The Martian and extraterrestrial UV radiation environment--1. Biological and closed-loop ecosystem considerations

The Martian surface is exposed to both UVC radiation (<280 nm) and higher doses of UVB (280-315 nm) compared to the surface of the Earth. Terrestrial organisms have not evolved to cope with such high levels of UVC and UVB and thus any attempts to introduce organisms to Mars, particularly in closed-loop life support systems that use ambient sunlight, must address this problem. Here we examine the UV radiation environment of Mars with respect to biological systems. Action spectra and UV surface fluxes are used to estimate the UV stress that both DNA and chloroplasts would experience. From this vantage point it is possible to consider appropriate measures to address the problem of the Martian UV environment for future long term human exploration and settlement strategies. Some prospects for improving the UV tolerance of organisms are also discussed. Existing artificial ecosystems such as Biosphere 2 can provide some insights into design strategies pertinent to high UV environments. Some prospects for improving the UV tolerance of organisms are also discussed. The data also have implications for the establishment of closed-loop ecosystems using natural sunlight on the lunar surface and elsewhere in the Solar System.     

Ozone concentrations and ultraviolet fluxes on Earth-like planets around other stars

Coupled radiative-convective/photochemical modeling was performed for Earth-like planets orbiting different types of stars (the Sun as a G2V, an F2V, and a K2V star). O(2) concentrations between 1 and 10(-5) times the present atmospheric level (PAL) were simulated. The results were used to calculate visible/near-IR and thermal-IR spectra, along with surface UV fluxes and relative dose rates for erythema and DNA damage. For the spectral resolution and sensitivity currently planned for the first generation of terrestrial planet detection and characterization missions, we find that O(2) should be observable remotely in the visible for atmospheres containing at least 10(-2) PAL of O(2). O(3) should be visible in the thermal-IR for atmospheres containing at least 10(-3) PAL of O(2). CH(4) is not expected to be observable in 1 PAL O(2) atmospheres like that of modern Earth, but it might be observable at thermal-IR wavelengths in "mid-Proterozoic-type" atmospheres containing approximately 10(-1) PAL of O(2). Thus, the simultaneous detection of both O(3) and CH(4) - considered to be a reliable indication of life - is within the realm of possibility. High-O(2) planets orbiting K2V and F2V stars are both better protected from surface UV radiation than is modern Earth. For the F2V case the high intrinsic UV luminosity of the star is more than offset by the much thicker ozone layer. At O(2) levels below approximately 10(-2) PAL, planets around all three types of stars are subject to high surface UV fluxes, with the F2V planet exhibiting the most biologically dangerous radiation environment. Thus, while advanced life is theoretically possible on high-O(2) planets around F stars, it is not obvious that it would evolve as it did on Earth.     

月面和近月空间环境及其影响

月球探测器所经历的月面和近月空间环境主要包括：月面低重力、月面温度、近月空间辐射、月壤、月尘、月面地形地貌、月面静电等。文章在对月面和近月空间环境研究的基础上,结合国外月球探测器在月球环境方面的研究成果,分析了我国月球探测器所经历的月面和近月空间环境特点及其影响效应,并提出相应的改进措施或必要的试验验证,可为月球探测器的研制提供参考。     

Human locomotion and workload for simulated lunar and Martian environments

Human locomotion in simulated lunar and Martian environments is investigated. A unique human-rated underwater treadmill and an adjustable ballasting harness simulate partial gravity in order to better understand how gravity determines the biomechanics and energetics of human locomotion. This study has two research aspects, biomechanics and energetics. The fundamental biomechanics measurements are continuously recorded vertical forces as exerted by subjects of the treadmill which is instrumented with a force platform. Experimental results indicate that peak vertical force and stride frequency decrease as the gravity level is reduced. Foot contact time is independent of gravity level. Oxygen uptake measurements, VO2, constitute the energetics, or workload, data for this study. As theory predicts, locomotion energy requirements for lunar (1/6-g) and Martian (3/8-g) gravity levels are significantly less than at 1-g. The observed variation in workload with gravity level is nonmonotonic, however, in over half the subject population. The hypothesis is offered that energy expenditure increases for lunar, as compared with Martian, locomotion due to the subject "wasting energy" for stability and posture control in simulated lunar gravity. Biomechanics data could influence advanced spacesuit design and planetary habitat design, while workload data will help define oxygen requirements for planetary life support systems.     

