Evaluation of a combined electrostatic and magnetostatic configuration for active space-radiation shielding

Developing successful and optimal solutions to mitigating the hazards of severe space radiation in deep space long duration missions is critical for the success of deep-space explorations. A recent report (Tripathi et al., 2008) had explored the feasibility of using electrostatic shielding. Here, we continue to extend the electrostatic shielding strategy and examine a hybrid configuration that utilizes both electrostatic and magnetostatic fields. The main advantages of this system are shown to be: (i) a much better shielding and repulsion of incident ions from both solar particle events (SPE) and galactic cosmic rays (GCR), (ii) reductions in the power requirement for re-charging the electrostatic sub-system, and (iii) low requirements of the magnetic fields that are well below the thresholds set for health and safety for long-term exposures. Furthermore, our results show transmission levels reduced to levels as low as 30% for energies around 1000 MeV, and near total elimination of SPE radiation by these hybrid configurations. It is also shown that the power needed to replenish the electrostatic charges due to particle hits from the GCR and SPE radiation is minimal.     

Analytical-HZETRN model for rapid assessment of active magnetic radiation shielding

The use of active radiation shielding designs has the potential to reduce the radiation exposure received by astronauts on deep-space missions at a significantly lower mass penalty than designs utilizing only passive shielding. Unfortunately, the determination of the radiation exposure inside these shielded environments often involves lengthy and computationally intensive Monte Carlo analysis. In order to evaluate the large trade space of design parameters associated with a magnetic radiation shield design, an analytical model was developed for the determination of flux inside a solenoid magnetic field due to the Galactic Cosmic Radiation (GCR) radiation environment. This analytical model was then coupled with NASA’s radiation transport code, HZETRN, to account for the effects of passive/structural shielding mass. The resulting model can rapidly obtain results for a given configuration and can therefore be used to analyze an entire trade space of potential variables in less time than is required for even a single Monte Carlo run. Analyzing this trade space for a solenoid magnetic shield design indicates that active shield bending powers greater than ∼15 Tm and passive/structural shielding thicknesses greater than 40 g/cm² have a limited impact on reducing dose equivalent values. Also, it is shown that higher magnetic field strengths are more effective than thicker magnetic fields at reducing dose equivalent.     

Active shielding for long duration interplanetary manned missions

For long duration interplanetary manned missions the protection of astronauts from cosmic radiation is an unavoidable problem that has been considered by many space agencies. In Europe, during 2002–2004, the European Space Agency supported two research programs on this thematic: one was the constitution of a dedicated study group (on the thematic ‘Shielding from cosmic radiation for interplanetary missions: active and passive methods’) in the framework of the ‘life and physical sciences’ report, and the other an industrial study concerning the ‘radiation exposure and mission strategies for interplanetary manned missions to Moon and Mars’. Both programs concluded that, outside the protection of the magnetosphere and in the presence of the most intense and energetic solar events, the protection cannot rely solely on the mechanical structures of the spacecraft, but a temporary shelter must be provided. Because of the limited mass budget, the shelter should be based on the use of superconducting magnetic systems. For long duration missions the astronauts must be protected from the much more energetic galactic cosmic rays during the whole mission period. This requires the protection of a large habitat where they could live and work, and not the temporary protection of a small volume shelter. With passive absorbers unable to play any significant role, the use of active shielding is mandatory. The possibilities offered by superconducting magnets are discussed, and recommendations are made about the needed R&D. The technical developments that have occurred in the meanwhile and the evolving panorama of possible near future interplanetary missions, require revising the pioneering studies of the last decades and the adoption of a strategy that considers long lasting human permanence in ‘deep’ space, moreover not only for a relatively small number of dedicated astronauts but also for citizens conducting there ‘normal’ activities.     

Materials trade study for lunar/gateway missions.

The National Aeronautics and Space Administration (NASA) administrator has identified protection from radiation hazards as one of the two biggest problems of the agency with respect to human deep space missions. The intensity and strength of cosmic radiation in deep space makes this a 'must solve' problem for space missions. The Moon and two Earth-Moon Lagrange points near Moon are being proposed as hubs for deep space missions. The focus of this study is to identify approaches to protecting astronauts and habitats from adverse effects from space radiation both for single missions and multiple missions for career astronauts to these destinations. As the great cost of added radiation shielding is a potential limiting factor in deep space missions, reduction of mass, without compromising safety, is of paramount importance. The choice of material and selection of the crew profile play major roles in design and mission operations. Material trade studies in shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of space mission's to two Earth-Moon co-linear Lagrange points (L1) between Earth and the Moon and (L2) on back side of the moon as seen from Earth, and to the Moon have been studied. It is found that, for single missions, current state-of-the-art knowledge of material provides adequate shielding. On the other hand, the choice of shield material is absolutely critical for career astronauts and revolutionary materials need to be developed for these missions. This study also provides a guide to the effectiveness of multifunctional materials in preparation for more detailed geometry studies in progress.     

