模拟载人探月中航天员空间辐射风险评估

空间辐射是长期载人航天飞行任务中影响航天员健康的重要风险因素。为了探求载人探月过程中对空间辐射的合理防护方式,文章借助空间辐射场模型对"嫦娥三号"飞行任务在不同质量厚度材料屏蔽下的舱内空间辐射环境进行了仿真计算,并确定了航天员各器官接受的空间辐射剂量、剂量当量以及有效剂量等辐射防护量以进行辐射风险评估。结果表明,随着屏蔽厚度的增加,航天员的各组织或器官的吸收剂量和剂量当量以及有效剂量均明显降低;采用质量屏蔽的方法对低于100 Me V的质子具有很好的防护效果,但对高能质子或重离子的防护效果不明显。计算和分析显示,载人探月过程中,只要采取适当的防护措施,航天员的空间辐射风险是可控的。     

Radiation transport modeling and assessment to better predict radiation exposure, dose, and toxicological effects to human organs on long duration space flights.

NASA is very interested in improving its ability to monitor and forecast the radiation levels that pose a health risk to space-walking astronauts as they construct the International Space Station and astronauts that will participate in long-term and deep-space missions. Human exploratory missions to the moon and Mars within the next quarter century, will expose crews to transient radiation from solar particle events which include high-energy galactic cosmic rays and high-energy protons. Because the radiation levels in space are high and solar activity is presently unpredictable, adequate shielding is needed to minimize the deleterious health effects of exposure to radiation. Today, numerous models have been developed and used to predict radiation exposure. Such a model is the Space Environment Information Systems (SPENVIS) modeling program, developed by the Belgian Institute for Space Aeronautics. SPENVIS, which has been assessed to be an excellent tool in characterizing the radiation environment for microelectronics and investigating orbital debris, is being evaluated for its usefulness with determining the dose and dose-equivalent for human exposure. Thus far. the calculations for dose-depth relations under varying shielding conditions have been in agreement with calculations done using HZETRN and PDOSE, which are well-known and widely used models for characterizing the environments for human exploratory missions. There is disagreement when assessing the impact of secondary radiation particles since SPENVIS does a crude estimation of the secondary radiation particles when calculating LET versus Flux. SPENVIS was used to model dose-depth relations for the blood-forming organs. Radiation sickness and cancer are life-threatening consequences resulting from radiation exposure. In space. exposure to radiation generally includes all of the critical organs. Biological and toxicological impacts have been included for discussion along with alternative risk mitigation methods--shielding and anti-carcinogens.     

Radiation: risk and protection in manned space flight.

Space radiation is the primary source of hazard for orbital and interplanetary space flight. Radiation levels for different space mission durations, have been established in order to determine the level of hazard. The risk of exceeding the established levels should not be more than 1%. Radiation environment models have been developed to estimate these values. It is possible to build spacecraft shielding based on the calculation of doses and the risk of exceeding these. By reviewing various calculated estimates of the risk, the radiation hazard and the efficiency of protective measures can be established for specific flights.     

Space radiation analysis: Radiation effects and particle interaction outside the Earth's magnetosphere using GRAS and GEANT4

In order to explore the Moon and Mars it is necessary to investigate the hazards due to the space environment and especially ionizing radiation. According to previous papers, much information has been presented in radiation analysis inside the Earth's magnetosphere, but much of this work was not directly relevant to the interplanetary medium. This work intends to explore the effect of radiation on humans inside structures such as the ISS and provide a detailed analysis of galactic cosmic rays (GCRs) and solar proton events (SPEs) using SPENVIS (Space Environment Effects and Information System) and CREME96 data files for particle flux outside the Earth's magnetosphere. The simulation was conducted using GRAS, a European Space Agency (ESA) software based on GEANT4. Dose and equivalent dose have been calculated as well as secondary particle effects and GCR energy spectrum. The calculated total dose effects and equivalent dose indicate the risk and effects that space radiation could have on the crew, these values are calculated using two different types of structures, the ISS and the TransHab modules. Final results indicate the amounts of radiation expected to be absorbed by the astronauts during long duration interplanetary flights; this denotes importance of radiation shielding and the use of proper materials to reduce the effects.     

Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110?nm) as well as the martian UV spectrum (λ≥200?nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.     

Radiation problems in manned spaceflight with a view towards the Space Station.

With the advent of a permanently manned Space Station, the longstanding problems of radiation protection in manned spaceflight have acquired an immediacy. This paper endeavors to emphasize the gaps of our knowledge which must be closed for effective radiation protection. The information that is required includes the accurate determination of the exposure inside the space station to the various components of the ionizing radiation, the evaluation of the biological importance of the different radiation qualities and the depth-dose distribution of the less penetrating component. There is also the possibility of an interaction with weightlessness. It is necessary to establish adequate radiation protection standards and a system of dosimetric surveillance. There is a need for studies of methods on the possibilities of hardening selective shielding of the space station. Spaceflight experiments, which might contribute to the solution of some of these problems are discussed.     

Feasibility study of astronaut standardized career dose limits in LEO and the outlook for BLEO

Cosmic Study Group SG 3.19/1.10 was established in February 2013 under the aegis of the International Academy of Astronautics to consider and compare the dose limits adopted by various space agencies for astronauts in Low Earth Orbit. A preliminary definition of the limits that might later be adopted by crews exploring Beyond Low Earth Orbit was, in addition, to be made. The present paper presents preliminary results of the study reported at a Symposium held in Turin by the Academy in July 2013. First, an account is provided of exposure limits assigned by various partner space agencies to those of their astronauts that work aboard the International Space Station. Then, gaps in the scientific and technical information required to safely implement human missions beyond the shielding provided by the geomagnetic field (to the Moon, Mars and beyond) are identified. Among many recommendations for actions to mitigate the health risks potentially posed to personnel Beyond Low Earth Orbit is the development of a preliminary concept for a Human Space Awareness System to: provide for crewed missions the means of prompt onboard detection of the ambient arrival of hazardous particles; develop a strategy for the implementation of onboard responses to hazardous radiation levels; support modeling/model validation that would enable reliable predictions to be made of the arrival of hazardous radiation at a distant spacecraft; provide for the timely transmission of particle alerts to a distant crewed vehicle at an emergency frequency using suitably located support spacecraft. Implementation of the various recommendations of the study can be realized based on a two pronged strategy whereby Space Agencies/Space Companies/Private Entrepreneurial Organizations etc. address the mastering of required key technologies (e.g. fast transportation; customized spacecraft design) while the International Academy of Astronautics, in a role of handling global international co-operation, organizes complementary studies aimed at harnessing the strengths and facilities of emerging nations in investigating/solving related problems (e.g. advanced space radiation modeling/model validation; predicting the arrivals of Solar Energetic Particles and shocks at a distant spacecraft). Ongoing progress in pursuing these complementary parallel programs could be jointly reviewed bi-annually by the Space Agencies and the International Academy of Astronautics so as to maintain momentum and direction in globally progressing towards feasible human exploration of interplanetary space.     

航天员空间活动接受辐射剂量限值的研究

空间生物学辐射效应是由空间辐射环境引起的,空间辐射环境的变化受太阳活动性影响。空间辐射水平比地表面水平高,航天员在空间所接受剂量比地面人员接受的吸收剂量高出100倍甚至更高,并且高能重离子的生物效应显著。文章简要阐述了空间辐射环境、空间辐射生物学效应与航天员的辐射剂量限值等问题。     

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.     

Superconducting magnets and mission strategies for protection from ionizing radiation in interplanetary manned missions and interplanetary habitats

