Static rock splitters based on high temperature shape memory alloys for planetary explorations. (January 2016)

• Record Type: Journal Article
• Authors: Benafan, O.; Noebe, R.D.; Halsmer, T.J.
• Is Part Of: Acta astronautica. Volume 118(2016)
• Page Start: 137
• Page End: 157
• Publication Date: 2016-01
• Subjects: Shape memory alloys -- Rock splitting -- NiTiHf -- Geologic excavation -- Blocking force; Astronautics -- Periodicals; Outer space -- Exploration -- Periodicals; Astronautics; Periodicals; 629.405
• DOI: 10.1016/j.actaastro.2015.10.009
• Languages: English
• ISSNs: 0094-5765

Abstract

Abstract: A static rock splitter device based on high-force, high-temperature shape memory alloys (HTSMAs) was developed for space related applications requiring controlled geologic excavation in planetary bodies such as the moon, Mars, and near-Earth asteroids. The device, hereafter referred to as the shape memory alloy rock splitter (SMARS), consisted of active (expanding) elements made of Ni50.3 Ti29.7 Hf20 (at%) that generate extremely large forces in response to thermal input. The pre-shaping (training) of these elements was accomplished using isothermal, isobaric and cyclic training methods, which resulted in active components capable of generating stresses in excess of 1.5 GPa. The corresponding strains (or displacements) were also evaluated and were found to be 2–3%, essential to rock fracturing and/or splitting when placed in a borehole. SMARS performance was evaluated using a testbed consisting of a temperature controller, custom heaters and heater holders, and an enclosure for rock placement and breakage. The SMARS system was evaluated using various rock types including igneous rocks (e.g., basalt, quartz, granite) and sedimentary rocks (e.g., sandstone, limestone). Highlights: A static rock splitter based on high-temperature shape memory alloys was developed. The precipitation strengthened NiTiHf alloy provided activation temperatures above 100 °C. The NiTiHf alloy was capable of generating stresses in excess of 1.5 GPa after training. Isothermal and isobaric training methodologies were used to condition the material. Igneous rocks (e.g., basalt) and sedimentary rocks (e.g., limestone) were successfully split.