A Novel Magnetic Configuration for Space Radiation Active Shielding

Space radiation has been identified as the main health hazard to crews involved in manned Mars missions. Active shielding is more effective than passive shielding to the very energetic particles from cosmic rays. Particle motion in a magnetic field is studied based on the single-particle theory and Monte Carlo method. By comparing the shielding efficiency of different magnetic field configurations, a novel active magnetic shielding configuration with lower mass cost and power consumption is proposed for manned Mars missions. The new magnetic configuration can shield 92.8% of protons and 84.4% of alpha particles with E < 4 GeV·n-1, when considering the passive shielding contribution of 10.0 g·cm-2 Al Shielding, the required magnetic stiffness can be reduced from 27 Tm to 16 Tm. The detailed analysis of mass cost and power consumption shows that active shielding will be a promising means to protect crews from space radiation exposure in manned Mars missions.      

载人小行星探测的总体方案设想

载人探测近地小行星的工程规模和技术难度介于载人探月和载人火星探测之间,是人类开展载人火星探测和飞向更遥远深空的跳板,对于航天技术的发展和科学问题的探索有着极其重要的意义。在调研国外载人小行星探测方案设想的基础上,结合我国航天技术现状和发展趋势,提出了一种载人小行星探测的总体方案设想,并梳理了载人小行星探测的关键技术。研究成果可以作为我国载人小行星探测任务论证和设计的有益参考。     

A lunar L2-Farside exploration and science mission concept with the Orion Multi-Purpose Crew Vehicle and a teleoperated lander/rover

A novel concept is presented in this paper for a human mission to the lunar L2 (Lagrange) point that would be a proving ground for future exploration missions to deep space while also overseeing scientifically important investigations. In an L2 halo orbit above the lunar farside, the astronauts aboard the Orion Crew Vehicle would travel 15% farther from Earth than did the Apollo astronauts and spend almost three times longer in deep space. Such a mission would serve as a first step beyond low Earth orbit and prove out operational spaceflight capabilities such as life support, communication, high speed re-entry, and radiation protection prior to more difficult human exploration missions. On this proposed mission, the crew would teleoperate landers/rovers on the unexplored lunar farside, which would obtain samples from the geologically interesting farside and deploy a low radio frequency telescope. Sampling the South Pole-Aitken basin, one of the oldest impact basins in the solar system, is a key science objective of the 2011 Planetary Science Decadal Survey. Observations at low radio frequencies to track the effects of the Universe’s first stars/galaxies on the intergalactic medium are a priority of the 2010 Astronomy and Astrophysics Decadal Survey. Such telerobotic oversight would also demonstrate capability for human and robotic cooperation on future, more complex deep space missions such as exploring Mars.     

深空探测器自主天文导航技术综述

在深空探测中,单独使用无线电测控存在精度、实时性、覆盖性等方面的限制。作为无线电测控的有效补充,自主天文导航是保证深空探测任务成功的关键技术之一。面向深空探测对自主天文导航的迫切需求,概述了深空探测器自主天文导航的基本原理,简要介绍了深空探测器自主天文导航的研究进展,并重点分析探讨了深空探测器自主天文导航的关键技术和发展趋势。分析结果可为我国未来深空探测器天文导航系统研制提供参考,并为深空探测任务的总体设计提供帮助。     

Deep space environments for human exploration.

Mission scenarios outside the Earth's protective magnetic shield are being studied. Included are high usage assets in the near-Earth environment for casual trips, for research, and for commercial/operational platforms, in which career exposures will be multi-mission determined over the astronaut's lifetime. The operational platforms will serve as launching points for deep space exploration missions, characterized by a single long-duration mission during the astronaut's career. The exploration beyond these operational platforms will include missions to planets, asteroids, and planetary satellites. The interplanetary environment is evaluated using convective diffusion theory. Local environments for each celestial body are modeled by using results from the most recent targeted spacecraft, and integrated into the design environments. Design scenarios are then evaluated for these missions. The underlying assumptions in arriving at the model environments and their impact on mission exposures within various shield materials will be discussed.     