Optimization of measurements of the Earth’s radiation belt particle fluxes

The Earth’s radiation belts discovered at the end of the 1950s have great scientific and practical interest. Their main characteristics in magnetically quiet periods are well known. However, the dynamics of the Earth’s radiation belts during magnetic storms and substorms, particularly the dynamics of relativistic electrons of the outer belt, when Earth’s radiation belt particle fluxes undergo significant time variations, is studied insufficiently. At present, principally new experiments have been performed and planned with the intention to better study the dynamics of the Earth’s radiation belts and to operationally control the space-energy distributions of the Earth’s radiation belt particle fluxes. In this paper, for spacecraft designed to measure the fluxes of electrons and protons of the Earth’s radiation belts at altitudes of 0.5–10000 km, the optimal versions for detector orientation and orbital parameters have been considered and selected.     

Martian polar expeditions: problems and solutions.

The Martian polar ice caps are regions of substantial scientific interest, being the most dynamic regions of Mars. They are volatile sinks and thus closely linked to Martian climatic conditions. Because of their scale and the precedent set by the past history of polar exploration on Earth, it is likely that an age of polar exploration will emerge on the surface of Mars after the establishment of a capable support structure at lower latitudes. Expeditions might be launched either from a lower latitude base camp or from a human-tended polar base. Based on previously presented expeditionary routes to the Martian poles, in this paper a "spiral in-spiral out" unsupported transpolar assault on the Martian north geographical pole is used as a Reference expedition to propose new types of equipment for the human polar exploration of Mars. Martian polar "ball" tents and "hover" modifications to the Nansen sledge for sledging on CO2-containing water ice substrates under low atmospheric pressures are suggested as elements for the success of these endeavours.Other challenges faced by these expeditions are quantitatively and qualitatively addressed.     

A socio-economic evaluation of the lunar environment and resources: II. Energy for the selenosphere

This first of several study papers, based on a fundamental paper presented in 1972, provides an independent conceptual analysis and evaluation of the lunar environment as industrial base and habitat. A selenosphere system strategy is outlined. The underlying concept is that of one or several lunar industrial zones for resource extraction and on-surface processing, integrated with a circumlunar zero-g processing capability, serving markets in geolunar space. A classification of lunar elements by utilization category is presented. Lunar oxygen is a prime candidate for being an initial economic “drawing card”, because of its value for fast transportation in geolunar space, requiring significantly fewer ships for equal transfer capability per unit time than electric transports which, however, have value, especially between geosynchronous and lunar orbit. The reduced development difficulties of controlled fusion outside the atmosphere and its advantages for extracting oxygen and other elements in quantity are summarized. Examples of lunar cycle management as fundamental exoindustrial requirement for economic resource enhancement are presented. The principal initial socio-economic value of lunar industry lies in the use of lunar resources for exoindustrial products and operations designed to accelerate, intensify and diversify Earth-related benefits. In the longer run, lunar settlements are a highly suitable proving ground for studying and testing the complex matrix of technological, biological, cultural, social and psychological aspects that must be understood and manageable before large settlements beyond Earth can have a realistic basis for viability. The lunar environment is more suitable for experimentation and comparatively more “forgiving” in case of failures than is orbital space.     

Lunar oxygen: Economic benefit for transportation systems and in situ production by fluorination

