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PubMed2003

[Continuous target of China's manned space project and research direction of space medico-engineering].

The subject of space medico-engineering which takes manned space flight as its own task, played an important role in China's manned space project, and developed rapidly. According to China's next three manned space objectives: 1) to develop the technology of extra-vehicle activity (EVA) and test the astronauts' performance ability of EVA; 2) to develop the technology of docking with other object spacecraft in space; 3) to found a relatively large space lab, the research directions and key technology of space medico-engineering have been given, including astronaut's selection and training; requirements and evaluation of medicine and ergonomics of the space lab design; the researches of fields in astronauts' medical monitoring and space medicine; technology of environmental control and life support system in space module; technology of EVA or docking; and technology of simulation of astronaut's training.

Aerospace Medicine↗

PubMedDate not supplied

Radiation protection of astronauts in LEO.

Radiological protection for space flights is often perceived as a technico-scientific problem. All this is the result of the effects of radiation encountered in space and manned flight conditions. The main characteristics of this radiation come from its complex composition and its large energy spectrum which must be taken into account as well as flux variations by both solar activity and the vehicle position on orbit. Inside a vehicle, structures constitute irregularly distributed shields and lead to a specific dose at each location. To be able to protect the crew, it is first necessary to understand the threat and therefore to identify the radiation environment: extraterrestrial and orbital. As the environment varies with both the orbit position and time, the dose received in each critical organ during missions must be determined and compared with acceptable limits. To counter the threat, which may exceed acceptable limits, a strategy is required, including the complementary aspects of prevention, detection, protection and possibly treatment.

Atlantic Ocean↗

PubMed2001

Radiation dose from reentrant electrons.

In estimating the crew exposures during an extra vehicular activity (EVA), the contribution of reentrant electrons has always been neglected. Although the flux of these electrons is small compared to the flux of trapped electrons, their energy spectrum extends to several GeV compared to about 7 MeV for trapped electrons. This is also true of splash electrons. Using the measured reentrant electron energy spectra, it is shown that the dose contribution of these electrons to the blood forming organs (BFO) is more that 10 times greater than that from the trapped electrons. The calculations also show that the dose-depth response is a very slowly changing function of depth, and thus adding reasonable amounts of additional shielding would not significantly lower the dose to BFO.

Aerospace Medicine↗

PubMed1997

Cardiovascular and hormonal changes induced by a simulation of a lunar mission.

BACKGROUND: This is the first simulation of a 14-d lunar mission including 6 d on the Moon. HYPOTHESIS: We hypothesized that a lunar gravity simulation in the middle of a head-down tilt (HDT) might result in some reversal of body fluid/hormonal responses, and influence cardiovascular deconditioning. METHODS: Six men (28 +/- 2.5 yr) were placed in bed rest (BR): in (HDT) (-6 degrees) to simulate microgravity during the travel (two 4-d periods), and in head-up tilt (HUT) (+10 degrees) (6-d period) to simulate lunar gravity (1/6 g). Muscular exercise was performed during the HUT period to simulate 6 h of lunar EVA. Heart rate variability (HRV) and hormonal responses were studied. RESULTS: An orthostatic arterial hypotension was observed after the BR (tilt test) in 4 of the 6 subjects. Plasma volume measured at D14 decreased by -11.1% (vs. D-3, sitting position). A decrease in atrial natriuretic peptide (26 +/- 3.5 pg.ml-1 (D14) vs. 37.9 +/- 3.5 pg.ml-1 (D-3, sitting) and an increase in plasma renin activity (198 +/- 9.2 mg.L-1.min-1 (D14) vs. 71 +/- 9.2 mg.L-1.min-1 (D-3, sitting) were observed during the BR, more pronounced in HUT at 7:00 p.m. Sympathetic-parasympathetic balance (HRV) at rest showed a decrease in parasympathetic indicator and an increase in sympathetic indicator in BR (p < 0.05), without differences within HDT and HUT periods. CONCLUSION: These changes were mostly similar to those reported in spaceflights, and HDT. Although the exposure to 1/6 g with exercise modified some hormonal and body fluid responses, this partial gravity simulation was not sufficient to prevent the decrease in orthostatic tolerance observed here as well as after Apollo lunar missions.

Adult↗

PubMed2003

Effect of heavy ions on neuro-endocrine regulations.

