GATRS: Gators' Agricultural Tower Research System

The Gators’ Agricultural Tower Research System (GATRS) is an innovative growth chamber designed by an undergraduate team at the University of Florida. While maintaining the size limitations of an ISS double express locker (50 x 50 x 50cm), the GATRS is highly efficient, accessible, and self-sustainable. Overall, the entire unit is horizontally split into two halves. Each half contains two quadrants, with each quadrant capable of holding three lettuce plants. Doubling the capacity of NASA’s current Veggie system, the GATRS can grow up to twelve romaine lettuce heads. The flexibility of this system enables crew members to grow several batches of differently-aged lettuce plants, or a variety of vegetables with different lighting requirements. In addition to this flexibility, GATRS has many more features that are adaptable to the environment of the International Space Station, the Moon, and beyond.

The outer framework of the system is a 3D printed 50 x 50 x 50cm cubic frame. 3D-printing this frame minimizes the deployed volume and keeps the assembly uncomplicated. Furthermore, a printed framework can easily be duplicated to cultivate even more plants. The top, bottom, and back face of the chamber are enclosed by a sheet of reflective poly plastic. The front face can be left open to the cabin atmosphere, or can be enclosed by a transparent plastic sheet to retain humidity. Water reservoirs are broad and flat, housed at the very top and the very bottom of the design. Between the reservoirs, the GATRS contains one central console and four discrete quadrants for growing vegetables. Each quadrant is a 3D printed tray which can hold up to three plant pillows for growing romaine lettuce plants. The central console contains a ventilation system which filters and circulates air throughout the entire GATRS. The lights are housed on either face of the console, and can be extended closer to the plants.

The ability to simultaneously grow multiple types of vegetables is essential for long term space travel. Individual, separated quadrants allow the GATRS to grow different vegetable breeds/species at the same time. Since reflective dividers block the light, the quadrants can contain plants with completely different photoperiods, light recipes, and light intensity requirements. The plant pillows are held in place by thin, powerful magnets so crew members can easily remove or replace individual plants. Each quadrant can hold up to three romaine lettuce plants within each 22.5 x 50cm quadrant. Interchangeable plant pillows allow crew members to insert many smaller plant pillows (for herbs), or insert one large plant pillow (for microgreens or tomatoes). Although the GATRS uses plant pillows, these pillows can be easily replaced with different growth medium technologies. If an even-aged monoculture is grown, the barriers separating the quadrants can be removed.

The air filtration system is based on the technology currently used in the Veggie growth chamber. Air is pulled from the main cabin by a 6cm fan located at the front of the central console. This air passes through a chamber of air filters (including an ethylene filter). After leaving the filters, the air is allowed to circulate inside an open space within the console. Holes direct the air into the individual quadrants. Each of the quadrants is equipped with a HOBO data logger U12-013 sensor, which monitors temperature, relative humidity, and CO2 level, and sends the data back to Earth. Other environment sensors may be placed throughout the GATRS.

The GATRS contains an individual lighting unit, powered by an arduino, for each of the quadrants within the chamber. A single lighting unit contains a thin plate of LED lights attached to adjustable arms that can extend closer to the leaves below. Plant growth stages require distinct light recipes, so the GATRS is designed to provide red, green, and blue light that can be pre-set or remotely controlled to provide the best combination as the plants develop. The four light systems are independent of each other, separated by reflective dividers, to allow for different light recipes to be applied to different crops. For over 90% reflection of light, the GATRS prototype is equipped with VIVOSUN Black and White Poly Film.

The GATRS is equipped with two irrigation systems. One complete system contains a 3D printed reservoir that is 2 cm tall and 0.5 cm thick, capable of holding 2.4 liters of water. An extension hose carries the water from the reservoir to a ball valve which feeds the water to wicks connecting to each plant pillow. In order for a quadrant of plants to be removed, the system needs to be able to cease the flow of water. For this purpose, the system is equipped with a servo motor and arduino. When the quadrant is removed from the back panel, the servo will rotate the ball valve, disconnecting the flow of water until the quadrant is put back into place. The arduino is also programmed to monitor the moisture in the packs of growth medium to guarantee that the appropriate level of water is maintained for optimal plant growth. The crew will easily be able to refill the reservoirs via an extractable tube.

The GATRS has multiple features to enhance the ease of access for crew members. Each of the four quadrants can be removed, allowing astronauts to reach each set of plants for harvesting and care. The GATRS lighting/ventilation panel is also easy to remove, so maintenance is extremely simple and does not require the entire system to be taken apart. In addition, the irrigation system is carefully designed to make sure crew interactions are uncomplicated and run smoothly.

Although the GATRS is very easy for crew members to access, it is designed to run effectively without crew member intervention. Each key operating system (light, water, and power) is carefully configured to make this possible. The lighting recipe and photoperiod for each quadrant can be remotely operated or set on a timer. The adjustable legs attached to the light source can also be controlled remotely or they can be fixed in place, depending on the needs of each crop. The water reservoir also operates for an extended period of time without intervention. Each reservoir is able to support six adult lettuce plants for up to 3 days before needing to be refilled. Immature plants require significantly less water, and can last much longer without additional irrigation. Consistent electricity is highly important for growing plants in controlled environments. If the system loses electricity for longer than a day, the yield could be at risk. To combat this potential issue, the GATRS has room on the central panel for batteries to be attached to either side. Although the GATRS would not need to use these batteries regularly, in the context of a potentially unstable situation, these batteries could mean the difference between success or failure of an entire mission.

NASA has big plans for the future of long term space travel, and the GATRS is fully equipped to take them on. The system is optimized for food production on even the toughest of missions. The GATRS perfectly fits the size constraints for use on the ISS and could easily be utilized on other spacecraft. Its ability to grow different species of plants enables crew members to cultivate a variety of new crops on future missions. The GATRS is also battery operable, which will keep the plants safe from power outages for upcoming missions on the Moon and beyond.

Contributors:

Sara Humphrey, Plant Health & Protection, junior

Brooke Gaster, Aerospace Engineering, senior

Megan Wnek, Aerospace Engineering, freshman

Tyler Less, Mechanical and Aerospace Engineering, sophomore

Shane Lovello, Mechanical and Aerospace Engineering, sophomore