High-Level Project Summary
We developed an ergonomic, reusable, compactable and self-contained crop production system that requires very little supervision from the crew. It has a maximum capacity of 37 plants on one floor (removable and replaceable when a plant dies or stops producing food) with a hydroponic growing system that will allow to supply a crew of 4 astronauts during their journey back to Earth for an estimated of one or two years. This solves the challenge since we consider the main aspects of size, weight, autonomy, nutrition facts and a hydroponyc system to develope our prototype. The system is important since it raises a possible solution to the issue of feeding astronauts during long space trips.
Link to Project "Demo"
Link to Final Project
Detailed Project Description
Design
A compressible hexagonal cabin design with soft, collapsible walls was proposed to protect against radiation. The design was chosen in a hexagonal way since “A hexagon is the shape that best fills a plane with equal size units and leaves no wasted space. Hexagonal packing also minimizes the perimeter for a given area because of its 120-degree angles. With this structure, the pull of surface tension in each direction is most mechanically stable, which is why even though bees make their honeycombs with circular units, the end result when the wax hardens into place is hexagonal. " With this idea in mind we design our system thinking and considering the future connection between greenhouses to build a “honeycomb”.
To fold the system, tubes are proposed with a mechanism like the ones of travel suitcases, which also allows the height of the LED panel to be adjusted according to the growth of the plants. In turn, the base of the plants is planned to be compressed within the base (leaving the respective space at the base) to obtain the maximum compression of the system.
At the base of the system, it is considered to use polymers since they are light, resistant, and easy to replace materials; In this section you will find the control circuit, the source, the pumps for irrigation, extraction and supply of nutrients to the water with the respective water container and the nutrient container.
Within the base in which the plants will be located will be the water supply and extraction channels as well as sensors for the control of the water flow, extraction of this and census of nutrients in the plant, etc.
The folding wall is made of a material similar to NASA's Veggie system, to protect the plants and keep the levels inside the greenhouse controlled. On one side of the hexagon the curtain can be lowered to access the plants.
The led ceiling contains a set of adjustable LEDs according to the needs of the plants, in turn it contains a fan to maintain air flow and keep the system in balance.
We considered that carbon fiber is the best option for our system because it is characterized by it's high flexibility, high strength, and low thermal expansion. It can be combined with other materials, such as graphite, forming carbon-carbon compounds, highly resistant to high temperatures and even fire. In the face of variations in temperature, it retains its shape. It is five times stronger than steel, with equal strength, and it is lighter than aluminum.
The structures made with this material have properties such as: enormous resistance to high temperatures, great capacity to support loads, excellent resistance to friction, low weight and great capacity for mechanical resistance. Carbon fiber is a synthetic fiber that is made from a polymer called polyacrylonitrile.
Prototype weight:
- Microcontroller: 37 grams
- Sensors (PH, CO2, temperture, humidity, soil humidity): 432 grams
- LED's: 500 grams
- Water tank: 4 kg
- 3 Water pump: 81 grams
- 3 Selenoide valves: 180 grams
- Walls structure, bases structures, 3 retractable cylindrical supports, waterways, Roof: 14 kg
TOTAL WEIGHT: 19.23 kg
Crops (Feeding, hydroponics and portion calculations)
For the astronauts diet, we propose to grow broccoli, pepper, spinach, lettuce and chard, these vegetables are ideal as they are rich in vitamins A, B1, B2, B3, B6, C, E and K. These vegetables grow in similar environmental conditions, so they can be grown in a space with common temperature, light and humidity. They also share the same mineral requirements in the hydroponic fertilizer solution that will be added to the water and will be responsible for providing nutrients for the optimal development of the crop.
Our hydroponic growing system consists of 7 basket carrier tubes (5cm in diameter each basket) with inert rockwool-type substrate, which will provide an accommodation space for 37 plants. The tubes will be placed crosswise on the hexagonal frame base plate.
By using a sustainable system such as hydroponics, we take advantage of every space destinated to crops, eliminate the need to use herbicides, provide cleaner and high-quality crops by allowing more precise control of the amount of water and nutrients that are used in crops. In addition, irrigation water is used more efficiently as it can be reusable through a recirculating cycle in which up to 50% of water and nutrients can be saved.
Crops system aims to produce 303 portions of food, this will feed an astronaut with two portions of 500 grams each per day, the whole production will be enough for approximately a month (30-37 days) and it will be able to feed 4 persons. The advantage of our system is that we can remove the rockwool of a dead crop to plant new ones, that is because by using a hydroponic system it is easy to remove. This will extend the life of our system and allow the crew to get food for a long trip.