The use of oxygen produced on the Moon—called “MOONLOX”—is considered as a propellant component for a reusable Earth-Moon transportation system consisting of an aeroassisted orbital transfer vehicle and a lunar bus for lunar descent/ascent. Conditions for economic benefit are discussed and the processing concept of a lunar oxygen plant based on fluorination is presented. It is shown that the necessary mass of supply from Earth for MOONLOX-production is an important parameter, which may not be neglected due to its strong influence on the economy. In the ideal case where no supplies from Earth are required a reduction of up to 50% in masses to be launched into low Earth orbit can be obtained for a typical lunar mission with use of MOONLOX compared to a reference scenario with Earth-derived propellant. Mass-saving decreases, however, significantly with increasing supply from Earth until a critical supply-rate is reached—measured in percentage of MOONLOX-mass produced and consumed—beyond which mass-saving and thus economically promising lunar oxygen production is no longer possible. This critical supply-rate depends on the scenario for MOONLOX-utilization and is much larger in the case of in situ use of MOONLOX on the lunar surface, e.g. as ascent propellant for the lunar bus, than in the case of export for complete refuelling of both space vehicles. The latter scenario therefore requires significantly more autonomy for MOONLOX-production. The reduction of masses to be transported into low Earth orbit and corresponding MOONLOX-consumption define for given specific Earth-to-LEO transportation costs an upper limit on MOONLOX-production costs beyond which economic benefit is not possible. Depending on the MOONLOX-utilization strategy this upper limit varies between 3000 and 55000 $/kg for current Earth-to-LEO transportation costs.     

行星表面巡视探测器遥操作技术研究

行星表面巡视探测器的遥操作,是整个行星遥科学探测过程的重要组成部分。文章首先对遥操作的基本概念和行星表面巡视探测器遥操作的基本特性做了初步的分析,然后对成功发射到月球和火星表面并进行巡视探测的8个巡视探测器进行了归纳与总结,最后对行星表面巡视探测器的遥操作技术进行了总结与展望,并建议在我国首次登陆的月面巡视探测器上采用以遥操作为主,同时设置遥操作加半自主的操作模式。     

The past and future of the earth-moon system

The lunar orbit is presently expanding due, we believe, to tidal friction, i.e. the attraction of the moon for the tides it raises on the rotating Earth. The Moon may therefore have been significantly closer to the Earth in the distant past, a point of great interest to those studying the lunar origin. This work presents the results of the integration of the equations which govern the rates of change of the lunar orbit elements and the angular momentum of the Earth. Results are presented for both the past and future of the Earth-Moon system.     

月球坑内空间环境热流的分布研究

文章推导获得了月面阳光矢量和月球坑内探测器表面关系的表达式,采用蒙特卡罗法数值计算探测器各表面的辐射热流,分析了月球坑内环境辐射热流的分布特征。讨论了月面纬度、月球坑尺寸、月面发射率等参数对探测器表面热流的影响。计算表明:月面纬度增加及月球坑坑口半径的减小均会导致某些时刻阳光无法照射到坑底,从而与其他工况有较大的计算差别,两参数对探测器各面热流的影响规律不同;月面发射率对探测器表面热流的影响作用较大,增加月面发射率能明显降低探测器某些表面的辐射热流。     

Illumination of the Earth’s ionosphere by the vacuum ultraviolet radiation reflected by the moon

The spectral curve of the flux density of the radiation, which is reflected by the full moon towards the Earth’s ionosphere within a wavelength range of 200–1700 Å, has been presented. This curve is obtained by the approximation of space experiment data available in the scientific literature on the lunar spectral albedo and solar spectrum. Estimates of maximum values of spectral densities of fluxes reflected by the full moon in the neighborhood of wavelengths of ionization of basic ionospheric particles (neutral atoms of H I, He I, N I, O I, and Ar I and ions of He II, N II, O II, Ar II, N III, O III, and Ar III, as well as molecules of H₂, N₂, and O₂) are given.     

Self-sustaining Mars colonies utilizing the North Polar Cap and the Martian atmosphere

