**1. Introduction**

Just as some imaginative descriptions on the interplanetary traveling in scientific fictions, human beings through decades' striving have made a great step forward to that scenery. From the successful launch of Sputnik, the first man-made earth satellite in 1957 [1] to the first man-made lunar landing in 1969 to collect lunar soil samples [2] and the Rosetta Landing Project launched in 2014 on Comet 67P to collect asteroid rocks [3], mankind's extraterrestrial explorations have covered the vast majority of planets, satellites and asteroids in the solar system. However, it should be noted that although tremendous advancements are achieved in space exploration, mankind also suffered a great loss, especially when astronauts encounter emergency risks even lost their lives for various technical reasons [4, 5]. Hence, as deep space exploration having been conducted, an up-and-coming replaceable solution by employing unmanned robots has been gradually acceptable to carry out some uncertain and dangerous tasks, such as interplanetary drilling and coring activities [6–8].

[19]. The following Luna 20 detector launched in 1972 landed on a lunar plateau with a similar sampling device to the Luna16 and was forced to stop drilling at 250 mm depth due to multiple times of overheat fault, eventually sampling only 55 g lunar soil [20]. The last sampling task Luna 24 in 1976 applied a threshold-based approach to autonomously control the drill tool. When the detected penetrating force exceeds a preset threshold, the impact motor will be activated in time to overcome the drilling resistance. Based on this drilling strategy, the received remote data revealed that in the Luna 24 detector's drilling process the impact motor was frequently switched on and finally the sampler reached to a depth about 2250 mm, returning about 171 g lunar soil sample [21]. Although the applied threshold-checking strategy indeed improved the automation level of the unmanned drill tool, it should point out that there exists a high probability of tripping and need a long time to wait (often hours to days) for human troubleshooting from afar [22]. Hence, this simple limit-checking strategy may be more suitable for shallow drilling missions like Mars Science Laboratory drill (50 mm depth).

Intelligent Drilling and Coring Technologies for Unmanned Interplanetary Exploration

http://dx.doi.org/10.5772/intechopen.75712

19

After laboratory tests aboard NASA's Phoenix Mars Lander identified water in a soil sample at Green Valley, Mars (Arctic pole) in 2008 [23], NASA has been preparing for an another Mars exploration mission to search for biomolecular evidence for life around 2018. The proposed "Icebreaker" mission would use an automated rotary-percussive drill to reach and retrieve samples from up to 1.2 m deep in the ground ice at Mars Arctic pole [24]. To support for this drilling mission, NASA Ames, together with Honeybee Robotics Ltd., and Georgia Tech., proposed a novel drilling faults diagnosis control method by acquiring the vibration signals from external laser doppler vibrometers (LDVs) to identify drilling faults [25, 26]. Based on two diagnostic methods of rules and model prediction, the "Icebreaker" drill can recognize six types of drilling faults (e.g. auger chocking, hard material, etc.) and switch to the preset recovery parameters. Test results from the recent Arctic and Antarctic field campaigns

The above drilling strategy relatively improved the automation level of the system, however, besides drilling loads or power consumption, soil's coring morphology should also be considered in designing its control method. As the primary goal of interplanetary exploration is to exam the evidence of lie by scamping the subsurface soils, it is extremely important to acquire as much soil core as possible under acceptable drilling loads. Furthermore, as the stratification information of planetary samples reflects the evolutionary history of early stars [28], it is necessary to preserve its stratification during the coring process for further analysis. Therefore, the authors proposed a novel flexible tube coring method to preserve the stratification of soil sample [29]. In order to comprehend the core flowing characteristics and optimize the final coring results, a non-contact type measurement based on ultrasonic wave reflection mechanism and vision techniques is applied to online monitor the coring and removal characteristics [30]. Once the drill-soil interaction mechanism comprehended, suitable drilling parameters for different types of drilling formations considering both power consumption

Apart from suitable drilling parameters, to identify what kind of formation the drill bit is currently drilling is another key point to the unmanned drill tool. Only if these two key parameters matched correspondingly, the unmanned drill tool may be smoothly penetrated into the

demonstrated this drill has been already capable of a hands-off ability [27].

and coring morphology can be optimized then.

For future interplanetary exploration, there is an urgent demand for a reliable method to pierce the planetary surface to a specified depth and effectively collect soil samples [9, 10]. Once the in-situ soil sample acquired, the original geological information at the sampling site can be investigated for further usage. Compared with other soil failure technological solutions, such as explosion, melting, etc., the traditional drilling and coring method by only utilizing the compound motion of rotation and penetration still has great advantages in extracting the subsurface soil sample in a relatively efficient and convenient way [11, 12]. Therefore, this method has been widely applied to previous interplanetary missions. Considering the technical advantages of unmanned robots and the unique space drilling and coring conditions, interplanetary drilling and coring compared with terrestrial drilling could be more dependent on intelligent drilling techniques.

