while revolving about the second axis in a second direction, opposite to the first direction.