Fatty acid composition of plasma lipids and erythrocyte membranes during simulated extravehicular activity

Ten subjects (from 27 to 41 years) have been participated in 32 experiments. They were decompressed from ground level to 40-35 kPa in altitude chamber when breathed 100% oxygen by mask and performed repeated cycles of exercises (3.0 Kcal/min). The intervals between decompressions were 3-5 days. Plasma lipid and erythrocyte membrane fatty acid composition was evaluated in the fasting venous blood before and immediately after hypobaric exposure. There were 7 cases decompression sickness (DCS). Venous gas bubbles (GB) were detected in 27 cases (84.4%). Any significant changes in the fatty acid composition of erythrocyte membranes and plasma didn't practically induce after the first decompression. However, by the beginning of the second decompression the total lipid level in erythrocyte membranes decreased from 54.6 mg% to 40.4 mg% in group with DCS symptoms and from 51.2 mg% to 35.2 mg% (p<0.05) without DCS symptoms. In group with DCS symptoms a tendency to increased level of saturated fatty acids in erythrocyte membranes (16:0, 18:0), the level of the polyunsaturated linoleic fatty acid (18:2) and arachidonic acid (20:4) tended to be decreased by the beginning of the second decompression. Insignificant changes in blood plasma fatty acid composition was observed in both groups. The obtained biochemical data that indicated the simulated extravehicular activity (EVA) condition is accompanied by the certain changes in the blood lipid metabolism, structural and functional state of erythrocyte membranes, which are reversible. The most pronounced changes are found in subjects with DCS symptoms.     

Oxygen regimen in the human peripheral tissue during space flights.

A survey of the results of the experiment "Oxygen," carried out within the scope of the INTER-KOSMOS program in members of the permanent crews and of international visiting expeditions to the Soviet orbital station Salyut-6, is given. During the 7-day space flights of the international visiting expeditions a significant decrease in pO2ic by 3.28 kPa was observed. Local oxygen utilization reduced significantly by 0.44 kPa. During hyperventilation testing after return to earth a statistically significant decrease in the peak value by 1.39 kPa was noted. In the long-term crews of the orbital station Salyut-6 the highest decrease in pO2ic of 3.8 kPa and the absolutely lowest value of 3.4 -/+ 0.5 kPa during space flight were observed. The decrease in local oxygen utilization during the flight of 0.8 kPa/min was greater than that of the visiting crews. The results indicate the importance of investigating the dynamics of the oxygen regimen for medical control of the crew members both during the space flight and during the readaptation phase after return to earth.     

The feasibility of Doppler monitoring during EVA

During extravehicular activities (EVA) outside the spacecraft, astronauts have to work under reduced pressure in a space suit. This pressure reduction induces the risk of decompression sickness (DCS) by the formation of gas bubbles from excess nitrogen dissolved in the organism by breathing air at normal pressure. Under laboratory conditions the gas bubbles moving in the blood stream can be detected by the non-invasive ultrasonic Doppler method. By early detection of excessive bubble formation the development of DCS symptoms may be prevented by early application of preventative measures. The method could also be useful when applied in the space suit in order to compare the results of laboratory tests with operational results, because there is a discrepancy according to the DCS risk of laboratory experiments and actual EVA missions, where no symptoms have been reported yet. A prototype Doppler sensor has been developed and implemented in the Russian Orlan suit. To investigate the feasibility of this method under simulated space conditions, the equipment has been used in a series of 12 thermovacuum chamber tests with suited subjects, where intravenous bubble formation was compared to unsuited control experiments. In more than 50% of the suited tests good Doppler recordings could be achieved. In some cases with unsatisfying results the signal could be improved by breathholding. Although the results do not yet allow any conclusion about a possible difference between suited and unsuited subjects due to the small number of tests performed, the method proved its feasibility for use in EVA suits and should be further developed to enhance the safety of EVA procedures.     

