 BUILDING WITH TETRAHEDRAL STRUCTURE FOR PLANETARY SURFACES AND FOR ANALOG MODELING ON THE EARTH BY THE HUNVEYOR CONCEPT. T. P. Varga 1, I. Szilágyi 1, R. K. Varga 2, Sz. Bérczi 3. 1 VTPatent Kft. H-1111 Budapest, Bertalan L. u. 20. Hungary, (info@vtpatent.hu), 2 Eötvös József High School, H-2890 Tata, Tanoda tér 5. Hungary, (vargakingareka@freemail.hu), 3 Eötvös University, Institute of Physics, Dept. Materials Physics. H-1117, Budapest, Pázmány P. s. 1/a. Hungary (bercziszani@ludens.elte.hu)  Introduction: The subject of our study is a tetrahedral building concept which is directly placeable on the Lunar or Martian surface, and is also suitable for Earth based surface analog experiments and educational programs. Summary: The essence of the building construct is a tetrahedral outer frame supported by a tripod base. The design is inspired by the supporting structure of the Surveyor probes, which landed on the Moon in the 1960s, and the recent Phoenix lander. This supporting structure is also known in relation to the Hunveyor educational space probe model described in our previous works [1,2,3]. In this scenario however the utilization of the tetrahedral construct is implemented in a larger scale, serving as the core of a surface building. The construct enables the building of a base or habitation module on the planetary surface which can enable long term human habitation and which in it's preferred embodiment is also capable of executing industrial and scientific activities.  The described structure can serve as a central residence module, as well as a command center and coordination center. During the first part of it's development the structure is able to support and coordinate outside surface activities, and is also redeployable to various locations on the planetary surface to retain it's usefulness during later stages of human exploration. The above surface structure can be built as a terrestrial analog model, thus it is well utilizable for planetary surface analog experiments, and in the education. The building can serve as a hub modul for a larger systems located on the planetary surface during activities relying on mobile or fixed modules. The preferred utilization includes independent communication capabilities with other surface modules, orbiters and with Earth [3]. Background:  Outside constraints and circumstances on the Moon and Mars: Solid however uneven surfaces. The local surface materials are Lunar regolith and the Martian soil. Dusty mixtures with water or CO2 ice can also alter the physical properties of the local materials. There are several plain or sloped surface areas, which are suitable sites for buildings and industrial activities. Local gravity is weaker than on the Earth, 1/6 g for the Moon, and approximately1/3 g for Mars. This reduces the weight of building parts, and construction blocks, as compared to their weight on the Earth's surface. The results of this effect are beneficial for in-situ construction and assembly. Local temperatures change widely on the Moon due to the lack of atmosphere, and to a lesser extent also on Mars. Extreme temperatures make construction processes more difficult, thus for optimal efficiency time intervals with optimal temperature values should be utilizied for the assembly and installation. Atmosphere: Practically none on the Moon, however electrostatically levitated fine dust can cause harmful effects. The surface pressure of the Martian atmosphere is very low and it's contents does not pose problems, however seasonal dust storms ar present which endanger the construction or installation process. Cosmic radiation and meteorite impacts present a significant threat even on short time scales on the Lunar surface, while on Mars these effects manifest significantly only over longer time periods. These outside parameters must be taken into consideration during the design of the outer cover, and during the choosing of it's material. Practical considerations:  Special design aspects: The base tetrahedron structure consists of linear parts along its edges e.g.: rods, tubes or skeleton holders reinforced in the longitudinal direction. The length of the edges (L) in a given case is 10-20 m, thus they can be manufactured as a single element, however multiple joinable building elements can also be used. The height (H) of the final tetrahedron would be 8-16 m depending on the steepnes of it's sides and the distance (S) of the footpoints.    Fig.1. Basic structure of a tetrahedral building for planetary surfaces in cross section and in top view  The structural designs of the platforms: The edges of the platforms, located between the edges of the tetrahedron, can consist of the same building elements as the edges of the tetrahedron. The individual platforms must be sufficiently load bearing and must be able to pass the load applied to them at their joinings to tetrahedron's edges. The method of joinings between the edges of the platforms and the edges of the tetrahedron must be decided based on the loads expected. Several different methods exist for the solution of his problem. The setup of the platforms: The platforms can be prepared depending on the requirements of the utilization, and they are variable and changeable even after the finish of the man construction process. The modules on each platform can be air-tight, or tempered. The air-tight areas can provide space for human habitation of varying lengths. Outside coating and protection: An outside layer of protective materials can easily be applied to the whole tetrahedron, as the sides are all flat surfaces. The purpose of this outside layer is the protection from the planetary environment e.g.: radiation shielding, temperature protection, and micrometeorite protection. Feasibility study:  Assembly and installation: The base structure can be assembled from building blocks on the surface or also in space. For the surface assembly the building blocks must first be transported to the planetary surface via a proper transportation vehicle, and assembled using a human workforce or robots. With current capabilities this step requires at least some extent of direct human involvement. Another option is to assemble the base structure in orbit, and lower it to the surface as a whole using a sky-crane system similar to the one utilized in the Curiosity mission. Assembly in space: The direct assembly of the core structure in orbit provides several direct advantages, as it is possible even at a space station in low-Earth orbit. Over recent decades significant practical experience is accumulated regarding space based constructions, and reliable launch capabilities have also been provided. Orbital assembly is greatly aided by the microgravity of the environment as it is only the positioning of the parts which requires effort. The personnel undertaking the assembly can also move more freely, and there is no need for heavy cranes, and lifting equipments. The unwanted effects of the surface environments can also be eliminated e.g. long Lunar nights, the presence of fine regolith dust, or the dust storms encountered in Mars. Orbital construction would also allow the construction of structures with edges several tens of meters long.  The three-point support design does not require the preparation of the landing site, thus the entire structure with platforms and equipments installed can be lowered to the surface using a sky-crane. The lower surface gravity of the Moon and Mars greatly enhances the effectivity of this method, and the structure can be used right after the successful touchdown.  Fig.2.The tetrahedral building on a theoretical planetary surface with the communication relations  Terrestrial aspects: Analog experiments and educational utilization are applicable on Earth. The educational utilization of this design can be developed based on the already existing Hunveyor educational space probe model program [1,3]. This uses a central unit installed on a planetary analog site, and several other optional fixed or free moving units placed on different planetary analog sites. The tetrahedral structure would serve as a central unit which is in connection with several ground based or orbiting units, and also oversees and controls the units located in other planetary analog sites. The units with fixed locations could be measuring, data collecting, or observational stations, or stations with the purpouse of human habitation or industrial activities. Moving units can be vehicles, e.g. modeled after the HUSAR rover model, or individual persons working on the planetary surface. The advantages of the terrestrial analog model is that it's simplicity allows the practicing of it's assembly and the modeling of planetary surface activities This allows that not only potential members of future missions, but the wider audience would also be able to take part in preparing for the surface activities and in the process of improving the design and the logistics of the structure. This aspect holds great possibilities in the education of space sciences, as well as the education of physics and informatics. References: [1] Bérczi et al. Űrkutatás és Technológia (Space research and Technology), Published by ELTE Space Research Group © 2007; [2] Magyar et al.: Inner Design of a Habitat Module for Planetary Surfaces, 44th LPSC #2893, (2013); [3] Cseh et al.: Educational Relationships the Development of the Hunveyor 13 Informatics Architecture, 43 LPSC #1183 (2012)  
