Introduction: OctoGarden - Gardening Concept for Use on the International Space Station
For the Growing Beyond Earth contest, I decided to create a cube enclosure that could not only serve as a suitable environment for plant growth in microgravity, but one which would also have compartments to hold tools, water supply bags, electronics, and wiring.
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 offer the ability to grow as many plants as possible. This design would run into problems when trying to grow plants on Earth, but if you were in Space it seems foolish not utilize the lack of gravity right?
In working through this design it seems like it would be most beneficial for seed to early stage plant growth. Taking this into account, the cube would probably be best suited for research purposes to test various lighting setups as well as conducting experiments on how different amounts of water affect plant growth.
However, this could also eventually be a great way to incubate early stage plants and then transfer them to a larger enclosure after they have started to mature.
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Step 1: Outer Framework
The outer framework was designed with the idea that a prototype could be 3D printed entirely on a commercial size 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 reworked so the entire framework could be built out of aluminum (or another space grade alloy) for increased strength and durability.
The framework features a storage space for supplies and replacement parts in the top left corner, two triangular water supply areas in the bottom, and four guide rails to allow for the insertion of the OctoGarden frame.
Step 2: Stepper Motor System
Next are two stepper motor systems located along the bottom sides of the framework to help transfer water from supply bags to the plants themselves via interconnected tubing.
The stepper motor is housed 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 rod are connected to screw nuts that are joined with a sliding wedge that will move back and forth to squeeze 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, 2 push button switches (per side), screw nuts, threaded rod, and straight rod.
Step 3: Accordion-Style Water Supply Bag
Inside the bottom triangle holding areas are open spaces designed to hold accordion-style bags which are filled with a water supply.
Whereas a normal bag of water may be susceptible to getting hung up, twisting, or catching on parts, this accordion style bag would be beneficial in squeezing water in a straight line direction while ensuring that all droplets are forced to the front.
As seen in the picture, the stepper motor system squeezes water in these bags to the front which is done using attached forward and backward push button switches. Since there would be a lack of suction force in space, this would be a viable method for transferring water from the accordion bags through the attached tubing to the garden.
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 customization gives astronauts a way to test multiple light combinations on separate plants which would allow for easy 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 intended to keep out any gases (such as ethylene) or particles from entering into the enclosure unwantedly. There will also be a temperature regulator included which can 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 that is meant to store electronics and wiring used to power LED strips, stepper motor systems, the air scrubber, and a front touch screen to control the LED's.
The top of this triangle is also the location of the connection point where the LED Tube is joined to give a power source to the LED strips. The wiring is fed from inside the Power Triangle through the center of the LED tube where it is fitted into its sections.
Step 7: OctoGarden Frame
Similar to the outer framework, the OctoGarden frame is intended to be 3D printed in one solid piece. The garden is meant to act as a removable holder that can store up to 24 separate plants and have integrated tubing to water each one 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 then connected to a water receptacle on the front of the structure.
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 built into the OctoGarden frame to be connected with each pillow.
Step 10: OctoGarden Insert
The OctoGarden frame has 4 guides 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 the accordion bag's water supply up through a 3-way valve thus filling the syringe.
After the syringe is filled, the 3-way valve should be switched to open the valve to the water receptacle on the front of the OctoGarden. This water is then pushed out of the syringe into the designated plant pillow via the integrated tubing. Using the syringe design allows for measurements of how much water is being supplied to each individual plant pillow.
Step 12: Concerns
One downside of this garden is that plant growth may be limited compared with a traditional setup. As the growth height is shorter than a bottom up design (approximately 160mm in this build), this prototype is probably more beneficial for volume growing and testing. As mentioned earlier though, this could also be a great option for incubating seed to small growth plants which can then be transferred to larger enclosures.
Another concern I have is possible damage to the LED Tube sticking out through the middle. I think this is remedied some by making the OctoGarden frame removable, but I do have concerns about the LED Tube being accidentally bumped into and broken with an errant hand or tool.
When designing this I didn't consider the small diameter of the tubing for transferring water, but after research I have worries that it may be difficult for water to reach the plant pillows due to capillary flow issues. 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. The good news is that the setup could be easily adjusted to accommodate larger diameter tubing for water transfer if needed.
Step 13: Areas for Upgrade/Improvement
After designing this, I noticed that 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.
Another area that may need tweaking is the LED Tube. With the current design, there may be light spillover onto other plants, so redesigning the dividers may help in narrowing the light to shine directly over each individual plant.
One 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 tubing into the frame of the OctoGarden is something that could be helpful for later versions. I don't think it would be terribly difficult to hollow out part of the frame where tubing could then be snaked through. Keeping loose tubing out of the way seems like it would be highly desired in the tight confines of a spacecraft.
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 would 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, this water transfer method may be able to be done by hand or with a simple manual design.
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 structure of a cube. However, this is something that needs attention to make the entire OctoGarden functional.
I wasn't able to find dimensions for Plant Pillows so the design may need to be adjusted to fit the pillows into the OctoGarden frame, but it shouldn't provide too much difficulty if it needs some tweaking.
Ultimately I feel that a design involving space missions needs to have the utmost focus on functioning properly and not breaking down. The key to that is by creating an enclosure and components which are not overly complex. I think 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.
This is an entry in the
Growing Beyond Earth Maker Contest