Date of Award

January 2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Space Studies

First Advisor

Pablo de León

Abstract

Experiments with Ecological Closed Life Support Systems (ECLSS) for moderate sized crews have shown instability when supporting crews over long periods of time required for deep space travel. Tests such as Russia’s BIOS series, NASA’s Lunar-Mars Life Support Test Project (LMLSTP), ESA’s Micro-Ecological Life Support System Alternative (MELiSSA), and Japan’s Closed Ecology Experiment Facilities (CEEF) have shown that microalgae and higher plants combined with physical-chemical material converters can be a successful part of a Biological Life Support System or a Closed Ecological Life Support System. LMLSTP, MELiSSA, and CEBAS experiments as well as commercial Ecosphere products have proven stability at small-scale with direct dependence, closed-loop systems for both short and extended time periods. This shows that when the dependencies and factors are known and understood creating a small-scale stable environment with known measuring points can be easily accomplished.

However, the larger experiments, such as Biosphere2 or Bios3, have shown that the more complex environment, the more stability issues arise and give way to critical transitions. Further, instability in one subsystem or cycle can cause a cascading effect through multiple subsystems. These transitions are sudden and often irreversible, leading to the collapse of the system. Given the time and scale required to test these dependencies and conditions, knowing the precursors of an impending transition or being able to predict critical transitions in these systems is highly desirable. Generalized models can achieve this and may even reduce the amount of time series data required to validate the stability of a given system.

The objective of this research is to defining stability for these complex systems as linked through closure degree and tropic network complexity, examine possible early warning signs of critical transactions, and gain further insight into the stability of these complex systems. This link is explored mathematically and then demonstrated by comparing overall observed closure levels of the NASA Johnson Space Center (LMLSTP) with the proposed closure index and stability level calculations. To demonstrate the applicability of the closure index and stability level calculations, they are examined with longer duration closure simulations. Additionally, a generalized framework model is constructed to attempt to detect early warning signals of critical transitions and demonstrate the overall stability or instability of the system under observation. These models are tested and demonstrated using computer simulation of theoretical Ecological Closed Life Support Systems (ECLSS) habitats based on the LMLSTP experiments.

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