载人深空探测任务的空间环境工程关键问题

对载人深空探测过程中将遭受的太阳宇宙射线、银河宇宙射线、微重力、尘与尘暴、深空微生物等环境进行分析。对不同深空环境给航天员带来的威胁进行了探讨。从物理屏蔽防护、辐射风险的监测和预警、辐射防护药物、航天员选拨等角度对采取的措施进行了阐述。从空间辐射对航天员的损伤机理、抗辐射和微重力药物开发、空间辐射屏蔽防护结构与材料、航天服自清洁、抗微生物侵蚀材料的研发等多个角度对需要进一步开展的工作进行了讨论。     

深空测控新技术研究进展

测控系统是航天工程不可或缺的重要组成部分,其导航通信能力在深空探测任务中尤为重要。深空探测任务远距离、长延迟、弱信号、易中断条件下高精度导航测量和高速可靠数据传输始终是深空测控技术需要重点解决的问题。围绕这些问题重点介绍了在天线组阵、再生伪码测距、连接端站干涉测量、相位参考干涉测量和容延迟网络等一系列新技术方面开展的研究工作和部分成果,可以看到,这些成果的应用将丰富深空测控技术手段,在未来更复杂、更遥远的深空探测任务中将会发挥重要作用。     

Adaptive response studies may help choose astronauts for long-term space travel.

Long-term manned exploratory missions are planned for the future. Exposure to high-energy neutrons, protons and high charge and energy particles during a deep space mission, needs protection against the detrimental effects of space radiation. It has been suggested that exposure to unpredictable extremely large solar particle events would kill the astronauts without massive shielding. To reduce this risk to astronauts and to minimize the need for shielding, astronauts with highest significant adaptive responses should be chosen. It has been demonstrated that some humans living in very high natural radiation areas have acquired high adaptive responses to external radiation. Therefore, we suggest that for a deep space mission the adaptive response of all potential crew members be measured and only those with high adaptive response be chosen. We also proclaim that chronic exposure to elevated levels of radiation can considerably decrease radiation susceptibility and better protect astronauts against the unpredictable exposure to sudden and dramatic increase in flux due to solar flares and coronal mass ejections.     

载人深空探测磁场主动辐射防护技术研究

基于单粒子轨道理论和蒙特卡洛方法建立了一种磁场主动屏蔽防护分析方法,针对理想磁场构型分析了屏蔽磁场强度、厚度和结构对屏蔽效果的影响。研究结果表明：屏蔽效率随磁刚度BL增大且当磁刚度BL一定时,增加磁场强度B比增加磁场厚度L更有效;对于有限长屏蔽磁场构型,端盖区需加强防护;桶状区与端盖区采用直线型屏蔽磁场的构型防护效果最好,能够对典型银河宇宙线能谱屏蔽90%的高能粒子。     

Uncertainties in radiation effect predictions for the natural radiation environments of space.

Future manned missions beyond low earth orbit require accurate predictions of the risk to astronauts and to critical systems from exposure to ionizing radiation. For low-level exposures, the hazards are dominated by rare single-event phenomena where individual cosmic-ray particles or spallation reactions result in potentially catastrophic changes in critical components. Examples might be a biological lesion leading to cancer in an astronaut or a memory upset leading to an undesired rocket firing. The risks of such events appears to depend on the amount of energy deposited within critical sensitive volumes of biological cells and microelectronic components. The critical environmental information needed to estimate the risks posed by the natural space environments, including solar flares, is the number of times more than a threshold amount of energy for an event will be deposited in the critical microvolumes. These predictions are complicated by uncertainties in the natural environments, particularly the composition of flares, and by the effects of shielding. Microdosimetric data for large numbers of orbits are needed to improve the environmental models and to test the transport codes used to predict event rates.     

在轨3D打印及装配技术在深空探测领域的应用研究进展

以太阳帆深空探测为引子,对以在轨3D打印及装配技术为基础的在轨制造技术的必要性和可行性进行分析,分别阐述了在轨3D打印技术的技术优势、技术可行性以及在轨装配的最新研究进展,并重点研究了美国NASA资助的“蜘蛛制造”在轨制造技术,此项研究成功地将在轨3D打印和空间自主装配有机结合起来,有望突破目前空间可展开机构无法达到万米量级的技术局限性,为中国深空探测的发展提供了一种可供选择的发展思路。     

中国月球及深空空间环境探测

深空探测承载着人类航天技术发展、探索宇宙奥秘和寻找地外生命及人类宜居地的重任,成为各航天大国关注的热点。我国月球与深空探测虽然起步晚,但起点高,正在追赶并将实现领先。简要回顾了我国月球及深空空间环境探测的载荷情况、数据结果、理论和应用研究成果,简述了当前在研的自主火星空间环境探测目标以及规划中的未来深空探测任务,并根据当前国际发展态势,及我国在研、规划中的月球及深空探测任务情况,分析了我国月球及深空空间环境探测的关键科学问题、载荷技术发展趋势、理论与模拟的研究需求,最后对深空环境探测进行了展望。     

Uncertainties in estimates of the risks of late effects from space radiation.

