Modular spacecraft bus system and associated methods

A method for manufacturing a modular spacecraft system, the method comprising:

• assembling a propulsion assembly, the propulsion assembly including a fuel tank, a plurality of legs, and a frame that connects the fuel tank and at least one of the legs, wherein the plurality of legs are exterior to the fuel tank for supporting the propulsion assembly, and each one of the plurality of legs includes a top end and a bottom end;
• testing the propulsion assembly for spaceworthiness;
• assembling a top plate assembly, the top plate assembly including a top plate, the top plate including a first set of bolt holes and a first set of openings, the first set of bolt holes for attachment of the top plate to top ends of the legs of the propulsion assembly, and the first set of openings for attachment of a top payload thereto;
• independently testing the top plate assembly for spaceworthiness;
• assembling a bottom plate assembly, the bottom plate assembly including a bottom plate, the bottom plate including a second set of bolt holes and a second set of openings, the second set of bolt holes for attachment of the bottom plate to bottom ends of the legs of the propulsion assembly, and the second set of openings for attachment of a bottom payload thereto;
• independently testing the bottom plate assembly for spaceworthiness;
• and
• integrating the propulsion assembly, the top plate assembly, and the bottom plate assembly to form the modular spacecraft system,
• wherein integrating the propulsion assembly, the top plate assembly, and the bottom plate assembly includes:
• affixing the top plate attached with the top payload to the top end of each one of the plurality of legs through the first set of bolt holes, wherein the top plate is the top of the fuel tank in an assembled modular spacecraft system, and
• affixing the bottom plate attached with the bottom payload to the bottom end of each one of the plurality of legs through the second set of bolt holes such that the top plate assembly and the bottom plate assembly are spaced apart from one another by the propulsion assembly disposed therebetween, wherein the bottom plate is the bottom of the fuel tank in the assembled modular spacecraft system.