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The current design philosophy of a Mars orbiting vehicle, takeoff and landing systems and the transport return vehicle was taken into consideration for calculating the equivalent doses imparted to cosmonaut's organs and tissues by galactic cosmic rays, solar rays and the Earth's radiation belts, values of the total radiation risk over the lifespan following the mission and over the whole career period, and possible shortening of life expectancy. There are a number of uncertainties that should be evaluated, and radiation limits specified before setting off to Mars.

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Russian space experiment "Matryeshka-R" was conducted in 2004-2005 to study dose distribution in the body of anthropomorphous phantom inserted in a spacesuit imitating container mounted on outer surface of the ISS Service module (experiment "Matryeshka"). The objective was to compare doses inside the phantom in the container to human body donned in spacesuit "Orlan-M" during extravehicular activity (EVA). The shielding function was calculated using the geometric model, specification of the phantom shielded by the container, "Orlan-M" description, and results of ground-based estimation of shielding effectiveness by gamma-raying. Doses were calculated from the dose attenuation curves obtained for galactic cosmic rays, and the AE-8/AP-8 models of electron and proton flows in Earth's radiation belt. Calculated ratios of equivalent doses in representative points of the body critical organs to analogous doses in phantom "Matryeshka" H(ORLAN-M)/H(Matryeshka) for identical radiation conditions vary with organs and solar activity in the range from 0.1 to 1.8 with organs and solar activity. These observations should be taken into account when applying Matryeshka data to the EVA conditions.

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According to recent workups, the Mars mission spacecraft will be designed with an electrical jet microthrusters rather than a power reactor facility. The article contains analysis of the main sources of radiation hazard during the exploration mission using this cost-efficient, ecological, easy-to-operate propulsion powered by solar arrays. In addition, the authors make predictions of the generalized doses of ionizing radiation for mission durations of 730 and 900 days behind various shielding thicknesses, and on the Martian surface. Calculation algorithms are described and radiation risks are estimated for the crew life span and possible life time reduction in consequence of participation in the mission.

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The article deals with the prime sources of radiation hazard in a mission to Mars, compares the radiation risk values in flight and over the life span with consideration for various shielding thicknesses in habitable compartments and radiation shelter, and estimates possible life shortening. Given the stochastic nature of solar cosmic rays effects in a two-year mission and probability of powerful solar proton events, calculated were not only the mean tissue-equivalent doses behind various thickness of the shelter but also probability of their violation, risks of immediate and delayed radiation consequences and conceivable approaches to risk mitigation.

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Sampling irradiation of spacesuit "Orlan-M" allowed construction of a simulation model of the spacesuit shielding function for critical body organs. The critical organs self-shielding model is a Russian standard anthropomorphic phantom. Radiation protective quality of the spacesuit was assessed by calculating the dose attenuation rates for several critical body organs of an ISS crewmember implementing EVA. These calculations are intended for more accurate assessment of radiation risk to the ISS crews donning "Orlan-M" in near-Earth orbits.

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The paper presents results of the 14-year studies (1966-1980) with dogs irradiated by presumable doses of the galactic cosmic rays (GCR) and solar cosmic rays (SCR) that might affect cosmonauts during a flight to Mars. Along with data of chronic experiments with small laboratory animals exposed to a broad variety of dose rates, our data formed a basis for construction of mathematical models of processes of radiation damage to living organisms, and growth of the probability of mammal death or life span reduction caused by repeated acute and chronic irradiation by different dose rates. Described are present-date estimates of equivalent doses from GCR and SCR behind various shields, and radiation risks for cosmonauts of different age on a mission to Mars. Also compared are values of total radiation risks over the length of life, risks of cancer and lifetime reduction after the planetary mission derived by the mathematical modeling and calculation.

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Proposed is a procedure of calculating the self-screening function of a point on the human body model. The procedure has been developed for the anthropomorphic phantom approved in Russian standard GOST 25645.203-83. The procedure allows extrapolation of the self-shielding calculations to a different body model and a partially protected human body (intra- and extravehicular spacesuit, etc). Results can be useful in precise determination of radiation risks with consideration of the organs self-shielding factor.

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Analysis of the radiation conditions during a piloted expedition to Mars made it evident that the radiation safety system will be one of the most critical components of life support aboard the future Martian vehicle. The concept and main functions of the system have been considered. The authors give their vision of the radiation monitoring system based on the present-day radiation safety postulates, comparison and contrasting methods and equipment applied for the purpose in current orbital and projected interplanetary flights.

