> For the complete documentation index, see [llms.txt](https://2025.istvs.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://2025.istvs.org/submissions/papers/6650.md). # 6650 - RELIABILITY OF GRAVITY OFFLOAD FOR LUNAR ROVER WHEEL PERFORMANCE {% hint style="info" %} Paper presented at ISTVS 2025 | 55th Conference of the International Society for Terrain-Vehicle Systems {% endhint %} **Authors:** *James Hurrell, Keisuke Takehana, Kentaro Uno, Kazuya Yoshida* **Keywords:** Terramechanics; Single-wheel test; Lunar rover; Grouser wheel; Lunar regolith simulant; Reduced gravity **Abstract:** Purpose: The impact of gravity and use of gravity offload on rover tractive performance is evaluated and compared between Earth and lunar environments. Single-wheel experiments and discrete element method (DEM) simulations of a micro-rover wheel modelled on the Rashid-1 rover designed for the Emirates lunar mission are conducted. The wheel's interaction with Toyoura sand and FJS-1 lunar regolith simulant is studied. Consideration is made for why the use of gravity offloading has been prominent and other options that are available. Methods: Slip conditions, traction coefficient and grouser pitch for single-wheel experiments are measured for a range of fixed slip values at the expected rover load of 24.5 N at a nominal 0.02 m/s, termed a low-speed regime. Single-wheel simulations have been previously verified by comparison with experimental results. Lunar simulations can predict lunar gravity performance. Results: Wheel performance regarding traction coefficient and tractive efficiency under lunar gravity matches that under Earth gravity. Traction performance in tractive force and resistive torque is reduced by the ratio of Earth to lunar gravity, 1/6, for the same mass. Earth gravity results for 4.1 N are understood to over-predict the traction coefficient compared to lunar conditions. Using load matching of 24.5 N in lunar gravity reduces performance. Conclusion: Gravity offloading is unsuitable. Depending on the aspect desired to study the influence of gravity on the rover, consideration should be made to use either Earth conditions, granular scaling laws, or a full-scale reduction of the rover. This may change with a transition to high-speed wheel motion. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://2025.istvs.org/submissions/papers/6650.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.