Are Self-Replicating Machines Feasible?

Recent developments in three-dimensional printing technology have introduced the prospect of self-replication in the context of robotic in situ resource utilization on the moon. The value of three-dimensional printing lies in its potential to implement universal construction. A universal constructor is a machine capable of fabricating any physical product given an appropriate program of instructions, suitable raw materials, and a source of energy in an appropriate form. Such physical products include a copy of itself; a universal constructor is by definition a self-replicating machine. A step in this direction is represented by the RepRap three-dimensional printer that can print copies of its own plastic components. The three-dimensional printing of actuators and associated control electronics would represent an existence proof that an appropriately designed robotic three-dimensional printer system would constitute a universal constructor. In this paper, preliminary attempts have been outlined to develop self-replicating machines by addressing the three-dimensional-printable actuator and electronics aspects within the materials limits imposed by the moon. It is concluded that physical self-replicating machines are within reach. This lunar infrastructure offers space-based geoengineering solutions in the short term and solar power satellite solutions in the long term to the global climate crisis.