A recent paper Automated Additive Construction (AAC) for Earth and Space Using In-situ Resources is a meta snapshot of current thinking about building big stuff off planet (AAC) and is worth a read for anyone interested in the subject of off-planet 3D printing.
Launching mass into space is difficult due to the gravity well of the Earth which requires a
change in velocity impulse (Delta-V) of 9.3 – 10 km/s. This means that complicated space
transportation vehicles must be used to provide a large amount of energy transfer through the use
of chemical rocket propulsion. An additional Delta-V of 6.4 km/s would be required to land this
mass on the surface of Earth’s moon. If in-situ materials could be used on the moon (such as
regolith or regolith derived concrete), to build large civil engineering structures, then large
amounts of mass launched from Earth could be avoided, making space exploration more
More economical should be replaced with economically possible. They somewhat understand the major economic problems facing this field. At the current rate of $/gram to leave earth, there is no way we will be able to build anything significant off-planet because it would require a significant % of global economic output, which will never happen for political realities.
I was recently discussing with a Japanese acquaintance why Asia doesn’t have a competitive presence in the space. It struck me that the space industry is almost totally based on the standard of infrastructure, both machine and ‘human capital’ and that technology plays a secondary role. When asked why he located Space X in Southern California, Elon Musk’s answer indicated it was because it had the largest pool of space talent. If this is the case then it also means that any efforts for Automated Additive Construction off-planet will fail if they are not sufficiently robust and simple. Which should automatically disqualify several branches of research from consideration. For example, using ionic liquids or phosphoric acid for metal extraction seems incredibly complicated to scale to be of any use.
However, I do like the Molten Regolith Electrolysis (MRE) method for material extraction due to producing a metal alloy as well as a ceramic slag. It seems, as a general principle, that producing two distinct materials, especially one with favorable ductility, would open many more construction options. Multi-tools are going to be king in space construction for the same reasons an axe is preferable to a rapier for a frontiersman.
Which also leads me to believe that many solutions for space construction and in situ automated additive construction can be found by looking at the ways we overcame similar challenges crossing oceans for the first time or colonizing a virgin land.
It is also interesting to note that despite a clear upsurge in interest for in situ automated additive construction, Gartner doesn’t seem to have included it on their hype cycle anywhere.