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A pyramidal ISRU lunar habitat design based on topological interlocking of sintered regolith blocks
Lukas Schnelle, Kai-Uwe Schröder, Alice C. Niemeyer, Yuri Estrin
TL;DR
Transporting construction materials to the Moon is prohibitively expensive, motivating habitat designs using lunar regolith. This paper evaluates a pyramidal habitat assembled from topologically interlocked regolith blocks, reporting that it remains substantially intact when individual blocks are missing.
Problem
Transporting construction materials to the Moon is prohibitively expensive and logistically impractical, motivating use of lunar regolith for construction.
Source: §1 · p. 1Method
Results
The simulations demonstrate feasibility and significant structural integrity even when individual blocks are missing.
Source: §5 · p. 9Takeaways & Limitations
The design can accommodate sintered regolith’s brittleness, carry internal pressurisation loads, and allow future reuse of blocks through expansion.
Source: §5 · p. 10The block gaps do not provide a hermetic enclosure, so the design assumes a membrane and gas-tightness remains for future work.
Source: §5 · p. 10
Abstract
from arXiv · showhide
In this framing study, we propose a new lunar-habitat design based on topological interlocking of the building blocks. The design combines block geometries that permit interlocking without binders or connectors with a pyramidal overall structure. This approach is well suited for ISRU-enabled extraterrestrial construction. Finite element simulations employing the Drucker-Prager model confirm that habitats manufactured from lunar regolith using this concept are tolerant to local failures or missing blocks. We further suggest that this approach can be extended and improved by optimising the geometry of the interlockable building blocks.
1. Introduction to the design of lunar habitats
Lunar habitat construction motivates using local regolith, but conventional modular joints and habitat geometries pose material and design challenges. The paper proposes a pyramidal structure of topologically interlocked blocks and evaluates its mechanical viability with finite-element simulations that account for block damage.
1. Introduction to the design of lunar habitats
- Transporting construction materials to the Moon is prohibitively expensive and impractical, motivating ISRU approaches that use sintered lunar regolith blocks.Regolith properties vary with local soil composition, and sunlight can provide sintering energy.Source: §1 · p. 1
- Modular construction supports progressive expansion, robotic assembly, recycling, and reconfiguration, while helping mitigate sintered regolith’s brittleness.The design also seeks few block variants and blocks sized for easy handling.Source: §1 · p. 1
- Conventional modular blocks need adhesives, mortar, or connectors, which are problematic because of lunar pressure, water scarcity, and connector-induced stress concentrations.Adhesive joints also carry uncertainties because they cannot be tested non-destructively.Source: §1 · p. 2
- Most reported topological-interlocking geometries are planar, whereas habitats need substantial volume and motivate a three-dimensional design using few identical blocks.Interlocking assemblies hold through block geometry and arrangement rather than binders or connectors.Source: §1 · p. 2
- A hemisphere complicates traditional modular construction because mapping a planar assembly onto it distorts blocks, while pressure and lunar gravity motivate avoiding vertical walls.The design rationale seeks to balance pressure normal to the enclosure with downward gravity.Source: §1 · p. 2
- The proposed habitat uses a pyramid whose triangular faces comprise monolayers of identical, topologically interlocked blocks that constrain displacement normal to each layer.The paper presents hollow pyramids and uses finite-element simulations accounting for block damage to assess mechanical viability.Source: §1 · p. 2
2. Geometry of the building blocks and arrangement into a pyramid
The design uses identical interlocking blocks to form an expandable, square-based pyramidal habitat. A double-Starfish block geometry tiles each triangular face, while edge and apex blocks close the structure; the assembled example provides usable living space.
2.1. Design considerations for the overall structure
- A square-based pyramid with equilateral triangular faces supports expansion or contraction using the same tiles, while balancing usable base area, height, and low-clearance space.The selected example uses a square base edge of approximately 7.5 m.Source: §2.1 · p. 3
- Topological interlocking makes the structure redundant: losing one block need not cause total structural failure, while an inner membrane can provide gas-tightness.The authors give micrometeorite or equipment impact as examples of block loss.Source: §2.1 · p. 3
2.2. The individual block
- Each triangular face is tiled with manageable blocks no larger than 1 m, with tile fineness adjustable to fabrication and assembly constraints.Selecting a finer tiling can preserve the structure's overall size while reducing individual block size.Source: §2.2 · pp. 3–4
- The double-Starfish block is formed by interpolating three parallel p6 tilings, with alternating inward and outward vertex displacements, to fill a 400 mm thickness without gaps or intersections.The original and modified triangular domains are spaced 200 mm apart; applying the modification consistently on all three sides preserves the tiling.Source: §2.2 · p. 4
2.3. Edges and apex
- Four triangular faces form the pyramid, while edge blocks fill the gaps between faces and a separate apex block closes the remaining void without intersections.The example has nine blocks along each face base, giving 81 blocks per face; edge blocks are rotationally symmetric for greater assembly flexibility.Source: §2.3 · p. 5
- The four faces comprise 81 interior blocks total, plus 36 edge blocks and one apex; assuming a 7.5 m internal base, usable volume is ≈198.87 m3.The external base length is ≈8.6 m and height ≈6.1 m; the geometry is scalable using additional blocks of the same geometry.Source: §2.3 · p. 6
3. Numerical analysis
The numerical analysis evaluates whether the proposed pyramid maintains structural integrity under lunar loads, including when blocks are missing or locally damaged. Its simulations use a Drucker-Prager material model and assess both global displacement and local failure.
