Thermal Mining of Lunar Ices

June 2020

George Sowers

6/24/2020

Agenda

• Background

• Ice at the lunar poles

• From resource to reserve

• Propellant production architecture

• Ice extraction system

• Proof of concept testing

• Conclusions

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• Mounting evidence that water ice exists in large quantities near the lunar poles

• Water has many uses for sustainable space exploration & development• Essential for all life• Oxygen for breathing air• Radiation shielding• LO2/LH2 rocket propellant

• Use of space-sourced propellant dramatically lowers the cost of all beyond Low Earth Orbit (LEO) transportation• Enables the commercialization of cislunar space• Enables affordable Mars missions

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Background

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• Surface ice indications of up to 30wt%

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Lunar Polar Surface Ice

Li, S, Lucey, P.G., Milliken, R.E., Hayne, P.O., Fisher, E., Williams, J.P., Hurley, D.M., Elphic, R.C., Direct evidence of surface exposed water ice in the lunar polar regions. PNAS (2018). https://doi.org/10.1073/pnas.1802345115

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https://doi.org/10.1073/pnas.1802345115

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Developing a Proven Reserve

CRIRSCO, Committee for Mineral Reserves International Reporting Standards, Standard Definitions, 2012.

http://www.crirsco.com/news_items/CRIRSCO_standard_definitions_oct2012.pdf

We are here

Where we need to be

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Lunar Ice Resource Exploration Roadmap2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031

Mine dev.

Modeling

Ground truth mission(s)

Cubesat & impactor swarms

Tethered sensor lander(s)

Rover/ sampler

Technology development

Full scaleindustrial

production

Mining HW developmentDeployment & set-up

HW development

Technology demonstrations

Launch Mission Ops

Geologic modeling & resource mapping

Technology development

HW development

Launch Mission Ops

Technology development

HW development

Launch Mission Ops

Technology development

HW development

Launch Mission Ops 6

• Discrete Element Modeling initiated at both Colorado School of Mines (CSM) and University of Central Florida (UCF)

• Initial uniform distribution of ice on lunar surface

• Evolution through impact gardening over billions of years

• Heterogenous distribution of ice, but stays near surface

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Lunar Polar Ice Modeling

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4wt%

UCF Model

(10cm initial ice layer)

CSM Model

• The Veritas mission concept developed by CSM to determine ground truth in a deep, cold PSR location

• Existing CLPS lander using only battery power

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Veritas

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• High TRL instruments

• Squirrels: ejectablesensor packages with ground penetrating radar

Instrumentation layout on LM McCandless Lander

Squirrel ejection concept

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Veritas Site Selection

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23 days per year line of site to Earth

Propellant production system

Ice extraction system

Capture Tent

Cold Traps

Secondary Optics

Mobility systemsWater to

propellant processing system

Storage systemsSolar energy

systemPower system

Communications link

Propellant Production System Elements

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Credit: ULA

Sized for 1100 mT/year

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Thermal Mining NIAC

Paragon ISRU BAAOxEon Tipping PointBlue Origin Tipping

Point

Transformers NIAC

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Ice Extraction Concept

Sublimation

sunlight from crater rim

Impermeable walls with reflective inner surface

Not to scaleOptional conducting rods or heating elements

Cold Trap

Ice hauler

Cold Trap

Ice hauler

Transparent membrane (IR reflective inner surface)

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Secondary optics (mirror)

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Ice Extraction System in a Lunar PSR

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Overall Process Flow

Launch & LandDeploy &

Set-up(re)Position

tent & mirrors

Collect ice in cold trap

Transport iceto refinery

Purification

Heat surface with reflected

sunlight

ElectrolysisPropellantstorage & handling

Active

Passive

Non-recurring

Liquefaction

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Deployment & Setup TimelineYear 1 Year 2

Launches(Vulcan)

Landings (XEUS)

Heliostats

Landing pad const.