A revolutionary new concept for the early establishment of robust, self-sustaining Martian colonies is described. The colonies would be located on the North Polar Cap of Mars and utilize readily available water ice and the CO2 Martian atmosphere as raw materials to produce all of the propellants, fuel, air, water, plastics, food, and other supplies needed by the colony. The colonists would live in thermally insulated large, comfortable habitats under the ice surface, fully shielded from cosmic rays. The habitats and supplies would be produced by a compact, lightweight (~4 metric tons) nuclear powered robotic unit termed ALPH (Atomic Liberation of Propellant and Habitat), which would land 2 years before the colonists arrived. Using a compact, lightweight 5 MW (th) nuclear reactor/steam turbine (1 MW(e)) power source and small process units (e.g., H2O electrolyzer, H2 and O2 liquefiers, methanator, plastic polymerizer, food producer, etc.) ALPH would stockpile many hundreds of tons of supplies in melt cavities under the ice, plus insulated habitats, to be in place and ready for use when the colonists landed. With the stockpiled supplies, the colonists would construct and operate rovers and flyers to explore the surface of Mars. ALPH greatly reduces the amount of Earth supplied material needed and enables large permanent colonies on Mars. It also greatly reduces human and mission risks and vastly increases the capability not only for exploration of the surrounding Martian surface, but also the ice cap itself. The North Polar Cap is at the center of the vast ancient ocean that covered much of the Martian Northern Hemisphere. Small, nuclear heated robotic probes would travel deep (1 km or more) inside the ice cap, collecting data on its internal structure, the composition and properties of the ancient Martian atmosphere, and possible evidence of ancient life forms (microfossils, traces of DNA, etc.) that were deposited either by wind or as remnants of the ancient ocean. Details of the ALPH system, which is based on existing technology, are presented. ALPH units could be developed and demonstrated on Earth ice sheets within a few years. An Earth-Mars space transport architecture is described, in which Mars produced propellant and supplies for return journeys to Earth would be lifted with relatively low DeltaV to Mars orbit, and from there transported back to Earth orbit, enabling faster and lower cost trips from Earth to Mars. The exploration capability and quality of life in a mature Martian colony of 500 persons located on the North Polar Cap is outlined.     

On the problem of lunar radiation environment

In connection with projects of manned bases on the Moon it becomes topical to estimate radiation danger for their inhabitants. In this paper we describe a method of evaluation of the radiation environment on the lunar surface produced by galactic and solar cosmic rays. The roles of both primary and secondary radiations generated in the depth of the lunar soil under the action of high-energy protons and nuclei are taken into account. Calculated fluxes of particles are used in order to estimate annual averaged absorbed and equivalent local dose rates in tissues. It is established that in the lunar rock the contribution of secondary neutrons to the dose rate exceeds that of protons. The contribution of the secondary particles generated by nuclei of galactic cosmic rays to the dose rate is estimated.     

Estimation of radiation risk for astronauts on the Moon

The problem of estimating the risk of radiation for humans on the Moon is discussed, taking into account the probabilistic nature of occurrence of solar particle events. Calculations of the expected values of tissue-averaged equivalent dose rates, which are created by galactic and solar cosmic-ray particle fluxes on the lunar surface behind shielding, are made for different durations of lunar missions.     

计算模拟月壤颗粒吸收及散射特性的一种球叠加模型

针对模拟月壤复杂的外形特征以及多相非均质的微观结构,提出了一种计算模拟月壤颗粒吸收及散射特性的球叠加模型。根据模拟月壤颗粒的形状指数和分形特征识别结果,归纳了4种主要的模拟月壤颗粒类型,并采用蒙特卡罗光线跟踪法研究了这4种颗粒在单色平行光照射下的吸收及散射特性。与已有的非球形颗粒辐射特性的算法比较显示,该模型具有良好的计算准确性。在数值计算的基础上,分析了颗粒尺度参数及光学常数对其自身辐射特性的影响,并通过改变平行光照下的光线入射角度,分析了非球形颗粒的朝向对其自身辐射特性的影响。由计算结果推断,该模型不仅可以应用于计算模拟月壤颗粒的辐射特性,还可以满足其他适用于几何光学近似的非球形粒子。     

Scientific investigations at a lunar base.

