Title of Presentation: The Low-force Sample Acquisition System (LSAS)

Primary (Corresponding) Author: Scott Stanley

Organization of Primary Author: Alliance Spacesystems, LLC

Co-Authors: Sean Dougherty, Jacques Laramee


Abstract: Current science for Mars and lunar exploration demands that rock fines from a wide variety of rock types ranging from soft shale to very hard basalts be acquired for geologic evaluation. Tools to acquire these samples must be light weight, draw minimal power, and induce low loads on their robotic platforms. The drills and other sample acquisition systems that have been produced to date do not meet one or more these requirements.

Alliance Spacesystems, LLC produced a rotary percussive drill designed for light weight space robotic arms and rovers under a NASA-funded Mars Instrument Development Program (MIDP) project – the Low-force Sample Acquisition System (LSAS). The flight-like drill prototype that was the end result of the project successfully drilled and acquired 1 cm³ samples from a variety of rocks and soils including the hardest anticipated Martian rock (basalt) and frozen soil. This ability was demonstrated not only in ambient conditions but also in a thermal/vacuum chamber replicating Mars pressure and extreme temperatures.

The LSAS drill design, though derived from extensive analysis and empirical testing, is simple in concept and operation. The drill is driven by a single electric motor that rotates the bit and drives the rotary cam hammer mechanism. To operate, the LSAS is pressed against the target with a force of approximately 35 N, compressing a seal and internal preload spring and activating a position sensor that indicates the preloaded position. Drilling begins and fines are transported by the fluted bit into a sample bin. Once the bit has extended to a predetermined depth that will yield the appropriate sample size (1 cm³ in the original version), another position sensor is tripped and drilling ceases. The sample bin is then pushed against an instrument container orifice, forcing open spring-preloaded sections and ejecting the sample. The complete LSAS unit weighs 440 g and requires less than 20W to operate.

The paper will include discussions on current percussive drilling practice, the theoretical approach to establishing percussive drilling parameters, background testing on Mars stimulant samples, and a description of the prototype design and performance tests.