415 Hammering Mechanism for HP 3 Experiment (InSight)  

Jerzy Grygorczuk1,2, Łukasz Wiśniewski1,2, Bartosz Kędziora1,2, Maciej Borys1,2, Rafał Przybyła1,2,  Tomasz Kuciński1,2, Maciej Ossowski3, Wojciech Konior1,2, Olaf Krömer4, Tilman Spohn5,   Marta Tokarz2 and Mateusz Białek1,2  

Abstract    This paper  provides a description of the specific design features and nuances of the Hammering  Mechanism, a drive unit for the HP3 mole- type penetrator for NASA ’s InSight mission. State  of the art for  this type of mechanism  and an overall system overview  are provided. P articular attention is focused on key  components of the system that make it an effective mechanism.  The main des ign changes introduced to  the mechanism are related to three main domains :  mechanism architectur e and principl es, increase of  efficiency and simplification of the design, and functionality. A few critical lessons learnt are also described.  

Introduction  

The following paper discusses the development of the Hammering Mechanism (HM) for the HP3 mole- type  penetrator – the drive unit of DLR’s heat probe instrument for NASA’s InSight mission. The Hammering  Mechanism is a drive system of the HP3 penetrator whose purpose is to transport thermal sensors more than the required three meters below Martian surface (5 meters being the desired depth)  [4]. The original  concept of the mole- type penetrator mechani sm was provided by Gromov  et al. in [1] and then evolved  through the PLUTO instrument for  the Beagle2 mission [2], the proposal  for an ExoMars instrument [3], to  implementation in the InSight mission [4]. The most recent development of the Hammering Mechanism was  done by Astronika and the Space Research Centre of the Polish Academy of Sciences  (CBK) , under  contract and in close cooperation with DLR. Even though the concept remains the same, the final design,   as implemented by Astronika for the purpose of this mission,  significantly improved the system’s  performance with respect to the previous ones.  

The article begins  with a general introduction of the penetrator ’s design and their  known solutions ( state of  the art). The s pecific system architecture of the HP3 Hammering Mechanism is provided in  the System  Overview section. The core of the paper comprises particular design features that made the mechanism  more effective and improved its  performance. This includes spring distribu tion, cam optimization, bearing   description, dedicated roller design, multiple locking/unlocking launch lock system , and the mechanism’s   lubrication and coatings principles that significantly simplified  the mechanism and increased  its  performance with respect to previous versions.  Provided at the end are t hree lessons learned,  which  concern problems with cracking of tungsten alloys, r emoval of a spring clutch and the improper harness  tensioning that may lead to a decrease in the penetrator ’s performance if not properly done .  

State of the Art 

The Hammering Mechanism (HM) mentioned in this text is part of a bigger system of a mole- type penetrator   HP3 and its Support S tructure onboard the InSight l ander  (Figure 1) . A mole -type penetrator , in general , is  an assembly that consists of three main assemblies: Hammer  (HA), Suppressor Mass  (SM) , and Outer                                                    1 ASTRONIKA Sp. z o.o., Warsaw, Poland   2 Space Research Centre of the Polish Academy of Sciences , Warsaw, Poland    3 Warsaw University of Technology, Warsaw, Poland   4 German Aerospace Center (DLR), Institute of Space Systems, Bremen, Germany   5 German Aerospace Center (DLR), Institut e of Planetary Research, Berlin, Germany  

Proceedings of the 43rd Aerospace Mechanisms Symposium, NASA Ames Research Center, May 4-6, 2016