Traditional additive manufacturing processes, especially those that make use of liquid resin as the feedstock, are constrained by the gravity environment on Earth. Gravity prevents extrusion into free space without sagging, which requires the use of support material to prevent. In a microgravity environment, extrusions into free space that would normally sag can proceed unimpeded, allowing for the creation of structures that could not be produced in a gravity environment.
Our original approach demonstrated this using a hybrid extrusion process we developed, which can create 3D structures (such as coils) from feedstocks of flexible metal wire and photocurable resin, where the wire is bent into a 3D shape and evenly coated with the resin. We then pivoted to creating flexible "skins" in the desired shape that would then be filled with liquid resin and cured with UV light through the skins. These skins are very lightweight and flexible and are incapable of holding their shape in 1g, but still form the resin into the desired geometry. These skins can be produced on Earth and transported to space compactly, before being unfurled and used to create the shapes out of resin. After the resin cures, the skins can be cut away leaving the finished part.
In November 2022, this experiment was flown to the ISS aboard CRS-26, a NASA resupply mission operated by SpaceX with their Cargo Dragon capsule atop a Falcon 9 rocket, for a 45-day stay in space. Multiple skins were filled with resin, and then cured along with static pre-filled samples.
NASA chose to feature this experiment in their pre-launch coverage:
- NASA Press article
- NASA Video
- Interview with team member Martin Nisser before the Nov 22 launch attempt
Additional sample of varying geometries will be flown on an additional parabolic flight, focusing on rapid filling and curing of the skins - to fit in the short windows of microgravity that the parabolic flight affords. The increase mass and volume allowance of the parabolic flight will allow for many more samples of additional geometries to be generated, along with more powerful curing lights.