14:00 〜 14:15
[PPS02-02] Simulating the Lunar Soil: a Japanese Lunar Soil Simulant FJS-1 and Its Properties
★Invited Papers
キーワード：月土壌、模擬土壌、FJS-1、模擬土壌特性、凍結土壌
Going back to the Moon is a world-wide trend of space exploration based on the international cooperation as the Global Exploration Roadmap (GER3) stated. JAXA also proposed future human exploration missions around 2030 within the international cooperation. All scenarios have their bases on the scientific observation that a plenty of water (hydrogen) is trapped in the polar regions, especially inside the craters of permanent shadow. In order to investigate those water and other existing volatiles, however, many engineering challenges wait for human and robotic missions even only from the view of lunar soil, such as traversing the soft soil, drilling and/or excavating the soil, and handling the soil for desired sample collections and scientific processes, and more for the in-situ resource utilization and human missions. Thus, the ground tests prior to launches are of great importance to increase the possibility of mission success.
In order to offer opportunities for the community to perform ground tests, we have manufactured a lunar soil simulant, called FJS-1. The investigation of FJS-1 shows that many properties of FJS-1 lies close to the data collected from Apollo samples. For instance, the particle size distribution lies below 2 [mm]; the median particle size is between 70 and 75 [micro-m]; the shear strength, i.e. cohesion c, is 0 to 10 [kN/m2]; and the internal friction angle, phi, is 30 to 50 [deg]. The chemical composition is also close to Apollo samples with slight difference that FJS-1 contains more ferric oxide and Alkaline components than Apollo samples.
In addition to the basic properties, we started investigating the strength of frozen lunar soil using FJS-1. Determining the optimized configuration of a sampler such as a drill or an excavator needs the information of actual lunar soil; however, nobody knows the actual state, in other words, the ground truth of lunar water/ice yet. We therefore decided to investigate the strength of frozen soil, utilizing FJS-1, for the future use for drill or excavator designs. The qualitative observation from our first experiment is that the frozen FJS-1 at temperature below 0 [degC] became slightly loose when FJS-1 contained 0.5 to 1.0 [wt%] of water, and that the strength drastically increased above 2 [wt%]. We will conduct more experiments to collect a set of frozen soil strength to offer the estimates of the strength of lunar soil for future lunar exploration missions.
In order to offer opportunities for the community to perform ground tests, we have manufactured a lunar soil simulant, called FJS-1. The investigation of FJS-1 shows that many properties of FJS-1 lies close to the data collected from Apollo samples. For instance, the particle size distribution lies below 2 [mm]; the median particle size is between 70 and 75 [micro-m]; the shear strength, i.e. cohesion c, is 0 to 10 [kN/m2]; and the internal friction angle, phi, is 30 to 50 [deg]. The chemical composition is also close to Apollo samples with slight difference that FJS-1 contains more ferric oxide and Alkaline components than Apollo samples.
In addition to the basic properties, we started investigating the strength of frozen lunar soil using FJS-1. Determining the optimized configuration of a sampler such as a drill or an excavator needs the information of actual lunar soil; however, nobody knows the actual state, in other words, the ground truth of lunar water/ice yet. We therefore decided to investigate the strength of frozen soil, utilizing FJS-1, for the future use for drill or excavator designs. The qualitative observation from our first experiment is that the frozen FJS-1 at temperature below 0 [degC] became slightly loose when FJS-1 contained 0.5 to 1.0 [wt%] of water, and that the strength drastically increased above 2 [wt%]. We will conduct more experiments to collect a set of frozen soil strength to offer the estimates of the strength of lunar soil for future lunar exploration missions.