First order evaluations for active shielding based on superconducting magnetic lenses were made in the past in ESA supported studies. The present increasing interest of permanent space complexes, to be considered in the far future as ‘bases’ rather than ‘stations’, located in ‘deep’ space (as it has been proposed for the L1 libration’s point between Earth and Moon, or for Stations in orbit around Mars), requires that this preliminary activity continues, envisaging the problem of the protection from cosmic ray (CR) action at a scale allowing long permanence in ‘deep’ space, not only for a relatively small number of dedicated astronauts but also to citizens conducting there ‘normal’ activities.Part of the personnel of such a ‘deep space base’ should stay and work there for a long period of time. It is proposed that the activities and life of these personnel will be concentrated in a sector protected from Galactic CR (GCR) during the whole duration of their mission. In the exceptional case of an intense flux of Solar Energetic Protons (SEP), this sector could be of use as a shelter for all the other personnel normally located in other sectors of the Space Base.The realization of the magnetic protection of the long permanence sector by well-established current materials and techniques is in principle possible, but not workable in practice for the huge required mass of the superconductor, the too low operating temperature (10–15 K) and the corresponding required cooling power and thermal shielding.However the fast progress in the production of reliable High Temperature Superconducting (HTS) or MgB₂ cables and of cryocoolers suitable for space operation opens the perspective of practicable solutions. In fact these cables, when used at relatively low temperature, but in any case higher than for NbTi and Nb₃Sn, show a thermodynamically much better behavior. Quantitative evaluations for the protection of the sector of the ‘Space Base’ to be protected from GCRs (and therefore from SEPs also) are presented.For possible large outer radius solutions it must in the meantime solve the problem of the assembling or deploying in space the conductors for returning the electric current.     

EXPOSE-E: an ESA astrobiology mission 1.5 years in space

The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110?nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10?s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.     

地球内辐射带核心区环境特征分析及质子屏蔽的蒙特卡罗模拟

辐射带粒子是近地空间卫星总剂量辐射的主要来源。文章分析了内辐射带不同高度轨道的辐射环境特性;并利用Geant4程序,针对内辐射带质子环境进行不同材料的屏蔽效能计算。结果表明:虽然传统的低?高?低原子序数材料三明治屏蔽结构对电子具有较高的屏蔽效能,却并不适用于以质子环境为主的轨道;对于工作在3000 km圆轨道、5年寿命的卫星,若要将总剂量降至30 krad(Si)以下,使用PE屏蔽材料可比Al屏蔽减重28%。     

Assessment of space environmental factors by cytotoxicity bioassays

Cellular bioassays for detection of cyto- and genotoxicity are useful in the risk assessment of space environmental factors. Such bioassay systems have the potential complement the physical detector systems used in space, insofar as they yield intrinsically biologically weighted measures of cellular responses. The experiment Cellular Responses to Radiation in Space (CERASP) has been selected by NASA/ESA to be performed on the International Space Station. It will supply basic information on the cellular response to radiation applied in microgravity. One of the biological endpoints under investigation will be survival reflected by radiation-dependent reduction of constitutive expression of the enhanced variant of green fluorescent protein (EGFP), originally isolated from the bioluminescent jellyfish Aequorea victoria. In this ground based study, the usefulness of this approach in comparison to standard techniques (colony forming ability test, MTT test) is shown.     

Cosmic radiation exposure of biological test systems during the EXPOSE-E mission

In the frame of the EXPOSE-E mission on the Columbus external payload facility EuTEF on board the International Space Station, passive thermoluminescence dosimeters were applied to measure the radiation exposure of biological samples. The detectors were located either as stacks next to biological specimens to determine the depth dose distribution or beneath the sample carriers to determine the dose levels for maximum shielding. The maximum mission dose measured in the upper layer of the depth dose part of the experiment amounted to 238±10 mGy, which relates to an average dose rate of 408±16 μGy/d. In these stacks of about 8?mm height, the dose decreased by 5-12% with depth. The maximum dose measured beneath the sample carriers was 215±16 mGy, which amounts to an average dose rate of 368±27 μGy/d. These values are close to those assessed for the interior of the Columbus module and demonstrate the high shielding of the biological experiments within the EXPOSE-E facility. Besides the shielding by the EXPOSE-E hardware itself, additional shielding was experienced by the external structures adjacent to EXPOSE-E, such as EuTEF and Columbus. This led to a dose gradient over the entire exposure area, from 215±16 mGy for the lowest to 121±6 mGy for maximum shielding. Hence, the doses perceived by the biological samples inside EXPOSE-E varied by 70% (from lowest to highest dose). As a consequence of the high shielding, the biological samples were predominantly exposed to galactic cosmic heavy ions, while electrons and a significant fraction of protons of the radiation belts and solar wind did not reach the samples.     

