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Sheltering Habitats in Extreme Lunar Domains�(SHIELD)

LIANNE LEWIS

7 MAY 2024

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Contents

Context

Rationale

Mission Architecture

Phase 1

Phase 2

Phase 3

Future Studies

Conclusion

References

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Context

In 2012, NASA’s Gravity Recovery and Interior Laboratory (GRAIL) spacecraft mapped variations in the lunar gravity field

Resulting images show anisotropic gravity field anomalies around the Moon, particularly in equatorial and lower-mid latitude regions (see right) [1]

Currently, governments and private businesses are demonstrating interest in lunar habitation

Payload deliveries

NASA’s Commercial Lunar Payload Services (CLPS) initiative enables U.S. companies to deliver science and technology to the lunar surface

Multiple deliveries scheduled between 2024 – 2026 [2]

Lunar payload delivery also offered by the European Space Agency (ESA) in conjunction with Lunar Logistics Services SAS & Astrobotic [3]

Manned missions

Artemis program will put astronauts on the Moon in 2026 [4]

The lunar surface is subject to micrometeoroid impacts, temperature fluctuations, and radiation exposure [5]

Not a safe environment for long-term habitation

Back in 2012, NASA’s GRAIL spacecraft mapped variations in the lunar gravity field. The resulting images, like the one on this slide, show anisotropic gravity field anomalies around the Moon, particularly in the equatorial and lower-mid latitude regions.

This is important because governments and private businesses are actively demonstrating renewed interest in habitation on the Moon. For example, several agencies are working to deliver science and technology payloads to the Moon over the next two years, and NASA’s Artemis program intends to put astronauts on the lunar surface in 2026.

When assessing possibilities for establishing a human presence on the Moon, it is critical to recognize that the lunar surface is not a safe environment for long-term habitation. Specifically, the absence of a lunar atmosphere causes the surface to be subjected to a barrage of micrometeoroids, extreme temperature fluctuations, and excessive radiation exposure.

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Rationale

Environmental conditions on the lunar surface are not conducive to establishing a long-term presence on the Moon

Researchers found 33% more craters (≥10m diameter) than predicted by previous best estimates [6]

The Moon is full of lava tubes that could provide a temperate, stable, and safe environment for long-term lunar exploration, habitation, and asset storage

Lunar lava tubes are generally sheltered from radiation, temperature swings, and small meteorite impacts
Lava tubes are far more common in equatorial regions than polar regions [7]

Equatorial region offers unique benefits for early Artemis exploration

Structural simulations verified that it is feasible to pressurize a small lunar lava tube with breathable air [8]

Related studies

Researchers are currently building and testing a deployable habitat in Icelandic lava tubes as a lunar analogue [9]
ESA planned detailed studies addressing different phases of a potential mission to a lunar lava tube

Tethered micro-rover for semiautonomous exploration of lava tubes
Using gravimetric surveying to map lava tubes from the Moon’s surface
Hopping rovers for exploration
Surface-to-cave wireless power and data transmission via robotic crane
Deep autonomy descent and exploration of lava tubes [10]

Max Space plans to create expandable habitats to enable human settlements in lunar lava tubes

A full-size prototype of the first flight unit is built and currently being used for ground testing [11]

We know that the environmental conditions on the lunar surface are not conducive to establishing a long-term presence on the Moon; however, the GRAIL mission suggests to us that the Moon is full of lava tubes. These subsurface features may provide the temperate, safe, and stable environment necessary for long-term human habitation and high-value asset storage. This is because lunar lava tubes are generally shielded from radiation, temperature swings, and small meteorite impacts. Structural simulations have also verified the feasibility of pressurizing a small lava tube with breathable air. Since the GRAIL mission indicated that lunar lava tubes are more common in equatorial regions, this area offers unique benefits for early Artemis exploration.

There are several ongoing studies related to this topic. For example, researchers are currently building and testing a deployable habitat in Icelandic lava tubes as a lunar analogue. The ESA has planned detailed studies addressing the different phases of a potential mission to a lunar lava tube, and a company called Max Space has plans to create expandable habitats to enable human settlements in lunar lava tubes.

