Introduction: ISS Plant Habitat Design Concept

About: Making a variety of stuff

This is an entry into the highschool division.

I designed this concept for the Growing Beyond Earth contest. Since one of the objectives is to maximize growing space, I started thinking of the most optimal way of housing plants. I had an idea of having all the plants inside a massive tube and light in the center. I really liked this idea because it used the fact that there is no gravity in space to its advantage. The problem was I couldn't really think of a way to easily plant the plants in a tube, so I eventually thought of using an octagon as the frame since it had 8 straight edges that I could use.

Though it was not a requirement of the contest, I tried my best to also take into account the use of the "Made in Space" 3D printer aboard the ISS. Almost all frame pieces can be printed on the printer as I designed them with the printer's print volume in mind. Since quite a few pieces are large volume-wise but not necessarily heavy, I think 3D printing them on the ISS would be a perfect solution, since you would only have to transport the compact filament up to the ISS and then print the pieces later.

This design fulfills many requirements such as producing the proper amount of light, surpasses the daily water requirement for 32 fully grown plants and more.

This is an entry into the highschool division.

Step 1: Frame

The first part of this project was making a frame. Since one of the requirements is to remain within a 50cm cube, I decided to design this first. I chose to make the outer frame of 20mm by 20mm T slot framing for a few reasons. The first being if I were to make a prototype of this, I could very easily construct the frame since T slot framing just snaps together. Secondly, other types of T Slot framing has already been 3D printed on the ISS printer, so this could be aswell(though it would have to be printed in sections because of the volume limitations). After this, I added a triangle in each corner to hold racks for the growing beds. These also act as corner supports.

Step 2: Growing Beds

To house the plants, I decided to make these growing trays. To house the plants and soil I decided to go with the same concept that NASA is already using with "plant pillows". Unlike the already in use plant pillows which have quick connect couplings for water, I decided to use my own method. I was trying to think about how plants absorb water in space and I thought that just spraying water on the top of soil wouldn't really work since water doesn't want to naturally fall down in zero gravity. I then came up with the idea of a water "needle" to inject water at the bottom of the plant pillows. In the photo of the whole bed, you can see how there are the needles along the water tube which are stuck into the plant pillows.

I also made each bed have a track that matched the racks on the frame so each bed could be pulled out individually. They also all have the same track so they can be swapped around the octagon for whatever reason. You will also notice there aren't any dividers between the plant pillows like there currently is on the "Veggie" system. This is for future modularity. If a study were to be ran where there is only 1 massive plant pillow, that is completely possible since there aren't any dividers in the way. Because of this, I was able to fit 4 plant pillows a bed, but that could be way more or way less depending on how the pillows are arranged.

The growth beds along with "water needles" would be all 3d printed and the tubing would be 1/4 irrigation tubing.

Step 3: Water System

The water system in this design is actually pretty simple. Firstly there is a tank that holds about 3200 ML of water which satisfies the requirement of 100 ml/day once plants are fully grown assuming there are 32 plants. This then is routed through a tube to an array of peristaltic pumps. I chose peristaltic pumps for 2 reasons. Firstly, they are very precise, which is necessary in knowing how much water each plant is getting. Secondly, no components are ever in contact with the water(not counting the tube) which is good because that means no impurities will be in the water stream. These are all mounted under 1 of the grow beds in the corner of the frame. Lastly, this water is pumped to each plant bed where there is a quick connect on the end of each tray (see image).

I should note that in the photo there are 8 peristaltic pumps. I did this just so you can have individual control in what each plant bed is getting, but this is not necessary. If all the plants are getting the same amount of water, 1 pump will suffice and if you want each individual pillow to get their own water, you can have 32 pumps(I was actually able to fit 32 pumps into empty space in the frame). Also, It looks like none of the tubes are connected in the photo but I just could not get all of them in 1 screenshot.

Step 4: Air Filtration System

After reading how the veggie system currently operates, I read that filtration of the air in the growth chamber is necessary since the air aboard the ISS is extremely different than the air on earth. I also read how toxic the gas Ethylene(which is present on the ISS) is to plants was so I decided to build in a filtration system. This was made up of 2 parts, an intake, and exhaust. The intake is at the top corner of the frame and the exhaust is on the opposite bottom corner of the frame so air will properly circulate. For the intake, the first part is an Ethylene filter followed by a standard air filter, then 2 high-efficiency fans. This will bring in clean air for all the plants to intake. I then made an exhaust system as well. This is pretty similar to the intake system but instead of intaking air, it is exhausting it. It has a filter as well to filter out any particulate in the growth chamber from going into the main station of the ISS. If a veggie pillow were to break and soil was to be shot out of an exhaust fan, the results could be disastrous. Having a filter before the exhaust fan remedies this. This system can also be used to control temperature and humidity by intaking or exhausting cooler or warmer air.

Step 5: Movable Light Rod

To give the plants light to grow, I put an octagonal rod in the center of the chamber. I then lined the entirety of it with UV led strips to simulate sunlight. Originally I was just going to connect it to the backplate of the frame but I had an idea. Let's say each growth bed had a different type of plant, and one of them was getting very tall and was about to run into the light. This would obviously be problamatic and you would be forced to harvest the plant. To remedy this, I made the light movable through an arm. Shown above is a video showing all positions the linkage could move in. As you can see with just 2 simple arms, you can move the grow light anywhere, to be closer or farther away from a certain plant. The wire would be fed through the arm and to the bottom of the frame(not shown in the animation).

Just to be clear, the arm is not motorized. It is just moving in that video to show the possibilities of how It can move. It can also perfectly stay in the center of the chamber if needed.

Step 6: Sensors and Control

To better control and monitor the plants I have added an Adafruit Grand Central board along with various sensors as well as a touch screen for control. Besides growing crops, another big purpose for starting to grow plants in space is for data gathering. To precisly monitor this data, accurate sensors are key. In the growth chamber, are 4 humidity/temperature sensors (4 placed in various locations to avoid outliers in data), a flow rate sensor going to each growth bed, an air quality sensor to detect harmful gasses in the chamber, and finally a touch screen for manual growth light and pump control. All of these sensors will make sure the plants are in an optimal growing environment constantly. Data can also be gathered from all of these sensors and more.

The board and electronics would be housed under one of the grow beds just like the pump array. The touch screen would be on one of the triangular panels on the front side for easy use. The touch screen would just be for basic commands such as manually turning lights, pumps, or fans on or off or manually overriding the system.

Step 7: Thanks for Reading/conclusion

Thanks for reading! A few notes on this project: I think that If I were selected I could quickly construct a prototype for phase 2 of the competition. As I have mentioned throughout this lots of the components are very easily 3D printable(which I have access to) so I could quickly make this a reality.

You may notice that the plumbing and electronics are not completely fleshed out. I tried to design more around the use of space and making sure I was within the boundaries and not so much the specificities. Despite this, I think I would be able to make both the electronics and plumbing work well if I were to make a prototype. I think both the electronics and plumbing would be quite easy for phase 2 since only 1 pump would be needed since all of the plant beds would have the same water requirements(since they are all growing the same plant). I am quite familiar with Arduino programming and development so I could precisly control everything with my prototype. Finally, all of those sensors and electronic parts that I mentioned in steps earlier? All of them are available from Adafruit(Thanks for sponsoring this!)

Thanks again!

Growing Beyond Earth Maker Contest

Runner Up in the
Growing Beyond Earth Maker Contest