Irrigation and Extraction System
Being a hydroponic system, we will use channels to provide water to each basket (which contains the corresponding substrate of the plant), the tube is considered 8cm in diameter to keep the system compact and because the roots of the chosen plants do not grow more than 8cm. The water channel will be supplied by a pump and regulated by a solenoid valve which will be managed by the microcontroller to allow or restrict the flow of water given by the pump. Each channel will have the baskets inserted (these will have a removable plug to secure that in case of not having a plant in the basket, the water won’t scape from there, and it can be covered when we are not using the hole for planting) with substrate so that when the water flows enough, it reaches all the plants.
Tests of the mentioned system were performed using a solenoid valve, a 5V 400mA mini water pump, and an Arduino UNO. The water flow tube was arranged in a way to present difficulties to reach the other side, thus trying to slightly simulate the conditions presented in microgravity. At the end of the experiment the system gave approximately 10ml every 10s. Taking into account information from the Veggie, that system occupied approximately 165ml for each plant, and information from the APH, where the maximum flow rate is 2L / day (1.4ml / minute), our small pump would work, but given the conditions of the 8cm channel we must look for a pump with greater power such as the ultra-silent brushless submersible water pump, which operates at 12V DC with 4.8W power.
We considered solenoid valves because the WRADS (Water Recovery And Distribution Subassembly) system of the APH greenhouse uses 4 solenoid valves for pressure control inside tubes.
For the extraction system, a prototype similar to the irrigation system is considered, with an extractor, a solenoid valve and the same tube, but in such way that the controller closes the valve that supplies the water, opens the one of the extractor and returns the water to the container to be recycled in another irrigation cycle.
The nutrients will be injected into the water container so that the water has sufficient nutrients for the plants at each stage of growth. The mechanism for this should be similar to irrigation but a smaller valve or an injector can be considered to supply the nutrients.
Autonomous control system
Maintaining an environment in optimal conditions for growing crops is probably the most important thing of all. In addition to considering all the environmental variables that the environment will present for of our system, it is pertinent to know the different ranges of values or "ideal" parameters, with which our cultivation system will remain on the sidelines.
Control System
The environmental control system for our greenhouse has different subsystems, whose main objective is to provide the appropriate conditions to the vegetables for their growth. These subsystems provide the adjustment of humidity and temperature of the environment, levels of PH and electrical conductivity in the substrate, level of carbon dioxide, level of light and the distribution of water.
Light system
The light system is an arrangement of LEDs in parallel, which has the colors red, green and blue (studies done with Veggie and the APH showed that those light colors were ideal for the crops to grow), for varying the light levels the controller will send the signal as it recives the data from the sensor according to the growth of our crops, since in each stage they will need to receive different length waves of visible light to achieve proper growth. It is important to clarify that the adjustment of the intensity with which the grow cabin will be illuminated, depends on both environmental conditions (such as the temperature in the cabin), the distance between the plants and the light panel, as well as the human interaction. With that in mind our system has the option of raising and lowering the LED panel thanks to the retraction system of the supports. For example, the control system adjusts the light intensity to 50% of the current intensity, when it detects that the cabin has been opened so as not to harm human eyesight. This is achieved by using a light blocking (interruption) sensor, arranged in the upper part of the cultivation system. To adjust the light intensity, pulse width modulation (PWM) was implemented. This signal is sent from our controller and through an arrangement of transistors, we get the different levels of light.
Table containing APH environmental control system nominal operating parameters
Ventilation System
In zero gravity, gases accumulate in parts of the chamber instead of circulating. Are not flowing means that the stomata (pores on the surface of the leaves that allow the movement of gases in and out of the plant) cannot obtain the carbon dioxide they need to grow and carry out photosynthesis. So the fans in the chamber are crucial to keep the air circulating.
Considering that, our system has the following sensors to provide and adjust the perfect environment for the crops at the levels indicated.
Carbon Dioxide (CO2)
• CO2 Controlled/Monitored: 400-5000 ppm (±50 ppm)
• Internal CO2 Sensor
• CO2 Draw-Down Capability
Air Quality
• Air Flow: Controlled between 0.3-1.5 m/s
• Ethylene: Scrubbed to ≤ 25 ppb
• Air Filtration
• Air Sampling Ports
Temperature System
Rockwool temperature is even more important than air temperature in our system.
A temperate soil must be obtained, so that the seeds germinate and the root cuttings develop. The ideal temperature for germination of most seeds is 18-25 ° C.
It is difficult to regulate the temperatures. Therefore, it is convenient to have a ventilation system on the roof or have a shading mesh on the outside. Temperature levels of the system should be between 18-30 ° C (± 1 ° C)
Humidity System
Plants prefer a relative humidity of the air between 45 and 60%. For its control, humidity sensors are placed inside. High humidity favors the transmission of pests and diseases, and low humidity could dry out the plant. The perspiration of the leaves increases the humidity of the system. If the humidity level is too low, we can raise it by wetting the soil or vaporizing the plants periodically.
