This paper presents the foundation of a modular robotic system comprised of\nseveral novel modules in the shape of a tetrahedron. Four single-propeller\nsubmodules are assembled to create the Tetracopter, a tetrahedron-shaped\nquad-rotorcraft used as the elementary module of a modular flying system. This\nmodular flying system is built by assembling the different elementary modules\nin a fractal shape. The fractal tetrahedron structure of the modular flying\nassembly grants the vehicle more rigidity than a conventional two-dimensional\nmodular robotic flight system while maintaining the relative efficiency of a\ntwo-dimensional modular robotic flight system. A prototype of the Tetracopter\nhas been modeled, fabricated, and successfully flight-tested by the Decision\nand Control Laboratory at the Georgia Institute of Technology. The results of\nthis research set the foundation for the development of Tetrahedron rotorcraft\nthat can maintain controllable flight and assemble in flight to create a\nFractal Tetrahedron Assembly.\n