总剂量探测技术的空间应用

空间辐射对飞行器可造成辐射损伤甚至失效,对航天员的生命健康安全存在着威胁。随着航天活动的深入,对空间辐射探测技术的发展提出了更高的要求。通过辐射敏感场效应晶体管（RADFET）探测技术设计研制了总剂量探测器,介绍了探测器的设计原理和测试数据分析,以及研究发展方向和空间应用展望。     

Toroidal magnetic fields for protecting astronauts from ionizing radiation in long duration deep space missions

Among the configurations of superconducting magnet structures proposed for protecting manned spaceships or manned deep space bases from ionizing radiation, toroidal ones are the most appealing for the efficient use of the magnetic field, being most of the incoming particle directions perpendicular to the induction lines of the field. The parameters of the toroid configuration essentially depend from the shape and volume of the habitat to be protected and the level of protection to be guaranteed. Two options are considered: (1) the magnetic system forming with the habitat a unique complex (compact toroid) to be launched as one piece; (2) the magnetic system to be launched separately from the habitat and assembled around it in space (large toroid).     

卫星空间辐射效应及防护技术飞行试验初步设想

文章分析了国内外卫星空间辐射效应飞行试验的现状和发展趋势,根据我国卫星空间辐射效应及防护技术的具体情况,对卫星空间辐射效应及防护技术空间飞行试验的开展提出了建议。     

The BOSS and BIOMEX space experiments on the EXPOSE-R2 mission: Endurance of the desert cyanobacterium Chroococcidiopsis under simulated space vacuum,Martian atmosphere,UVC radiation and temperature extremes.

The proposed space experiments BOSS (Biofilm Organisms Surfing Space) and BIOMEX (BIOlogy and Mars experiment) will take place on the space exposure facility EXPOSE-R2 on the International Space Station (ISS), which is set to be launched in 2014. In BOSS the hypothesis to be tested is that microorganisms grown as biofilms, hence embedded in self-produced extracellular polymeric substances, are more tolerant to space and Martian conditions compared to their planktonic counterparts. Various microbial biofilms have been developed including those obtained from the cyanobacterium Chroococcidiopsis isolated from hot and cold deserts. The prime objective of BIOMEX is to evaluate to what extent biomolecules are resistant to, and can maintain their stability under, space and Mars-like conditions; therefore a variety of pigments and cell components are under investigation to establish a biosignature data base; e.g. a Raman spectral library to be used for extraterrestrial life biosignatures. The secondary objective of BIOMEX is to investigate the endurance of extremophiles, focusing on their interactions with Lunar and Martian mineral analogues. Ground-based studies are currently being carried out in the framework of EVTs (Experiment Verification Tests) by exposing selected organisms to space and Martian simulations. Results on a desert strain of Chroococcidiopsis obtained from the first set of EVT, e.g. space vacuum, Mars atmosphere, UVC radiation, temperature cycles and extremes, suggested that dried biofilms exhibited an enhanced survival compared to planktonic lifestyle. Moreover the protection provided by a Martian mineral analogue (S-MRS) to the sub-cellular integrities of Chroococcidiopsis against UVC radiation supports the endurance of this cyanobacterium under extraterrestrial conditions and its relevance in the development of life detection strategies.     

Reliability analysis and utilization of PEMs in space application

More and more plastic encapsulated microcircuits (PEMs) are used in space missions to achieve high performance. Since PEMs are designed for use in terrestrial operating conditions, the successful usage of PEMs in space harsh environment is closely related to reliability issues, which should be considered firstly. However, there is no ready-made methodology for PEMs in space applications. This paper discusses the reliability for the usage of PEMs in space. This reliability analysis can be divided into five categories: radiation test, radiation hardness, screening test, reliability calculation and reliability assessment. One case study is also presented to illuminate the details of the process, in which a PEM part is used in a joint space program Double-Star Project between the European Space Agency (ESA) and China. The influence of environmental constrains including radiation, humidity, temperature and mechanics on the PEM part has been considered. Both Double-Star Project satellites are still running well in space now.