Primary Structure

Purpose

Provide the physical skeleton and pressure envelope that contains, supports, and protects all other Ark systems for 100+ years of autonomous operation on the lunar surface, surviving thermal cycling, micrometeorite impacts, seismic events, and radiation exposure

Context

L1-STR is the foundational physical system upon which every other L1 system is mounted, routed, or enclosed. It provides the pressure vessel(s) that maintain internal atmosphere (if biologic payloads are active), the structural framework that bears all loads (static, dynamic, thermal), the airlocks enabling robotic ingress/egress, the foundations anchoring the Ark to the regolith, and the standardized expansion ports for future module attachment. L1-STR interfaces with every other L1 system either directly (mounting, containment) or through penetrations and feedthroughs.

Principles

• ▸Pressure vessels must contain 1 atm (101.325 kPa) internal atmosphere against external vacuum with positive margin of safety
• ▸Thermal cycling induces cyclic stress in structural members requiring fatigue-rated design (lunar day/night: -173C to +127C)
• ▸Micrometeorite shielding requires multi-layer or sacrificial bumper approaches (Whipple shield concept)
• ▸Modular construction allows phased deployment and future expansion without compromising existing pressure integrity
• ▸Structural redundancy through multiple load paths prevents catastrophic failure from single-element loss
• ▸Sealed penetrations are single-point failure risks requiring redundant sealing and leak monitoring
• ▸Foundation design must account for low lunar gravity (1.62 m/s2), regolith bearing capacity, and thermal ground coupling

Typical implementations

• ▸ISS pressurized modules (aluminum alloy cylindrical shells, ~4.2m diameter)
• ▸Bigelow B330 expandable modules (Vectran/Kevlar soft-shell, ~6.7m diameter)
• ▸NASA Gateway HALO module (aluminum-lithium alloy)
• ▸Lunar surface habitat concepts: rigid metallic shells, inflatable structures, 3D-printed regolith shells
• ▸Whipple shield and stuffed Whipple for MMOD protection
• ▸Common Berthing Mechanism (CBM) and NASA Docking System (NDS) for module-to-module connections

Lunar considerations

• ▸No atmospheric pressure outside: full 1 atm differential across vessel walls
• ▸Thermal cycling -173C to +127C imposes severe fatigue requirements over 100 years (~1200 cycles)
• ▸Regolith can be used as shielding mass (radiation, MMOD, thermal) if placed over structure
• ▸Lunar dust is abrasive, electrostatically charged, and penetrates seals/mechanisms
• ▸Low gravity (1/6 Earth) reduces dead loads but dynamic and pressure loads dominate
• ▸Moonquakes (shallow and deep) require seismic design considerations
• ▸No on-site heavy manufacturing initially: structure must be delivered or assembled from pre-fabricated components
• ▸Vacuum welding and cold-welding effects on exposed metal surfaces
• ▸Robotic assembly required: all structural connections must be robot-compatible

Specifications

Interfaces

Decomposes into

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