Thermal Comfort Under Weightlessness Exposure: A Discriminant Analysis

摘要

Astronauts under weightlessness or microgravity would have differences in thermal comfort due to several adaptive physiological changes caused by the absence of the gravity. In this study, the Mahalanobis distance discriminant was conducted to investigate the classifications of the mean thermal comfort votes (MTCV) in weightlessness, in terms of the ratio of low-frequency power (LF) and high-frequency power (HF) of the heart rate variability (HRV). The ratio was abbreviated as LF/HF and it represented the balance of the autonomous nervous system and acted as an indicator of the thermal comfort. This study was based on our previous research data that had been acquired from 6 male participants under simulated weightlessness through heard-down bed rest (HDBR) model. Results showed that when LF/HF 1.442, participants under simulated weightlessness gave comfort feedbacks, including the neutral comfort and warm comfort, while participants under normal condition felt thermally comfort when LF/HF = 1.232 and felt uncomfortable thereafter. When 1.442 LF/HF 2.073, all participants under simulated weightlessness reported cool comfort. When the mean LF/HF was greater than 2.073, however, participants under simulated weightlessness reported thermal discomfort. In addition, results indicated that participants under simulated weightlessness could not distinguish neutral comfort from warm comfort, but they could report the cool comfort quickly, which suggested that the human body in weightlessness might be more sensitive to the cool environments. Finally, the corresponding comfortable air temperature (t(a)) range under simulated weightlessness was estimated as 26celcius = t(a) 30celcius according to the discriminant results of the MTCV.