Resin Development for On-Orbit Fabrication of Spacecraft Structures by Direct Solar Photopolymerization

One of the paradoxes of spacecraft design is that spacecraft are destined to operate in orbit where maneuvering thruster firings produce stresses below 0.01 G, but the spacecraft must be strong enough (and heavy enough) to survive the roughly 10 G’s of linear acceleration and 50 G’s of vibration in a rocket launch. In this paper, we follow on previous work to develop and test an alternative: the post-launch freeform additive manufacture of a major communications satellite structural element in UV cured resin, using solar UV to trigger polymerization. Here we develop the chemistry of a UV curable liquid resin that not only has a very low (below our chamber limit of 0.2 kPa) vapor pressure post-degassing, but also is not dependent on oxygen presence to activate the thermal inhibitors that prevent premature polymerization. In tests, we successfully freeform 3D printed a small (60 mm) parabolic dish at chamber limit pressure using simulated solar UV flooding the chamber.