The time for solar power satellites is now as a clean, scalable form of renewable energy that does not suffer the problem of intermittent supply. Our climate has reached a point of urgency that requires imminent address. Most solutions for renewable energy cannot supply baseload power or suffer from political constraints. Furthermore, renewables are expected to contribute only 10-20% of global power in most assessments. Yet, solar power satellites can solve these problems. However, the high cost barrier to solar power satellites has imposed an insurmountable hurdle. The source of this cost barrier is the cost of launching assets into space from Earth. We propose a solution that bypasses this problem by exploiting the emerging technology of self-replication. This is premised on the coincidence of deep in-situ resource utilisation of lunar material, robotics and 3D printing. We shall show how our efforts in developing 3D printing of electric motors, neural net-based electronics and magnetrons in particular indicate how self-replicating machines may be constructed from lunar material - we require only iron, nickel, cobalt, tungsten, selenium, silicon, and regolith volatiles sourced from lunar regolith and nickel-iron asteroid material associated with the south pole Aitken basin. In particular, we shall show how energy generation can be accomplished with greater efficiency using solar concentrators and thermionic conversion rather than photovoltaic cells. Selfreplication yields an exponential population of machines - universal constructors - That can 3D print enormous numbers of small solar power satellites and pump them into Earth orbit. The capital cost is in the initial launch of a 10-15 tonne seed to the Moon from which the solar power satellite spawns.

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Keywords 3D printing, In-situ resource utilization, Self-replicating machines, Solar power satellites
Conference 68th International Astronautical Congress: Unlocking Imagination, Fostering Innovation and Strengthening Security, IAC 2017
Ellery, A. (2017). Exponential populations of solar power satellites tending to zero specific cost. In Proceedings of the International Astronautical Congress, IAC (pp. 8354–8366).