Engineering Issues for Early Lunar‐Based Telescopes

A telescope on the Moon is needed for astronomy and can be constructed in this decade or early in the next century. Design for this telescope will be fundamentally different from the design of free‐flying telescopes. Its design will be more like the new Keck telescope being completed on a mountaintop in Hawaii than the Hubble Space Telescope, in low Earth orbit. Success of the lunar‐based telescope will depend on an appropriately engineered structure, a suitable interface (foundation) in the lunar soil, and a carefully thought out construction process. Participation of engineers in identifying and resolving issues for this extraterrestrial engineering and construction project is a natural extension of the traditional engineering role, and will prepare the engineering and construction communities for the subsequent greater challenges associated with basing on the Moon. These communities need to document now the types of data and information that NASA should obtain in the next early lunar missions so that construction on the Moon will be facilitated.     

MALEO: Modular Assembly in Low Earth Orbit: Alternate Strategy for Lunar Base Development

Modular assembly in low Earth orbit (MALEO) is a new strategy for building an initial operational‐capability lunar habitation base, the main purpose of which is to safely initiate and sustain early lunar base buildup operations. In this strategy the lunar base components are brought up to low Earth orbit (LEO) by the Space Transportation System (STS), and assembled there to form the complete lunar base. Specially designed propulsion systems are then used to transport the MALEO lunar base, complete and intact, all the way to the moon. Upon touchdown on the lunar surface, the MALEO lunar habitation base is operational. The strategy is unlike conventional concepts, which have suggested that the components of the lunar base be launched separately from the Earth and landed one at a time on the moon, where they are assembled by robots and astronauts in extravehicular activity (EVA). The architectural drivers for the MALEO concept are, first, the need to provide an assured safe haven and comfortable working environment for the astronaut crew as safely and as quickly as possible, with the minimum initially risky EVA, and secondly, the maximum exploitation of the evolutionary benefits derived from the assembly and operation of space station Freedom (SSF‐1). Commonality and inheritability from the space station assembly experience is expected to have an advantageous impact on both the space station program as well as the MALEO lunar base.     

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.     

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.     

Overview of Existing Lunar Base Structural Concepts

Various structural concepts for lunar bases have been proposed and considered during the past three decades, each balancing the multitude of lunar constraints and anticipated base functions with a different distribution of weighting factors. This paper provides a brief review of the study of lunar base structures as well as an overview of current ideas. Lunar environmental characteristics are highlighted, and questions of structural functionality are categorized. In an appendix to the overview report, building systems proposed for lunar applications are categorized according to applications, application requirements, types of structures, material considerations, structures technology drivers, and requirement definitions. Another appendix presents a short list of the most important references related to these issues, as ranked by the task committee. This document contains a brief overview rather than an exhaustive review of concepts proposed for lunar outposts. The original documents, including those cited as references, are not replaced by this paper. However, this review is intended to be reasonably complete. There has been no conscious intention to ignore any work in this area of extensive ongoing activity.     

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.     

Lunar Habitat Micrometeoroid and Radiation Shielding: Options, Applications, and Assessments

Various shielding approaches to protect lunar habitats from micrometeoroid and radiation hazards present major trade-off considerations. Popular scenarios that envision covering modules with in situ regolith will necessitate means to excavate and move large amounts of material; will complicate evolutionary outpost growth; and may require long tunnels between connecting pressurized elements. Strategies that incorporate shielding materials into module structures or internal shelters add very substantial launch mass penalties. Utilization of water bladders can make efficient use of consumable/recyclable supplies, but may impose excess capacity deliveries at early development stages. This paper addresses these different shielding approaches from a top-level application perspective, highlighting pros and cons of each. Examples draw upon research and design investigations undertaken by the Sasakawa International Center for Space Architecture 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 released as public information.     

Lunar‐Base Construction Equipment and Methods Evaluation

A process for evaluating lunar‐base construction equipment and methods concepts is presented. The process is driven by the need for more quantitative, systematic, and logical methods for assessing further research and development requirements in an area where uncertainties are high, dependence upon terrestrial heuristics is questionable, and quantitative methods are seldom applied. Decision theory concepts are used in determining the value of accurate information and the process is structured as a construction‐equipment‐and‐methods selection methodology. Total construction‐related, earth‐launch mass is the measure of merit chosen for mathematical modeling purposes. The work is based upon the scope of the lunar base as described in the National Aeronautics and Space Administration's Office of Exploration's “Exploration Studies Technical Report, FY 1989 Status.” Nine sets of conceptually designed construction equipment are selected as alternative concepts. It is concluded that the evaluation process is well suited for assisting in the establishment of research agendas in an approach that is first broad, with a low level of detail, followed by more‐detailed investigations into areas that are identified as critical due to high degrees of uncertainty and sensitivity.     

Engineering for a 21st Century Lunar Observatory

The design process required for a lunar base observatory is considered. An observatory on the moon with significant capability could be operational by the year 2015. Astronomical observations from a lunar base will require one or more of a wide variety of instruments. Optical telescopes, optical interferometers, radio telescopes, and radio interferometers have often been suggested. Possibilities also exist for options such as high‐energy photon detectors, cosmic ray detectors, and neutrino astronomy instruments on the lunar surface. Successful designs for any of these options will require a step‐by‐step process involving close collaboration of many disciplines. Critical issues to be resolved include those relating to communications, data handling, controls, structures, materials, soil mechanics, and foundation engineering, as well as the research and development sequences and logistical problems.     

