Structural Design of a Lunar Habitat

A lunar base is an essential part of all the new space exploration programs because the Moon is the most logical first destination in space. Its hazardous environment will pose challenges for all engineering disciplines involved. A structural engineer’s approach is outlined in this paper, discussing possible materials and structural concepts for second-generation construction on the Moon. Several different concepts are evaluated and the most reasonable is chosen for a detailed design. During the design process, different solutions—for example, for the connections—were found. Although lunar construction is difficult, the proposed design offers a relatively simple structural frame for erection. A habitat on the Moon can be built with a reasonable factor of safety and existing technology. Even so, we recognize the very significant difficulties that await our return to the Moon.     

Multiproject Planning and Resource Controls for Facility Management

Facility managers face the challenges of managing many different types of small, geographically dispersed construction projects. Depending on the complexity and distribution of projects, the time required to prepare for production consumes a large percentage of the total time required to complete the job. Increasing crews’ productive hours is a key objective when planning multiproject schedules. Existing methods, however, lack the effective means to explicitly model, analyze, and optimize resource utilization for these multiple concurrent projects. As a result, few facility managers fully exploit the potential to better manage their often limited budget and resources. This paper presents an explicit model of the mobilization requirements of multiple crews performing a variety of different activities over a geographic space. The model allows the facility manager to explicitly investigate the impact of crew composition, crew specialization, and depot locations. Using work rule decisions regarding alternative crew allocations, facility managers may dynamically allocate resources to optimize resources and to complete projects in a minimum amount of time. To verify and validate this new model, a computerized system, called FIRS (Facility/Infrastructure Resource Scheduler), was created to analyze the multiproject resource plans with data from two military organizations and a university campus. FIRS utilizes a new genetic algorithm that was developed specifically to work with multiproject scheduling. Using FIRS, facility managers can develop and test alternative crew allocations based on the qualifications of the crews available and the type of operation being performed.     

Lunar Astronomical Observatories: Design Studies

The best location in the inner solar system for the grand observatories of the 21st century may be the Moon. A multidisciplinary team including university students and faculty in engineering, astronomy, physics, and geology, and engineers from industry is investigating the Moon as a site for astronomical observatories and is doing conceptual and preliminary designs for these future observatories. Studies encompass lunar facilities for radio astronomy and astronomy at optical, ultraviolet, and infrared wavelengths of the electromagnetic spectrum. Although there are significant engineering challenges in design and construction on the Moon, the rewards for astronomy can be great, such as detection and study of Earth‐like planets orbiting nearby stars, and the task for engineers promises to stimulate advances in analysis and design, materials and structures, automation and robotics, foundations, and controls. Fabricating structures in the reduced‐gravity environment of the Moon will be easier than in the zero‐gravity environment of Earth orbit, as Apollo and space‐shuttle missions have revealed. Construction of observatories on the Moon can be adapted from techniques developed on the Earth, with the advantage that the Moon's weaker gravitational pull makes it possible to build larger devices than are practical on Earth.     

Engineering, Design and Construction of Lunar Bases

How do we begin to expand our civilization to the Moon? What are the technical issues that infrastructural engineers, in particular, must address? This paper has the goal of introducing this fascinating area of structural mechanics, design, and construction. Published work of the past several decades about lunar bases is summarized. Additional emphasis is placed on issues related to regolith mechanics and robotic construction. Although many hundreds of papers have been written on these subjects, and only a few tens of these have been referred to here, it is believed that a representative view has been created. This summary includes environmental issues, a classification of structural types being considered for the Moon, and some possible usage of in situ resources for lunar construction. An appendix provides, in tabular form, an overview of structural types and their lunar applications and technology drivers.     

Design and Construction of Shielded Lunar Outpost

The construction of an outpost on the Moon in which humans can live and work for periods exceeding six months will require special countermeasures to adapt to the hostile environment present at the lunar surface. Various inherent dangers such as meteoroids, galactic cosmic radiation, solar proton events, and large thermal extremes will drive the design configuration of the outpost. Other considerations such as lunar soil mechanics, equipment performance, mass delivery, risk, reliability, and tele‐operability act strongly as constraints that shape and control the design alternatives. Analysis of these fundamental relationships have resulted in lunar civil engineering guidelines, which are unique to this domain, and these in turn have pointed to research areas needing further attention. A preliminary design is presented for a lunar outpost shelter. Additionally, the design methodology is explored, and early enabling technologies are identified to facilitate an understanding of lunar shelter designs from an integrated system standpoint.     

