Design and Construction Considerations for Lunar Outpost

Engineers utilize various codes in the process of design, whether structural, mechanical, or otherwise. Reliance on a code for design is based on the knowledge that a tremendous amount of time and effort was spent by experienced engineers to codify theories and good practice in a particular design discipline. Good practice in structural design implies cognizance of materials, structural behavior, environmental loadings, assumptions made in analysis and behavior, and the uncertainties inherent in all of these. The American Institute of Steel Construction's (AISC) Manual of Steel Construction is such a codification for the design and construction of steel structures. It includes information, some tabular and the rest in the form of specifications and commentaries, necessary to design and provide for the safe erection of steel‐framed structures. The design equations are generally semiempirical, that is, they are based on a mix of theoretical analysis, experimental data, and factors of safety. Each of these components has associated implicit assumptions. Some of these assumptions were explored to understand how and if the Earth‐based design code could be used for the design of a lunar outpost. Topics discussed come from the AISC Code of Standard Practice and the commentaries, and issues such as scaling of loads and strength in the 1∕6 g lunar environment, thermal cycling effects and fatigue, stiffening and buckling are briefly discussed. Important topics for further detailed study include: (1) The relationships between severe lunar temperature cycles and fatigue; (2) very low temperature effects and the possibility of brittle fractures; (3) outgassing for exposed steels and other effects of high vacuum on steel∕alloys; (4) factors of safety originally developed to account for uncertainties in the Earth design∕construction process undoubtedly need adjustment for the lunar environment; (5) dead loads∕live loads under lunar gravity; (6) buckling∕stiffening and bracing requirements for lunar structures that will be internally pressurized; and (7) consideration of new failure modes such as high‐velocity micrometeorite impacts.     

Experimental Studies on Mechanics of Lunar Excavation

One of the first construction operations for building a stationary habitat on the moon or Mars will be excavation of soil. The reasons for this necessity are manyfold and range from the need to protect inflatable habitats against radiation to creating an underground space for building electrical power plants. Despite the tremendous amount of earth movement that has taken place on this globe, a sound theoretical basis for designing soil‐moving machines does not exist. This paper describes the results of experiments that were developed to evaluate empirically if and how soil could be excavated on the moon. No attempt has bee made to optimize or promote a particular method. The goal of the present study is rather to establish a sound knowledge base to use for the more‐detailed studies needed to design an operational system that will be successful on the moon.     

Considerations for Design Criteria for Lunar Structures

The development of design criteria for lunar structures must begin soon in order to establish adequate criteria. Some of the items that need consideration in such criteria are discussed. The categorization of the structures will provide designers with information on the purpose and level of complexity of the structure. Various construction materials and structure types that will be critical for the design of lunar structures, are considered. The environment of the moon and its possible effects on structures are presented and lead to the development of a few load cases that need to be considered in design. A probabilistic format for the criteria and design lifetimes are also discussed.     

Top-Level Considerations for Planning Lunar/Planetary Habitat Structures

This paper highlights important considerations to guide overall planning and element design of lunar/planetary surface habitat structures. Driving influences include stringent launch/landing payload limitations; high costs of human time for surface deployment and operational readiness; influences of the harsh environment on structures, devices and crews; and a paucity of equipment and human and consumable resources that necessitates extreme economies. General habitat concept options are proposed along with desired attributes for comparative assessments of figure of merit (FOM) rankings. Eight broad FOM categories are applied as a basis for top-level option evaluations: (1)?launch optimization features, (2)?landing optimization features, (3)?habitat capacity and functionality, (4)?environmental factors and features, (5)?deployment and operational readiness, (6)?reliability and maintainability, (7)?commonality with other surface systems, and (8)?pathways and potentials for growth. Much of the content of this paper draws on investigations conducted by the Sasakawa International Center for Space Architecture (SICSA) in support of separate National Aeronautics and Space Administration (NASA) contracts awarded to teams headed by Boeing and ILC-Dover for a “Minimum Functionality Habitation Systems Concept Study.” Comprehensive team study results were presented to NASA in February 2009 and have been publicly released to all interested parties.     

