“…Experiments have shown that the coring results are determined by the physical properties of the soil and the kinematic parameters of the drill tool (Zhang & Ding 2017; Tang et al. 2018 a , b ). In the experiment, we use two types of simulated lunar soils (Carrier 2003) with grey basaltic pozzuolana as the main component.…”
Section: Methodsmentioning
confidence: 99%
“…More details on the functionality of the soft bag can be found in Tang et al. (2018 b ). Figure 4.Schematic of the internal channel.…”
Section: Continuum Modelmentioning
confidence: 99%
“…Tang et al. (2018 a , b ) illustrated the coupling between the granular flow in the auger flight and that in the coring tube. Specifically, these experimental results revealed that the coring results crucially depend on the drilling conditions, characterized by an index called the penetration per revolution (PPR).…”
From geotechnical applications to space exploration, auger drilling is often used as a standard tool for soil sample collection, instrument installation and others. Focusing on granular flow associated with the rotary drilling process, we investigate the performance of auger drilling in terms of sampling efficiency, defined as the mass ratio of the soil sample collected in the coring tube to its total volume at a given penetration depth, by means of experiments, numerical simulations as well as theoretical analysis. The ratio of rotation to penetration speed is found to play a crucial role in the sampling process. A continuum model for the coupled granular flow in both coring and discharging channels is proposed to elucidate the physical mechanism behind the sampling process. Supported by a comparison with experimental results, the continuum model provides a practical way to predict the performance of auger drilling. Further analysis reveals that the drilling process approaches a steady state with constant granular flow speeds in both channels. In the steady state, sampling efficiency decreases linearly with the growth of the rotation to penetration speed ratio, which can be well captured by the analytical solution of the model. The analytical solution also suggests that the sampling efficiency is independent of gravity in the steady state, which has profound implications for extraterrestrial sample collection in future space missions.
“…Experiments have shown that the coring results are determined by the physical properties of the soil and the kinematic parameters of the drill tool (Zhang & Ding 2017; Tang et al. 2018 a , b ). In the experiment, we use two types of simulated lunar soils (Carrier 2003) with grey basaltic pozzuolana as the main component.…”
Section: Methodsmentioning
confidence: 99%
“…More details on the functionality of the soft bag can be found in Tang et al. (2018 b ). Figure 4.Schematic of the internal channel.…”
Section: Continuum Modelmentioning
confidence: 99%
“…Tang et al. (2018 a , b ) illustrated the coupling between the granular flow in the auger flight and that in the coring tube. Specifically, these experimental results revealed that the coring results crucially depend on the drilling conditions, characterized by an index called the penetration per revolution (PPR).…”
From geotechnical applications to space exploration, auger drilling is often used as a standard tool for soil sample collection, instrument installation and others. Focusing on granular flow associated with the rotary drilling process, we investigate the performance of auger drilling in terms of sampling efficiency, defined as the mass ratio of the soil sample collected in the coring tube to its total volume at a given penetration depth, by means of experiments, numerical simulations as well as theoretical analysis. The ratio of rotation to penetration speed is found to play a crucial role in the sampling process. A continuum model for the coupled granular flow in both coring and discharging channels is proposed to elucidate the physical mechanism behind the sampling process. Supported by a comparison with experimental results, the continuum model provides a practical way to predict the performance of auger drilling. Further analysis reveals that the drilling process approaches a steady state with constant granular flow speeds in both channels. In the steady state, sampling efficiency decreases linearly with the growth of the rotation to penetration speed ratio, which can be well captured by the analytical solution of the model. The analytical solution also suggests that the sampling efficiency is independent of gravity in the steady state, which has profound implications for extraterrestrial sample collection in future space missions.
“…In the forthcoming Chang'E-5 mission (CE-5), the lander will carry a driller to the lunar regolith in order to collect regolith samples up to 2 kg. The penetration depth is planned to reach 2 m [5,6]. This mission will not intend to probe subsurface heat flow, but will still permit exploration of the subsurface regolith thermal properties of the moon.…”
Chang’E-5 will be China’s first sample−return mission. The proposed landing site is at the late-Eratosthenian-aged Rümker region of the lunar nearside. During this mission, a driller will be sunk into the lunar regolith to collect samples from depths up to two meters. This mission provides an ideal opportunity to investigate the lunar regolith temperature variation, which is important to the drilling program. This study focuses on the temperature variation of lunar regolith, especially the subsurface temperature. Such temperature information is crucial to both the engineering needs of the drilling program and interpretation of future heat-flow measurements at the lunar landing site. Based on the real-time illumination, and particularly the terrain obscuration, a one-dimensional heat equation was applied to estimate the temperature variation over the whole landing region. Our results confirm that while solar illumination strongly affects the surface temperature, such effect becomes weak at increasing depths. The skin depth of diurnal temperature variations is restricted to the uppermost ~5 cm, and the temperature of regolith deeper than ~0.6 m is controlled by the interior heat flow. At such a depth, China’s future lunar exploration is adequate to measure the inner heat flow, considering the drilling depth will be close to 2 m.
“…Commonly speaking, interplanetary drilling control architecture contains remote control from Earth and autonomous drilling control on the planet [13]. Since time delay inevitably exists in the long distance remote communication, remote control mode is usually employed to deal with serious drilling faults and in the majority of the cases the sampling drill should work in an autonomous way [14,15]. Furthermore, restricted by the delivery capacity of rocket and limited power consumption, interplanetary drilling system can hardly apply plenty of sensor resources and sufficient penetrating force to accomplish the online control.…”
The robotic technology, especially the intelligent robotics that can autonomously conduct numerous dangerous and uncertain tasks, has been widely applied to planetary explorations. Similar to terrestrial mining, before landing on planets or building planetary constructions, a drilling and coring activity should be first conducted to investigate the in-situ geological information. Given the technical advantages of unmanned robotics, utilizing an autonomous drill tool to acquire the planetary soil sample may be the most reliable and cost-effective solution. However, due to several unique challenges existed in unmanned drilling and coring activities, such as long-distance time delay, uncertain drilling formations, limited sensor resources, etc., it is indeed necessary to conduct researches to improve system's adaptability to the complicated geological formations. Taking drill tool's power consumption and soil's coring morphology into account, this chapter proposed a drilling and coring characteristics online monitoring method to investigate suitable drilling parameters for different formations. Meanwhile, by applying pattern recognition techniques to classify different types of potential soil or rocks, a drillability classification model is built accurately to identify the current drilling formation. By combining suitable drilling parameters with the recognized drillability levels, a closed-loop drilling strategy is established finally, which can be applied to future interplanetary exploration.
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