E-STEP: Extraterrestrial Surface Terrain EVA CramPon

Eric Miller - ASTE 527

December 13th 2022

Current Physiological & EVA Issues with Partial Gravity

• Biological maladaptation

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• Slow & physically taxing

• Historically prone to imbalance - slipping and falling

Astronaut Harrison Schmitt - Apollo 17

The Problem with Partial Gravity

• Humans evolved to walk in Earth-like conditions

• Toe-toe step

• Soleus deactivation, gastrocnemius activation

Muscles of the lower leg

Next Generation: Artemis xEMU EVA Suit

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• Major improvements over Apollo EVA suits

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• Lower pressure, increased mobility, increased range

• Facilitates new technologies to address some partial gravity issues

• Expected to remove bunny-hopping and allow for some form of lunar walking

Apollo and Artemis EVA suits

Context

• Extraterrestrial Exploration - Moon as a case study

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• Most permanently shadowed regions are inaccessible to EVA

• Current EVA requirement is a 20° slope

• Limited Exploration – Walk back range – 1.38 km

• EVA following lander touchdown

Artemis Pressurized Rover Concept Art

Operations Rationale

• Geological exploration needs unplanned EVA

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• Landing location determined by landing terrain and accessible nearby features for EVA

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Red = 100m landing circle (slope <5°. Yellow = max walking range 1.38 km radius

Potential Artemis III Landing and First EVA Location (de Gerlache-Shackleton ridge)

E-STEP Concept

• External crampon system

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• Attaches around Artemis xEMU EVA Boot

• Interfaces with each step to “grab” on to the Moon

• Removable in case of issue

STEP: Side View

STEP: Bottom View

• Sealed bearings and orifices to keep lunar dust out

• Ratcheting mechanism to lock foot in place similar to snowboarding shoe

Goals

• Create external downwards force during EVA

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• Potentially allow for EVA over more difficult terrain

• Increase stability over uneven terrain

• Facilitate a more Earth-like gait

Apollo 17 - Lunar Crater near Station 1

Operation

• Retractable needles are a relatively passive component

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• Actuated by pressure sensor under the ball of the foot

• Microspines are sole active component

Microspines

Needles

Traction Mechanism

• Needles angled to aid in walking and provide more traction

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• Needles retract when stepping on rocks

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Toe

Heel

• Microspines available to catch on any rock under step

• Needles catch on irregular topography of regolith or sink into lunar dust

Some Hard to Access Extraterrestrial / Lunar Features

• Tops of boulder and between them – to emplace payload

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Lunar Lava Tube

• Areas inaccessible to rovers

• Lips of lunar lava tube skylight

• Cliff faces

• Steep slopes

• Crevices

Increasing Scientific Capabilities

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• Allows access to more permanently shadowed regions - key scientific points of interest

• Facilitate sampling of lunar boulders and steep rocky surfaces

Harrison Schmitt - Apollo 17

• Allow for determination if sufficient cold traps exist in PSRs to retain volatiles

Extending EVA

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• Rappel into ravines and allow for vertical EVA

• Can be paired with other mountaineering tools

• Facilitate safer exploration of lunar caves

Rappel Concept Art

Merits

• More Earth-like gait - more natural/intuitive

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• Decrease consumable usage

• Lessen fatigue and improve balance

• EVA becomes more ergonomic

• Make EVA faster and more productive

• Allow for EVA over a wider range of terrain

Limitations

• May be difficult to design around current xEMU Artemis Suits

• Difficult to test and optimize on Earth

• Will require study & test before being used

• TPS unfinished for xEMU boot for lunar south pole

Further Potential Merits

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• May improve or compensate for some biological maladaptation

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• May reduce body’s tendency to switch from using gastrocnemius muscle over soleus muscle

• May facilitate heel-toe walking

Lips of Lava Tube Skylights

Future Studies

• Simulated terrain testing with a partial lifting harness

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• Parabolic flights

• Neutral and partial buoyancy testing

• Partial gravity treadmill

• Develop alternate prototypes - specialized based off terrain

• Decide on best microspine and needle design

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Methods

Data

• Space qualification - electrostatic lunar dust

• Ease of stowage - minimize footprint

• Minimize mass, risk to EVA suit, and increase durability

• Materials testing

Questions?

Sources

Miller, Matthew & Claybrook, Austin & Greenlund, Suraj & Marquez, Jessica & Feigh, Karen. (2017). Operational Assessment of Apollo Lunar Surface Extravehicular Activity. 10.13140/RG.2.2.28009.80487. Link

Mackin, M., Gonia, P. and Lombay-Gonzalez, J. (2010) Effective presentation of metabolic rate information for lunar extravehicular activity (EVA) - NASA technical reports server (NTRS), NASA. NASA. Available at: https://ntrs.nasa.gov/citations/20100039148 (Accessed: November 22, 2022).

Yoshinobu, O. (2022). 6th Global Moon Village Workshop; Symposium. In Plenary Session 1. Los Angeles, CA.

Scoville, Z. (n.d.). Artemis III Eva Mission Capability for de Gerlache-Shackleton Ridge - NASA Technical Reports Server (NTRS). NASA. Retrieved December 6, 2022, from https://ntrs.nasa.gov/citations/20210026296

XEVA System Requirement Document Attachment J-02 80JSC021R0006, (2021), NASA

Sustained Phase Human Landing System (HLS) Program System Requirements Document, (2021), NASA, HLS-RQMT-006

Merriam, E. G., Berg, A. B., Willig, A., Parness, A., Frey, T., &amp; Howell, L. L. (2016). Microspine Gripping Mechanism for Asteroid Capture. BYU ScholarsArchive. Retrieved November 9, 2022, from https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1187&amp;context=studentpub

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