Scientific investigations to be carried out at a lunar base can have significant impact on the location, extent, and complexity of lunar surface facilities. Among the potential research activities to be carried out are: (1) Lunar Science: Studies of the origin and history of the Moon and early solar system, based on lunar field investigations, operation of networks of seismic and other instruments, and collection and analysis of materials; (2) Space Plasma Physics: Studies of the time variation of the charged particles of the solar wind, solar flares and cosmic rays that impact the Moon as it moves in and out of the magnetotail of the Earth; (3) Astronomy: Utilizing the lunar environment and stability of the surface to emplace arrays of astronomical instruments across the electromagnetic spectrum to improve spectral and spatial resolution by several orders of magnitude beyond the Hubble Space Telescope and other space observatories; (4) Fundamental physics and chemistry: Research that takes advantage of the lunar environment, such as high vacuum, low magnetic field, and thermal properties to carry out new investigations in chemistry and physics. This includes material sciences and applications; (5) Life Sciences: Experiments, such as those that require extreme isolation, highly sterile conditions, or very low natural background of organic materials may be possible; and (6) Lunar environmental science: Because many of the experiments proposed for the lunar surface depend on the special environment of the Moon, it will be necessary to understand the mechanisms that are active and which determine the major aspects of that environment, particularly the maintenance of high-vacuum conditions. From a large range of experiments, investigations and facilities that have been suggested, three specific classes of investigations are described in greater detail to show how site selection and base complexity may be affected: (1) Extended geological investigation of a complex region up to 250 kilometers from the base requires long range mobility, with transportable life support systems and laboratory facilities for the analysis of rocks and soil. Selection of an optimum base site would depend heavily on an evaluation of the degree to which science objectives could be met. These objectives could include lunar cratering, volcanism, resource surveys or other investigations; (2) An astronomical observatory initially instrumented with a VLF radio telescope, but later expanding to include other instruments, requires site preparation capability, "line shack" life support systems, instrument maintenance and storage facilities, and sortie mode transportation. A site perpetually shielded from Earth is optimum for the advanced stages of a lunar observatory; (3) an experimental physics laboratory conducting studies requiring high vacuum facilities and heavily instrumented experiments, is not highly dependent on lunar location, but will require much more flexibility in experiment operation and EVA capability, and more sophisticated instrument maintenance and fabrication facilities.     

基于多圆锥曲线法的着陆器奔月轨道设计与特性分析

针对载人登月任务中人货分运飞行模式,精确快速设计了着陆器(LM)的奔月轨道,分析了轨道窗口特性。以着陆器的奔月出发时刻、纬度幅角和加速脉冲为设计变量,基于多圆锥曲线法动力学模型,利用序列二次规划（SQP）优化算法对奔月轨道快速求解。在地心白道系下提出了近月点伪经度判别准则,该方法可为轨道设计参数初值提供正确参考。最后以伪倾角为窗口特性分析参数,发现了近月点窗口、近地点出发位置的变化规律。仿真结果表明,本文提出的伪经度搜索方法能够快速求解着陆器地月转移轨道,同时揭示了环月到达轨道(LLO)与近地出发轨道(LEO)之间的内在联系,研究结论可为未来载人登月工程提供借鉴。     

嫦娥五号平动点拓展任务轨道方案研究

中国嫦娥五号探测器成功实现月球采样返回任务,为最大限度利用任务资源,研究了利用嫦娥五号轨道器的平动点拓展任务轨道方案,设计了平动点轨道及其转移轨道.首先,给出了任务轨道设计的轨道动力学模型,包括圆型限制性三体问题模型和精确力模型.其次,基于嫦娥二号和嫦娥5T1平动点拓展任务设计经验,介绍了平动点轨道直接转移与入轨等轨道...     

进入火星大气的高温真实气体效应与气动加热研究

针对火星和地球大气分子热力学和化学行为的差异性,采用理论分析和数值模拟两种手段,研究探测器进入过程高超声速流动的分子振动激发、离解反应及热力学和化学非平衡等真实气体效应,获得不同气体模型条件下的高超声速气动加热规律,探究引起地火差异的根本原因。分析认为,探测器进入火星大气层的稀薄气体效应明显;激波层内发生CO 2气体为主的大规模离解,在极高温环境下O 2和CO也将离解;沿进入轨道的高超声速流动基本处于化学非平衡但热力学平衡状态;激波层内能量储存和分配模式因分子振动激发和化学反应而改变,分子振动激发会增强气动加热量,但均介于化学反应模型的完全非催化和完全催化壁结果之间;相同来流条件下CO 2介质高超声速气动加热强于空气介质,但真实的火星进入热载荷因大气稀薄而弱于地球再入环境。相关研究为我国未来火星探测器热防护系统设计提供技术支持。