Unmanned Systems Technology 025 | iXblue DriX I Maintenance I UGVs I IDEX 2019 I Planck Aero Shearwater I Sky Power hybrid system I Delph Dynamics RH4 I GCSs I StreetDrone Twizy I Oceanology Americas 2019

24 Dossier | iXblue DriX modern DDG 1000-class destroyers. Its small area, and the fact that it enables the maximum waterline length for a given hull size, contribute to minimising propulsive resistance. Above the hull, the most prominent feature is the main mast that supports the navigation and comms antennas, lights and other equipment that helps the vessel to see and be seen in maritime traffic. The mast is hollow and contains what Eudeline calls a scabbard, from which the drop-keel that supports the underwater sensor payload gondola emerges. Fully extended, this drop-keel positions the gondola 2 m below the bottom of the hull. Doing so distances the sensor from the hull and any bubbles near the surface, Eudeline says, and helps to keep it properly oriented with regard to the seabed it is mapping. To explain that, he suggests visualising a vessel with a V-shaped hull and a payload underneath riding a transverse wave. “You will see that the V-shaped hull has a pronounced angle all the way through the wave, and that the payload is not going to be truly perpendicular to the sea bottom; it will rock sideways a lot,” he says. “Now imagine a ballasted ping pong ball riding the same wave: the ballast is going to remain perfectly perpendicular to the bottom of the sea. From the naval architecture point of view, the DriX behaves like a ballasted ping pong ball, and that is because of the drop-keel.” While this weight distribution does not totally eliminate relative movement between the sensor and the seabed, it smooths it out to a point at which the sensors can cope with it. “That is why we are able to operate in a very high sea state compared with traditional surface assets,” Eudeline says. “We have been working on seabed mapping in sea states from four to five, and at speeds of eight to 10 knots.” The DriX’s mast also presents a fairly small surface area to catch the wind. In addition, there are a number of devices to reduce movements induced by the wind, but Eudeline was unwilling to share details of those. The hull is made from a blend of composite materials more commonly found in aircraft than ships or boats, reflecting a more adventurous approach to their use than is typical in this sector. However, iXblue is involved in the EU FibreShip project, an international initiative funded under the EU’s Horizon 2020 scheme to build the entire hull and superstructure of large (more than 50 m) ships in fibre-reinforced plastics. As part of that, iXblue is building sections of a 150 m cargo vessel in composites. April/May 2019 | Unmanned Systems Technology Atop the DriX’s mast are a Lidar (left), a GNSS antenna, radio including satcom antennas, radar signature enhancing devices and a broadband radio (right) on a vertical rail (Courtesy of University of New Hampshire) The payload gondola is deployed beneath the hull to isolate it from any bubbles, hull flow and radiated machinery noise (Courtesy of iXblue)