Masten Space Systems proposes a Phase I SBIR effort in support of the preliminary development of a 25,000 lbf additively manufactured (AM), aluminum alloy, liquid oxygen (LOX)/methane engine for in-space propulsion. The use of AM processes have the potential to realize transformative mass, cost, and schedule savings over current state of the art in the 25,000 lbf thrust class that will enable human and robotic missions to Mars and beyond. The proposed effort will utilize Masten?s experience in engine design and fabrication as well its experience with AM processes. Masten has prior experience in the use of additive manufacturing for high thrust engine hardware and will build on this heritage for the in-space propulsion application proposed in this Phase I effort. Specifically, the proposed AM engine design approach employs innovative regenerative cooling channel geometries that leverage the design freedom of AM to maintain adequate chamber cooling.