Metabolic assessments during extra-vehicular activity

Extra-vehicular activity (EVA) has a significant role during extended space flights. It demonstrates that humans can survive and perform useful work outside the Orbital Space Stations (OSS) while wearing protective space suits (SS). When the International Space Station 'Alpha' (ISSA) is fully operational, EVA assembly, installation, maintenance and repair operations will become an everyday repetitive work activity in space. It needs new ergonomic evaluation of the work/rest schedule for an increasing of the labor amount per EVA hour. The metabolism assessment is a helpful method to control the productivity of the EVA astronaut and to optimize the work/rest regime. Three following methods were used in Russia to estimate real-time metabolic rates during EVA: 1. Oxygen consumption, computed from the pressure drop in a high pressure bottle per unit time (with actual thermodynamic oxygen properties under high pressure and oxygen leakage taken into account). 2. Carbon dioxide production, computed from CO2 concentration at the contaminant control cartridge and gas flow rate in the life support subsystem closed loop (nominal mode) or gas leakage in the SS open loop (emergency mode). 3. Heat removal, computed from the difference between the temperatures of coolant water or gas and its flow rate in a unit of time (with assumed humidity and wet oxygen state taken into account). Comparison of heat removal values with metabolic rates enables us to determine the thermal balance during an operative medical control of EVA at "Salyut-6", "Salyut-7" and "Mir" OSS. Complex analysis of metabolism, body temperature and heat rate supports a differential diagnosis between emotional and thermal components of stress during EVA. It gives a prognosis of human homeostasis during EVA. Available information has been acquired into an EVA data base which is an effective tool for ergonomical optimization.     

Probabilistic assessment of radiation risk for astronauts in space missions

Accurate estimations of the health risks to astronauts due to space radiation exposure are necessary for future lunar and Mars missions. Space radiation consists of solar particle events (SPEs), comprised largely of medium energy protons (less than several hundred MeV); and galactic cosmic rays (GCR), which include high-energy protons and heavy ions. While the frequency distribution of SPEs depends strongly upon the phase within the solar activity cycle, the individual SPE occurrences themselves are random in nature. A solar modulation model has been developed for the temporal characterization of the GCR environment, which is represented by the deceleration potential, ?. The risk of radiation exposure to astronauts as well as to hardware from SPEs during extra-vehicular activities (EVAs) or in lightly shielded vehicles is a major concern for radiation protection. To support the probabilistic risk assessment for EVAs, which could be up to 15% of crew time² on lunar missions, we estimated the probability of SPE occurrence as a function of solar cycle phase using a non-homogeneous Poisson model [1] to fit the historical database of measurements of protons with energy>30 MeV, Φ₃₀. The resultant organ doses and dose equivalents, as well as effective whole body doses, for acute and cancer risk estimations are analyzed for a conceptual habitat module and for a lunar rover during space missions of defined durations. This probabilistic approach to radiation risk assessment from SPE and GCR is in support of mission design and operational planning for future manned space exploration missions.     

EVA design: lessons learned

Extravehicular Activities (EVAs) are very demanding and specialized space flight activities. There are many aspects to consider in the design of hardware, tools, and procedures to be used on an EVA mission. To help minimize costs and optimize the EVA productivity, experience shows that astronauts should become involved early in the design process.     

Evaluation of safety of hypobaric decompressions and EVA from positions of probabilistic theory

Formation and subsequent evolution of gas bubbles in blood and tissues of subjects exposed to decompression are casual processes in their nature. Such character of bubbling processes in a body predetermines probabilistic character of decompression sickness (DCS) incidence in divers, aviators and astronauts. Our original probabilistic theory of decompression safety is based on stochastic models of these processes and on the concept of critical volume of a free gas phase in body tissues. From positions of this theory, the probability of DCS incidence during single-stage decompressions and during hypobaric decompressions under EVA in particular, is defined by the distribution of possible values of nucleation efficiency in "pain" tissues and by its critical significance depended on the parameters of a concrete decompression. In the present study the following is shown: 1) the dimensionless index of critical nucleation efficiency for "pain" body tissues is a more adequate index of decompression stress in comparison with Tissue Ratio, TR; 2) a priory the decompression under EVA performed according to the Russian protocol is more safe than decompression under EVA performed in accordance with the U.S. protocol; 3) the Russian space suit operated at a higher pressure and having a higher "rigidity" induces a stronger inhibition of mechanisms of cavitation and gas bubbles formation in tissues of a subject located in it, and by that provides a more considerable reduction of the DCS risk during real EVA performance.     

Main medical results of extended flights on space station Mir in 1986-1990

During 1986-1990 seven prime spacecrews (16 cosmonauts) have flown on-board the Mir orbital complex. The longest space mission duration was 366 days The principal objectives of the medical tasks were the maintenance of good health and performance of the spacecrews and conducting medical research programs which included study of the cardiovascular, motor, endocrine, blood, immune, and metabolic systems. Results obtained point to the ability of humans to readily adapt to a year-long stay in space and maintain good health and performance. Readaptation had a similar course as after other previous long-term space flights of up to 8 months in duration. Primary body system changes were not qualitatively different from findings after flights aboard the Salyut 6 and 7 space stations. In this case, during and after an 11-12 month flight, body system alterations were even less severe which was a result of adequate countermeasure use, their systematic and creative employment and maintenance of required environments to support life and work in space.     

