Fuel grain for spherical boost-sustain rocket motor

Claim 1

In a spherical solid rocket motor for delivering boost-sustain operation having a rocket motor casing; a thrust nozzle, a fuel grain igniting means, a fuel grain within said rocket motor casing, comprising: an internal cavity formed by a plurality of regressively burning star point first segments and a plurality of second segments, having parallel side walls, positioned between the star point segments and extending into the cavity a greater distance than the star point segments; said second segments having side walls substantially parallel to the side walls of the star point segments; said second segments having means, including the parallel side walls, for providing a large burning surface and a sharp transition from boost to sustain operation; means, for providing a plurality of radially extending slots at the forward end of said fuel grain; and means for providing an unrestricted burning area at the end of the fuel grain adjacent the thrust nozzle.