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The paper presents the analysis of the Russian experience gained in the operations of Salyut-6, 7 and Mir orbital stations. The main factors determining their effectiveness and safety are considered and the main requirements to the EVA suit, as the most important tool for the EVA, are formulated.
The current multi-layer insulation used in the extravehicular mobility unit (EMU) will not be effective in the atmosphere of Mars due to the presence of interstitial gases. Alternative thermal insulation means have been subjected to preliminary evaluation by NASA to attempt to identify a material that will meet the target conductivity of 0.005 W/m-K. This study analyzes numerically the thermal conductivity performance for three of these candidate insulating fiber materials in terms of various denier (size), interstitial void fractions, interstitial void media, and orientations to the applied temperature gradient to evaluate their applicability for the new Mars suit insulation. The results demonstrate that the best conductive insulation is achieved for a high-void-fraction configuration with a grooved fiber cross section, aerogel void medium, and the fibers oriented normal to the heat flux vector. However, this configuration still exceeds the target thermal conductivity by a factor of 1.5.
Presented are results of gas bubbles monitoring in decompressed humans with the use of an ultrasonic pulse-Doppler locator (PDL). Unlike the classic Doppler bubbles detectors with continuous US emission, PDL is adjusted for reception of echo from a chosen volume of the right ventricle cavity; thus, the clutter due to cardiac beats and human locomotion is successfully rejected. During simulation of Russian EVAs, venous gas bubbles were detected in 3 out of 5 experiments with test-subjects clothed in everyday wear and in 2 out of 3 experiments with suited test-subjects.
The paper describes a mathematical model of and methods of calculating thermal-humidity fields in a spacewalking suit. The authors made an integral calculation of thermal and mass transfer in the spacesuit. A system of equations is solved analytically and numerically with the use of a combined method. As a result of model calculations, determined were integral spacesuit characteristics including total amount of rejected heat, heat rejected by the WC suit, humidity rejected by ventilation, and humidity accumulated in different spacesuit layers. Comparison of calculation and experimental data for spacesuit Orlan showed that maximal differences in temperature, humidity, thermal and humidity flows, and other system parameters did not exceed 13%.
BACKGROUND: Thermal control in the EVA spacesuit requires attention from the astronaut which is not always desirable or feasible. Improvements in thermal control involve implementation of an automatic thermal control system operating independently of the knowledge of the working astronaut. METHODS: A control system was designed, developed, and tested to automatically maintain a subject's thermal neutrality while wearing a liquid cooling garment (LCG). Measurement of CO2 production as an indication of metabolic rate was used as a signal to initiate the control response. Mean body temperature, computed as a function of ear canal temperature and mean skin temperature, provided feedback to account for the thermal state of subjects as they were being cooled by the LCG. The control algorithm was tested on nine subjects, six males and three females, who performed a varying 90-min metabolic profile using an arm cranking ergometer. A total of 27 tests, three for each subject, were conducted in a thermal chamber at three different environmental temperatures: 10 degrees C, 18.3 degrees C and 26.7 degrees C. RESULTS AND CONCLUSIONS: Evaluation of subjective comfort rating and quantitative energy storage indicates good performance of the controller in maintaining thermal neutrality for the subject over a wide range of environmental and transient metabolic states. Measurements of metabolic rate effectively initiated controller response, and feedback of mean body temperature to the controller proved very capable of accounting for various steady-state environmental conditions and inter-subject variability.
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Systems supporting human life and survival range from small items like oxygen masks or protective suits to the global biosphere. However, in a long run, the former ones cannot work without proper functioning of the latter. A consequence for biomedical research is the challenge to more fully understand, and to take into account, complex ecophysiological systems interdependencies. The development of life support systems (LSS) as used in manned flight significantly contribute to our understanding of life on a grand scale. A "medium-sized" materially closed LSS model is Biosphere 2, which completely recycles waste, provides clean air, potable water, and nutrient-dense food to a crew of 8 for basically unlimited time.
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