EVA 2000: a European/Russian space suit concept

For the European manned space activities an EVA space suit system was being developed in the frame of the Hermes Space Vehicle Programme of the European Space Agency (ESA). The space suit was to serve the needs for all relevant extravehicular activities for the Hermes Columbus operations planned to begin in 2004. For the present Russian manned space programme the relevant EVAs are performed by the Orlan-DMA semi-rigid space suit. The origin of its development reaches back to the 1970s and has since been adapted to cover the needs for extravehicular activities on Salyut and MIR until today. The latest modification of the space suit, which guaranteed its completely self-contained operation, was made in 1988. However, Russian specialists considered it necessary to start developing an EVA space suit of a new generation, which would have improved performance and would cover the needs by the turn of the century and into the beginning of the next century. Potentially these two suit developments could have a lot in common based on similarities in present concepts. As future manned space activities become more and more an international effort, a safe and reliable interoperability of the different space suit systems is required. Based on the results of the Munich Minister Conference in 1991, the European Space Agency and the Russian Space Agency agreed to initiate a requirements analysis and conceptual design study to determine the feasibility of a joint space suit development, EVA 2000. The design philosophy for the EVA 2000 study was oriented on a space suit system design of: space suit commonality and interoperability; increased crew productivity and safety; increase in useful life and reduced maintainability; reduced development and production cost. The EVA 2000 feasibility study was performed in 1992, and with the positive conclusions for EVA 2000, this approach became the new joint European Russian EVA Suit 2000 Development Programme. This paper gives an overview of the results of the feasibility study and presents the joint requirements and the proposed design concept of a jointly developed European Russian space suit.     

Improvement of the extravehicular activity suit for the MIR orbiting station program

Since 1977, EVA suits of the semi-rigid type have been used to support sorties from Russian orbiting stations. Currently, within the MIR station program, the Orlan-DMA, the latest modification of the Orlan semi-rigid EVA suit is used by crewmembers. Quite some experience has been gained by Russia in operations of the Orlan type suits. It has proved the advantages of the EVA suit of a semi-rigid configuration, featuring donning/doffing through a hinged backpack door with a built-in life support system. Meanwhile there were some wishes and comments from the crewmembers addressed to the enclosure design and some LSS components. Currently a number of ways and methods are being developed to improve operational characteristics of the suit as well as to enhance its reliability and lifetime. The forthcoming EVAs to be performed by the STS-MIR crewmembers and future EVAs from the common airlock of the International Space Station Alpha make implementation of the planned improvements even more consistent. The paper analyzes the experience gained in the Orlan-DMA operation and discusses planned improvements in light of the forthcoming activities. In particular the Orlan enhancement program is aimed to make the donning/doffing easier, enhance enclosure mobility, improve the condensate removal unit, increase the CCC (Contamination Control Cartridge) operation time and simplify the onboard subsystem design concept.     

Long-term operation of "Orlan" space suits in the "Mir" orbiting station: experience obtained and its application

The started assembly of the International Space Station (ISS) and its further operation will call for a great number of extravehicular activity sorties (EVA) to be performed by ISS crews. Therefore, of great importance is to make use of the EVA experience gained by cosmonauts in the process of 15-year operation of the Mir orbiting station (OS). Over the 15-year period, Mir crewmembers wearing Orlan type semi-rigid space suits have accumulated 158 man/sorties from the orbiting station. Crewmembers used 15 suits in orbit and some of the suits were in operation for more than 3 years. The paper presents principal design features, which provide effective and safe operation of orbit-based suits, and briefly describes procedures for preparation and maintenance of suit systems, which ensure long-term operation of space suit in orbit. The paper gives results of the space suit modifications, presents suit performance characteristics and lists novel or upgraded components of the space suit and its systems. The paper also summarizes improvements in the Orlan type suits described in some earlier publications. They refer, in the first run, to the improvement of space suit operations characteristics and reliability, and the utilization of the Orlan type space suit in the ISS program. The paper analyses the experience gained and drawbacks detected and observations made, and gives statistical data on long-term space suit operations aboard the Mir station. The paper reviews certain problems in the process of EVAs performed from the station, and describes the ways of their solution as applied to the further utilization of the suit within the ISS program.     

