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62 W hen an unmanned vehicle needs to operate across long distances or extreme environments that make wireless data links or human intervention impossible, no failure of its mechanics, sensor measurements, software or structure can be permitted, as technicians cannot hope to carry out repairs or remote diagnostics. It must therefore be built to a high level of AI and survivability. Over the past few years, Stone Aerospace has regularly sent its Sunfish AUV across such distances and extremes. The Sunfish is a battery-electric AUV with a dry weight of 50 kg, and a housing that measures 161 cm long, 47 cm wide and 20 cm tall. The housing protects a range of hardware and software that has been tailored to achieve autonomous exploration to a degree not achieved by most other unmanned systems. The company, based in Austin, Texas, was founded in 2007 by William Stone, who had previously worked on spacecraft systems and UGVs at the National Institute of Standards and Technology in Gaithersburg, Maryland. “The root of Stone Aerospace and the Sunfish was essentially work I had done on perception systems for UGVs,” he says. “That was in 1995, when we were autonomously driving Humvees at 100 kph; it would be another 15 years before the advent of autonomous cars in the commercial space.” Towards the end of the 1990s, Stone led an expedition sponsored by National Geographic to Wakulla Springs, in Florida, to ascertain whether a craft could perform real-time 3D mapping of an underground aquifer as it travelled through it. Stone programmed a prototype vehicle using his UGV experience, which resulted in a human- guided unmanned system. “That machine was 3 m long, 40 cm in diameter and weighed about 180 kg, but the divers drove it for about 10 km underwater, through passages about 50 m in diameter and 100 m deep, and came back with 3D maps of the whole thing,” Stone says. Over the following two years, Stone considered how the decision-making processes of exploratory cave divers Whether it’s exploring terrestrial or off-world oceans, ruggedness and intelligence are essential in an AUV. Rory Jackson cites this prime example Built to last December/January 2021 | Unmanned Systems Technology The Sunfish uses 3D SLAM to navigate through submerged caves – and in the future, beneath the ice of moons such as Europa and Enceladus (Images courtesy of Stone Aerospace)