During American and Russian short and long-term space flights neuroimmune dysregulations have been observed in man and rats for up to three months after the return. During Extra-Vehicular Activity, radiation exposure risk is greater to elicit short and/or long-term deleterious effects on the functional capacity of the neuroimmune system. In order to assess the effects of high LET events on neuroimmune networks, our preliminary ground-based study was to investigate brain inflammatory responses in mouse after low dose radiation exposure with high LET particles (12C, 95MeV/u, 42 mGy). Plasma corticosterone levels were rapidly (6 hours) increased by two-fold, then decreased 24 hours post-irradiation. At 3 days plasma corticosterone and ACTH concentrations were also two- to three-fold increased. Plasma ACTH levels were still elevated up to seven days to two months. Furthermore immune functions are under current assessment. The results of this study should allow a greater understanding of the effects of high LET particles on neuroimmune system.

Adrenocorticotropic Hormone↗

PubMed1999

EVA dosimetry in manned spacecraft.

Extra Vehicular Activity (EVA) will become a large part of the astronaut's work on board the International Space Station (ISS). It is already well known that long duration space missions inside a spacecraft lead to radiation doses which are high enough to be a significant health risk to the crew. The doses received during EVA, however, have not been quantified to the same degree. This paper reviews the space radiation environment and the current dose limits to critical organs. Results of preliminary radiation dosimetry experiments on the external surface of the BION series of satellites indicate that EVA doses will vary considerably due to a number of factors such as EVA suit shielding, temporal fluctuations and spacecraft orbit and shielding. It is concluded that measurement of doses to crew members who engage in EVA should be done on board the spacecraft. An experiment is described which will lead the way to implementing this plan on the ISS. It is expected that results of this experiment will help future crew mitigate the risks of ionising radiation in space.

Animals↗

PubMed2006

Gas embolism and surfactant-based intervention: implications for long-duration space-based activity.

Intravascular gas embolism can occur with decompression in space flight, and it commonly occurs during cardiac and vascular surgery. Intravascular bubbles may be deposited into any end organ such as the heart or the brain. Surface interactions between the bubble and the endothelial cells lining the vasculature result in serious impairment of blood flow and can lead to heart attack, stroke, or even death. Surfactant-based intervention is a novel treatment for gas embolism. Intravascular surfactant can adsorb onto the gas-liquid interface and compete with blood-borne macromolecules for interfacial occupancy. Surfactants can retard the progress of pathophysiological molecular and cellular events stimulated by the bubble surface, including endothelial cell injury and initiation of blood clotting. Bulk and surface transport of a surfactant to provide competition for interfacial occupancy is a therapeutic strategy because surfactant adsorption can dominate protein (or other macromolecule) adsorption. The presence of surfactant along the gas-liquid interface also induces variation in the interfacial tension, which in turn affects the blood flow and the bubble motion. We describe the interplay between biological transport processes and physiological events occurring and the cellular and molecular level in vascular gas embolization. Special consideration is given to modeling the transport and hydrodynamic interactions associated with surfactant-based intervention.

Adsorption↗

PubMed2002

Passive dosimetry aboard the Mir Orbital Station: internal measurements.

Passive radiation dosimeters were exposed aboard the Mir Orbital Station over a substantial portion of the solar cycle in order to measure the change in dose and dose equivalent rates as a function of time. During solar minimum, simultaneous measurements of the radiation environment throughout the habitable volume of the Mir were made using passive dosimeters in order to investigate the effect of localized shielding on dose and dose equivalent. The passive dosimeters consisted of a combination of thermoluminescent detectors to measure absorbed dose and CR-39 PNTDs to measure the linear energy transfer (LET) spectrum from charged particles of LET infinity H2O > or = 5 keV/micrometers. Results from the two detector types were then combined to yield mean total dose rate, mean dose equivalent rate, and average quality factor. Contrary to expectations, both dose and dose equivalent rates measured during May-October 1991 near solar maximum were higher than similar measurements carried out in 1996-1997 during solar minimum. The elevated dose and dose equivalent rates measured in 1991 were probably due to a combination of intense solar activity, including a large solar particle event on 9 June 1991, and the temporary trapped radiation belt created in the slot region by the solar particle event and ensuing magnetic storm of 24 March 1991. During solar minimum, mean dose and dose equivalent rates were found to vary by factors of 1.55 and 1.37, respectively, between different locations through the interior of Mir. More heavily shielded locations tended to yield lower total dose and dose equivalent rates, but higher average quality factor than did more lightly shielding locations. However, other factors such as changes in the immediate shielding environment surrounding a given detector location, changes in the orientation of the Mir relative to its velocity vector, and changes in the altitude of the station also contributed to the variation. Proton and neutron-induced target fragment secondaries, not primary galactic cosmic rays, were found to dominate the LET spectrum above 100 keV/micrometers. This indicates that in low earth orbit, trapped protons in the South Atlantic Anomaly are responsible for the major fraction of the total dose equivalent.

