Analysis of the Hammering Mechanism of a Special Percussive System for Planetary Exploration

Abstract

Special percussive mechanisms, e.g. Auto Gopher and Ultra Sonic/Sonic Driller/Corer (USDC) have been developed by Honeybee Robotics Spacecraft Mechanisms Corporation and NASA Jet Propulsion Laboratory to explore the Lunar, Martian, and other planetary bodies subsurface and extract soil (regolith)/rock samples for further study. This paper presents the analysis of the interaction between the hammer (free mass) and the drill bit of this percussive mechanism. The impact between the free mass and the drill bit is analyzed using solid body collision analysis. The impulse and the energy transferred to the drill bit by the free mass are obtained using impulse momentum principle and determining the change in kinetic energy due to impact, respectively. Finally the contact force and duration of impact is determined by an energy balance method (Cox method). The contact force is seen to increase gradually with a sinusoidal shape, reaching a maximum value at the maximum deflection of the rod and decreasing until it becomes equal to zero at the end of impact. The duration of contact is compared to that obtained by wave propagation analysis and is observed to be in close agreement considering the difference in the assumptions of each method.