Methods used to project risks in low-Earth orbit are of questionable merit for exploration missions because of the limited radiobiology data and knowledge of galactic cosmic ray (GCR) heavy ions, which causes estimates of the risk of late effects to be highly uncertain. Risk projections involve a product of many biological and physical factors, each of which has a differential range of uncertainty due to lack of data and knowledge. Using the linear-additivity model for radiation risks, we use Monte-Carlo sampling from subjective uncertainty distributions in each factor to obtain an estimate of the overall uncertainty in risk projections. The resulting methodology is applied to several human space exploration mission scenarios including a deep space outpost and Mars missions of duration of 360, 660, and 1000 days. The major results are the quantification of the uncertainties in current risk estimates, the identification of factors that dominate risk projection uncertainties, and the development of a method to quantify candidate approaches to reduce uncertainties or mitigate risks. The large uncertainties in GCR risk projections lead to probability distributions of risk that mask any potential risk reduction using the "optimization" of shielding materials or configurations. In contrast, the design of shielding optimization approaches for solar particle events and trapped protons can be made at this time and promising technologies can be shown to have merit using our approach. The methods used also make it possible to express risk management objectives in terms of quantitative metrics, e.g., the number of days in space without exceeding a given risk level within well-defined confidence limits.     

Integration of In-Situ Resource Utilization into lunar/Mars exploration through field analogs

The ability to extract and process resources at the site of exploration into useful products such as propellants, life support and power system consumables, and radiation and rocket exhaust plume debris shielding, known as In-Situ Resource Utilization or ISRU, has the potential to significantly reduce the launch mass, risk, and cost of robotic and human exploration of space. The incorporation of ISRU into missions can also significantly influence technology selection and system development in other areas such as power, life support, and propulsion. For example, the ability to extract or produce large amounts of oxygen and/or water in-situ could minimize the need to completely close life support air and water processing system cycles, change thermal and radiation protection of habitats, and influence propellant selection for ascent vehicles and surface propulsive hoppers. While concepts and even laboratory work on evaluating and developing ISRU techniques such as oxygen extraction from lunar regolith have been going on since before the Apollo 11 Moon landing, no ISRU system has ever flown in space, and only recently have ISRU technologies been developed at a scale and at a system level that is relevant to actual robotic and human mission applications. Because ISRU hardware and systems have never been demonstrated or utilized before on robotic or human missions, architecture and mission planners and surface system hardware developers are hesitant to rely on ISRU products and services that are critical to mission and system implementation success. To build confidence in ISRU systems for future missions and assess how ISRU systems can best influence and integrate with other surface system elements, NASA, with international partners, are performing analog field tests to understand how to take advantage of ISRU capabilities and benefits with the minimum of risk associated with introducing this game-changing approach to exploration. This paper will describe and review the results of four analog field tests (Moses Lake in 6/08, Mauna Kea in 11/08, Flagstaff in 9/09, and Mauna Kea in 1/10) that have begun the process of integrating ISRU into robotic and human exploration systems and missions, and propose future ISRU-related analog field test activities that can be performed in collaboration with non-US space agencies.     

Estimation of Galactic Cosmic Ray exposure inside and outside the Earth’s magnetosphere during the recent solar minimum between solar cycles 23 and 24

The evidently low solar activity observed between solar cycles 23 and 24 during the years 2008–2010 led to a substantial increase in the Galactic Cosmic Ray (GCR) intensity in comparison with preceding solar minima. As the GCRs consist of highly-ionizing charged particles having the potential to cause biological damage, they are a subject of concern for manned missions to space. With the enhanced particle fluxes observed between 2008 and 2010, it is reasonable to assume that the radiation exposure from GCR must have also increased to unusually high levels. In this paper, the GCR exposure outside and inside the Earth’s magnetosphere is numerically calculated for time periods starting from 1970 to the end of 2011 in order to investigate the increase in dose levels during the years 2008–2010 in comparison with the last three solar minima. The dose rates were calculated in a water sphere, used as a surrogate for the human body, either unshielded or surrounded by aluminium shielding of 0.3, 10 or 40 g/cm².     

Radiation hazards on space missions outside the magnetosphere.

Future space missions outside the magnetosphere will subject astronauts to a hostile and unfamiliar radiation environment. An annual dose equivalent to the blood-forming organs (BFOs) of approximately 0.5 Sv is expected, mostly from heavy ions in the galactic cosmic radiation. On long-duration missions, an anomalously-large solar energetic particle event may occur. Such an event can expose astronauts to up to approximately 25 Gy (skin dose) and up to approximately 2 Sv (BFO dose) with no shielding. The anticipated radiation exposure may necessitate spacecraft design concessions and some restriction of mission activities. In this paper we discuss our model calculations of radiation doses in several exo-magnetospheric environments. Specific radiation shielding strategies are discussed. A new calculation of aluminum equivalents of potential spacecraft shielding materials demonstrates the importance of low-atomic-mass species for protection from galactic cosmic radiation.