Construction Technique and Strength of Connected Regolith Bag Structures

Abstract

Masonry Arches have been used from a long time in construction of bridges, domes and other structures. They are constructed out of voussoirs and their stability is determined by drawing a funicular polygon representing force flow through the structure. If this line remains inside the structure then its stable, otherwise it forms hinges at the locations where the line comes outside of the structure, and collapses. The work presented in this thesis implements the use of funicular polygons in determining the stability of lunar structures prototypes made out of bags filled with regolith (lunar soil). These structures are made in the shape of a catenary arch using center connected and top connected bags. Various structures are developed at Auburn University and MSFC, to test their stability. Structures made out of top connected bags are found to be more stable, as demonstrated by construction of a simply hanging beam made out of top connected bags. During construction at Auburn University and MSFC, both the top and center connected bags are filled with vermiculite because of its light weight and also because of lack of regolith on Earth. These structures are constructed on frames which are removed after the structure is built completely. The structures are designed to be stable under their own load so the frames are not required once the construction is over. They are also designed such that the construction process can be carried out by taking minimum amount of material from Methods of filling the bags with regolith are also investigated and a screw conveyor system is found to be the most reliable. The stability of these structures is found by constructing funicular polygons, under given load conditions, in Solid Edge. This technique of determining the stability is found useful and reliable in construction of lunar structures that are based on masonry arches.