3. Numerical analysis
- The pyramid’s bottom row, edge blocks, and apex remain unfixed in the proposed assembly, so finite-element simulations test whether its geometry still maintains structural integrity.The analysis considers expected lunar environmental conditions.Source: §3 · p. 6
3.1. Simulation setup and assumptions
- Abaqus 2024 Explicit with Drucker-Prager plasticity models the contact-rich, fundamentally static problem to improve convergence, despite higher computational cost.The setup uses hard contact with zero friction as a first approximation because geometry and arrangement primarily enable interlocking.Source: §3.1 · p. 7
3.2. Lunar environment
- The simulations apply lunar gravity, omit external atmospheric loads, and include about 0.8 atm internal pressure plus 0.15 N mm2 external pressure from proposed regolith overburden.Radiation shielding is not evaluated.Source: §3.2 · p. 7
3.3. Material and damage model
- The brittle-regolith model uses Drucker-Prager yielding and treats plastic-strain regions as failed, while assembly failure includes global integrity loss or local damage that removes interlocking capacity.The tensile yield stress is 5 MPa; local damage is acceptable if the remaining block still interlocks.Source: §3.3 · p. 8
4. Results
The simulations find that the pyramid remains structurally acceptable with a block missing at tested heights, despite increased deformation and localized plastic yielding. The affected regions leave the topological interlocking intact.
4. Results
- After loads were fully applied, internal and kinetic energies levelled off, indicating equilibrium and load transfer between blocks rather than continued motion.The four simulations comprise one intact assembly and three assemblies with a block removed.Source: §4 · p. 8
- All four variants appear structurally acceptable because principal equivalent stress remains below the 5 MPa tensile yield stress, although small localized regions show non-zero plastic strain.The simulations test one missing block near the base, at mid-height, or near the apex, as well as an intact assembly.Source: §4 · p. 8
- Non-zero PEEQ occurs only in double-Starfish blocks, which the analysis maps at locations exceeding its 1 10−7 threshold.The mapping is based on PEEQ values and spatial coordinates exported from the simulations.Source: §4 · p. 8
- −0.071 mm was the full assembly’s maximum absolute Y-deformation, versus −1.56 mm, −1.61 mm, and −1.60 mm for bottom-, mid-height-, and near-apex-missing cases.Figure 7 shows total deformation for the intact and three missing-block variants on a uniform millimetre scale.Source: §4 · p. 8, Figure 7 · p. 9
- Plastic yielding lies on three planes while the intervening block bulk remains intact, preserving interlocking; its magnitude and extent are greater in all missing-block cases.The increase is consistent with the higher maximum PEEQ and deformation in those cases.Source: §4 · p. 9
5. Discussion
The study reports numerical feasibility for a largely ISRU-built interlocked habitat that retains integrity under block loss, while identifying material, access, gas-tightness, and geometry-design limits.
5. Discussion
- Numerical evaluation supports TIA habitat feasibility, with significant integrity retained after block loss and internal pressurisation loads carried effectively.Tests included an intact habitat and variants missing a block near the bottom, mid-height, or apex; the design also allows block reuse through expansion.Source: §5 · pp. 9–10, Figure 8 · p. 10
- Most structural material can be sourced on the lunar surface, supporting largely ISRU construction given current understanding of available material.The approach is presented as accommodating sintered regolith brittleness.Source: §5 · pp. 9–10
- Terrestrial analogue materials may have properties that differ substantially from actual lunar regolith, limiting confidence in the assumed material properties.Source: §5 · p. 10
- The proposed habitat lacks entry and exit provisions, and a dedicated system might need to be transported from Earth.Integrating such a system into a TIA design remains outside this study's scope.Source: §5 · p. 10
- Gas-tightness relies on an assumed membrane because inter-block gaps do not form a hermetic enclosure and may change under load.The authors identify gas-tightness of TIA structures as an issue for future work.Source: §5 · p. 10
- The habitat uses an existing geometry with minor modifications; a lunar-purpose-optimised block design might perform better.TIAs have many parameters that determine exact block geometry.Source: §5 · p. 10