Mechanical model of hollow-external-screw drill rod for lunar soil particle vertical conveying
This paper presents a mechanical model of drilling rod in lunar soil deep drilling process by expanding the theory of vertical screw conveyor. Space systems on lunar surface need to adapt to extremely bad environment and a drilling system would represent the fittest tool to collect soil sample to be analyzed in lunar exploration. Hollow-external-screw drill rod is a kind of most commonly used and reliable drill rod configuration which is one of the core executive components of lunar drilling- sampling mechanism. Drilling cuttings at the bottom of the hole are continuously sent to the lunar surface and the interaction between the drilling rod and the soil is difficult to model by numerical tools. Solid vertical transport theory in vertical screw conveyor and a soil-transporting mechanical model of long earth boring auger are applied to model the aforementioned interaction. In this force analysis of the mechanical model, not only the spiral angle variation is considered, but also the radial distribution and soil pressure in the particle vertical conveying. All these make the theoretical analysis more comprehensive than traditional methods. This paper also provides mathematical simulation of the soil-transporting process and the validation of the theoretical model mentioned above will be confirmed by the numerical and physical experiments.
A drill-soil system modelization for future Mars exploration
Abstract This paper presents a first approach to the problem of modeling a drilling process to be carried on in the space environment by a dedicated payload. Systems devoted to work in space present very strict requirements in many different fields such as thermal response, electric power demand, reliability and so on. Thus, models devoted to the operational behaviour simulation represent a fundamental help in the design phase and give a great improvement in the final product quality. As the required power is the crucial constraint within drilling devices, the tool–soil interaction modelization and simulation are finalized to the computation of the power demand as a function of both the drill and the soil parameters. An accurate study of the tool and the soil separately has been firstly carried on and, secondly their interaction has been analyzed. The Dee-Dri system, designed by Tecnospazio and to be part of the lander components in the NASA's Mars Sample Return Mission, has been taken as the tool reference. The Deep-Drill system is a complex rotary tool devoted to the soil perforation and sample collection; it has to operate in a Martian zone made of rocks similar to the terrestrial basalt, then the modelization is restricted to the interaction analysis between the tool and materials belonging to the rock set. The tool geometric modelization has been faced by a finite element approach with a Langrangian formulation: for the static analysis a refined model is assumed considering both the actual geometry of the head and the rod screws; a simplified model has been used to deal with the dynamic analysis. The soil representation is based on the Mohr–Coulomb crack criterion and an Eulerian approach has been selected to model it. However, software limitations in dealing with the tool–soil interface definition required assuming a Langrangian formulation for the soil too. The interaction between the soil and the tool has been modeled by extending the two-dimensional Nishimatsu's theory for rock cutting for rotating perforation tools. A fine analysis on f.e.m. element choice for each part of the tool is presented together with static analysis results. The dynamic analysis results are limited to the first impact phenomenon between the rock and the tool head. The validity of both the theoretical and numerical models is confirmed by the good agreement between simulation results and data coming from the experiments done within the Tecnospazio facilities.
The Modification of the Test Unit of the Screw-gas Bulk Sucking and Taking Equipment
A modification is made on the first test unit of the screw-gas buck sucking and taking equipment by adding a centrifugal separator,a blower blade and a screw blade support and by removing the equalizer and keeping reversing screw off,etc.The new test unit strengthens the separation effect effectively with the result of smaller separated-grain size and faster separating speed.