Sprout Cube - the Microgravity Space Garden
by LuLusWorld in Workshop > Science
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Sprout Cube - the Microgravity Space Garden
I'm entering Sprout in the high school category for the Growing Beyond Earth contest.
Sprout Cube is a garden designed to work very efficiently in microgravity. When I first saw this contest I immediately was thinking about how the most plants could fit in a cube. I chose utilize the microgravity environment and use all six surfaces of the cube to grow plants on. Although transparent gardens look cool it may interfere with the direction the plants grow due to outside lighting. That is why I chose to have the walls mostly opaque. The structure of the cube is made so that it can be opened up from multiple sides for easy access. And that is the story of how Sprout came to be! In this instructable I will go over my research methods and my design for Sprout Cube. I hope you enjoy reading my instructable!
Note: The objects in the background are purely for decoration. The 50cm cube is the actual garden. Also note that I'm still a beginner with working in Tinkercad, so keep in mind that the renders aren't exactly accurate.
Understanding Microgravity
The definition of microgravity(sometimes called zero gravity) is when there is a very little amount of gravity. Some people think that there is ‘zero gravity’ in space although this is untrue, in order for planets to orbit correctly there needs to be a small amount of gravity. After reading some of NASA’s articles on microgravity I found out that 90% of earth's gravity touches the International Space Station(ISS). Like I was, you’re probably thinking “What makes everything float then?” The reason why things appear to float on the ISS is because they’re all in a free fall going at the same speed. Crazy right?
Knowing how microgravity works will help in making a space garden. I will have to make it carefully so that water and soil won’t be loose and just float away because this could result in damaging the station. Microgravity can also be an advantage, since there's very little gravity I don’t have to worry about what side the plants are facing. The plants can grow upside down rightside up or even horizontally!
Here are some websites with more information on microgravity:
https://www.nasa.gov/audience/forstudents/5-8/feat...
Growing Red Lettuce:
Before I start designing the garden I must first understand how red lettuce normally grows. In my research I found that red lettuce is usually planted about 1 inch apart in rows that are around 1 foot apart. That’s a lot of space(Ha-ha space)! The optimal growing temperature for the plants is around 50-75 degrees Fahrenheit. Luckily the ISS's temperature is usually at that range meaning the plant won’t need much temperature regulation. Red lettuce takes about 45-55 days to grow and the roots need to be kept moist but not with too much water.
In NASA's garden ‘Veggie’ the plants are really close together. Since it is a microgravity environment the plants leafs will be reaching for the light so it is less likely for them to get too crowded. Also since the lettuce are in separate pouches(plant pillows), each with their own soil then the roots won’t get tangled with other plants.
Check out this article:
Drafting a Design
This is a draft of my design based off the research I have done. The layout of Sprout, when it lays out flat, would be the shape of a cross. When the cube structure is put together the door would open downward instead of sideways. The different parts of the cube would be able to be 3d printed and would be attached together with magnetic hinges. The magnets would be strong enough to hold together but would still allow astronauts to unfold the cube for easy access to the plants. The plant trays would hold about 6-9 plants each, they could also allow smaller plant to grow under them when the other plants are taller. For the lighting it would be a sphere or a cube hanging in the middle either horizontally or sideways, one of the wires would be connected to power the other would be attached to the cube using a magnet. The water system will use a pump and carry the water to each plant through tubes. Each tube would have two or more flaps to control water flow.
Plant Watering System
Click the image above it's a GIF!
Now that I know about microgravity I understand that the water can just float away unless it’s absorbed into something. Water acts similar to gel in microgravity, this causes air bubbles to get stuck in the water. The current garden on the ISS named “Veggie” used plant pillows which were basically little pillows with a small slit for a plant to come out of. To water the plant pillows they used syringes to insert water into a tube that was connected to a plant pillow. This means that every time the plants need to be watered they have to manually inject water into six plant pillows! That's a problem that definitely needs to be fixed.
