Solid rocket motor with vortex inducing feature

A method comprising:

• burning a propellant grain structure in a solid rocket motor, the propellant grain structure defines an axial bore for flow of combustion materials and defines a propellant grain central axis (A), and the axial bore defines an axial bore central axis (A2) that is offset from, and parallel to, the propellant grain central axis (A);
• and
• generating a vortex flow of the combustion materials in the axial bore using a vortex inducing feature that includes a plurality of linear off-radial slots each defining a central axis that is non-intersecting with the axial bore central axis (A2), the linear off-radial slots are evenly distributed around the axial bore so as to form a pinwheel shape in which respective opens ends of the linear off-radial slot at the axial bore are uniformly spaced around the axial bore and respective closed ends of the linear off-radial slots are circumferentially offset by an angle from a respective radial axis passing through the axial bore central axis (A2) and the corresponding open end, wherein each closed end is circumferentially offset in the same circumferential direction, the linear off-radial slots upon burning of the propellant grain structure directing flow of particles of solid energetic and combustion gas radially inwardly toward the axial bore such that ejection of the flow in to the axial bore produces a vortex flow about the axial bore central axis (A2).