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The paper describes the procedure of estimating total radiation risk to crewmembers during lifetime and possible lifetime reduction in consequence of participation in the Mir and ISS missions in different periods of the solar activity. The procedure includes analysis of data of vehicle and personal dosimetry, and calculations of radiation doses in various Mir compartments and accumulated by body tissues of cosmonauts. Calculated doses showed good consistency with the doses measured with R-16 on board Mir and personal dosimeters. To a first approximation, estimation of doses to cosmonauts and radiation risk as a result of participation in ISS missions took into account similarity of the Mir and ISS basal modules (geometry, dimensions and mass values) and was performed with the use of the space station shielding model that had been described elsewhere. The model of ISS radiation shielding will be updated as data of dosimetry of ISS compartments and phantom studies are available.

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The paper presents results of calculating mean daily values of absorbed and equivalent doses from galactic cosmic rays (GCR) and Earth's radiation belts (ERB) to crew members on orbital missions aboard Mir and the International space station during solar minimum and maximum. Calculated doses were corrected in accordance with the dosimetric and spectrometric data from Mir missions 18 through to 23 that took place in the period of solar minimum. Contribution of local and albedo neutrons to equivalent dose was also taken into account. Presented are calculated total radiation risk and tumor risk over life time for Mir and ISS crews following missions of varying duration, and predictions for reduction in life span in view of recent dosimetric data.

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Compared and contrasted were models of radiation shielding of habitable compartments of the basal Mir module that had been used to calculate crew absorbed doses from space radiation. Developed was a model of the ISS Service module radiation shielding. It was stated that there is a good agreement between experimental shielding function and the one calculated from this model.

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Described is the algorithm for calculating the radiation risk to cosmonauts on orbital missions during different solar phases. The algorithm and the Fortran calculation program lie in the basis of presented radiation risk estimations for orbital manned missions of varying duration. The dependence of in-flight radiation risk on mission length, solar phase, and cosmonaut's age was analyzed. Magnitudes of radiation risk to cosmonauts were compared with the national demographic risk of male lethality over a similar period of time.

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The algorithm of estimation of the radiation risk to cosmonauts on long-term interplanetary missions stems from new approaches to the estimation of radiation hazard, calculation of generalized dose inputs from various space radiations, hypothesized probability of human death due to exposure to varying doses of standard radiation. These data allow calculation of radiation risk from deterministic sources along the flight trajectory and stochastically distributed in time solar flares. Results of this calculation can be further used to correlate the in-flight radiation risk with mission length, shield thickness, solar cycle, and age of cosmonauts. They may be additionally used to compare the in-flight radiation risk with the national demographic risk of male lethality over a similar period.

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A technique for calculating the SS MIR absorbed doses from the galactic cosmic rays, protons of the Earth's radiation belts and solar flares is described. Calculated daily doses for different compartments along the MIR main axis are compared with doses calculated for the location of board radiometer R-16 in various periods of solar activity. Maximal doses in MIR compartments (in the absence of phantom) were compared with the doses in referential depths of a spherical phantom representing the blood forming tissue, skin, enteric epithelium, and the absorbed dose in the dosimeter location. This comparison allows more precise estimation of radiation hazard to cosmonauts in space flight.

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One of the serious disadvantages of the U.S. (AP-8 and AE-8) and Russian trapped radiation models is the lack of data concerning the dynamics of trapped particles fluences within a time interval shorter than the solar cycle. The available models are capable to predict the energy spectra of trapped particles only for periods in the vicinity of the solar minimum or maximum. The current models are also lacking data about the angular distribution of trapped particles. Meanwhile, these facts are important in conjunction with the problems of radiation safety of space crews. DOZA-A1 incorporating 7 semiconductor detector with a dose sensitivity of 2.4. 10(-4) muGy/pulse and a temporal resolution of 15 seconds, and a reading and charging unit were delivered to MIR in September, 1995; the experiment began in January, 1996. Measurements were made in three locations of the basal module. The articles deals with the analysis and comparison of experimental data with results of other dosimetric determinations and predictions of the trapped radiation models.

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Proposed is a technique for estimation of radiation loading of cosmonauts' body from the data of the space station radiation monitoring system by bringing the objective to a linear mathematical model. Resulted matrix ratios allow to work out the challenge; test calculations illustrating efficiency of the proposed technique are included.

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