Graduation Year

2024

Document Type

Thesis

Degree

M.S.E.E.

Degree Name

MS in Electrical Engineering (M.S.E.E.)

Degree Granting Department

Engineering

Major Professor

Arash Takshi, Ph.D.

Committee Member

Ehsan Sheybani, Ph.D.

Committee Member

Stephanie Carey, Ph.D.

Keywords

gas exchanges, gas sensors, open-loop system, plant development, plant health

Abstract

Space exploration has been a topic of interest in the scientific community, such as the planned missions to Mars. To accomplish this would require being able to provide astronauts with a steady supply of food beyond freeze-dried foods leading to the need to grow food in space. Although this is a topic still being investigated, the CubeSat platform opens the possibility of carrying out studies on plant growth under more strenuous space conditions unlike that in the International Space Station (ISS). Developing a plant-focused mission for a CubeSat, though, entails being able to develop a system to sustain plant life autonomously and monitor the conditions of the plant as it grows with limited resources. With that in mind, it is evident that to approach this problem it would first require an establishment of metrics that can discern plant condition and gauge how resources are to be allocated to it, which is where this research contributes towards.

In this thesis, an open-loop system was developed for two purposes. One is to provide the candidate plant, red romaine lettuce, with its necessities. This includes lighting, air circulation, and water supply. The second is to collect data on the condition the plant is growing in, the gas exchanges that are occurring, and the visible structure of the red lettuce through a sensor array and three camera system. From there the data collected and images captured are analyzed to discern any notable patterns regarding the condition of the plant in its development. Water consumption is also a factor that is monitored when the water container in the setup is being cleaned and changed out.

There are two samples that are grown in this plant growth and health monitoring system. The first is from a plant grown in the system for four weeks, or essentially the typical growth cycle for red lettuce. This is focused on analyzing how well the plant can develop under constrained conditions. In the second batch, the focus is on assessing the quality and limitations of the experimental setup through a half-growth cycle where the red lettuce is developed for only two weeks. For the second group, a control sample is also grown under the same conditions (but in an open space instead of being in a chamber) as the experimental one. Additionally, a preliminary growth was done where the red lettuce was grown in a grow tent to serve as a reference on what should be anticipated regarding their development, making this the third sample.

Results from these experiments show that the ideal case is when photosynthesis is the dominant process the plant undergoes. This would mean that from a weekly perspective there is a decrease in carbon dioxide concentration and increase in oxygen. Alcohol concentration was found to be a possible indicator of plant development due to how an increase in it was occurring at the same time as when the red lettuce undergoes major changes. Two of the images taken from the setup were processed in MATLAB to provide a rudimentary pixel count to determine the area of the leaves, demonstrating its ability to discern an increase in the surface area of the leaves. Regarding water consumption, there was a noted pattern where the water intake was higher in the first week to allow for the seed to germinate before this decreased in the second week. Afterwards, this consumption increases for the plant to develop further with a greater water loss indicating more growth taking place.

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