Particle Size Distribution of Lunar Soil

Meteorite impact on the lunar surface produces a consistent, broadly graded soil. In this note, the geotechnical and geological systems are compared to characterize lunar soil. In geotechnical terms, the lunar soil particle size distribution is described as sandy silt/silty sand, well-graded. In geologic terms, it is described as very fine sand, very poorly sorted, nearly symmetrical, and mesokurtic. Because of its broad particle size distribution, lunar soil may be internally erodible.     

Compaction of Lunar‐Type Soil

Soil plays an important role in the construction of foundations of roads and buildings. The utilization of soil traditionally involves the compaction of the in‐situ or previously loosened material to achieve a desired strength. The paper reports an initial investigation on the effect of the percentage of fines on the densification and strength of lunar‐soil simulant. The results of vibratory and static compaction tests in the laboratory suggest that the amount of fines should be reduced from the existing 50% that is typical for lunar regolith. The measurement of density and cone resistance of soil mix with only 10% showed large differences when compared to soils with 30% or 50% fines. No attempt has been made to find optimal soil mixes for compaction.     

Considerations for Return to the Moon and Lunar Base Site Selection Workshops

The establishment of a lunar base with a permanent human presence is on the horizon. The scientific importance of the Moon and the potential use of local resources at a lunar base provide valuable concepts to consider. Importantly, there are significant ideas, concepts, and reports from the past, the products of a wealth of “mental calorie” inputs, which should be reconsidered; herein, many of these are placed within an historical perspective, in hopes that we may learn by our past experiences. The 1994 Clementine mission, its instrumentation and returned data, provides the first global coverage of the composition, structure, and topography of the Moon. The planned 1997 Lunar Prospector will add significantly to this database. These new global data are requisite for the selection of a lunar base. It is paramount to consider thoroughly the rationale for site selection, and much of the groundwork for this rationale has already been performed. The selection process should be led by a strategic purpose or vision that considers (1) scientific objectives, both on the Moon, as well as from the Moon (e.g., astronomy); (2) resource utilization; and (3) operational considerations, both orbital and surface. Many of the relationships between these factors were explored during workshops convened at Johnson Space Center by the National Aeronautics and Space Administration (NASA) in April and August 1990. However, these workshops have not resulted in official, catalogued NASA publications. The merits of numerous potential sites were analyzed in terms of lunar geoscience, geophysics, space physics, astronomy, and lunar resources, as well as operational constraints. The considerations and recommendations of the NASA Site Selection Committee should provide the basis for a realistic site selection for a human presence at an outpost on the lunar surface.     

Geotechnical Behavior of JSC-1 Lunar Soil Simulant

To facilitate the modeling and simulation of lunar activities and natural processes, various lunar soil simulants have been created. In particular, Johnson Space Center Number One lunar soil simulant (JSC-1) has come into wide use by a variety of investigators. In any physical experiment, the behavioral properties of this simulant will have a profound impact on the results. To better understand these soil properties, a variety of conventional and unconventional experiments were conducted on JSC-1 to determine its friction angle and appropriate low strain elastic constants. These experiments were conducted on JSC-1 at a variety of relative densities to quantify the response of the soil over the range of possible conditions. Further, the samples were prepared through vibratory densification, allowing for a better simulation of probable lunar surface packing arrangements.     

Thermodynamic Analysis on Lunar Soil Reduced by Hydrogen

Although many experiments have been performed to reduce the lunar soil by hydrogen, no systematic thermodynamic analysis has been developed to design and optimize these experiments. Applying a thermodynamic model to the system of simulant lunar soil and hydrogen, this study analyzes and discusses the thermodynamic behavior of the system in detail. The calculations demonstrate that iron is the only metal that can be extracted significantly from the lunar soil. The amount of hydrogen in the system drastically affects the processes of iron extraction and water production. However, the effect of system pressure can be neglected in the process. The yields of metallic iron and water from the lunar soil as functions of temperature and hydrogen content are investigated in this study. Additionally, the calculations explain the metallic iron on the surface of the moon from the thermodynamic point of view.     