Atlantic Ocean↗

PubMed1994

The EVA space suit development in Europe.

The progress of the European EVA space suit predevelopment activities has resulted in an improved technical reference concept, which will form the basis for a start of the Phase C/D development work in 1992. Technology development work over the last 2 years has resulted in a considerable amount of test data and a better understanding of the characteristics and behaviour of individual parts of the space suit system, in particular in the areas of suits' mobility and life support functions. This information has enabled a consolidation of certain design features on the one hand, but also led to the challenging of some of the design solutions on the other hand. While working towards an improved situation with respect to the main design drivers mass and cost, the technical concept has been improved with respect to functional safety and ease of handling, taking the evolving Hermes spaceplane requirements into consideration. Necessary hardware and functional redundancies have been implemented taking the operational scenario with Hermes and Columbus servicing into consideration. This paper presents the latest design status of the European EVA space suit concept, with particular emphasis on crew safety, comfort and productivity, in the frame of the predevelopment work for the European Space Agency.

Aerospace Medicine↗

PubMedDate not supplied

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.

Adult↗

PubMedDate not supplied

Emergency and rescue considerations for manned space missions.

Man in space is totally dependent upon spacecraft systems. particularly those providing Environmental Control and Life Support (ECLS). It is therefore required that the design of manned spacecraft systems include provision for backup emergency and rescue modes of operation to insure adequate crew safety margin. This paper discusses safety, emergency and rescue provisions included in the Space Transportation System (STS), with emphasis on ECLS subsystems. Similar discussion is included for systems projected for use in future, extended duration manned space missions.

Emergencies↗

PubMed1985

Using computer graphics to enhance astronaut and systems safety.

Computer graphics is being employed at the NASA Johnson Space Center as a tool to perform rapid, efficient and economical analyses for man-machine integration, flight operations development and systems engineering. The Operator Station Design System (OSDS), a computer-based facility featuring a highly flexible and versatile interactive software package, PLAID, is described. This unique evaluation tool, with its expanding data base of Space Shuttle elements, various payloads, experiments, crew equipment and man models, supports a multitude of technical evaluations, including spacecraft and workstation layout, definition of astronaut visual access, flight techniques development, cargo integration and crew training. As OSDS is being applied to the Space Shuttle, Orbiter payloads (including the European Space Agency's Spacelab) and future space vehicles and stations, astronaut and systems safety are being enhanced. Typical OSDS examples are presented. By performing physical and operational evaluations during early conceptual phases. supporting systems verification for flight readiness, and applying its capabilities to real-time mission support, the OSDS provides the wherewithal to satisfy a growing need of the current and future space programs for efficient, economical analyses.

Astronauts↗

PubMed1988

Radiation dose and shielding for the Space Station.

Significant differences in dose prediction for Space Station arise depending on whether or not the magnetic field model is extrapolated into the future. The basis for these calculations is examined in detail, and the importance of the residual atmospheric layer at altitudes below 1000 km, with respect to radiation attenuation is emphasized. Dosimetry results from Shuttle flights are presented and compared with the computed results. It is recommended that, at this stage, no extrapolation of the magnetic field into the future be included in the calculations. A model adjustment, to replace this arbitrary procedure is presented. Dose predictions indicate that, at altitudes below 500 km and at low inclination, and with nominal module wall thickness (0.125 in. aluminum), orbit stay times of 90 days in Space Station would result in quarterly radiation doses to the crew, which are well within present limits both for males and females. Countermeasures would be required for stay times of a year or more and the measure of increasing shielding is examined.

Aluminum↗

PubMedDate not supplied

Simulation by personal workstation for man-machine interface design.

This paper presents a simulation tool which has been developed for Man-Machine interface (MMI) design study, in the context of the European EVA Space Suit System development, under contract of ESA/ESTEC. The main new point is that this simulation is based on a personal workstation, and not on a heavy real-time computer, as in most simulation centres. It will be used in ESTEC to perform low cost simulations of the front part of a manned system, to improve and develop MMI with efficiency.

