Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

David Klaus

Second Advisor

James Nabity

Third Advisor

Louis Stodieck

Fourth Advisor

Patrick Kociolek

Fifth Advisor

Alexander Hoehn

Abstract

Algal-based life support systems offer a promising bioregenerative technology for future human space missions by performing the functions of air revitalization, water recycling, and food production. However, despite six decades of active research, no algal-based life support systems have yet been used in a spacecraft. This dissertation analyzes key factors affecting the implementation of an algal photobioreactor into a spacecraft life support system.

A comprehensive set of optimum parameters for growing Chlorella vulgaris in a spacecraft was defined to identify research gaps regarding the influence of atmospheric pressure, gravity, contaminants, and radiation as unique cabin environmental factors. From this starting point, the first known comprehensive publication featuring an international and fully historical review of algal spaceflight experiments was completed. Then, using a newly developed and validated flow-through test stand to measure algal metabolism and growth under altered gas compositions and pressures, it was demonstrated that altered total cabin pressure within spacecraft relevant ranges (8.2-14.7 psia) while maintaining normoxic conditions did not affect algal growth or metabolism for the conditions evaluated. Additionally, this dissertation features the first known combination of metabolic measurements with metagenomic analysis of non-axenic cultures representative of spacecraft operational environments. Promoting bacterial contamination, together with a variety of green algal taxa, provides novel insight for interpreting results across different algal metabolism studies. The effect of select typical spacecraft chemical contaminants was also assessed. Finally, a first-order feasibility analysis was conducted that established a minimum algal culture volume of 15 liters as being sufficient to support one human in terms of air and water regeneration under ideal performance conditions. This finding was then used to derive the accompanying infrastructure and support requirements that were incorporated into a conceptual design of the system.

The data obtained from this work can be used to support an Equivalent System Mass (ESM) analysis or trade study for spacecraft implementation. Additionally, this thesis serves as a basis for future modelling and experimental verification work needed to increase the Technology Readiness Level (TRL) of algal life support systems that can ultimately help enable sustainable, long-duration human exploration of space.

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