Unmanned Systems Technology 028 | ecoSUB Robotics AUVs I ECUs focus I Space vehicles insight I AMZ Driverless gotthard I InterDrone 2019 report I ATI WAM 167-BB I Video systems focus I Aerdron HL4 Herculift

The operators can monitor all of these through the GUI at the control station. “Before you launch it, you check that it is still at 500 hPa,” Sloane says. “If it leaks air it is going to leak water, so you know whether it is sound.” Another benefit of this approach is that it eliminates the need for nuts and bolts around the end caps, and the associated threaded holes in the aluminium case, which are potential weak points. Like all the polymer parts, the free- flooding nose cone and tail sections are 3D-printed in nylon by Digits To Widgets (DTW) in London and then treated by a DTW subcontractor in Germany to make them waterproof. These plastic components also include the tray that holds the circuit board (which is part of the internal chassis), the battery box and, in the larger vehicles, some internal chassis ribs. While some internal parts are screwed into place, the use of 3D printing has kept fasteners to a minimum. For example, the tray that holds the circuit boards in each vehicle is a single printed nylon component with integral lugs and stand-offs for the boards, which simply click into place. AUVs are generally operated with a slight positive buoyancy to give them a tendency to float if anything goes wrong. Keeping them down consumes energy, so the buoyancy is carefully calculated to keep it to a minimum. That said, providing enough buoyancy was a particular challenge for the smallest vehicle (the μ5) while still accommodating all the equipment and batteries inside. “Buoyancy/weight is always a trade- off,” Sloane says. “In the deep-diving one with its 2500 m pressure case, making it strong enough to withstand the pressure but light enough to preserve buoyancy has been a challenge.” With the m5, the 500 m-depth version of the larger vehicle, the aluminium pressure case is much thinner and lighter, so the company needed to add some ballast to reduce its buoyancy