Computer Simulation↗

PubMed1991

Preliminary medical results of the Mir year-long mission.

The basic goal of medical investigations during and after the 366-day mission was to accumulate data about physiological responses to such a long exposure to microgravity. In flight, cardiovascular and other systems were examined in detail and the efficacy of countermeasures used was assessed. After flight, physiological systems were also followed very carefully. According to the preliminary data, the medical results obtained during and after flight give evidence that man can well adapt to a year-long space flight, maintaining good health and adequate work capacity. The readaptation process was very similar to that observed after shorter flights (6-11 months). As compared to former flights, no new or qualitatively different changes in the vital systems of the body were seen. The observations indicate that the duration of manned space missions can be further increased.

Adaptation, Physiological↗

PubMed1991

The physiology of spacecraft and space suit atmosphere selection.

The majority of the environmental factors which comprise the spacecraft and space suit environments can be controlled at "Earth normal" values, at optimum values, or at other values decided upon by spacecraft designers. Factors which are considered in arriving at control values and control ranges of these parameters include physiological, engineering, operational cost, and safety considerations. Several of the physiological considerations, including hypoxia and hyperoxia, hypercapnia, temperature regulation, and decompression sickness are identified and their impact on spacecraft and space suit atmosphere selection are considered. The past experience in controlling these parameters in U.S. and Soviet spacecraft and space suits and the associated physiological responses are reviewed. Current areas of physiological investigation relating to environmental factors in spacecraft are discussed, particularly decompression sickness which can occur as a result of change in pressure from Earth to spacecraft or spacecraft to space suit. Physiological considerations for long-term lunar or Martian missions will have different impacts on atmosphere selection and may result in the selection of atmospheres different than those currently in use.

Atmospheric Pressure↗

PubMed1991

European EVA decompression sickness risks.

For the first manned flight of Hermes there will be a capability of performing EVA. The European EVA Space Suit will be an anthropomorphic system with an internal pressure of 500 hPa of pure oxygen. The pressure reduction from the Hermes cabin pressure of 1013 hPa will induce a risk for Decompression Sickness (DCS) for the EVA crewmember if no adequate protective procedures are implemented. Specific decompression procedures have to be developed. From a critical review of the literature and by using knowledge gained from research conducted in the past in the fields of diving and aerospace medicine safe protective procedures are proposed for the European EVA scenario. An R factor of 1.2 and a tissue half-time (t1/2) of 360 minutes in a single-tissue model have been identified as appropriate operational values. On the basis of an acceptable risk level of approximately 1%, oxygen prebreathing times are proposed for (a) direct pressure reduction from 1013 hPa to a suit pressure of 500 hPa, and (b) staged decompression using a 700 hPa intermediate stage in the spacecraft cabin. In addition, factors which influence individual susceptibility to DCS are identified. Recommendations are also given in the areas of crew selection and medical monitoring requirements together with therapeutic measures that can be implemented in the Hermes scenario. A method for demonstration of the validity of proposed risks and procedures is proposed.

Aerospace Medicine↗

PubMed1991

The European space suit, a design for productivity and crew safety.

In order to fulfill the two major mission objectives, i.e. support planned and unplanned external servicing of the COLUMBUS FFL and support the HERMES vehicle for safety critical operations and emergencies, the European Space Suit System baseline configuration incorporates a number of design features, which shall enhance the productivity and the crew safety of EVA astronauts. The work in EVA is today--and will be for several years--a manual work. Consequently, to improve productivity, the first challenge is to design a suit enclosure which minimizes movement restrictions and crew fatigue. It is covered by the "ergonomic" aspect of the suit design. Furthermore, it is also necessary to help the EVA crewmember in his work, by giving him the right information at the right time. Many solutions exist in this field of Man-Machine Interface, from a very simple system, based on cuff check lists, up to advanced systems, including Head-Up Displays. The design concept for improved productivity encompasses following features: easy donning/doffing thru rear entry, suit ergonomy optimisation, display of operational information in alpha-numerical and graphical form, and voice processing for operations and safety critical information. Concerning crew safety the major design features are: a lower R-factor for emergency EVA operations thru increased suit pressure, zero prebreath conditions for normal operations, visual and voice processing of all safety critical functions, and an autonomous life support system to permit unrestricted operations around HERMES and the CFFL. The paper analyses crew safety and productivity criteria and describes how these features are being built into the design of the European Space Suit System.

Communication↗