Aeroponics in Space - High School Category

Growing vegetables and plants on the International Space Station (ISS) is very important, but there is not a lot of extra space on the ISS to grow vegetables and plants. There are many reasons why having vegetables and plants on the ISS is important. Growing vegetables and plants is important because it helps astronauts with homesickness because it reminds them of Earth and many people find taking care of plants relaxing. Having the ability to eat vegetables on the ISS is important because vegetables have a lot of nutritional value and gives the astronauts something fresh to eat. For our project, we chose to use aeroponics to grow Red Romaine Lettuce because it is a technique that has been proven by NASA to grow healthy vegetables and plants in space. When using aeroponics, plants grow larger and faster. There is also a decrease in water, fertilizer, pesticide usage as well as the amount of plant disease. This challenge was aimed to maximize the space in a 50cm by 50cm by 50cm box. We decided to make a square pyramid, turn it upside down, and cut the top off of the pyramid. We did this because it utilizes the most space and makes a funnel for aeroponics. We utilized fans and capillary action to divert the water to the pump. Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules which allows the water to flow down the base of our pyramid back to the pump. We used an Arduino board in order to make most of the work automated allowing the astronauts to be as involved as they wished in growing the plants. The materials we used were just used for the ease of making a model, but you could use different materials.

300 L/h submersible pump

Clear food grade plastic tubing

Arduino controlled fans x 8

LED Grow lights x 4

Miracle Grow Aeropot Grow Baskets x 60

Seed pillows x 60

Corrugated Plastic 6 clear sheets and 5 black sheets

Reflective self adhesive paper x 1 roll

360 degree Aeroponic misters x 8

Duct Tape

Aluminum Tape

Craft knife

Drill with 1.25 inch drill bit

Measuring Tape and ruler

Temperature Sensor, Light Intensity Sensor, Humidity Sensor, CO2, Water Level Sensor, EC Sensor, and pH Sensor

3D printer with food grade ABS

Red romaine lettuce seeds

Water with nutrients specific for aeroponics

First, cut out six 50cm x 50 cm squares of white corrugated plastic to build your box. Then, cut out five 50cm x 50 cm squares of reflective self adhesive paper to reflect the light so it increases the amount of light distributed throughout the box. Stick each piece of adhesive paper to five of the corrugated plastic pieces. Next, use duct tape and aluminum foil tape to put the box together with the duct tape on the outside edges and the aluminum foil tape on the inside edges. Put the tape only on one side of the lid so that it can be opened. Attach a full spectrum LED light strip is to the middle of each sidewall or on the base to function as a grow light.

Cut out 4 trapezoid pieces from black corrugated plastic that are 49cm at the top and 8cm on the bottom. Next, drill fifteen 3.5 cm circles spaced 6 cm apart in each side of the pyramid. Each side holds fifteen plants making allowing the growth of 60 plants at a time. Use duct tape to join the sides together into an inverted pyramid.

Using TinkerCAD, create a slightly angled base with a flat surface in the middle for the pump. The base has multiple triangular channels that helps the water flow to the pump using capillary action. The base was printed out of food safe ABS on a 3D printer.

Using TinkerCAD, design a mister. The mister can be printed on a 3D printer with food safe ABS. First, make 4 arms in the shape of a plus sign. On each arm insert one misting head facing down and one facing the side wall for a total of eight misters that completely cover the roots.

Two 70 x 3 cm strips of corrugated plastic are glued together for strength. The mister is glued to the middle of the plastic strip. Two arduino fans are attached to the strip on each side of the mister. A second srip was made and two fans were attached, one on each side.

Outside the pyramid, on the bottom of the box, center a 20cm x 20cm x 5 cm plastic drip pan. In a corner, next to the drip pan, mount an Arduino board. Mount one fan on each side of the base to blow air up against the plants to circulate the Oxygen and Carbon Dioxide to and away from the plants. Attache the fans and pump to the board. Next, attach a pH sensor, an electric conductivity (EC) sensor, a thermometer, a humidity sensor, a CO2 sensor, a water level sensor and a light intensity sensor to the Arduino board.

Seeds are placed in the bottom of the seed pillows like those sold by Aeroponics International. These pillows look like a mesh, and allow the seeds to germinate and the roots to grow out of the pillow and into the chamber. The pillows are placed into grow baskets. We used empty baskets made by Miracle Grow for the Aerogarden, however, you can use any grow basket. The grow baskets are placed into the holes in the walls of the pyramid.

Place the inverted pyramid inside the drip pan. Inside the base of the pyramid, place the aeroponic chamber capillary base. In the middle of the base, place a 3.5 cm x 2.5 cm 300 L/h submersible pump. This pump was chosen for its small size and because the water enters from the bottom. Next, connect a food grade, clear, vinyl tubing with a 3/8 inch internal diameter to the pump. Then, attach the two supports with the mister and fans across the top of the pyramid laying them perpendicular to each other and extending them from one corner to the opposite corner making an X. The tubing is then attached from the top of the pump to the mister. Finally, the fans are attached to the Arduino board.

Aeroponic growth requires specific nutrients to be added to the water since there is no soil being used. The optimal pH of the water is between 5.8 and 6.3. The optimal EC (electrical conductivity) is 1.6. This measures the concentration of minerals in the water. There are many brands of liquid fertilizer that can be used, but one with an NPK (nitrogen/phosphorus/potassium) ratio of 8-15-36 would work well.

When the lettuce is ready to be harvested, the pyramid can be removed from the top of the box. An alternative is to attach the sidewalls with duct tape only on the bottom and a clasp at the top so each wall can be opened individually. This would allow for easy access for harvesting. In between growth cycles the pyramid can be easily removed for cleaning.