The rocks on extraterrestrial objects contain plenty of original geological and biological information. Drilling and sampling are an essential task in lunar exploration or future explorations of other planets like mars. Due to the limitation of payloads, energies, and drill pressure, the investigation of a lightweight and low-powered rock-drilling device is crucial for explorations of distant celestial bodies. The ultrasonic drill driven by piezoelectric ceramics is a new drilling device that can adapt to the arduous space rock-drilling tasks in weak gravitational fields. An ultrasonic drill suitable for mounting on a planetary rover’s robotic arm is developed. The ultrasonic transducer’s energy conversion from electric energy to acoustic energy and the energy transmission from the horn’s high-frequency vibration to the drill stem’s low-frequency impact motion are analyzed to guide the design of the drill. To deeply understand the percussive drilling mechanism under high-speed impact, the interaction between the drill stem and the rock is simulated using LS-DYNA software. Drilling experiments on rocks with different hardness grades are conducted. The experiment results illustrate that the ultrasonic drill can penetrate into the hard rocks only taking a force of 6 N and a power consumption of 15 W. The study of ultrasonic drill will provide a reference method for sample collection of extraterrestrial rocks.
Unmanned in-situ exploration is an important technique to study the physical and mechanical parameters of lunar composition and evolution. The impact penetrator is an effective device for in-situ detection of the lunar soil profile at predetermined depth. Because of the lack of real lunar soil samples, it is very difficult to study and evaluate the performance of the impact penetrator. In order to truly reflect the interaction between the impact penetrator and lunar soil particles, a simulation model of the lunar soil body was established by means of discrete-element analysis, and the model parameters were matched and verified by the experimental method. Based on this model, the interaction behaviors between the penetrators with different head configurations and the lunar soil body were simulated. The stress field distribution in the lunar soil body and particle movement patterns during the penetrating process were revealed, which reflects the working principle and performance of the penetrator. The numerical simulation on the interaction process between the impact penetrator and lunar soil particles provides a feasible and effective method for the design and optimization of the penetrator, which will contribute to the development of lunar subsurface in-situ exploration technologies.
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