Conceptual Design of Unpressurized Shelters on Lunar Surface

Three concepts for the shelters on the moon are presented here. It is envisaged that the first robots will land on the moon and start preparing sites for advanced bases and also for future human presence. These robots will encounter severe radiation and micrometeor hits when they are exposed to the lunar atmosphere. During the period of intense solar radiation these robots have to be temporarily sheltered, since shielding on the robots may not be adequate to protect the instruments. The construction of these shelters has to be performed with very little equipment support. This paper presents concepts and their feasibility analysis for the fabrication of shelters under such stringent constraints.     

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.     

Technical Issues for Lunar Base Structures

The establishment of a permanent human presence on other planets will require establishing permanent infrastructure in new environments. Civil engineers select, define, and implement solutions to infrastructure design problems in unique environmental contexts. Wind and seismic loading are two examples of constraints long familiar to terrestrial civil engineering. Designing structures for lunar exploration, development and eventual settlement will make use of the same design processes already practiced by the civil engineering profession. However, the extensive experience base resulting from centuries of terrestrial work does not adequately prepare civil engineers for the unprecedented constraints and environmental conditions that are encountered in space. The limited knowledge we already have about the Moon (mostly from the Apollo program) is a place to start. By assimilating and working with this knowledge, those pursuing the design of lunar base structures can begin to produce realistic and valid design solutions. The paper presents technical, operations, and programmatic issues that the writers consider fundamental to understanding the facts of life in this promising new design arena.     

Developing a Resource Supply Chain Planning System for Construction Projects

The high variability of construction environments results in high construction-cost variation, especially in material costs. Inadequate planning may cause material shortages that delay the project schedule or, alternatively, a substantial increase in inventory costs by producing or supplying materials earlier than they are needed at the construction site. In order to solve these problems, this paper studies steel rebar production and supply operations and establishes an optimal model that minimizes the integrated inventory cost of the supply chain. Based on the optimal model, this paper develops a decision-support system to generate a production and supply plan for a supplier and buyers of steel rebar. After utilizing the decision-support system to create the supply and production plan, this paper analyzes the results to study the influence of transaction constraints on inventory cost. This paper also discusses cases of global optimization of the inventory cost for the entire supply chain and compares them with cases of local optimization for individual members.     

Mechanical Equipment Requirements for Inflatable Lunar Structures

Inflatable structures have been proposed by a number of authors. Several structural forms have been conceptually designed, including spherical, pillow‐shaped, semicylindrical, and domed saucer. Regardless of structural form, all inflatables require mechanical equipment to initiate and maintain inflation. This paper identifies the mechanical equipment and operations required to support an inflatable structure. A previously proposed semicylindrical structure is selected for this study, but the principal results are applicable to all inflatable structures. The results indicate that air for inflatable structures should be transported to the moon in a liquid (cryogenic) state. The liquefied air can be evaporated and heated to the proper temperature using solar energy and a conventional pumping system. Removing the air from the facility is an entirely different problem and requires different equipment. There are two alternatives: (1) Discharge the air to the moon; and (2) reclaim the air for reuse. The first alternative is not likely to be cost‐effective and might well be scientifically unacceptable. The second alternative presents numerous technical problems but appears technically feasible.     

Lunar Structures Generated and Shielded with On‐Site Materials

Lunar base structures can be constructed in situ and∕or shielded using unprocessed or minimally processed lunar resources with technologies utilized in harsh terrestrial regions for the past four millennia. Single‐ and double‐curvature compression shell structures constructed using the techniques of building without centering can be applied on the lunar surface, where the low gravity and resultant small angle of repose allow for greater spans than under terrestrial condition. Suggested construction materials range from meteorites and lunar rocks to lunar adobe created from unprocessed regolith. Magma structures can be generated and cast based on natural formation, such as lava tubes and voids, using focus sunlight, microwave, plasma, and nuclear energy. Ceramic modules can be “thrown” on a centrifugally gyrating platform. These techniques integrate high‐tech and low‐tech construction methods of Western, Eastern, and Native American cultures, allowing for direct interaction with nature while working to economical and technical advantage by using primarily local lunar resources and human skills.     

Resource Sharing in Linear Construction

In the method developed, the conventional method of allocating resources are not used. Instead, resource‐hour units are employed. This enables to allocate resources precisely and the analysis becomes realistic unlike any other method. The method uses linear programming to determine the maximum rate of construction and the resource requirements in various activities. Sharing of resources which are available in limited quantities and balanced trades are all catered for in this development. The economics of using additional resources, working overtime and the optimal usage of all resources are the more important aspects of this paper. The step by step process of introducing additional resources and overtime ease the decision making process considerably. The method also helps to determine whether it is more economical to invest in additional resources or introduce work on overtime. If there is no proper method to compute resource requirements, a considerable waste in resource utilization would result. If resources are under utilized, even by a very small quantity, a considerably large delay of time would incur.     

