Drilling Systems for Extraterrestrial Subsurface Exploration

Abstract

Drilling consists of 2 processes: breaking the formation with a bit and removing the drilled cuttings. In rotary drilling, rotational speed and weight on bit are used to control drilling, and the optimization of these parameters can markedly improve drilling performance. Although fluids are used for cuttings removal in terrestrial drilling, most planetary drilling systems conduct dry drilling with an auger. Chip removal via water-ice sublimation (when excavating water-ice-bound formations at pressure below the triple point of water) and pneumatic systems are also possible. Pneumatic systems use the gas or vaporization products of a high-density liquid brought from Earth, gas provided by an in situ compressor, or combustion products of a monopropellant. Drill bits can be divided into coring bits, which excavate an annular shaped hole, and full-faced bits. While cylindrical cores are generally superior as scientific samples, and coring drills have better performance characteristics, full-faced bits are simpler systems because the handling of a core requires a very complex robotic mechanism. The greatest constraints to extraterrestrial drilling are (1) the extreme environmental conditions, such as temperature, dust, and pressure; (2) the light-time communications delay, which necessitates highly autonomous systems; and (3) the mission and science constraints, such as mass and power budgets and the types of drilled samples needed for scientific analysis. A classification scheme based on drilling depth is proposed. Each of the 4 depth categories (surface drills, 1-meter class drills, 10-meter class drills, and deep drills) has distinct technological profiles and scientific ramifications.

Drills as Tools for Media Penetration and Sampling

“…The drill, called the Apollo Lunar Surface Drill (ALSD), was a 500 W rotary-percussive drill with a coring bit capable of acquiring a continuous 2 cm diameter core and an auger for carrying cuttings to the surface (Figure 1.17). Increasingly, the objectives of planetary exploration missions involve in situ sampling and analysis, but the challenges are significantly more complex than most scientific drilling on Earth (Briggs and Gross, 2002;Zacny et al, 2008; Chapter 6 of this book). Drilling a hole without astronaut control on a distant planetary body can be compared to driving a planetary rover in complete darkness with no view of the road ahead.…”

Drilling Load Model of an Inchworm Boring Robot for Lunar Subsurface Exploration

“…Scientific targets such as the physical and mechanical properties and heat flux of regolith are critical evidences for human studying the planetary origin and evolution [1]. Drilling is an effective method and is widely utilized in the planetary subsurface exploration missions [2,3].…”

Impact Dynamics of a Percussive System Based on Rotary-Percussive Ultrasonic Drill

“…Drilling is an important method for rock samples collection [1][2][3][4]. In the existing sample drilling devices, ultrasonic drill is a kind of sampling device which can drill into the rocks under low weight on bit and low power consumption.…”