73 Lessons Learned from Q ualification of HDRM for U ltralight LP -PWI Boom for   ESA JUICE M ission.  

Maciej Borys*, Ewelina Ryszawa* , Łukasz Wiśni ewski*, Maciej Ossowski*  and Jerzy Grygorczuk*  

Abstract  

The paper presents the complications appearing during the qualification campaign of the Langmuir Probe  – Plasma Wave Instrument (LP -PWI). The article focuses  on one subsystem of LP -PWI: the Hold Down  and Release Mechanism (HDRM). After the qualification vibration test , the HDRM was supposed to open  to release the LP -PWI boom.  However , the mechanism was blocked.  The analysis present ed reveals  several root causes of this failure. The following root causes  were identified:  an optimistic functional  analysis, in correct integration processes , and neglected finishing of the parts . The second part of the paper  shows the improvements  implemented in the HDRM and the result of these changes. Finally, the lessons  learned from the qualification process of the LP -PWI and HDRM failure are presented.  

Introduction  

The LP -PWI is one of the instruments within the Radio & Plasma Wave Investigat ion experiment on board  ESA’s JUICE (Jupiter Icy Moon Explorer) mission. The experiment  consists of four identical LP -PWIs  mounted on the edges of JUICE Spacecraft  (S/C) . The  main objective of the instrument is to provide crucial  information about the bulk  plasma surrounding Jupiter’s icy moons. The instrument is built  in cooperation  with the Swedish Institute of Space Physics in  Uppsala under contract with ESA  Prodex .  

The article begins with a general description of the LP -PWI architecture and an introduction to the main  environmental  and technical requirements . The state- of-the-art section presents  an overview of the boom  with a short description of the main subsystems.  The paragraph on system over view gives a detailed  description of HDRM . The next chapters of the article focus on the qualification campaign and problems  that appeared after the vibration test.  The core of the article is  the analysis of the HDRM ’s failure  to open.  The root causes of this failure and further solutions  are described.  As a summary , the paper  presents all   HDRM  design and process  improvements  that helped overcome al l the problems encountered with the  opening of the HDRM . Final conclusions and lessons learned can be found in the last chapter .  

State of the A rt 

The HDRM is a part of the bigger instrument -  the LP-PWI (Figure 1). The LP -PWI is a two -section boom  ended with Langmuir Probe  (LP) [1]. The LP is a spherical sensor made of titanium and covered with TiA lN  (Titanium Aluminum Nitride). The LP on board JUICE mission is 100 mm in diameter , which is two times  larger than those on board Rosseta [2] and Cassini missions [ 3]. The two sections  of the boom are made  of CFRP  (Carbon Fibers Reinforced Plastic)  tubes  ended with titanium interfaces  and covered with Single  Layer Insulation . The interfaces allowed to link  the tubes with  two hinges : Base and Central . Both are very  similar . They are equipped with clock springs , which drive the boom,  and a latching mechanism. The Central  Hinge opens to 180 deg, while the Base Hinge opens to 135 deg. In a deployed configuration all LP -PWIs  are positioned at an angle of  45 deg to the S/C longer edge.  

* ASTRONIKA Sp. z o.o., Warsaw, Poland 

Proceedings of the 45th Aerospace Mechanisms Symposium, NASA Johnson  Space Center, 2020