150 Conclusion  

In this paper the two mechanisms are presented to document the hardware and the function they fulfil l as  a part of the Mars 2020 rover, launching later this year. The Ram Mechanism is a compact, high force linear  actuator, while the Gripper Mechanism is a lower torque system featuring a unique flexurized output for  interacting with the Sample Tube.  

The Ram Mechanism uses a PRS rarely used in spacecraft mechanisms and is not rated for any amount  of cross -moment loading. While extensive characterization testing has not been performed in this body of  work, we s how that the PRS indeed has  capacity for cross -moment loads, making it a more robust  component than previously understood.  

Also used in the Ram Mechanism are cylinder and tapered roller bearings, again, rarely used in spaceflight  mechanisms. We describe the method used for installing a low preload vi a its threaded retainer by  characterizing the drag to preload relationship prior to the installation of the retainer. Despite the low  preload, the locking nature of the retainer holds it securely.   

The relative step size of the magnetic detent brake to t he mechanism hardstop resulted in conditions that  would not allow for preload to be maintained against the hardstop. The presented understanding of the  interaction allows for the problem to be avoided.  

We present the linear dyno, a mechanism for a high f orce linear thermal dyno testing , that worked  moderately well for its intended purpose. Because of the low stiffness of friction pad material,  the  mechanism was more difficult to operate than intended. The simpler alternative, a spring box, could have  been  used in this application to save time and effort during schedule sensitive thermal dyno testing.  

Acknowledgements  

The authors would like to thank the entire  SCS team and all the other unsung heroes at JPL. A special  thanks goes to the ACA I&T team and SCS Leadership. Big, complex missions don’t fly without wonderful ,  talented motivated people like you all. Semper Gumby.  

The work  was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a  contract with the National Aeronautics and Space Administration.  

References  

1. Silverman,  Milo,  Justin Lin. “ Mars 2020 Adaptive Caching Assembly: So Many  Challenges ”  Proceedings of the 45th Aerospace Mechanisms Symposium, ( 2020).    2. LoSchiavo, Michael , Robin Phillips, Rebecca Mikhaylov, Lynn Braunschweig. “ Mars 2020 Maxon  Commercial Motor Development from Commercial -Off-the-Shelf to Flight -Qualified Motors, Gearboxes,  and Detent Brakes: Overcoming Issues and Lessons Learned” Proceedings of the 45th Aerospace  Mechanisms Symposium, (2020).   3. SKF Roller Screw C atalog. < https://www.skf.com/binary/82 -153959/14489- EN---Roller -screw - catalogue.pdf > accessed Jan 24, 2020   4. Nook  Precision Screw Catalog, <http://www.nookindustries.com/Content/media/NOOK -Screw - Catalog.pdf > accessed Jan uary 24, 2020   5. Rolvis  Roller Screw Catalog < http://www.nookindustries.com/Content/media/NOOK -Screw - Catalog.pdf > accessed Jan uary 24, 2020   6. J.V. Poplawski & Associates, C OBRA AHS bearing analysis software  <http://www.bearingspecialists.com/software.asp > accessed January 24,  2020