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.     

Optimizing Resource Utilization during the Recovery of Civil Infrastructure Systems

Postdisaster recovery efforts of damaged civil infrastructure systems need to be optimized in order to alleviate the adverse impacts of natural disasters on local societies and economies. This paper presents an innovative framework that integrates two newly developed models for resource utilization and multiobjective optimization that are designed to optimize these recovery efforts. The developed models provide new and unique capabilities, including (1) allocating limited reconstruction resources to competing recovery projects, (2) estimating the reconstruction duration and cost associated with implementing specific recovery plans, and (3) generating optimal trade-offs between minimizing the reconstruction duration and cost. An application example is analyzed to evaluate the performance of the developed models and demonstrate their capabilities in identifying a wide spectrum of optimal reconstruction plans, where each provides a unique and nondominated trade-off between minimizing the recovery duration and cost. This allows decision makers in emergency management agencies to select and implement reconstruction plans that address various societal and economical needs in the aftermath of natural disasters.     

Managing Construction Projects Using the Advanced Programmatic Risk Analysis and Management Model

Risk management is an important part of construction management, yet the risk-based decision support tools available to construction managers fail to adequately address risks relating to cost, schedule, and quality together in a coherent framework. This paper demonstrates the usefulness of the Advanced Programmatic Risk Analysis and Management Model (APRAM) originally developed for the aerospace industry, for managing schedule, cost, and quality risks in the construction industry. The usefulness of APRAM for construction projects is demonstrated by implementing APRAM for an example based on an actual building construction project and comparing the results with other risk analysis techniques. The results show that APRAM simultaneously addresses cost, schedule, and quality risk together in a coherent, probabilistic framework that provides the information needed to support decision making in allocating scarce project resources.     

Performance Evaluation of Construction Enterprise Resource Planning Systems

To successfully evaluate investments related to integrated information management in the construction industry, causal loop diagramming was used to depict the qualitative system dynamics model for the study of the dynamics of construction enterprise resource planning systems (C-ERP). With the aid of system dynamics principles, together with literature review and two case studies, the major variables that influence the successful evaluation of C-ERP in the construction industry were evaluated. The major variables identified were validated with data from a survey. The validation procedure quantified associations between variables and perceived benefits from C-ERP stakeholders of construction-related firms. The model described in this paper aims at providing a holistic understanding of the C-ERP dynamics in construction. With this model, researchers and industry practitioners can develop an insight into C-ERP investments in practice.     

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.     

Efficient Hybrid Genetic Algorithm for Resource Leveling via Activity Splitting

Resource leveling problem is an attractive field of research in project management. Traditionally, a basic assumption of this problem is that network activities could not be split. However, in real-world projects, some activities can be interrupted and resumed in different time intervals but activity splitting involves some cost. The main contribution of this paper lies in developing a practical algorithm for resource leveling in large-scale projects. A novel hybrid genetic algorithm is proposed to tackle multiple resource-leveling problems allowing activity splitting. The proposed genetic algorithm is equipped with a novel local search heuristic and a repair mechanism. To evaluate the performance of the algorithm, we have generated and solved a new set of network instances containing up to 5,000 activities with multiple resources. For small instances, we have extended and solved an existing mixed integer programming model to provide a basis for comparison. Computational results demonstrate that, for large networks, the proposed algorithm improves the leveling criterion at least by 76% over the early schedule solutions. A case study on a tunnel construction project has also been examined.     

Structural Design of Lunar Radio Telescope Using Interactive CAD

Some astronomers are considering the moon as an attractive location within the inner solar system for a variety of astronomical observatories, some of which could be operational early in the 21st century. This paper describes the computer‐aided structural design of a 122‐m diameter, fully steerable, parabolic radio telescope to be located on the moon. The loads acting on such a reflector differ substantially from those acting on a reflector that must operate in earth's environment. The moon has excellent advantages as a location for such an instrument. The absence of atmosphere completely eliminates the wind, snow, and ice loads. The gravity field is only one‐sixth that of earth's. The thermal changes from night to day are severe, but structural problems can be avoided by using a thermally stable composite material. Structural elements for the reflector dish have been analyzed and designed for static loads with a specially written interactive graphical computer program. The resulting structure has a mass nearly 40 times less than its earth's counterpart made of steel. The evaluation of the results of the design studies supports the possibility of building a large‐aperture parabolic radio telescope on the moon.