A new preoxygenation procedure for extravehicular activity (EVA)

A 10.2 psi staged-decompression schedule or a 4-hour preoxygenation at 14.7 psi is required prior to extravehicular activity (EVA) to reduce decompression sickness (DCS) risk. Results of recent research at the Air Force Research Laboratory (AFRL) showed that a 1-hour resting preoxygenation followed by a 4-hour, 4.3 psi exposure resulted in 77% DCS risk (N=26), while the same profile beginning with 10 min of exercise at 75% of VO2peak during preoxygenation reduced the DCS risk to 42% (P<.03; N=26). A 4-hour preoxygenation without exercise followed by the 4.3 psi exposure resulted in 47% DCS risk (N=30). The 1-hour preoxygenation with exercise and the 4-hour preoxygenation without exercise results were not significantly different. Elimination of either 3 hours of preoxygenation or 12 hours of staged-decompression are compelling reasons to consider incorporation of exercise-enhanced preoxygenation.     

Geologic field work on Mars: Distance and time issues during surface exploration

Based on field experience at Analogue stations MDRS and FMARS and additional theoretical computations, motorized field work traverses were planned for various surface feature types on Mars, with emphasis on their horizontal dimension, maximal slope angle and cumulative vertical surface undulation or roughness. The aim was to explore the possibilities and characteristics of field work for different terrain types. Those terrain types are reviewed in the present study that have already been analyzed based on remote sensing data, and that are described in the scientific literature.Dunes, gullies, slope streaks, cross sections of valley networks and of lava channels might be analyzed during only one extra vehicular activity (EVA, e.g., pedestrian and vehicular field work) with the objective of a first in-situ exploration along an optimized traverse, in order to provide the most valuable scientific information on their general characteristics and origin. Smaller tectonic faults, lava flows, lobate debris aprons and outcrops of polar layered deposits can be analyzed only by several EVAs together. Analysis of large landslides, calderas and interior layered deposits produce even more difficulties on Mars, and require specialized technology. In cases where several EVAs are necessary for detailed analysis along the best traverse, mobile pressurized vehicles (with pressurized cabin for astronauts without spacesuits) or other methods would be necessary.Many of the geologic structures that have been analyzed only with remotely sensed data could not be surveyed during one field campaign, and in some cases because of high slope angle and large cumulative topographic undulation, their in-situ exploration could not be accomplished with the technological capabilities available, and in-situ analysis requires more advanced technology than long distance rovers can provide now. Hence, the prior location of important sites and the usage of robotic help will be of high importance.     

The Russian experience in medical care and health maintenance of the International Space Station crews

The main purpose of the medical support system aboard International Space Station (ISS) is crew health maintenance and high level of work capability assurance prior to during and after in space flights. In the present communication the Russian point of view dealing with the problems and achievements in this branch is presented. An overview on medical operations during flight and after finalization of the space missions based on Russian data of crew health and environment state monitoring, as well as data on the inflight countermeasures (prophylaxis) jointly with data on operational problems that are specific to ISS is presented. The report summarizes results of the medical examination of Russian members of the ISS and taxi crews during and after visits to the ISS.     

NEEMO 7 undersea mission

The NEEMO 7 mission was the seventh in a series of NASA-coordinated missions utilizing the Aquarius undersea habitat in Florida as a human space mission analog. The primary research focus of this mission was to evaluate telementoring and telerobotic surgery technologies as potential means to deliver medical care to astronauts during spaceflight. The NEEMO 7 crewmembers received minimal pre-mission training to perform selected medical and surgical procedures. These procedures included: (1) use of a portable ultrasound to locate and measure abdominal organs and structures in a crewmember subject; (2) use of a portable ultrasound to insert a small needle and drain into a fluid-filled cystic cavity in a simulated patient; (3) surgical repair of two arteries in a simulated patient; (4) cystoscopy and use of a ureteral basket to remove a renal stone in a simulated patient; and (5) laparoscopic cholecystectomy in a simulated patient. During the actual mission, the crewmembers performed the procedures without or with telementoring and telerobotic assistance from experts located in Hamilton, Ontario. The results of the NEEMO 7 medical experiments demonstrated that telehealth interventions rely heavily on a robust broadband, high data rate telecommunication link; that certain interventional procedures can be performed adequately by minimally trained individuals with telementoring assistance; and that prior clinical experience does not always correlate with better procedural performance. As space missions become longer in duration and take place further from Earth, enhancement of medical care capability and expertise will be required. The kinds of medical technologies demonstrated during the NEEMO 7 mission may play a significant role in enabling the human exploration of space beyond low earth orbit, particularly to destinations such as the Moon and Mars.     

