Abstract
Confinement experiments are essential to prepare long-term space exploration. The 180-day Chinese CELSS (Controlled Ecological Life Support System) study is unique in its design, including a closed-loop system and mid-mission simulation of Mars-like day–night cycle of 24 h 40 min for 36 days (days 72–108). Our aim was to study physiological and psychological consequences of this confinement in four healthy volunteers (one female). CELSS platform consisted of six interconnected modules including four greenhouses. Life support systems were controlled automatically. Body composition, fluid compartments, metabolic state, heart, large vessels, endothelial function, and muscle tone were studied using biological, functional, and/or morphological measurements. Behavioral activities were studied by ethological monitoring; psychological state was assessed by questionnaires. Body weight decreased by ∼2 kg mostly due to lean mass loss. Plasma volume and volume-regulating hormones were mostly stable. Carotid intima-media thickness (IMT) increased by 10–15%. Endothelium-dependent vasodilation decreased. Masseter tone increased by 6–14% suggesting stress, whereas paravertebral muscle tone diminished by 10 ± 6%. Behavioral flow reflecting global activity decreased 1.5- to 2-fold after the first month. Psychological questionnaires revealed decrease in hostility and negative emotions but increase in emotional adaptation suggesting boredom and monotony. One subject was clearly different with lower fitness, higher levels of stress and anxiety, and somatic signs as back pain, peak in masseter tone, increased blood cortisol and C-reactive protein. Comparison of CELSS experiment with Mars500 confinement program suggests the need for countermeasures to prevent increased IMT and endothelial deconditioning. Daily activity in greenhouse could act as countermeasure against psycho-physiological deconditioning.
Highlights
Long-term deep space flights and space colonization in the post-International Space Station (ISS) era will be challenged by extreme environment factors including stress, social and environmental confinement in an artificial setting, isolation, sensory deprivation, social monotony, diet modifications with limited available food, and disrupted circadian rhythms (Morphew, 2001)
The study protocol was approved by the ethical committee of the Astronaut Center of China (ACC) and complied with all guidelines stated in the Declaration of Helsinki
Sanitary and other wastewater went to the nutrient solution storage tank for plants, and condensate water from plants was purified with a modified membrane bio-reactor process (Li et al, 2018) and used for drinking and washing
Summary
Long-term deep space flights and space colonization in the post-ISS era will be challenged by extreme environment factors including stress, social and environmental confinement in an artificial setting, isolation, sensory deprivation, social monotony, diet modifications with limited available food, and disrupted circadian rhythms (Morphew, 2001). Deep space missions will require high levels of interpersonal compatibility, ability to cope with isolation and group dynamics, capacity for autonomous work, and adaptation to unforeseen challenges. These considerations make crew selection and maintenance of crew performance vitally important. Another constraint is the inability to resupply life-support materials Such missions will need artificial closed-loop ecosystems to provide crew members with enough breathable air, clean water, food, and a safe environment to live and work – a Controlled Ecological Life Support System (CELSS). There is a clear need for self-performed techniques to monitor health in space. Such tools should be validated on ground-based models
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