Surface Cleanliness Effect on Lunar Soil Shear Strength

Lunar soil consists of dry silty sand. Observations and measurements conducted during Surveyor, Apollo, and Luna missions indicated that the lunar soil is unusually cohesive. This is attributable to the fact that thick layers of adsorbed gases, which coat and lubricate soil particles on Earth, are absent in the ultrahigh vacuum on the Moon. “Surface cleanliness” is introduced as a new parameter for describing soils in different planetary environments. It is defined as the dimensionless inverse of adsorbate thickness on solid surfaces. By this definition, the ultrahigh vacuum on the Moon is associated with high surface cleanliness, while Earth's atmosphere is associated with low surface cleanliness. A model is developed to calculate surface cleanliness and its effect on shear strength in any planetary environment. Results obtained from the model compare well with data from previous ultrahigh vacuum and variable temperature laboratory experiments on Earth soils. It is shown that surface cleanliness is an important parameter with respect to lunar soil shear strength.     

Unsaturated Soil Mechanics in Engineering Practice

Unsaturated soil mechanics has rapidly become a part of geotechnical engineering practice as a result of solutions that have emerged to a number of key problems (or challenges). The solutions have emerged from numerous research studies focusing on issues that have a hindrance to the usage of unsaturated soil mechanics. The primary challenges to the implementation of unsaturated soil mechanics can be stated as follows: (1) The need to understand the fundamental, theoretical behavior of an unsaturated soil; (2) the formulation of suitable constitutive equations and the testing for uniqueness of proposed constitutive relationships; (3) the ability to formulate and solve one or more nonlinear partial differential equations using numerical methods; (4) the determination of indirect techniques for the estimation of unsaturated soil property functions, and (5) in situ and laboratory devices for the measurement of a wide range of soil suctions. This paper explains the nature of each of the previous challenges and describes the solutions that have emerged from research studies. Computer technology has played a major role in achieving practical geotechnical engineering solutions. Computer technology has played an important role with regard to the estimation of unsaturated soil property functions and the solution of nonlinear partial differential equations. Breakthroughs in the in situ and laboratory measurement of soil suction are allowing unsaturated soil theories and formulations to be verified through use of the “observational method.”     

Geotechnical Properties of JSC-1A Lunar Soil Simulant

For the success of planned missions to the moon in the near future, it is essential to have a thorough understanding of the geotechnical behavior of lunar soil. However, only a limited amount of information is available about geotechnical properties of lunar soils. In addition, the amount of lunar soils brought back to Earth is small. To help the development of new regolith moving machines and vehicles that will be used in future missions, a new lunar soil similant JSC-1A has been developed. A group of conventional geotechnical laboratory tests was conducted to characterize the geotechnical properties of the simulant, such as particle size distribution, maximum and minimum bulk densities, compaction characteristics, shear strength parameters, and compressibility.     

Engineering Properties of Lunar Soil Simulant JSC-1A

This study was carried out to assess the tensile and shear strength in lunar soil, and to examine the variation as a function of density and confinement. Geotechnical engineering properties of the lunar soil simulant designated Johnson Space Center Number One-A lunar soil simulant (JSC-1A) have been investigated experimentally. To better understand these soil properties, a variety of conventional and unconventional experiments were conducted on JSC-1A to determine its grain-size distribution, cohesion, friction angle, dilatancy angle, tensile strength, and appropriate low strain elastic constants. These experiments were conducted on JSC-1A at a variety of densities prepared through tamping densification to quantify the response of the soil over a range of conditions. To simulate lunar conditions, the samples were prepared at medium to very high relative densities. Grain-size distribution, shear strength, tensile strength, dilatancy angles, and elasticity modulus of the JSC-1A were compared with lunar soil and other simulants.     

