Designing for the Future: Optimising the structural form of regolith-based monolithic vaults in low-gravity conditions

This project will investigate the behaviour of monolithic, adobe structures in low-gravity conditions, concluding to an optimal structural design framework for supporting future space exploration. Such structures will act as shielding to protect critical assets (such as robots, fuel tanks and power stations) and future inflatable structures (e.g. living quarters) from extreme conditions (radiation, sandstorms, temperature fluctuations) in an extraterrestrial environment. Linear and nonlinear numerical structural modelling and parametric static and dynamic analyses will identify the optimal design approach for utilising indigenous materials to produce such structures to minimise the weight burden on future manned explorations. The analytical work will be validated by experimental centrifuge tests which can simulate low gravity conditions at prototype scale. This will be the first systematic approach towards sustainable extraterrestrial structural design using methods and concepts developed for Earth.

Until now, there have been isolated studies on conceptualising extraterrestrial structures given the challenges that needed to be addressed in such extreme environments, but there is not a systematic approach on how to realise these structures. Given the recent and ongoing research on the mechanical properties of regolith simulants, the proposed In-situ Resource Utilisation (ISRU) framework and the advances in 3D printing for extraterrestrial construction, it is timely to combine these fields with structural design strategies developed for Earth in order to identify optimal structural forms for use in low-gravity conditions, subject to extraterrestrial dynamic environmental actions.

The first step for achieving this is the static approach and to identify from a wide class of monolithic vaults which is the optimal for long-span structures in low-gravity environments. The next step would be to identify engineering demand parameters from extraterrestrial natural hazards related to Lunar and Martian strong ground motions (shallow and deep moonquakes, marsquakes if available from the InSight mission and meteorite-impact generated ground motions). Subsequently, numerical models simulating different structural dynamic configurations (including soil-structure interaction, rocking and seismic isolation) will be implemented to conduct extensive linear and nonlinear dynamic analyses using the identified engineering demand parameters. This will result in the assessment of the dynamic performance of each different model and thus to the best structural option. However, a critical part is to validate the numerical models used in this project by centrifuge tests under the same extraterrestrial excitations. Nevertheless, it is out of the scope of this project to investigate the properties of regolith-based structural material since regolith simulants will be used for the experimental part of the project.

The main benefit of this project is the establishment of a rigorous structural design framework regarding extraterrestrial structures and the identification and categorisation of the extraterrestrial strong ground motions as a first step for the quantification of the associated hazard. Aside from the aforementioned objectives related to space exploration and multi-planet colonisation, the potential applications of the results from this project can be: (a) the calibration and development of 3D-printing techniques incorporating regolith as a structural material; (b) the sustainable residential development of low- and middle-income countries using indigenous materials and (c) the optimal seismic design of submarine structures (arches in a global compression state under buoyancy/low gravity) that can prove useful for deep-ocean exploration and mining.

The beneficiaries have been grouped into two major categories:

1) Academia and Industrial stakeholders:
This will be the first systematic approach towards sustainable extraterrestrial structural design using methods and concepts developed for Earth. However, except the academic impact related to space exploration, the results of the project will be essential in defining the specification required of autonomous robotic 3D printing equipment. More specifically, the project, following the United Nations' sustainable development goals, will impact significantly: (a) the calibration and development of 3D-printing techniques incorporating soil as a structural material; (b) the sustainable residential development of low- and middle-income countries using indigenous materials and (c) the optimal seismic design of submarine structures (arches in a global compression state under buoyancy/low gravity) that can prove useful for deep-ocean exploration and mining. Especially with respect to case (b), the cost-effectiveness and the construction speed of these types of structures will be important for post-catastrophe scenarios (tsunamis, earthquakes) or refugee camps after significant human displacements.

The success of this project will also have an impact on UK industry. Foster+Partners (F+P) have already conducted a very thorough study regarding the conceptualisation of a Lunar habitat and a Mars outpost. The next logical step to follow this pioneering work, is to develop the design approaches necessary to realise such structures and identify their salient design features (e.g. structural geometry, layout, form and foundations). Additionally, civil engineering for space applications will create an opportunity for large engineering firms in the UK to explore collaboration opportunities with academia and governmental/federal agencies (ESA, UK Space Agency) and expand their R&D sectors towards space exploration. This clearly aligns with the UK's third industrial strategy pillar; taking on Grand Challenges to transform the future. Therefore, the success of this project could create a new streamline of investments, and thus of UK enterprise development, whether in the form of highly specialised start-ups or in expanding the R&D sectors of well-established engineering (and engineering-related) firms aligned with UK's Space Innovation and Growth Strategy. The success of this proposal will contribute to placing the UK at the forefront of extreme-environment (and space) habitation. Furthermore, the project will impact non-governmental organisations (NGOs) related to significant human displacements and post-catastrophe management; the results of this project can potentially lead to durable, optimally-designed structures that can be constructed in a fast and cost-effective way using indigenous materials.

2) Society:
Most importantly, the stakeholder who stands to benefit most by the project is society and therefore the UK's public. Companies such as SpaceX, Virgin Galactic and Boeing, together with NASA and the UK/European Space Agencies, have all already opened the door to space exploration, tourism and colonisation. Aside from providing humanity with alternatives for survival, Moon and Mars habitation can even lead to a gradual change of public consciousness towards a multi-planetary way of living. This change may need decades and require large investments to happen, but it must start from educating the next generations.