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Mission Architecture

Three-phase approach to establishing a habitable environment in lunar lava tubes

Phased implementation mitigates risk, allows for better resource planning, and enables making changes based on lessons learned

Characterize lunar lava tube environment using an in-situ payload
Demonstrate habitat technology readiness via unmanned test
Verify habitat life support capabilities and general human compatibility via manned test

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Phase 1

Problem

The lunar lava tube environment has never been characterized in-situ

Objective

Characterize the lunar lava tube environment using an in-situ payload

Plan

Use a small payload to ascertain key environmental information (e.g., thermal environment, radiation, regolith composition, data transmission capabilities) inside a lunar lava tube

Payload Details

Infrared thermometer [12]
Radiation detector [13]
Mineralogical spectrometer [14]
Wireless communication antenna [15]

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Phase 2

Problem

Habitat technologies and life support systems lack heritage in lunar lava tubes

Objective

Demonstrate habitat technology readiness via unmanned test

Plan

Assess the performance and capabilities of various pressurized habitats within lunar lava tubes

Earth-based testing (e.g. leak, thermal, etc.) can be conducted simultaneously with Phase 1

Structural Possibilities

Inflatable [16]
Modular [17]
Expandable/folded [18]
3D printed [19]

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Phase 3

Problem

Humans have not experientially tested lunar lava tube habitats in-situ

Objective

Verify habitat life support capabilities and general human compatibility via manned test

Plan

Prove that humans can navigate lunar lava tube entryways and construct pressurized habitats in-situ

Prove that those habitats can sustain human life for a predetermined period

Human Considerations

Size (total volume)
Breathable air
Water (potable & non-potable)
Nutrition
Waste

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Future Studies

Phase 1 Questions

What is the best shape for the payload?
Could multiple payloads be implemented to compare different sites within one or more lunar lava tubes?
How much data is needed to adequately assess the habitability of the environment?

Phase 2 Questions

What structural forms would perform best with respect to lunar transportation and habitat pressurization?

Phase 3 Questions

What is the safest way for humans to enter and exit lunar lava tubes?
How long will the life support systems of the in-situ habitat be utilized?
Can this technology be ready in time for the upcoming manned lunar missions?

There are still several outstanding questions that are fundamental to a successful mission. Since these topics are generally phase-specific, that’s how they’re being delineated on this slide. For example, before phase 1 launches, we need to know things like: what is the best payload shape? How much data is needed to adequately assess the habitability of the subsurface environment? Similarly, prior to phase 2, we need to know which structural forms would perform best with respect to lunar transportation and habitat pressurization. Some of the hardest questions arise when looking toward phase 3. For example, what is the safest way for humans to enter and exit lunar lava tubes? How long will habitat life support systems be utilized? And, most importantly, can this technology be ready in time for the upcoming manned lunar missions? Ultimately, being able to answer these questions relies on a host of future studies.

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Conclusion

The lunar surface is not a good place for long-term habitation or high-value asset storage due to excessive micrometeoroid impacts, temperature fluctuations, and radiation exposure

Because they are generally sheltered from radiation, temperature swings, and small meteorite impacts, lunar lava tubes could provide a temperate, stable, and safe thermal environment for habitation

GRAIL mission clearly indicated that the Moon has a multitude of cavities and subsurface features of interest

Research insights limited because all data was obtained through proxy measurements
Developing a thorough understanding of subsurface lunar features can only be accomplished through physical examination

A three-phase approach was developed to ultimately create a habitable environment within lunar lava tubes

Phase 1: Characterize the lunar lava tube environment using an in-situ payload
Phase 2: Demonstrate habitat technology readiness via unmanned test
Phase 3: Verify habitat life support capabilities and general human compatibility via manned test

The phased mission architecture mitigates risk and enables making changes, including to future studies, based on lessons learned

To wrap everything up, I can’t overemphasize that the lunar surface is not a safe place, regardless of whether we’re discussing human habitation or high-value asset storage. This is due to the constant bombardment of micrometeoroids, enormous temperature fluctuations, and excessive radiation exposure. This is why it is so important to investigate subsurface features, like lunar lava tubes, which could provide a temperate, stable, and safe environment for long-term habitation and asset storage.

From the results of the GRAIL mission, we learned that the Moon has a multitude of cavities and subsurface features of interest. However, our research insights were limited because all the data was obtained through proxy measurements. Developing a truly thorough understanding of the lunar subsurface is a task that can only be accomplished through on-site physical examination.

That’s why this project focused on a three-phase approach to creating a habitable environment in lunar lava tubes. As I detailed earlier in this presentation, the three mission phases can be summarized as:

Using an in-situ payload to characterize the lunar lava tube environment
Demonstrating technology readiness via unmanned test
Verifying life support capabilities and human compatibility via manned test

Not only does this phased approach allocate resources more effectively, but it also mitigates risk and enables incremental changes to be implemented based on lessons learned.

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References