Conceptual design of a fleet of autonomous regolith throwing devices for radiation shielding of lunar habitats

The National Aeronautics and Space Administration (NASA) in conjunction with Universities Space Research Association (USRA) has requested that the feasibility of a fleet of regolith tossing devices designed to cover a lunar habitat for radiation protection be demonstrated. The regolith, or lunar soil, protects the lunar habitat and its inhabitants from radiation. Ideally, the device will operate autonomously in the lunar environment. To prove the feasibility of throwing regolith on the Moon, throwing solutions were compared to traditional, Earth-based methods for moving soil. Various throwing configurations were investigated. A linear throwing motion combined with a spring and motor energizing system proved a superior solution. Three different overall configurations for the lunar device are presented. A single configuration is chosen and critical parameters such as operating procedure, system volume, mass, and power are developed. The report is divided into seven main sections. First, the Introduction section gives background information, defines the project requirements and the design criteria, and presents the methodology used for the completion of this design. Next, the Preliminary Analysis section presents background information on characteristics of lunar habitats and the lunar environment. Then, the Alternate Designs section presents alternate solutions to each of the critical functions of the device. Fourth, a detailed analysis of throwing the regolith is done to demonstrate its feasibility. Then, the three overall design configurations are presented. Next, a configuration is selected and the conceptual design is expanded to include system performance characteristics, size, and mass. Finally, the Conclusions and Recommendations for Future Work section evaluates the design, outlines the next step to be taken in the design process, and suggests possible goals for future design work

Conceptual design of a fleet of autonomous regolith throwing devices for radiation shielding of lunar habitats

This report presents refinements in two areas of the initial design presented in the report entitled 'Conceptual Design of a Fleet of Autonomous Regolith Throwing Devices for Radiation Shielding of Lunar Habitats'. The first section presents an evaluation of the critical areas of the design and presents alternative solutions for these areas. The areas for design refinement are the traction required by the device and the stability of the device when throwing regolith. Several alternative methods are presented to solve these problems. First, the issue of required traction is covered. Next, the design is refined to provide a more stable device. The issue of stability is addressed both by presenting solutions for the configuration chosen for the computer simulation and by presenting two more device configurations. The next section presents the selected solutions. To prevent inadequate traction, the depth of dig-per-pass is reduced. A method combining a dynamic counterweight and an outrigger is chosen to provide a stable device

Thermal Effects of In-Bed Rapid Prototyping Metastructures

Iuan effort. t.o produce higher quality Selective Laser Sint.ering (SLS) parts, a number of approaches have been taken. One such approach is t.he use of in-bed·metastructures, such as tortillas and canist.ers. In past. work, these metast.ructures have produced changes part qualit.y, but only qualitative analysis has been done. Using a model created during previous work, a numerical st.udy of these in-bed metastructures is undertaken, with the goal of systematically determining the thermal effectiveness of the various structures. The thermal behavior of in-bed st.ructures subjected t.o mixed mode convection and conduction is then determined. Result.s demonstrate that in-bed structures can be designed t.o spatially affectin-bed thermal transfer, providing SLS users t.he capability to remove or retain heat as a part's local geometry demands.Mechanical Engineerin

Forced Convection in a Polymeric Powders

In a Selective Laser Sintering (SLS) powder bed, thermal transfer occurs through multiple modes. Forced convection through the powder, or downdraft, has recently been implemented in SLS machines in an effort to enhance thermal transfer within the powder bed. In this paper, forced convection is analytically shown to be a significant thermal transfer mode for low porosities, such as seen in SLS powder beds. A polymeric powder bed subjected to downdraft is investigated with the goal of quantitatively determining thermal behavior. A numerical model describing heat transfer within a powder is presented. The design and construction of an experimental apparatus to measure the temperature profiles within a powder subjected to forced convection is described. Using the information gained in these experiments, it may be possible to better control the thermal environment of SLS powder beds, reducing growth and internal stress build-up.Mechanical Engineerin