MUPUS insertion device for the Rosetta mission

An original mechanical device designed to insert a penetrator into a cometary nucleus in an almost gravityfree environment is described. The device comprises a hammer and a power supply system that stores electrical energy in a capacitor. The accumulated energy is discharged through a coil forming a part of electromagnetic circuit that accelerates the hammer. The efficiency of converting the electrical energy to kinetic energy of the hammer is not very high (amounts to about 25%), but the system is very reliable. Additionally, the hammer energy can be chosen from four power settings, hence adjustment of the stroke's strength to nucleus hard- ness is possible. The device passed many mechanical, func- tional, thermal and vibration tests and was improved from one model to another. The final, flight model was integrated with the lander Philae and started its space journey to comet Churyumov-Gerasimenko in March 2004.