Based on how water floats in microgravity I made a 3d model and a GIF of what my system would look like(you can view the pictures above). There will be tubes on the sides of the space garden around six so that one would stick into every plant pillow. The tubes would have two or more flaps inside them so that when the plant pillows are being replaced it is less likely for water to escape. The tubing that carries the water to the plants will work in a similar way, it will have flaps in the tubing so it can easily be disconnected. This function will allow the different surfaces of the cube to be disconnected, making it accessible for repairs, or when replacing plants.
For the water container and pumping mechanism I needed to do some more research. It turns out that lots of pumps rely on gravity which won’t work in space. I found a few options that I thought would work well with my space garden. The first option would be to just use a syringe but all the tubes would be connected together making it less time consuming. Another option is a diaphragm pump, I found that this was used for plant automation watering systems often.
List of different types of pumps:
http://www.pumpscout.com/articles-scout-guide/pum...
Articles about liquids in space:
Lighting for the Plants
I think a sphere will work best for lighting. Previously I thought a cube might be better but it would take up more space and it also might not distribute the light to the plants as well as a sphere. For the lighting I will research more on what the exact light colors and brightness should be. I found in my researching that most plants don't actually need a night cycle, but it shouldn't hurt the lettuce if the light was off for 6-10 hours out of 24 hours to save some power.
In my research it seems the results of different lighting vary quite a bit across the web. Some have success with growing lettuce using far-red lights. Others have more success using a variety of different colors. In the end it seems to mostly come down to testing. The NASA's 'Veggie' garden uses mainly red, blue and green LEDs. Since they have actually seen results with it I would start off by testing Sprout with the same lighting.
Studies about growing lettuce in different lighting:
https://www.nasa.gov/mission_pages/station/researc...
Structure of Sprout
Above is the image of how the design of Sprout looks, it will use all possible surfaces to grow the plants. Every 8-10 days nine new plant pillows would be placed in the cube on one surface. Every time the plant pillows are inserted they should be in opposite directions of the current plants to avoid plants growing into each other. After the cube is full the nine plants that were inserted first would be harvested and then replaced. This system would allow the astronauts to have a consistent supply of lettuce.
Another advantage of my design is that it is able to be opened up for easy access to the plants. The hinges have magnets on them allowing the cubes sides to open. This design is made so that it could be 3d printed if desired.
Note: The objects in the background are decorative and are not actual parts of my design. The design is just the 50cm cube.
Combining Everything Together
Click the GIF above to see the different layers of Sprout when laid out!
The first image in the GIF shows the cube flattened out. Next it shows how the water system connects. The two black boxes are water pumps. There are two pumps instead of one so that the system doesn't get backed up with water. The white circles, with what may appear to be flowers inside, are fans. The four fans on the box will help to regulate airflow and help get oxygen to the plants roots. There is also room for some cables and sensors. If I were to make a prototype it would include a camera or two on the inside of the cube. It would also include a touchscreen LCD control panel connected to a Raspberry Pi Zero computer.
The plant pillows will be secured down with some absorbent fabric using Velcro to latch it down. The fabric will help to absorb any water that comes out of the plant. In the animation it shows how the plants will grow. The first set of 6-9 plants will be set on any surface of the cube. Then every 7-10 days another set of plants will be placed, but on the opposite side of where the first plant pillows were inserted. After that you just repeat the same steps until the cube is full. Once the cube is full you just harvest the plants that were placed in the cube first. Now you just rinse and repeat and you get to have fresh lettuce every eight days or so!
Final Notes
In the end this was a fun and interesting project. I learned a lot about space while doing research for my microgravity garden. I also got a lot better at using Tinkercad! Please keep in mind that this is the design phase in the contest so no testing has been done yet. If I get selected to build a prototype then I will test red romaine lettuce in the Sprout Cube and document the journey.
Thank you for viewing my instructable! If you liked it and want to support me, every comment, like, and vote helps!