First Advisor

Raúl Bayoán Cal

Term of Graduation

Spring 2022

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Mechanical Engineering


Mechanical and Materials Engineering





Physical Description

1 online resource (xix, 105 pages)


A simple means of watering plants in the low-g environment aboard orbiting spacecraft is not obvious. Since the beginning of spaceflight, numerous approaches have been pursued to water plants that seek to maximize plant viability and system reliability, while minimizing crew time and system complexity. The Plant Water Management experiments (PWM) seek to apply recent advances in low-gravity capillary fluidics to the challenges faced during plant growth operations aboard spacecraft. One primary challenge encountered in such applications is to establish Earth-like flows, minimizing the low-g specific adaptations required by the plants. This is difficult due to the fluid physics challenges associated with poorly-wetting multi-phase inertial-visco-capillary flows in geometrically complex conduits and containers which change dramatically throughout the life cycle of the plants. In this thesis, preliminary results for two recent experiments from the Plant Water Management series of experiments are presented and discussed.

The first portion of this thesis presents results from six days of 24-7 experiments testing 3 different plant root model geometries in a soil-based test cell aboard the International Space Station. Within each test cell, porous clay 'soil reservoirs' are arranged within a non-wetting host soil that serves the purposes of root oxygenation and as a wetting barrier to control fluid distribution within the soil. The experiment also demonstrates passive watering via a fluid reservoir with a capillary connection to the soil test cell. Despite wide variations in model plant resistances intended to demonstrate a 'falling' water table effect, all models converged towards similar, evaporation-rate limited performance. This behavior is explored and explained via a capillary flow model developed to capture the primary features of the flows.

The second portion of this thesis presents a selected set of preliminary results from six days of experiments with open hydroponic capillary channels and synthetic plant models. Tests performed during nearly 40 hours of flight operations include demonstrations of flow stability in single, parallel, and serial channel arrangements. Stability is explored across a range of flow rates, plant model types, and plant arrangements. Technology demonstrations of both passive aeration and gas-liquid phase separation are also explored. The hydroponics experiment presented here includes more than 430 individual test runs, the bulk of which have not yet been explored. To aid in future analyses, a catalog of experimental runs and associated metadata is created and provided. This catalog substantially reduces the barriers to accessing relevant experimental data and represents one of the primary contributions of this work. Data reduction processes and the methodology used to create the catalog are discussed.


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