Energy Storage for Ocean Worlds Exploration

Erik J. Brandon, Keith Billings, Kumar Bugga, Keith Chin, John-Paul Jones, Simon Jones, Charlie Krause, Ray Ontiveros, Jasmina Pasalic, Bernard Rax, Marshall Smart, Jason

Thomas and Will WestFebruary 23, 2018

© 2018 California Institute of Technology. Government sponsorship acknowledged.

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Power Options for Ocean Worlds Landers

Pre-Decisional Information -- For Planning and Discussion Purposes Only

Viking (1976)RTG + Ni-Cd rechargeable

batteries

Phoenix (2008)Solar array + Li-ion

rechargeable batteries

MER (2003)Solar array + Li-ion

rechargeable batteries

Juno (2016)Solar array

+ Li-ion rechargeable

batteries

• RTGs provide long life power, but not viable for all architectures and all destinations

• Solar arrays demonstrated at Jupiter distances, but only feasible for orbiters (where very large arrays are possible)

• Remaining option with adequate maturity are primary batteries

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Primary Batteries for Probes and Landers

Pre-Decisional Information -- For Planning and Discussion Purposes Only

Huygens Probe 2004: Li/SO2~2700 Wh<3 hours

Europa Lander scenarios contemplate 480 hours of operation on battery power alone, representing a new paradigm for primary

battery operations

Galileo Probe 1989: Li/SO2~580 Wh<1 hour

Europa Lander: ???~25,000 Wh~480 hours

Artist’s concept

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Europa Lander Concept Battery Needs

• High specific energy per unit mass (Wh/kg)– ~ 35 kWh for 20 day mission to support needed sampling/science

• Low self discharge– It may be 10 years between manufacture of cells and landing

• Must be compatible with planetary protection protocols

• Wide temperature operation may be important– Highly dependent on architecture and mission design

Pre-Decisional Information -- For Planning and Discussion Purposes Only

• Specific energy (Wh/kg) is the most critical metric to target

• More Wh per kg = less lander mass dedicated to batteries

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Extensive Screening of Battery Cell Options

Pre-Decisional Information -- For Planning and Discussion Purposes Only

Cell ChemistrySpecific

Energy, Wh/kg(20⁰C, 50 mA)

Li/SO2 420Li/SOCl2 421Li/MnO2 275Li/FeS2 350

Li/CFx-MnO2 514

Li/CFx 730

Battery Test Chambers at JPL

heritage

new

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Simple Battery Sizing Exercise

Pre-Decisional Information -- For Planning and Discussion Purposes Only

Cell ChemistrySpecific

Energy, Wh/kg(0⁰C, 50 mA)

Total battery with all cellsand packaging for 38

kWh battery (kg)Li/SO2 420 103

Li/SOCl2 421 103Li/MnO2 275 165Li/FeS2 350 130

Li/CFx-MnO2 514 89

Li/CFx 730 63

• Can reduce mass dedicated to battery by ~40 kg vs. heritage chemistries!

• Challenge: cell chemistry has no flight heritage

• Need to consider planetary protection

Location of batteries(notional)

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Planetary Protection Approaches• Typical dry heat microbial reduction conditions are in the range of

110⁰C to 150⁰C for 8 to 140 hours

• Significant loss of capacity observed under these conditions

• Investigating radiation as means to sterilize

• Requires extensive radiation testing

• Engaging Sandia National Lab for long term support

Pre-Decisional Information -- For Planning and Discussion Purposes Only

JPL Radiation Test FacilitiesCells in radiation test

fixtureTest chamber and source

j p l . n a s a . g o vPre-Decisional Information -- For Planning and Discussion Purposes Only

Radiation Does Not Appear to AffectBeginning-of-Life Battery Capacity

• 0 to 8 Mrad battery discharge curves all look similar = high radiation tolerance• What are the longer term impacts?• What about reliability of components?

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Destructive Physical Analysis of Irradiated Cells

Pre-Decisional Information -- For Planning and Discussion Purposes Only

Tear down of irradiated cell for analysisRolling out the

electrode “jellyroll”

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Separator Key Battery Component

Pre-Decisional Information -- For Planning and Discussion Purposes Only

Polyimide based separator

Conventional separator

Embrittled, with changes in composition after irradiation

no changes after irradiation

• Conventional battery separators appear susceptible to radiation damage

• Identifying alternatives that can better tolerate radiation

Infrared Spectroscopy of Irradiated Separators

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Summary and Plans Forward• Early technology investments by NASA Science Mission

Directorate are paying off

• Identified and developed battery technologies that enable future Ocean Worlds mission concepts

• Continue efforts to improve performance, ensure batteries are compatibility with planetary protection and capable of long life in high radiation environments

Batterymaterials

development

Rapid infusion and cell prototyping

Extensive testing of cells and components

Battery design and qualification

Pre-Decisional Information -- For Planning and Discussion Purposes Only

jp l .nasa.gov

Acknowledgements

This research was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology under a contract with the National

Aeronautics and Space Administration.