# Design and Dynamic Analysis of the Wire-Line Coring Robot for Deep Lunar Rocks
## 1 Introduction  
Sampling for extraterrestrial subsurface exploration is an important tool for human understanding of the solar system and the universe, and it can help humans understand the formation process of celestial bodies [1]. In addition, sampling can effectively probe the precious metals and rare elements in celestial bodies, which can provide a good foundation for humans to utilize celestial bodies in the future [2]. Additionally, sampling can provide the necessary guarantee for the establishment of permanent interstellar bases [3]. The moon is the closest extraterrestrial object to the Earth, and it is the preferred target for the sampling of celestial bodies. In the 1960s and 1970s, the Soviet Union and the United States carried out lunar exploration missions, namely the Luna program and the Apollo program [4]. There was also no lack of lunar surface sample return missions, such as the Apollo 17 mission. China also obtained lunar soil and returned it to Earth in 2020 [5]. Among the successful coring return missions, the Lunal6 swing arm shallow drilling and the Chang'e-5 fixed drilling both achieved surface lunar soil coring [6]. the Apollo project used the astronaut-held Apollo lunar surface drill (ALSD) to achieve subsurface lunar soil coring up to 3.05 m [7]. To understand the celestial bodies more deeply, researchers now continue to develop deep sampling devices. The current deep sampling devices for celestial bodies can be classified into two categories: multi-rod drilling sampling devices and wire-line sampling [8]. The multi-rod drilling sampling device is mature and stable. It is commonly loaded with multiple drilling rods and sampling tubes and achieves deep drilling by multiple combinations [9]. Therefore, institutions and researchers have built various devices to achieve deep sampling, such as the pneumatic multi-rod drilling device for lunar sampling [10], the Micro Robots for Scientific Applications 2 (RoSA2) [11], the Deep Drilling Rig (DeeDri) [12], and the Mars Astrobiology Research and Technology Experiment (MARTE) drilling system [13]. As a rule, the impact effect is applied by sampling devices in order to penetrate the deep hard layers more effectively [14]. However, in multi-rod drilling sampling devices, the energy lost due to thermal and rebound between drilling rods exceeds the energy used to destroy the terrain. Additionally, this phenomenon is further exacerbated by the increase in the number of connected segments in the sampling rod [15]. This makes multi-rod drilling sampling devices require more power and mass to achieve deep sampling. The wire-line sampling device is connected to the lander by the power cable and drills deeper by its own self-excavation capability. It is more prone to jamming and requires higher soil properties at the sampling site than the multi-rod drilling sampling device. At the same time, it is difficult to drill in shallow and loose layers since a stable anchorage cannot be achieved in this layer [8]. However, the wire-line sampling device has the advantages of a compact structure, high energy utilization, low reaction force, and lightweight. These advantages provide obvious benefits for wire-line sampling devices for deep sampling. The wire-line sampling device is also considered the preferred option for sampling devices when drilling over a 10 m depth. The wire-line drilling device is softly connected to the surface by cables, which makes it necessary to drill itself through the self-excavation capability. The self-excavation capability of wire-line drilling devices can be accomplished in various approaches, including anchored drilling, bionic mole, bionic inchworm, etc. The bionic mole and bionic inchworm are able to propel at depth in the subsurface without lifting the drill. The feature of the bionic mole and the bionic inchworm leads to the increased usage of in situ probe emplacements, such as the mole carried by insight with the bionic mole [16] and the inchworm drilling (ID) System with the bionic inchworm [17].