Rhombicube Microgravity Plant Growth Module

This submission is for the Professional category.

The Rhombicube Microgravity Plant Growth Module allows for the the growth of red romaine lettuce plants on each of the 18 square faces. This design is ideally suited for microgravity, using all dimensions of growing space, including the negative space beneath each plant as it grows. It is adjustable to keep the light just above the plants, to decrease the size of the module, and to chain modules together. The core of the chamber contains a growth medium and a tubing line to directly oxygenate all of the roots and deliver nutritive water. Below is a summary of all of its features:

- A Rhombicuboctahedron in shape, it has 18 square faces (for plants), 8 triangle faces (for pipe mounts and lighting).

- Angles maximize use of upper and lower negative spaces for plant growth (15x15 cm plant).

- Adjustable pipe lengths moves lighting closer and compresses the shape when plants are small.

- Pipes lighting positioned equally distant from all plants around the triangular faces.

- Core supports root growth medium on all square faces and tubing provides oxygenation to roots and delivery water.

- Pipes connectable to other growth modules to share water and oxygen delivery.

Custom made supplies:

- Laser cut acrylic 0.118 inch thick

- Laser cut Ripstop Nylon

Other supplies:

- 100% polyester

- 1/2 inch CPVC pipe at least 240 cm in length.

- CPVC 1/2 inch coupling x24

- Adhesive-backed Velcro

- Aquarium tubing

- Aquarium air pump

- Tubing connector (T shape)

- Syringe

Tools:

- Saw

- Scissors

I used Ponoko to cut my design into a sheet of 0.118 inch acrylic. I used acrylic for the prototyping because it was cheap, rigid, transparent, and not water permeable. I created the design using Inkscape software.

The template I designed allows for easy assembly and disassembly. It can be lain flat for transport and won't take up much space. After removing the protective film, the larger pieces can be quickly slotted into position to become the frame. There is plenty of open space between each of the compartments to allow root growth and air flow.

Once assembled, simple aquarium tubing can be slid though the designated hole on one of the triangular faces and an aquarium air stone attached. The purpose of the air stone is to diffuse the air in all directions, delivering it straight to the roots. When water is passed through the stone, it forms a fine mist which will function to wet the bottom-most surface of the growth medium.

Rationale: I decided to use 100% polyester for the prototype growth medium, which can be purchased at most craft stores. It is mold resistant, washable, and hypoallergenic. This medium doesn't possess great absorbent properties, making it a less than ideal growth medium on Earth, however, this may prove beneficial in microgravity where water does not drain and will cling to surfaces. In these conditions, polyester should be able to hold sufficient water without causing root rot as well as provide root support. It may prove to be a great lightweight alternative growth medium for microgravity.

The polyester needs to be cut to size to fit within each of the square faces of the frame.

The cover of the plant growth module was designed in Inkscape and cut using the online site, Ponoko. I chose ripstop nylon for the prototype because it is sturdy, thin, lightweight, water resistant, and breathable. The purpose of the cover is to prevent excess water loss and to hold the plant and growth medium in place.

I applied adhesive backed Velcro to the cover at areas which needed to be joined once wrapped around the frame. At this stage, the square faces will be covered, but the triangular faces will still be exposed. The 'X' in the middle of each square face is to provide room for planting the seed and growing the plant.

To cover the triangular faces and provide support for the pipes, I use the large and small triangle included in the original design. After applying the Velcro to the larger triangle, I push both it and the smaller triangle onto each side of a 1/2 inch CPVC coupling. The piece is then inserted into each of the triangular faces (8 total) and secured with Velcro to the cover.

The segmented pipes serve as adjustable legs for the module, stands for the LED lights, and a duct for the delivery of water and oxygen to the growth medium and plant roots.

To create the pipes, simply cut the 1/2 inch CPVC pipe into 10 cm sections with a saw and join together with 1/2 CPVC couplings. Add these to the existing couplings on each triangular face of the module. Three on each triangular face will result in a module that fits within a 50x50x50 cm cube. Note that it looks a couple cm too large in the bottom image because gravity is causing the legs to splay out a bit.

Take the length of tubing and splice in a T connector. One end should go directly into the air pump while the other connects to a syringe. The air will directly oxygenate the root systems of the plants and the airflow can be adjusted so it doesn't get too dry. The air will also push in the nutritive (containing fertilizer) water. It will form a fine mist coming out of the air stone in the core of the module, hydrating the roots directly. If multiple modules are connected together, further line splicing can deliver air and water to each of them.

Finish the module by adding LEDs to the ends of the module's arms. The arms are equally spaced between all the adjacent plants, providing uniform light to the module. As mentioned previously, the arms can also be shortened to bring the lights into closer proximity to the plants as they grow. While I used a battery operated LED in this prototype for illustration purposes, a fully wired system can be connected with the wires traversing the same pipe system as the water and air.