L2-PTC-STRUC ESSENTIAL THERMAL Level 2 · hardware

Thermal Structural Elements

Thermal Structural Design Elements and Thermal Doublers

Thermal structural elements integrate conductive paths, heat sinks, and thermal doublers directly into load-bearing habitat structures to manage heat transfer without drawing electrical power. Lunar day and night cycles generate severe temperature gradients across structural assemblies, causing mechanical distortion and altering thermal conductance across bolted joints. To stabilize internal environments over a 100-year operational life, aluminum 6061-T6 thermal doublers providing conductance exceeding 50 W/K spread concentrated equipment heat across bulkheads and honeycomb panels. Concurrently, titanium and fiberglass isolators limit conductance to below 0.1 W/K to thermally decouple hot and cold zones, using the structure's intrinsic mass to damp temperature fluctuations.

Structural elements designed with intentional thermal properties including thermal doublers, thermal isolators, heat sinks, and conductive paths engineered into the Ark's primary structure.

Purpose

Uses the structural mass of the Ark as a thermal resource -- conducting heat where needed, isolating cold from hot zones, and providing thermal mass for temperature stability, all without additional dedicated hardware.

Context

Bridges L1-PTC and L1-STR by embedding thermal design into the structural architecture, ensuring that structural joints, mounting interfaces, and bulkheads serve dual thermal and mechanical functions.

Principles

▸Structure already has thermal mass; designing thermal paths into it adds no mass penalty
▸Thermal doublers spread localized heat sources over larger areas for more uniform temperature
▸Thermal isolators (low-conductance standoffs) decouple temperature zones
▸Structural thermal mass provides natural temperature damping

Typical implementations

▸Aluminum thermal doublers bolted or bonded to electronics mounting panels
▸Titanium or fiberglass standoffs for thermal isolation between zones
▸Honeycomb sandwich panels with embedded heat spreader face sheets
▸Thermal interface materials at structural joints to control conductance
▸Beryllium-copper flexures for thermal isolation with structural compliance

Lunar considerations

▸Large temperature gradients across structure during lunar day/night
▸Structural thermal distortion must be managed for optical and mechanical alignment
▸Regolith burial option provides enormous passive thermal mass from lunar soil
▸Thermal conductance through bolted joints changes with temperature cycling
▸Coefficient of thermal expansion mismatch between dissimilar structural materials

Specifications

Functional

primary function	Engineer thermal properties into structural elements to provide heat spreading, thermal isolation, and temperature damping as part of the passive thermal design
inputs	Heat from adjacent components and subsystems, Environmental thermal loads
outputs	Controlled thermal conductance paths through structure, Thermal isolation between temperature zones
thermal doubler conductance w per k	>50
isolator conductance w per k	<0.1
structural thermal mass stability	maintained over 100 years

Physical

materials	Aluminum 6061-T6 thermal doublers, Titanium Ti-6Al-4V isolator standoffs, Silicone or indium thermal interface materials, Fiberglass composite isolators
vacuum	True
radiation tolerant	True

Operational

power consumption w	0
thermal range c	-173, 127
lifetime years	100

Interfaces

Provides

→Passive Thermal ControlStructural thermal pathsessential
Provides engineered thermal conductance and isolation within the Ark structure
→ALL_L1_SYSTEMSThermally managed mounting interfacesessential
Provides component mounting surfaces with designed thermal conductance or isolation