By Bill Stone

We are living in an extraordinary era where machines have begun to replace humans, initially in highly structured settings such as manufacturing and now in more complicated real-world settings such as self-driving vehicles. This presentation goes beyond that—tracing the roots of fully autonomous exploration in 3D unstructured and ultimately completely unknown environments. Cavers have always known the special sensation of exploring completely unknown places. Would it actually be possible to replace a caver with a robot?

Our initial experiments dealt with a simpler problem: building a real-time 3D cave map. We achieved this in 1998 using an inertial guidance unit to track the position and orientation of a mapping instrument in the underwater tunnels of Wakulla Springs, Florida. A helical array of acoustic sensors acquired tunnel cross-section measurements as the vehicle was flown through the tunnels, guided by a cave diver. We later built on this concept by using the just-created 3D map as a navigation tool, a concept known as SLAM (simultaneous localization and mapping).

Over the course of the next 15 years these concepts were refined in a series of NASA-funded sub-ice vehicles designed to test life-search concepts for the exploration of sub-surface oceans of outer-planet icy moons, such as Europa and Enceladus. A person-portable version of these concepts, known as SUNFISH, was tested initially in Peacock Springs, Florida, in 2016.  It used advanced behavior-based programming that emulated the way cave divers think. The ultimate test came in late 2019 when SUNFISH autonomously explored three of the world’s deepest cave diving sites in northern Namibia, to depths of 265 m and distances of half a kilometer from the water surface—well beyond the limits reached by divers in these locations, despite the use of helium breathing mixtures, rebreathers, and propulsion vehicles. Dragon’s Breath, Harasib Shaft, and Lake Guinas were all explored to their ends by SUNFISH.

A doorway has now been opened such that previously inaccessible cave diving sites—limited by human physiology, depth, length, visibility, or current—can now be explored. The same techniques employed in Namibia using an AUV (autonomous underwater vehicle) are laterally transferrable to aerial drones for performing the same maneuvers in air-filled caves. So far, neither of these approaches are suitable for crawling through breakdown, so, at least for a while, humans will remain the dominant cave explorers on Earth.

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