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. On the other hand, in most planetary drilling missions, there is not enough prior geological information in a longitudinal direction on sampling sites to guide the online drilling [16]. Given the uncertain and variable mechanical properties of drilling formations, the drill tool under above strict resources should adjust suitable drilling parameters correspondingly to overcome potential drilling faults and acquire as much as volume of the soil sample. To resolve the problems, researchers have been striving for decades to find effective solutions.

So far, the former Soviet Union's Luna series is the only unmanned detectors that successfully implemented the lunar subsurface soil's sampling and returning [17, 18]. Among them, the Luna 16 detector launched in 1970 with a stretched out arm mounted rig sampling method successfully drilled into 350 mm beneath the lunar surface, acquiring 101 g soil sample finally [19]. The following Luna 20 detector launched in 1972 landed on a lunar plateau with a similar sampling device to the Luna16 and was forced to stop drilling at 250 mm depth due to multiple times of overheat fault, eventually sampling only 55 g lunar soil [20]. The last sampling task Luna 24 in 1976 applied a threshold-based approach to autonomously control the drill tool. When the detected penetrating force exceeds a preset threshold, the impact motor will be activated in time to overcome the drilling resistance. Based on this drilling strategy, the received remote data revealed that in the Luna 24 detector's drilling process the impact motor was frequently switched on and finally the sampler reached to a depth about 2250 mm, returning about 171 g lunar soil sample [21]. Although the applied threshold-checking strategy indeed improved the automation level of the unmanned drill tool, it should point out that there exists a high probability of tripping and need a long time to wait (often hours to days) for human troubleshooting from afar [22]. Hence, this simple limit-checking strategy may be more suitable for shallow drilling missions like Mars Science Laboratory drill (50 mm depth).

**1. Introduction**

18 Drilling

Just as some imaginative descriptions on the interplanetary traveling in scientific fictions, human beings through decades' striving have made a great step forward to that scenery. From the successful launch of Sputnik, the first man-made earth satellite in 1957 [1] to the first man-made lunar landing in 1969 to collect lunar soil samples [2] and the Rosetta Landing Project launched in 2014 on Comet 67P to collect asteroid rocks [3], mankind's extraterrestrial explorations have covered the vast majority of planets, satellites and asteroids in the solar system. However, it should be noted that although tremendous advancements are achieved in space exploration, mankind also suffered a great loss, especially when astronauts encounter emergency risks even lost their lives for various technical reasons [4, 5]. Hence, as deep space exploration having been conducted, an up-and-coming replaceable solution by employing unmanned robots has been gradually acceptable to carry out some uncertain and dangerous

For future interplanetary exploration, there is an urgent demand for a reliable method to pierce the planetary surface to a specified depth and effectively collect soil samples [9, 10]. Once the in-situ soil sample acquired, the original geological information at the sampling site can be investigated for further usage. Compared with other soil failure technological solutions, such as explosion, melting, etc., the traditional drilling and coring method by only utilizing the compound motion of rotation and penetration still has great advantages in extracting the subsurface soil sample in a relatively efficient and convenient way [11, 12]. Therefore, this method has been widely applied to previous interplanetary missions. Considering the technical advantages of unmanned robots and the unique space drilling and coring conditions, interplanetary drilling and coring compared with terrestrial drilling could be more depen-

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. On the other hand, in most planetary drilling missions, there is not enough prior geological information in a longitudinal direction on sampling sites to guide the online drilling [16]. Given the uncertain and variable mechanical properties of drilling formations, the drill tool under above strict resources should adjust suitable drilling parameters correspondingly to overcome potential drilling faults and acquire as much as volume of the soil sample. To resolve the problems,

So far, the former Soviet Union's Luna series is the only unmanned detectors that successfully implemented the lunar subsurface soil's sampling and returning [17, 18]. Among them, the Luna 16 detector launched in 1970 with a stretched out arm mounted rig sampling method successfully drilled into 350 mm beneath the lunar surface, acquiring 101 g soil sample finally

tasks, such as interplanetary drilling and coring activities [6–8].

researchers have been striving for decades to find effective solutions.

dent on intelligent drilling techniques.

After laboratory tests aboard NASA's Phoenix Mars Lander identified water in a soil sample at Green Valley, Mars (Arctic pole) in 2008 [23], NASA has been preparing for an another Mars exploration mission to search for biomolecular evidence for life around 2018. The proposed "Icebreaker" mission would use an automated rotary-percussive drill to reach and retrieve samples from up to 1.2 m deep in the ground ice at Mars Arctic pole [24]. To support for this drilling mission, NASA Ames, together with Honeybee Robotics Ltd., and Georgia Tech., proposed a novel drilling faults diagnosis control method by acquiring the vibration signals from external laser doppler vibrometers (LDVs) to identify drilling faults [25, 26]. Based on two diagnostic methods of rules and model prediction, the "Icebreaker" drill can recognize six types of drilling faults (e.g. auger chocking, hard material, etc.) and switch to the preset recovery parameters. Test results from the recent Arctic and Antarctic field campaigns demonstrated this drill has been already capable of a hands-off ability [27].

