With respect to lunar projects, many studies have been done as to sizes of lunar materials to be used as the building blocks for a lunar base. Ideas such as domes, both geodesic and single piece structures, bricks made of lunar concrete and basalt and many others have been proposed. All these varying scenarios all require different types and sizes of construction equipment. Construction issues such as crane sizes, furnace size, and number of people must all be considered in any structural design. Advantages and Disadvantages With the construction of erectable structures comes many advantages and disadvantages. These are outlined in Table 9.5.Many of the advantages associated with erectable construction come from the versatility and experience already in place, while many of the disadvantages stem from the harsh and expensive space environment. Trade offs between erectable structures, both EVA and EVR assembled versus deployable systems can be made if each of these advantages and disadvantages are well understood. Characterization of the trade offs and a set of rules has been developed [Smith, 1992], but is still yet to be used because of a lack of information about the system. Table 9.5 Advantages and Disadvantages of Erectable Systems Advantages Versatile in Construction Operations Low Sensitivity to Changes in Operations Highly Adaptable to Operation Perturbation High Amount of Experience Current System Availability High Volumetric Packing Efficiency Short Assembly Time Disadvantages High Costs Repetitive Tasks Low Time Available Work Time (Pre-breath/Post-breathTimes) High Training Time Many Safety Issues As SPS moves into its commercial phase, space construction of erectable systems will have to move from an experimental phase to more of an operational phase. EVA is just beginning to be understood but more work on simulation and dynamics modeling is needed before it becomes a common task. Optimal decision making of sizing basic assembly elements and how much should be terrestrially built versus on orbit assembled also is just beginning to be researched. In contrast, many of the engineering overlap areas are well developed and are ready to be implemented, but in general many of the necessary technologies needed for the erection of structures are currently being developed to a degree such be used in an SPS by the time large scale commercial development takes place. 9.3.2 Deployable Structures Due to the limiting capability of current space transportation systems, and the necessity for simple construction operations, deployable structures are an option for manned and unmanned missions in the near and distant future [Natori, 1985]. Currently, deployable structures are used in solar arrays and reflector structures. They are classified as, the type of structural materials needed to carry out a mission profile, and whether the system requires a back-up structure or not. Various concepts can use combinations of both. Design Considerations The rationale for the design of all structures must start with a requirements definition and the environment of the mission. The design of deploy able structures involves consideration of three different environments; manufacturing, transportation, & operations. Each of these impact the
RkJQdWJsaXNoZXIy MTU5NjU0Mg==