<div class="htmlview paragraph">Extravehicular activity (EVA) is an essential part of space missions. When International Space Station ALPHA (ISSA) is fully operational, EVA assembly, installation, maintenance and repair operations will become everyday repetitive work activity in space. Due to the high cost of EVA sorties, a logical step is to try to improve the productivity of the EVA astronaut in order to increase the amount of labor per EVA hour and to optimize the work/rest regime. This is a main goal of decompression protocol development. In order to allow the astronauts sufficient productivity within the EVA space suit it is necessary to operate the suit with an internal pressure lower than 1 atmosphere. The suit pressure of approximately 0.3-0.4 atmosphere (30-40 kPa or 220-300 mm Hg ) induces the risk of decompression sickness (DCS) by the formation of gas bubbles (GB) from excess nitrogen dissolved in the organism by breathing air at normal pressure in the space cabin atmosphere. To avoid this risk, the astronaut has to undergo a staged decompression with gradual pressure reduction or to use oxygen prebreathing for denitrogenation. This prebreathing procedure consumes considerable time ( up to several hours ) with corresponding impact on the operational options for EVA. The GB moving in the blood stream can be detected using on Ultrasonic Doppler Detector (UDD), which is capable of detecting GB in venous blood vessels and the heart cavities by frequency shift of the reflected ultrasound signal. The differential signal is used for an automatic evaluation of bubbling frequency and for semiquantative assessment of GB concentration and size. This technique has been developed for decompression tests by Biophyspribor Company at St. Petersburg, Russia. The UDD has been used in our laboratory decompression trials as an objective method of decompression stress assessment during EVA simulations during the last decade. Usually the Doppler method shows the gradual appearance of GB before any symptoms of DCS occur, so the UDD can be used to : a) determine the limit of allowable decompression, and b) act as an early warning signal to avoid DCS with the understanding that not everyone with GB develops DCS symptoms.</div> <div class="htmlview paragraph">The first goal of this study is to elaborate a set of decompression protocols which minimize the risks of DCS and at the same time maximize labour efficiency during repetitive EVA's. The second goal is verification of modern decompression protocols and individual DCS susceptibility using the automatic UDD system. All of these tasks are in accordance with the overall aim of the space programme of ensuring maximum safety, efficiency and performance for Russian and American astronauts. The results of 239 tests of automatic UDD system usage during EVA simulation (0.5 h oxygen prebreathing and 40 kPa operational pressure mode) are presented. The probability of DCS and GB are computed as a regression functions of supersaturation ratio, physical activity, duration of hypobaric exposure and individual anthropometric data of 38 test subjects.</div>

The current United States space suit, called an extravehicular mobility unit (EMU), is pressurized with 100% oxygen at 0.29 atm (4.3 psi or 29.6 kPa) in the vacuum of space. This pressure is much lower than that on the earth or in the International Space Station, and prebreathing is required to avoid decompression sickness (DCS). Higher pressure can reduce the risk of DCS, but mobility would be sacrificed due to larger pressure differential between the inside and outside of the suit. To solve the issues regarding mobility, we employed elastic material. If high mobility is acquired, higher pressurization can be employed. Thus, we developed an elastic glove pressurized at 0.65 atm, which is the minimal pressure to avoid decompression sickness without prebreathing. Range of motion with the nonelastic glove at 0.29 atm, which is simulated current EMU, was similar to that of the elastic glove at 0.65 atm. However, the required force evaluated by electromyography during finger flexion using elastic glove at 0.65 atm was smaller than that using the nonelastic glove at 0.29 atm. These results will encourage further development and investigation of a new extravehicular activity suit.

Extravehicular activities (EVA), or space walks, are a critical and complex aspect of human spaceflight missions. To prepare for safe and successful execution of the required tasks, astronauts undergo extensive training in the Neutral Buoyancy Lab (NBL), which involves many hours of performing repetitive motions at various orientations, all while wearing a pressurized spacesuit. The current U.S. spacesuit-the Extravehicular Mobility Unit (EMU)-is pressurized to 29.6 kPa (4.3 psi) and requires astronauts to exert a substantial amount of energy in order to move the suit into a desired position. The pressurization of the suit therefore limits human mobility, causes discomfort, and leads to a variety of contact and strain injuries. Shoulder injuries are one of the most severe injuries that astronauts contend with, and are mainly attributed to the EMU's hard upper torso (HUT). While suit-related injuries have been observed for many years and some basic countermeasures have been implemented, there is still a lack of understanding of how humans move inside the spacesuit. The objective of this research is therefore to gain a greater understanding of this human-spacesuit interaction and potential for shoulder injury through two approaches: quantifying and analyzing the suit-induced pressures that arise in the shoulder region, and comparing the shoulder muscle forces that arise in the unsuited and suited conditions by modeling human-spacesuit interaction. The first approach provides an