Our system will have a Relative Humidity (RH) between this ranges:
• RH Controlled/Monitored: 50-86% (±5%)
• RH Condensate Measured and Recycled
Future Considerations
Our main proposal to use hexagonal systems arose with the idea of in the future connecting several panels to form a "honeycomb" with modular technology, which allows the system to have a single master microcontroller and even the same irrigation and extraction system, and when connecting the other panels a master-slave protocol is generated, this in order to save resources in the production of minor systems. One of the main purposes of this is to use the system on the Moon or Mars, so that we can create a larger plant system.
In the same way, it seeks to improve the design in order to be able to stack more than one system on another.
Space Agency Data
NASA:
We used this data to get inspiration about the irrigation system, controll systems (sensors, light, conditions, etc.) , crops and more.
- Advanced Plant Habitat
https://www.nasa.gov/sites/default/files/atoms/files/advanced-plant-habitat.pdf
- Nasa pathways Intern Employment Program
https://ntrs.nasa.gov/api/citations/20130013520/downloads/20130013520.pdf
- Plans for plant Research Opportunities on ISS
https://ntrs.nasa.gov/api/citations/20130000809/downloads/20130000809.pdf
- Veggie ISS Validation Test Results and Produce Consumption
https://core.ac.uk/download/pdf/42704157.pdf
- Future Food Production System Development Pulling From Space Biology Crop Growth Testing in Veggie
https://pdfs.semanticscholar.org/d208/26e86ed6962fa653be89e083099c9e6afad1.pdf
- Species and Media Testing for the VEGGIE Plant Production System for Space
https://ntrs.nasa.gov/api/citations/20110015868/downloads/20110015868.pdf
- Advanced Plant Habitat (APH)
https://ntrs.nasa.gov/citations/20160005065
- A New Plant Habitat Facility for the ISS
https://ttu-ir.tdl.org/bitstream/handle/2346/67664/ICES_2016_320.pdf?sequence=1
- NASA Activities in Controlled Environment Agriculture
https://ntrs.nasa.gov/api/citations/20180007212/downloads/20180007212.pdf
- Space Farming Challenges & Opportunities.
https://ntrs.nasa.gov/api/citations/20170006144/downloads/20170006144.pdf
- NASA’s Contributions to Controlled Environment Agriculture
https://ntrs.nasa.gov/api/citations/20160013269/downloads/20160013269.pdf
https://www.nasa.gov/pdf/582600main_TLA_ED_SP_ENERGYASTRONAUT_508.pdf
https://www.nasa.gov/centers/johnson/pdf/511989main_vol4iss2.pdf
https://www.nasa.gov/centers/langley/news/factsheets/MISSE.html
https://www.nasa.gov/mission_pages/tdm/missex/index.html
ESA
Hackathon Journey
We are 4 mechatronic students and 1 high school student and this was our first hackathon, when we found this hackathon since day one our excitement began to increase . We chose this challenge as we consider that it covered several multidisciplinary topics. We were hooked on the idea of developing a system that allows human kind to reach further into the cosmos and try to build a future among the stars with seeds from home.
From this challenge we learned a lot, from the various plant growing systems, to how to generate an irrigation system with solenoid valves and all the microgravity, radiation, use of optimized spaces, and more implications involved in the development of systems for space travel. This whole hackathon was a learning experience for each of us, in many aspects, working under pressure in a short time was a challenge that we managed to overcome with a good organization and we feel very excited to continue learning and looking to contribute to our partnership with the tools we have.
References
External Web Pages:
- https://www.labroots.com/trending/videos/10939/ever-wonder-why-there-are-so-many-hexagons-in-nature
- https://www.globecomposite.com/blog/3-different-types-of-radiation-shielding-materials
- https://agriculturers.com/plantas-para-hidroponia/
- https://hydroenv.com.mx/catalogo/index.php?main_page=index&cPath=49&gclid=CjwKCAjwhuCKBhADEiwA1HegObKiXMBIuKYohsO9GSL6tjGOjvuX-mOLywWjnUO2hrybVdZ6gqcxOxoC5gEQAvD_BwE
- https://www.climatizacionparapiscinas.es/noticias/hexagono-forma-mas-eficiente-naturaleza-inspiracion-diseno-fairland
- Ever wonder why there are so many hexagons in nature? | Videos (labroots.com)
- https://www.gob.mx/siap/articulos/hidroponia-sabes-que-es-y-como-funciona
- https://n9.cl/jw0e1
Apps and tools:
- Blender
- Arduino
- Paint 3D
- Sketchbook
Tags
#hardware #plants #Mars #Seeds #Crops
Global Judging
This project has been submitted for consideration during the Judging process.