Introduction: OctoGarden - Gardening Concept for Use on the International Space Station
For the Growing Beyond Earth contest, I created a 50cm cube enclosure that would not only serve as a suitable environment for plant growth in microgravity, but one which would also have compartments to hold supplies, tools, water supply bags, and electronics.
Instead of a traditional "bottom up" design, this prototype incorporates an octagonal cylinder garden to make use of the limited amount of working area and offers the ability to grow as many plants as possible. This design would obviously run into some problems when trying to test out on Earth, but if you were in Space it seems foolish not utilize the lack of gravity to your advantage.
Step 1: Outer Framework
The outer framework was designed with the idea that a Phase II prototype could be 3D printed entirely on a commercial or extra large print bed such as a Creality CR-10 S5 which has a 500 x 500 x 500mm print area.
When switching over to a production ready model, it would need to be adjusted so the entire frame could be built out of aluminum (or another space grade alloy) for increased strength and durability.
In the pictures above, the framework features a storage space for supplies, tools, and replacement parts in the top left corner. In the bottom two corners are triangular sections meant to hold and distribute the water supply. Finally there are four guide rail openings which allow for the insertion of the OctoGarden frame.
Step 2: Stepper Motor System
Next are two stepper motor setups that will be located along the bottom outside edges of the framework to help in transferring water from supply bags to the plants themselves via interconnected tubing.
The stepper motor is surrounded in a small case and connected to an 8mm threaded rod (on the bottom) and an 8mm solid rod (on the top).
The threaded and solid rods are connected to screw nuts which are joined to a sliding wedge that will move back and forth to squeeze the water supply bags stored in the bottom.
The following components may be used in building out the stepper motor systems: a sliding wedge, microcontroller, stepper driver, wiring, push button switches, screw nuts, threaded rod, and straight rods.
Step 3: Accordion-Style Water Supply Bag
Inside the bottom triangle holding spaces are areas designed to store accordion-style bags filled with a water supply.
Whereas a normal bag of water may be susceptible to getting hung up, twisting, or catching on parts; an accordion style bag would be useful by squeezing water in a straight line direction ensuring all droplets are forced to the front.
As seen in the picture, the stepper motor system works by squeezing and moving water in the bags forward using push button switches located on the front of the framework. Attached to these bags are quick connect nozzles that can link tubing between the supply bag and a syringe for purposes of water transfer (will be described in later sections).
Step 4: Addressable LED Tube
This custom tube allows addressable LED light strips to be fed and wired from a power source into separate compartments along the tube. It features 8 segmented rows and 3 different columns which allow for applying differing colors and light intensities to each individual plant
This element of customization gives astronauts a way to test multiple light combinations on individual plants which would allow for side by side comparisons and measurements of plant growth.
Step 5: Air Scrubber & Temperature Regulator
Attached to the top corner in the back of the framework is an Air Scrubber and Temperature Regulator. The Air Scrubber is intended to keep out any gases (such as ethylene) or unwanted particles from entering the enclosure. There is also a temperature regulator included which will suck airflow in and out from the surrounding environment to maintain optimal growth temperatures.
Step 6: Power Triangle (Hollowed Housing for Electronics & Wiring)
On the back side of the container is a hollowed triangle meant to store electronics and wiring used to power addressable LED strips, stepper motor systems, air scrubber, temperature regulator, and a touch screen to control the lighting.
In connecting the LED tube to the structure, the plan is to attach a neodymium ring magnet to the end of the tube and have attracting magnet(s) countersunk into the top of the triangle. The reasoning behind this is to allow for the tube to be semi-detachable while also acting as a safeguard in case it is bumped into and knocked off. This is something I feel I may need to work out a bit better and is explained more in the Concerns section below.
The wiring to power the LED's is fed from inside the Power Triangle through the center of the tube and magnets where it is then fitted into its individual sections. I intend on leaving as much slack in the wiring as possible to allow it to be moved around a bit when detached without damaging or pulling out the LED strips.
Step 7: OctoGarden Frame
Similar to the outer framework, the OctoGarden frame is intended to be 3D printed for a Phase II prototype. The garden is meant to act as a removable holder which can store up to 24 separate plants and has integrated tubing to water each plant individually.
Step 8: Water Receptacle & Tubing
After printing, tubing will be fed through three separate holes in the OctoGarden frame (8 sections in total) and connected to a water receptacle on the front of the structure. These receptacles are where water from the supply bags/syringe will be transferred to the plants themselves.
Step 9: Plant Pillows
Instead of creating my own plant containers, the garden is designed to hold Plant Pillows that have already been used successfully on the International Space Station (see above photos) as part of NASA's Veggie system.
These Plant Pillows contain a watering connection that will allow the tubing fed through the holes in the OctoGarden frame to be connected with each pillow.