The above drilling strategy relatively improved the automation level of the system, however, besides drilling loads or power consumption, soil's coring morphology should also be considered in designing its control method. As the primary goal of interplanetary exploration is to exam the evidence of lie by scamping the subsurface soils, it is extremely important to acquire as much soil core as possible under acceptable drilling loads. Furthermore, as the stratification information of planetary samples reflects the evolutionary history of early stars [28], it is necessary to preserve its stratification during the coring process for further analysis. Therefore, the authors proposed a novel flexible tube coring method to preserve the stratification of soil sample [29]. In order to comprehend the core flowing characteristics and optimize the final coring results, a non-contact type measurement based on ultrasonic wave reflection mechanism and vision techniques is applied to online monitor the coring and removal characteristics [30]. Once the drill-soil interaction mechanism comprehended, suitable drilling parameters for different types of drilling formations considering both power consumption and coring morphology can be optimized then.

Apart from suitable drilling parameters, to identify what kind of formation the drill bit is currently drilling is another key point to the unmanned drill tool. Only if these two key parameters matched correspondingly, the unmanned drill tool may be smoothly penetrated into the uncertain formations and finally retrieve valuable core samples. Since planetary regolith has a considerable number of geological and mechanical properties, it is rather difficult to identify all the parameters individually online. Hence, the authors proposed a control strategy based on planetary regolith drillability (PRD) recognition [31]. Herein, the drillability of formation is a consolidated index to stand for drilling difficulty. A recognition model based on support vector machine (SVM) has been established to evaluate the drillability of current formation and subsequently control the algorithms that can tune drilling parameters to adapt to the current drilling conditions.

space explorations, for example, the round-trip delay between Mars and Earth will be as long as 40 min, this long time delay by teleoperation will definitely not acceptable for interplanetary drilling and coring operations [35]. Hence, in general only when a serious abnormality occurs in the sampling process, the sampling device could be automatically forced to stop drilling and wait for the ground specialists to make a fault judgment and determine the corresponding treatment plan. Otherwise, the sampling device should work in a thoroughly

Intelligent Drilling and Coring Technologies for Unmanned Interplanetary Exploration

http://dx.doi.org/10.5772/intechopen.75712

21

Given the short execution time of Mars and asteroid exploration compared with the lunar exploration, the data of soils on Mars and asteroids are rarely found yet. Herein, this chapter mainly focuses on the physical properties of lunar soil. According to previous investigations on the material returned from the moon, the terrestrial term "regolith" is also used for the interplanetary exploration [36]. Regolith has been defined as a general term for the layer or mantle of fragmental and unconsolidated rock material. According to the published literature, lunar regolith ranges from granular soil to hard rocks [37, 38], and it mainly consists of five types of material: rock detritus, mineral dust, breccia, agglutinate and impacting molten glass. The physical characteristics of above lunar soil components are quite different and the distribution of different components of lunar soil in the depth direction at the sampling site is also uncertain. During future planetary drilling processes, either soil or rock will be randomly encountered, resulting in that the final coring quality and drilling loads may both be influenced by unpredictable properties. There are numerous parameters, including cohesion, friction angle, relative density, compression ratio, particle size distribution, etc., to describe the physical properties of lunar soil [39], further increasing the difficulty to identify the physical parameters of lunar soil at different depths one by one. Therefore, it is necessary to simplify

Similar to terrestrial mining, prior investigation on the sample site will extraordinarily guide the following drilling and coring activities. In the second phase of China lunar exploration, a novel lunar penetrating radar (LPR) has already been applied to detect the morphology of the lunar surface and stratification information of subsurface lunar regolith for supporting further detector's landing site's selecting, however, it should be noted that until now due to the mass and power constraints its detection accuracy can only reach to about 30 cm [40]. Considering that any unclear detected drilling formation may bring out a serious drilling fault once inappropriate drilling parameters are operated. Therefore, it is still difficult to apply the LPR's detecting geological layering information to guide the sampling drill before drilling begins. It indicates that the drill tool should better work in a passive adaptive control mode, in which the drill tool during the whole drilling and coring process should online switch suitable drilling parameters according to the recognized current drilling formation on the drill bit, nor in

autonomous condition.

the active control mode.

**2.2. Complicated and uncertain drilling formations**

the mechanical parameter identification of lunar soil.

**2.3. Lacking of prior investigation on sampling site**

The remainder of this paper is organized as follows. The unique challenges in interplanetary drilling and coring are discussed first. Next, the specific drilling and coring characteristics containing the drilling loads characteristics and soil flowing characteristics are elaborated. A drillability recognition method is proposed based on monitoring the signals then. Finally, an intelligent real-time drilling strategy is achieved based on drillability recognition and drilling experiments in multi-layered drilling formations indicated that this unmanned control method could effectively reduce the drilling loads and keep a relatively complete stratification.
