03499nas a2200229   4500008004100000245016600041210006900207260001200276300001100288490000700299520269000306653002302996653001503019653004103034653001603075653002403091653002003115100002203135700002203157700002403179856006603203       2021                        eng d00aSupporting simultaneous air revitalization and thermal control in a crewed habitat with temperate <i>Chlorella vulgaris</i> and eurythermic Antarctic Chlorophyta0 aSupporting simultaneous air revitalization and thermal control i  c08/2021  a7097460 v123 a<p>Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitalization and thermal control may aid in carbon loop closure for long-duration surface habitats. However, using water-based algal media as a cabin heat sink may expose the contained culture to a dynamic, low temperature environment. Including psychrotolerant microalgae, native to these temperature regimes, in the photobioreactor may contribute to system stability. This paper assesses the impact of a cycled temperature environment, reflective of spacecraft thermal loops, to the oxygen provision capability of temperate <i>Chlorella vulgaris</i> and eurythermic Antarctic Chlorophyta. The tested 28-min temperature cycles reflected the internal thermal control loops of the International Space Station (<i>C. vulgaris</i>, 9&ndash;27&deg;C; Chlorophyta-Ant, 4&ndash;14&deg;C) and included a constant temperature control (10&deg;C). Both sample types of the cycled temperature condition concluded with increased oxygen production rates (<i>C. vulgaris</i>; initial: 0.013 mgO<sub>2</sub> L<sup>-1</sup>, final: 3.15 mgO<sub>2</sub> L<sup>&ndash;1</sup> and Chlorophyta-Ant; initial: 0.653 mgO<sub>2</sub> L<sup>&ndash;1</sup>, final: 1.03 mgO<sub>2</sub> L<sup>&ndash;1</sup>) and culture growth, suggesting environmental acclimation. Antarctic sample conditions exhibited increases or sustainment of oxygen production rates normalized by biomass dry weight, while both <i>C. vulgaris</i> sample conditions decreased oxygen production per biomass. However, even with the temperature-induced reduction, cycled temperature <i>C. vulgaris</i> had a significantly higher normalized oxygen production rate than Antarctic Chlorophyta. Chlorophyll fluorometry measurements showed that the cycled temperature conditions did not overly stress both sample types (F<sub>V</sub>/F<sub>M</sub>: 0.6&ndash;0.75), but the Antarctic Chlorophyta sample had significantly higher fluorometry readings than its <i>C. vulgaris</i> counterpart (<i>F</i> = 6.26, <i>P</i> &lt; 0.05). The steady state <i>C. vulgaris</i> condition had significantly lower fluorometry readings than all other conditions (F<sub>V</sub>/F<sub>M</sub>: 0.34), suggesting a stressed culture. This study compares the results to similar experiments conducted in steady state or diurnally cycled temperature conditions. Recommendations for surface system implementation are based off the presented results. The preliminary findings imply that both <i>C. vulgaris</i> and Antarctic Chlorophyta can withstand the dynamic temperature environment reflective of a thermal control loop and these data can be used for future design models.</p>10aair revitalization10aAntarctica10abioregenerative life support systems10aChlorophyta10aMcMurdo Dry Valleys10athermal control1 aMatula, Emily, E.1 aNabity, James, A.1 aMcKnight, Diane, M.  uhttps://www.frontiersin.org/article/10.3389/fmicb.2021.70974602977nas a2200121   4500008004100000245014300041210006900184260005700253490001000310520246100320100002202781856005202803       2019                        eng d00aCharacterizing photobioregenerative technology for simulataneous thermal control and air revitalization of spacecraft and surface habitats0 aCharacterizing photobioregenerative technology for simulataneous  aBoulder, CObUniversity of Colorado Boulderc11/20190 vPh.D.3 a<p>Algal photobioreactors have been researched as potential solutions to air revitalization in a spacecraft cabin environment by absorbing CO<sub>2</sub> and producing O<sub>2</sub> through photosynthesis. This photosynthesis, and consumption of produced biomass, theoretically provides a closed-loop solution for long-duration spaceflight. Addressing multiple spaceflight requirements simultaneously with algae has the potential to reduce launch mass, power and volume of future Environmental Control and Life Support (ECLS) systems. Additionally, inoculating algal culture into a water-based thermal cooling loops (flight-proven standard of active cooling found on the International Space Station (ISS)) could incorporate simultaneous air revitalization and thermal control into a common system. However, this imparts rapid, extreme thermal swings on algal cells not evolved for culture in a transient thermal environment. Therefore, the effect of dynamic thermal environments on the CO<sub>2</sub>/O<sub>2</sub> turnover of algae was characterized to provide a first-order assessment of system feasibility. This research characterizes the effect of dynamic environments, both transient thermal environments and varying levels of CO<sub>2</sub> concentration, on metabolic processes of the algal culture. Experiments using Antarctic algal species were included to investigate if cold-acclimated algae are more efficient than Chlorella at CO<sub>2</sub>/O<sub>2</sub> turnover in the active cooling environment. The simultaneous heat and mass transfer coefficients of a nonporous, gas-permeable membrane were characterized, and membrane models developed for future design considerations. A photobioreactor system was designed with considerations for gravity-independence, prototyped, and tested using parameters defined by the ISS cabin environment. A failure modes and effect analysis distilled lessons learned from the previous experiments, which also informs the use of algae for bioregenerative life support. In conclusion, the resulting values from the previous characterization experiments, along with values found in literature, were used to make a first-order mass-balance comparison between current ISS ECLSS and photobioregenerative technologies. This work serves as an initial evaluation of the feasibility for using an algal photobioreactor for simultaneous air revitalization and active thermal control of a spacecraft or surface habitat.</p>1 aMatula, Emily, E.  uhttps://scholar.colorado.edu/asen_gradetds/258/