In the event that I wouldn't be able to get my hands on Plant Pillows, I have 210D Nylon-66 fabric that I could heat weld to form makeshift sealable pillows for the sake of prototyping. I have previously built fully sealed air bladders with functional valves for another project and feel I could use this knowledge to quickly build a pillow that has a water inlet and opening for plants to grow out of if needed.
Step 10: OctoGarden Insert
The OctoGarden frame has 4 guide rails on each side that are meant to be inserted into the framework. Once lined up, the garden can be slid into the back of the enclosure and locked in place via a sliding latch located on the front.
Step 11: Watering Via Measuring Syringe and 3-Way Valve
Emulating again off NASA's previous work, I incorporated the use of a syringe for measuring the amount of water supplied to each plant pillow. The syringe will be filled by pressing the forward push button switch on the stepper motor system to squeeze an accordion bag and force water up through a 3-way valve thus filling the syringe.
After the syringe is filled, the 3-way valve will be switched to open the valve to the water receptacle on the front of the OctoGarden. This water can then be pumped out of the syringe into the designated plant pillow via the built-in tubing. Using the syringe allows for accurate measurements of how much water is being supplied to each individual plant.
Step 12: Concerns
One downside of this garden is that plant growth may be limited compared to a traditional setup. As the growth height is shorter than a bottom up design (approximately 16 cm in this build), this prototype may be more beneficial for volume growing and testing.
Another concern I have is possible damage to the LED Tube sticking out through the middle. I think this is remedied a bit by making the OctoGarden frame removable and also having the LED tube detachable. However, I do have concerns about the LED tube being accidentally bumped into and broken with an errant hand or tool. I think making sure this particular component is sturdy is very important.
When designing this I didn't consider the small diameter of the tubing for transferring water, but after some research I have worries that it may be difficult for water to reach the plant pillows in a microgravity environment. I'm not sure if this would even be a problem, but would like to do more research to see if this needs a redesign.
Step 13: Areas for Upgrade/Improvement
After designing this, I noticed one huge upgrade could be achieved by adding hinges to the OctoGarden frame which would make it possible to roll out like a mat (see photos above). This would be extremely helpful upon removal as it would allow for easy access to trim, study, and measure plants outside of the small container space.
I wasn't able to find exact dimensions for Plant Pillows, but based on my research it seems they come in different sizes depending on the type of plant used. This current design may need to be adjusted to fit pillows into the OctoGarden frame, but it shouldn't provide too much difficulty if it requires some tweaking. (For reference, the size of the plant pillows in this current mockup are 12 x 12 cm). If necessary, the garden frame could even be shifted from an octagon to a hexagon to accommodate larger plant pillows.
Another possible addition that could be explored is the use of measuring towers (see 2nd picture). Between these towers an elastic band could be stretched from the front to the back of the OctoGarden frame. The distance in this example is spacing every 10mm to allow for measurements to be taken.
Building a tubing system inside the frame of the OctoGarden is something that could be helpful for finished versions, but for a Phase II prototype I intend on keeping them located on the outside of the OctoGarden frame. With that said, I don't feel it would be terribly difficult to hollow parts of the frame so that tubing could be snaked through at some point. Keeping this loose tubing out of the way seems important in the tight confines of a spacecraft.
You'll notice that there is a bit of an empty section in the top right area of the framework. This was intentionally left open for the time being as that area is being reserved for the Air Scrubber and Temperature Regulator design. With that noted, there should be extra room left over in that spot in which another cubbie can be added.
Finally, I feel the water supply bags and stepper motor system may be unnecessarily complex and could be simplified. In the interest of eliminating possible failure points, this is something that probably needs to be reworked to get rid of the numerous electrical components and physical parts. This may reduce the chance of component failure and have the added benefit of lower power usage. As the water supply bags aren't important for measurement since they are simply pumping water to the syringe, I've pondered whether this water transfer method may be better accomplished by hand or using a simple manually controlled system.
Step 14: Final Thoughts
You'll notice that schematics and diagrams for electronics weren't worked out in depth in this Instructable. I wanted to focus more on the structure and optimizing space within the confines of a cube. However, this is something that needs attention to make the entire OctoGarden functional.
I wanted to note that this submission is intended for the Professional category. If selected to grow "Outredgeous" red romaine lettuce for Phase II inside a prototype, my plan is to reach out to local contacts to aid in creating this structure as quickly as possible. I am currently the founder/inventor of a medical device startup which already utilizes 3D printing and electronics and am confident I could recruit and assemble a team with the necessary skills to help me if selected.
Ultimately I feel that a design involving space missions needs to have the utmost focus on functionality and reliability. The key to that is by creating an enclosure and components which are dependable and not overly complex. I feel this is a start, but I'd love to hear other people's opinions on the design and get thoughts on how it could be improved.
Runner Up in the
Growing Beyond Earth Maker Contest