Processing plant

Capture tent

System checkout

Production

H #1 setup

Crater rim

PSR

Landing pad construction

H #2 setupH #3 setup

H #1 ops

H #2 opsH #3 ops

Landing pad operations/launch pad construction

setup

setup

Operations

Operations

9 launches6 landings

Checkout

Production

18 month timeline: 1st launch to production

3 PSR XEUS’s become propellant storage

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• Key parameters: Tent diameter 30m, dwell time 44hr, Tent placements 156/yr, Average ice sublimation 16.1 kg/m2, 10% vapor loss

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Ice Extraction Operations

Collect iceIf ice level “full”

detach haulerTransit to

processing plant

Heat & release ice

Detach from processing plant

Monitor ice level

Attach to processing plant

Transit to capture tent

Hauler

Attach Cold Trap

ProcessingPlant

All operations semi-autonomous/tele-operated from Earth

Charge hauler

Attach Cold trap

• Tent must be frequently moved to meet required annual production rate

• Tent raises ontoskids

• Ice haulers tow tent to adjacent location

• Tent lowered to collection configuration

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Moving the Capture Tent

• Mud Pie• Liquid water mixed

with regolith, then frozen

• Water fills pore space, cements grains

• Very hard, concrete-like

• Granular Mix• Ice shaved and sieved

to small grains• Mixed with dry regolith• Sand-like, porous• Various grain size

distributions

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Icy Regolith Simulants

Ice Regolith

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Surface Heating of Icy Regolith Simulant

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Block 1 Test ApparatusSample container: 8.25cm diameter, 6.4 cm depth

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CSM Medium Vacuum Chamber

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Example Sublimation Results

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• 12wt% ice• Total ice sublimated vs time• Sublimation rate vs time

Preliminary

• Ice extraction from surface heating inhibited by the formation of a desiccated layer at the surface• Insulating barrier

• Vapor barrier

• Both effects mitigated by adding conducting “straws”

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The Straw Concept

0.704

Desiccated regolith

Unaffected icy regolith

Heat affected icy regolith

Straw

Container wall

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Perforated Copper Straw

0.704

Post test with desiccated regolith removed

Edge of desiccated zone

Addition of Straw increased ice production by 2-3X

• Small sample and proximity of LN2 boundary limits total ice sublimated

• No meaningful extrapolation to full scale

• Block 2 apparatusincreases sample size 10X and moves coldboundary away from heating zone

• Testing to begin July 2020

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Block 2 TestingHeat affected

Thermal Sink – LN 77 K

Lamp

Desiccated

Unaltered – 77K < T < 180 K

Sample container Freezer

• Block 1 testing key results• Surface ice is rapidly sublimated• Surface heating sublimates ice within the subsurface

• Desiccated layer at the surface grows over time• Heat affected zone at the sublimation boundary moves deeper

over time• Thermo-physics is complex

• Addition of straw(s) increases ice yield by 2-3X• Proximity of cold boundary artificially limits yield

• Block 2 testing to begin July 2020• Larger sample size: 18.4cm diameter, 15.2cm depth

• >10x volume

• Cold boundary farther away from heating zone

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Preliminary Testing Conclusions

• Thermal modeling of icy regolith subject to surface and subsurface heating initiated in late 2017• Contract from ULA to UCF

• Phil Metzger & Julie Brisset performed the analysis

• Finite difference analysis, 1-d, 2-d and 3-d models• Recent 3-d results currently in peer review• Preprint results

• Surface heating or solid subsurface heating elements• Surface heating seems more effective than just solid heating

elements• One model configuration very similar to current Thermal Mining

point design• 694W/m2 flux, 5wt% ice, 45hr dwell time produced 27.8 kg/m2 ice

• This compares to 1360W/m2, 44hr dwell time for 16.1 kg/m2 ice used in the Thermal Mining point design and economic analysis

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Recent Analysis Results

• Detailed business case updated and included in NIAC report

• Cost Update• 1100mt Propellant/yr

• Business case scenarios• Commercial only (8.8% IRR)• Commercial Public Private Partnership (PPP) + NASA Artemis

(15.8% IRR)• Commercial PPP + NASA Artemis + NASA Mars (15.4% IRR)

• NASA Savings• Artemis: $470M/yr• Mars: $5200M/yr, $12B per Mars Mission

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Updated Business Results

Cost Element Cost ($M)

Development 883

Production 614

Launch 1,062

Total 2,559

• Thermal Mining concept enhanced via Phase I NIAC study• Ice extraction system concept fleshed out• Con ops developed including deployment• Proof of concept testing validated basic Thermal Mining

idea• Lunar ice deposition and evolution analysis shows most

ice remains within the first meter• Thermal modeling indicates surface heating can produce

economically viable yields• Business case analysis shows viable commercial business

and enormous savings for NASA through public private partnership

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Conclusions

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