Development of a Lunar Regolith Transport System Utilizing Compliant Mechanisms for a Regolith Based ISRU-Process

Kurzfassung

As humanity looks to return to the Moon, the need for in-situ resource utilisation, that is, the use of materials present on the lunar surface, becomes increasingly important. The most abundant material usable for ISRU is the lunar regolith, covering the surface of the Moon. In all steps of a regolith-based ISRU process, regolith transport is required. While lunar regolith bears great possibilities for utilisation, it also poses a high risk to any hardware and crew stationed on the surface. Conventional mechanisms that incorporate sliding tribological pairs are inherently prone to excessive wear in this highly abrasive environment. To address this problem in an ISRU processing facility, this study develops a lunar regolith transport system that incorporates compliant mechanisms. These mechanisms achieve motion through elastic deformation, eliminating any sliding tribological pairs and thus providing implicit resilience to abrasive dust.

Six transport concepts were synthesised and evaluated against performance, environmental, and reliability requirements. The sawtooth conveyor concept emerged from the concept development as the optimal mechanism for intra-facility transport due to its flow continuity and adaptability to existing beneficiation architecture. To overcome the extreme temperatures of the lunar vacuum, shape-memory alloys (SMAs) were selected for actuation. Their immense volumetric energy density, as compared to competitive solutions, compensates for their inherent limitation of low actuation frequencies. The mechanism is guided by compliant flexure bearings to ensure precise parallel motion and achieve full implicit dust mitigation.

A custom two-dimensional system simulation was programmed and validated with tests under terrestrial conditions using quartz sand and glass beads. An optimiser was used to align the simulation to the real-world results by determining three empirical parameters. Utilising this validated simulation tool, a multi-objective genetic algorithm was employed to minimise both the specific energy per unit transported mass and the stroke frequency, accounting for the actuator's limitations. The final optimised lunar configuration successfully achieved a feed rate of 70.27 kg/h at a maximum transport slope of 40°, significantly exceeding the minimum requirement of 6 kg/h. This study demonstrates that pairing compliant mechanisms with SMA-actuators yields a highly capable lunar regolith transport solution, ensuring reliable long-term operation for future sustained operations on the lunar surface.