3D Printed Substrate

In preparation for long-term, manned, deep space missions, NASA requires a sustainable system for crop and food production. This system has a variety of benefits, including a fresh food supply, improvements in air quality, a lower need to resupply and psychological benefits for the gardeners. Specifically, NASA is attempting to improve and iterate their Vegetable Production System (VEGGIE), a plant growth unit currently aboard the International Space Station (ISS).

The VEGGIE unit is highly dependent on a variety of factors, including passive water delivery, growth lights, rooting pillows and cabin conditions. While previous teams have improved and redesigned water reservoirs, the primary objective of the project was to create a new substrate unit to replace the current rooting pillow design. The current design consists of an electrostatic bag filled with arcillite and a slow-release fertilizer pellet. The prototype design retains the fertilizer pellet for nutrient consistency, however the outer bag and arcillite fillings have been replaced with a 3D printed lattice block.

This lattice block has several key points that allow it to function in similar ways to the current design:

1. The lattice planes are porous, with each pore offset such that the overall porosity is the same as the arcillite filling.
2. The block demonstrates a wicking nature and is able to pull water upwards towards the roots. This minimizes time needed to integrate with the existing water reservoir.
3. The filament used is highly flexible and is able to pull apart to accommodate root growth.
4. The lattice planes are connected by microfibers left behind from the printing process. These fibers provide support for the growing roots and keep the lattice planes properly aligned.

The substrate block design seeks to reduce the payload costs by being entirely 3D printed. While filament would still need to be provided to the ISS, it is far less expensive than shipping arcillite due to the significantly lower weight. The final design has iterated the lattice plane concept and utilizes vertically placed planes with pores running parallel to the water reservoir. This design has reliably shown water uptake and retention and has been successful in growing multiple romaine lettuce plants. Future work should include further growth testing using multiple plant species, compost and reusability testing, food safety testing and microgravity growth testing.