Ultrasonic/Sonic Driller/Corer (USDC) as a Subsurface Sampler and Sensors Platform for Planetary Exploration Applications

摘要

The search for existing or past life in the Universe is one of the most important objectives of NASA's mission. For this purpose, effective instruments that can sample and conduct in-situ astrobiology analysis are being developed. In support of this objective, a series of novel mechanisms that are driven by an Ultrasonic/Sonic actuator have been developed to probe and sample rocks, ice and soil. This mechanism is driven by an ultrasonic piezoelectric actuator that impacts a bit at sonic frequencies through the use of an intermediate free-mass. Ultrasonic/Sonic Driller/Corer (USDC) devices were made that can produce both core and powdered cuttings, operate as a sounder to emit elastic waves and serve as a platform for sensors. For planetary exploration, this mechanism has the important advantage of requiring low axial force, virtually no torque, and can be duty cycled for operation at low average power. The advantage of requiring low axial load allows overcoming a major limitation of planetary sampling in low gravity environments or when operating from lightweight robots and rovers. The ability to operate at duty cycling with low average power produces a minimum temperature rise allowing for control of the sample integrity and preventing damage to potential biological markers in the acquired sample. The development of the USDC is being pursued on various fronts ranging from analytical modeling to mechanisms improvements while considering a wide range of potential applications. While developing the analytical capability to predict and optimize its performance, efforts are made to enhance its capability to drill at higher power and high speed. Taking advantage of the fact that the bit does not require rotation, sensors (e.g., thermocouple and fiberoptics) were integrated into the bit to examine the borehole during drilling. The sounding effect of the drill was used to emit elastic waves in order to evaluate the surface characteristics of rocks. Since the USDC is driven by piezoelectric actuation mechanism it can designed to operate at extreme temperature environments from very cold as on Titan and Europa to very hot as on Venus. In this paper, a review of the latest development and applications of the USDC will be given.