航天领域研究网络控制系统的必要性分析

给出控制系统的最新发展一网络控制系统的基本概念和典型结构,分析了网络控制系统相对集散控制系统的诸多优点;探讨了航天器底层控制系统采用集散控制系统的现状,并根据现代航天器智能性和自主性的发展要求,指出网络控制系统是未来航天器底层控制系统的发展方向;分析了CAN总线在航天领域的应用,明确了网络控制系统已成功应用到航天领域这一事实;最后通过对网络控制系统及其在航天应用研究现状的分析,得出航天领域迫切需要对网络控制系统的共性问题和航天应用的专有问题进行系统研究的结论.     

One hundred US EVAs: a perspective on spacewalks

In the 36 years between June 1965 and February 2001, the US human space flight program has conducted 100 spacewalks, or extravehicular activities (EVAs), as NASA officially calls them. EVA occurs when astronauts wearing spacesuits travel outside their protective spacecraft to perform tasks in the space vacuum environment. US EVA started with pioneering feasibility tests during the Gemini Program. The Apollo Program required sending astronauts to the moon and performing EVA to explore the lunar surface. EVA supported scientific mission objectives of the Skylab program, but may be best remembered for repairing launch damage to the vehicle and thus saving the program. EVA capability on Shuttle was initially planned to be a kit that could be flown at will, and was primarily intended for coping with vehicle return emergencies. The Skylab emergency and the pivotal role of EVA in salvaging that program quickly promoted Shuttle EVA to an essential element for achieving mission objectives, including retrieving satellites and developing techniques to assemble and maintain the International Space Station (ISS). Now, EVA is supporting assembly of ISS. This paper highlights development of US EVA capability within the context of the overarching mission objectives of the US human space flight program.     

Earth benefits from space life sciences

Contributions of space exploration which are widely recognized are those dealing with the impact of space technology on public health and medical services in both urban and remote rural areas. Telecommunications, image enhancement, 3-dimensional image reconstructions, miniaturization, automation, and data analysis, have transformed the delivery of medical care and have brought about a new impetus to the field of biomedicine. Many areas of medical care and biological research have been affected. These include technological breakthroughs in such areas as: (1) diagnosis, treatment, and prevention of cardiovascular diseases, (2) new approaches to the understanding of osteoporosis, (3) early detection of genetic birth defects, (4) emergency medical care, and (5) treatment of chronic metabolic disorders. These are but a few examples where technology originally developed to support space medicine or space research has been applied to solving medical and health care delivery problems on Earth.     

Energy utilization rates during shuttle extravehicular activities

The work rates or energy utilization rates during EVA are major factors in sizing of life support systems. These rates also provide a measure of ease of EVA and its cost in crew fatigue. From the first Shuttle EVA on the STS-6 mission in 1983, we have conducted 59 man-EVA and 341 man-hours of EVA. Energy utilization rates have been measured on each of these EVA. Metabolic rate was measured during each EVA using oxygen utilization corrected for suit leakage. From 1981–1987, these data were available for average data over the EVA or over large segments of the EVA. Since 1987, EVA oxygen utilization data were available at 2-minute intervals. The average metabolic rate on Shuttle EVA (194 kcal/hr.) has been significantly lower than metabolic rates during Apollo and Skylab missions. Peak rates have been below design levels, infrequent, and of short duration. The data suggest that the energy cost of tasks may be inversely related to the degree of training for the task. The data provide insight on the safety margins provided by life support designs and on the energy cost of Station construction EVA.     

Identification and status of design improvements to the NASA Shuttle EMU for International Space Station application

To meet the significant increase in EVA demand to support assembly and operations of the International Space Station (ISS), NASA and industry have improved the current Shuttle Extravehicular Mobility Unit (EMU), or "space suit", configuration to meet the unique and specific requirements of an orbital-based system. The current Shuttle EMU was designed to be maintained and serviced on the ground between frequent Shuttle flights. ISS will require the EMUs to meet increased EVAs out of the Shuttle Orbiter and to remain on orbit for up to 180 days without need for regular return to Earth for scheduled maintenance or refurbishment. Ongoing Shuttle EMU improvements have increased reliability, operational life and performance while minimizing ground and on-orbit maintenance cost and expendable inventory. Modifications to both the anthropomorphic mobility elements of the Space Suit Assembly (SSA) as well as to the Primary Life Support System (PLSS) are identified and discussed. This paper also addresses the status of on-going Shuttle EMU improvements and summarizes the approach for increasing interoperability of the U.S. and Russian space suits to be utilized aboard the ISS.