2016 NIAC Phase I Study Journey to the Center of Icy Moons Enceladus Vent Explorer Concept 2016 NIAC Phase I Study: Journey to the Center of Icy Moons 1 (C) 2017 California Institute of Technology. Government sponsorship acknowledged. Study Team Jet Propulsion Laboratory, California Institute of Technology PI: Dr. Masahiro (Hiro) Ono Dr. Karl Mitchel Dr. Aaron Parness Kalind Carpenter Dr. Aaron Curtis Dr. Mitch Ingham Dr. Charles Budney Dr. Tara Estlin Dr. Carolyn Parcheta Dr. Renaud Detry Jeremy Nash Dr. Jean-Pierre de la Croix Jessie Kawata Dr. Kevin Hand Università di Pisa Saverio Iacoponi Massachusetts Institute of Technology Ellie Simonson Acknowledgements This work was funded by the NASA Innovative Advanced Concepts (NIAC) program. We thank Penny Boston, Peter Willis, Morgan Cable, Florian Kehl, Matt Heverly, Noah Warner, Steve Sell, and Sabrina Feldman for valuable inputs. 2016 NIAC Phase I Study: Journey to the Center of Icy Moons 2 Table of Contents 1 Executive Summary ........................................................................................................ 5 2 Mission Concept ............................................................................................................ 11 2.1 System Configuration ......................................................................................................... 11 2.1.1 Descent module (DM) ........................................................................................................... 11 2.1.2 Surface module (SM) ............................................................................................................ 12 2.1.3 Carrier Relay Orbiter (CRO) .................................................................................................. 13 2.2 Mission Profile of EVE ........................................................................................................ 13 2.2.1 Launch, Cruise, Orbit Insertion, Landing ............................................................................... 13 2.2.2 Scout & eruption dynamics study ......................................................................................... 15 2.2.3 Sample return and in-situ science ........................................................................................ 15 2.3 Comparison with existing concepts .................................................................................... 16 2.3.1 Thermal Ice Probe (cryobot) ................................................................................................. 17 2.3.2 Mechanical Ice Probe ........................................................................................................... 18 2.3.3 Comparison with EVE ........................................................................................................... 19 3 Characterization of Environment in Enceladus Vents ..................................................... 21 3.1 Overview ........................................................................................................................... 21 3.2 Observed Data ................................................................................................................... 21 3.3 Dynamics Assumptions ...................................................................................................... 22 3.4 Vent dynamic model .......................................................................................................... 24 3.5 Diameter estimates ............................................................................................................ 29 3.6 Nozzle shape estimations ................................................................................................... 30 3.7 Suggestions for future study to better constrain key parameters ....................................... 30 4 Trade Studies ................................................................................................................. 32 4.1 Mobility System ................................................................................................................. 32 4.1.1 Mobility type ........................................................................................................................ 32 4.1.2 Attachment Mechanism ....................................................................................................... 33 4.2 Power System .................................................................................................................... 37 4.2.1 DM Energy Requirement ...................................................................................................... 37 4.2.2 Power Source Trade Study .................................................................................................... 44 4.3 Tether System .................................................................................................................... 47 4.4 Autonomy System .............................................................................................................. 49 4.4.1 Graceful degradation ............................................................................................................ 50 4.4.2 Goal-directed mobility .......................................................................................................... 50 4.4.3 Opportunistic science ........................................................................................................... 50 4.4.4 Software resilience ............................................................................................................... 51 4.5 Perception System ............................................................................................................. 51 4.5.1 Overview ............................................................................................................................... 51 4.5.2 Candidate Sensing Technologies .......................................................................................... 52 4.5.3 Discussion ............................................................................................................................. 54 4.6 Science Instruments ........................................................................................................... 56 4.6.1 Instruments on In-situ Science DM ....................................................................................... 56 4.6.2 Instruments on sample return DM ....................................................................................... 62 4.6.3 Instruments on SM ............................................................................................................... 63 5 Planetary Protection ...................................................................................................... 64 2016 NIAC Phase I Study: Journey to the Center of Icy Moons 3 6 Experimental Studies ..................................................................................................... 65 6.1 Energy required for ice screw insertion and removal .......................................................... 65 6.1.1 Thermal Chamber Experiments (-20 C) ................................................................................ 65 6.1.2 Conservative energy requirement estimate for the Insertion and Removal ........................ 68 of the Ice Screw ................................................................................................................................. 68 6.1.3 Conclusion ............................................................................................................................ 69 6.2 Ice screw’s resistance to sheer force .................................................................................. 69 6.2.1 Experiment Setup ................................................................................................................. 69 6.2.2 Results .................................................................................................................................. 70 6.2.3 Comparison with finite element model (FEM) ..................................................................... 72 7 Mechanical prototype design ......................................................................................... 74 7.1 Considered Configurations ................................................................................................. 74 7.1.1 Linear actuation vs joints ...................................................................................................... 74 7.1.2 Worm structure .................................................................................................................... 74 7.1.3 Four limbs head .................................................................................................................... 76 7.1.4 Two limbs .............................................................................................................................. 76 7.1.5 Two plus two limbs ............................................................................................................... 77 7.2 Linear actuators ................................................................................................................. 78 7.2.1 Actuator selection ................................................................................................................ 78 7.2.2 Final choice ..........................................................................................................................