Lunar and Planetary Institute

LPI Seminar Series

LPI seminars will be held on Thursdays.

LPI seminars are held from 3:30–4:30 p.m. in the Lecture Hall at USRA, 3600 Bay Area Boulevard, Houston, Texas. Refreshments are served at 4:30 p.m. For more information, please contact Martin Schmieder (phone: 281-486-2116; e-mail: or Nick Castle (phone: 281-486-2144; e-mail: A map of the Clear Lake area is available here. This schedule is subject to revision.

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See also the Rice University Department of Physics and Astronomy Colloquia and the Department of Earth Science Colloquia pages for other space science talks in the Houston area.

December 2018

Thursday, December 6, 2018 - Lecture Hall, 3:30 PM

Bill Stone, Stone Aerospace, Austin, TX
LPI Seminar: Ocean World and Martian Sub-ice Access and Exploration Technology: How close are we to viable flight vehicles?
The recent discovery of a possible (as-yet unverified) subglacial lake beneath the south pole ice cap of Mars has increased interest in reaching such places with robotic technology. During the past decade research has been conducted on ice penetrating “cryobots” and cryobot-deployed autonomous underwater vehicles (AUV) in preparation for sub-surface missions to Ocean Worlds. This talk will provide an overview of the current state of ice penetrating and sub-ice exploration technology that is being developed towards flight missions. Of primary importance is a nuclear power source, which can be optimized for cryobot operations. In addition, there are five cryobot operating regimes (starting, brittle ice transit, ductile ice transit, obstacle avoidance/passage, and breakthrough into voids or ocean). Each of these presents unique challenges to and constraints on a vehicle. Currently, four penetrator technologies have been identified that can be used either singly or collectively: passive thermal melt probes, closed-cycle hot water drills (CCHWD), laser penetration, and mechanical drills. All are currently being advanced in the NASA COLDTech program as each has certain tradeoffs. Mechanical drills have been shown to work in cold ice and are able to penetrate non-ice solids, but suffer from wear and binding. Lasers are extremely efficient in cutting through cold and warm ice, including in vacuum conditions, but require large amounts of electrical power. CCHWD systems can also cut through debris-laden ice and steer to avoid obstacles. In this presentation, we discuss pros and cons of each of these penetrator technologies in light of new nuclear power sources. We also discuss constraints on deployable sub-ice swimming rovers necessary to expand exploration radius from an initial breakthrough point into a sub-surface water body as well as the state of AI operating behaviors for such rovers that dramatically enhance autonomous exploration capabilities. Finally, we propose several new test facilities that will both advance these technologies to flight readiness and improve our understanding of Earth’s and extraterrestrial cryospheres.


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