Cable‐Based Lunar Transportation System

The establishment of an efficient transportation system is key to any human development on Earth or in space. Different technologies for transporting humans and goods have been developed, the diversity of which indicates that individual concepts have specific strengths and weaknesses. So far, transportation on the Moon has utilized a wheel‐based vehicle, the lunar rover. Present concepts for transporting goods and people in a lunar base of the future are generally based on using wheels and traction. While such systems have many advantages for a variety of applications, the hauling of heavy goods will require the preparation of stable and trafficable roadways, a challenging and potentially expensive undertaking. This paper presents an alternative based on using one of the fundamental means to move objects, namely ropes and cables. Because of their inherent characteristics, ropes have been used to lift and haul heavy loads for long distances with high levels of reliability. This mature and constantly perfected technology, not well known in this car‐oriented society, has been investigated for its use as a true alternative to the traditional wheel‐based transportation systems. As will be shown, innovative applications of cable‐based technologies may in effect provide many opportunities to leverage the differences between the Earth and the Moon for the purpose of creating efficient engineering products.     

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.     

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.     

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.     

月壤原位利用技术研究进展

月球矿物资源的原位利用技术是月球基地建立和后续深空探索的基础。由于月球特殊环境及地月运输成本的限制,现有矿冶技术难以直接应用于月球矿物的原位开发。各国的科研人员围绕月球矿物资源原位利用方向开展了卓有成效的研究工作,发展了几种极具应用潜力的技术。这些方法可分为材料化成型和提取冶金两类,其中材料化成型工艺如烧结法、3D增材制造法等,主要用于将月壤直接材料化成型以制备月球基地建材。提取冶金工艺包括碳/氢化学介质还原法、电解还原法以及真空热解法等,可生产月壤矿物对应的金属单质或其低价氧化物,并获得氧气。本文概述了已有月壤原位利用技术的一般原理、基本过程、热力学动力学基础及近期研究进展。探讨了这些方法的一些优缺点,并展望了其在月球矿物原位利用上的应用前景。      

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.     

Indigenous Resource Utilization in Design of Advanced Lunar Facility

The most important consideration in the establishment and support of a permanently manned lunar base will be resource utilization. Seven potential lunar construction materials were analyzed with respect to their physical properties, processes, energy requirements, and resource efficiency. Reviewing the advantages and disadvantages of each material led to the selection of basalt as the primary construction material for initial use on a lunar base. The team conceptualized a construction system that combines lunar regolith sintering and casting to make pressurized structures. The design uses a machine that simultaneously excavates and sinters the lunar regolith to create a cylindrical hole. The hole is then enclosed with cast basalt slabs, allowing the volume to be pressurized for use as a living or work environment. Cylinder depths up to 4–6 m in the lunar mare and 10–12 m in the lunar highlands can be achieved. Advantages identified in the construction system include maximum resource utilization, relatively large habitable volumes, interior flexibility, and minimal construction equipment needs. The conclusions of this study indicate that there is significant potential for the use of basalt as a low‐cost alternative to Earth‐based materials. It remains to be determined, during lunar base phasing, whether this construction method should be implemented.     

Silicon PV Cell Production on the Moon

A concept has been developed for the production of photovoltaic energy collection systems on the Moon by vacuum deposition directly onto the lunar surface. Using this technique it would be possible to quickly install quite large capacities of power on the Moon at relatively low cost. Most of the material required for photovoltaic devices is readily available on the Moon, and taking production machinery to the Moon can further lower the cost of power if the machinery can be operated for long periods of time. Low-cost energy on the Moon could enable a wide range of activities including support of robust human outposts, production of propellants for use on the Moon or for export, production of a wide range of other materials for use in space, and beaming of energy from the Moon to space and to Earth. A proposed strategy by which lunar power can be developed in the near future is closely connected to the establishment of a human outpost on the Moon.     

Some Comments on the Protection of Lunar Habitats against Damage from Meteoroid Impacts

The establishment of human habitats on the Moon and on Mars will require protecting them from the hazards of near-Earth and interplanetary space. In addition to solar radiation, another hazard to be faced by these habitats is the damage that can result from the high speed impact of a meteoroid on a critical structural component. Therefore, lunar habitats and their accompanying support facilities need to be designed with adequate levels of protection that will allow them to also withstand the damage that can result from a meteoroid impact. In this paper we discuss some approaches to shielding for lunar habitats, focusing on shielding that is intended primarily to provide protection against meteoroid impacts and on shielding approaches that use resources mined or extracted from the Moon. The Moon’s mineralogy is discussed and suggestions are presented for materials and material combinations that can be used to develop shielding for lunar habitats and which are comprised primarily or entirely of lunar materials. Several shielding mechanisms are also presented that could be effective against impacts by meteoroid particles having diameters on the order of that which are likely to strike a fairly large lunar habitat at least one or two times per year. The paper concludes with recommendations for continuing work in optimizing the design of meteoroid shielding for lunar habitats.     

Construction Engineering Approach for Lunar Base Development

Studies on lunar base construction conducted by the writers' research group are summarized. A desirable lunar base design was first discussed by employing a systems engineering approach and by defining an evolutionary scenario, which emphasized resource utilization. Several lunar-base-related concepts were examined from the viewpoint of construction engineering including construction materials, structural design, and construction methods. The research also addressed resource utilization for the production of oxygen and construction materials. A commericial approach toward future lunar development is proposed.