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51 Space vehicles | Insight the seafloors of Europa and Enceladus. A drill, designated Archimedes, is being designed as a probe that will bore into the ice using direct laser penetration. The 5 cm-diameter, 5 kW probe will descend through the ice under its own weight while the laser is transmitted by an optical fibre from a light source seated above the surface of the ice. A wavelength of 1070 nm has been chosen for the laser. At this band, the light is preferentially absorbed by the ice, with only a small portion of it being absorbed in the liquid water film below the probe’s nose, and even less energy being absorbed in the sidewalls of the hole being drilled. Several successful trials of a prototype have been conducted in a specially designed testing chamber in the company’s laboratory. The probe drilled through a wall of ice maintained at 77 K, at a rate 18 times faster and eight times more efficient than passive heating. Another system for exploring beneath off-world ice is being developed by NASA’s Jet Propulsion Laboratory (JPL). This is the Buoyant Rover for Under Ice Exploration (Bruie), a two-wheeled UGV measuring 1 m wide and designed to be positively buoyant. The buoyancy enables it to be pushed up by water and pressed against the underside of ice sheets. It also has spiked wheels, much like some four- wheeled autonomous rover models, to enable it to grip and stick to the ice as it drives without being pulled away or knocked off of its trajectory by currents. While gripped in place, it can power down its drive systems and limit power consumption to its measurement tools, to extend its endurance to weeks or months. Now undergoing trials with its third prototype, the project’s most recent tests took place in Antarctica, where the UGV’s sensors enabled its operators to closely view algal mats beneath the ice, as well as measuring their oxygen production rates; a tether linked to the surface enabled remote operation. The trials were also aimed at studying the traversability of the ice sheets’ undersides. The results unveiled a higher than expected frequency of craters, crevasses and other potential issues disrupting smooth driving. One proposed method for circumventing such obstacles is to install thrusters into the Bruie to enable it to jump across gaps in the ice. The expected next stage of the project however will focus on its abilities to operate autonomously and explore below the ice for weeks or months at a time. As with Mars, different forms of aerial thrust for exploring the surfaces of Europa and Enceladus are also in development. A concept for one such project, at JPL, aims to use steam as a renewable propellant for this purpose. The Sparrow (Steam-Propelled Autonomous Retrieval Robot) UAV project has received Phase I development funding, and could evolve in a few different directions. However, the principal embodiments consist of two parts: a lander spacecraft acting as a base station, and one or more Sparrows to be housed and refuelled by the lander. The landers would extract ice from the moons’ surfaces and melt it, before injecting it into the Sparrows’ tanks. There, the UAVs would boil the water in their engines and eject the resulting steam from distributed-lift thrusters positioned around their airframes. In the low-gravity and low-drag environment, that would be enough to carry them several miles. The project is ongoing, with calculations and evaluations of different models of propellant systems and flight modes being the current priorities. Conclusion It is notable that some major advances in the global space exploration industry have been focused on new forms of landers as logistical housings for unmanned systems. Also, innovations in autonomous control, navigation and power generation are being tested in well-established vehicle architectures being developed for use on the Moon and the moons of Jupiter and Saturn. Engineers looking to optimise unmanned vehicles, droneports and their associated logistics should therefore pay close attention to the rovers, aircraft and aquatic systems being sent into space. Just as space exploration has long contributed technological advances to consumer goods, materials science, electronics and a host of other industries, so unmanned systems across the Earth’s skies, roads and oceans could benefit enormously from the space industry’s innovations over the next few years. Unmanned Systems Technology | October/November 2020 The Bruie underwater rover uses its buoyancy and gripping wheels to roll along the undersides of ice caps. Eventually it will used in icy worlds such as Europa and Enceladus (Courtesy of NASA JPL)