冷轧卷取机关键技术参数计算研究

系统介绍了卷取机的一般构成及其主要部件结构；对卷取机卷简直径、径向压力、旋转油缸规格、电机功率、减速比等关键技术参数进行了研究；并提出了关键技术参数的选型设计方法。论文的研究计算总结，对于卷取机的方案选型设计和设备的基本设计，都具有较强的指导和实用价值。     

Microwave Sintering of Lunar Soil: Properties, Theory, and Practice

The unique properties of lunar regolith make for the extreme coupling of the soil to microwave radiation. Space weathering of lunar regolith has produced myriads of nanophase-sized Fe0 grains set within silicate glass, especially on the surfaces of grains, but also within the abundant agglutinitic glass of the soil. It is possible to melt lunar soil (i.e., 1,200–1,500°C) in minutes in a normal kitchen-type 2.45?GHz microwave, almost as fast as your tea-water is heated. No lunar simulants exist to study these microwave effects; in fact, previous studies of the effects of microwave radiation on lunar simulants, MLS-1 and JSC-1, have been misleading. Using real Apollo 17 soil has demonstrated the uniqueness of the interaction of microwave radiation with the soil. The applications that can be made of the microwave treatment of lunar soil for in situ resource utilization on the Moon are unlimited.     

NAO-1: Lunar Highland Soil Simulant Developed in China

A new lunar highland soil simulant, NAO-1, has been created in National Astronomical Observatories (NAO), Chinese Academy of Sciences. This simulant was produced by gabbro, which includes large quantity of feldspar (An>90). The simulant’s chemical composition, mineralogy, particle-size distribution, density, angle of internal friction, and cohesion have been analyzed and results demonstrated that most characteristics of NAO-1 are similar with lunar highland soil samples. NAO-1 will benefit the scientific and engineering research of lunar soil.     

螺纹件冷滚压工艺力学分析及数值模拟

对螺纹件冷滚压工艺进行了力学分析,并用DEFORM软件对螺纹冷滚压过程进行了数值模拟,得到了滚压力及扭矩随滚压时间的变化曲线,验证了理论分析结果的正确性。     

Continuum Mechanics of Lateral Soil–Pile Interaction

A rigorous mathematical formulation is presented for a flexible tubular pile of finite length embedded in a semi-infinite soil medium under lateral loading. In the framework of three-dimensional elastostatics and classical beam theory, the complicated structure–medium interaction problem is shown to be reducible to three coupled Fredholm integral equations. Through an analysis of the associated Cauchy singular kernels, the intrinsic singular characteristics of the radial, angular, and vertical interfacial load transfers are rendered explicit and incorporated into a rigorous numerical procedure. Detailed results on the three-dimensional load–transfer process, as well as their resultant one-dimensional analogs, are also provided for benchmark comparison and practical applications.     

严寒地区选矿厂节能设计

以内蒙古某多金属矿选矿厂为例,针对严寒天气对选矿的影响,详细介绍了多项适应严寒地区气候特点的节能措施,如多作业共厂房集中布置、设置良好的建筑朝向、采用半自磨工艺、高频细筛与球磨机形成闭路分级、摇床多层立体布置、选用耐磨管道、管道防冻、采用厂前回水和降低采暖温度梯度等,为严寒地区和寒冷地区建设选矿厂提供借鉴.     

严寒地区工业给排水设计要点

针对北方严寒地区冬季气温低的特点，工业企业给排水系统的设计应：采用安全可靠、经济合理的技术措施，以解决管道及设备的保温防冻问题，确保工业企业的正常生产。本文结合吉镍冶炼厂15kt／a镍技术改造项目的生产实践．分析探讨了严寒地区工业给排水的设计要点。