Unmanned Systems Technology Dec/Jan 2020 | Phoenix UAS | Sonar focus | Construction insight | InterGeo 2019 | Supacat ATMP | Adelan fuel cell | Oregon tour | DSEI 2019 | Copperstone Helix | Power management focus

22 I n Portsmouth, on the UK’s south coast not far from where Admiral Nelson’s flagship HMS Victory now rests, there is a cavernous building called The Drystack that was once used for building minesweepers for the Royal Navy. It is now lined on either side by racking used for storing pleasure boats. During the day the building is often busy with the hum of enormous forklift trucks that retrieve and return the boats to and from their allocated slots on each rack. After 5pm though it falls silent, and in the cold of an English March night, the dimly lit, 120 m-long corridor down the middle of it witnessed the first successful large-scale demonstration of a new type of aircraft. The Phoenix is a fully autonomous unmanned air system that has no engines but propels itself forward by varying its buoyancy. The prototype has a fuselage length of 15 m, a wingspan of 10.5 m and an all-up mass of about 150 kg. It was tested repeatedly over the full length of the building, performing about half-a-dozen transitions between heavier- than-air and lighter-than-air states on each flight, resulting in a sinusoidal flightpath and proving for the first time the concept of variable-buoyancy propulsion for a feasible, self-contained, autonomous aircraft system. The idea for the Phoenix project originated from a previous initiative by Athene Works that aimed to demonstrate the viability of the concept of a variable- buoyancy propulsion system on a small- scale demonstrator. That project achieved Andrew Rae details the development of this innovative unmanned air system, which uses a variable-buoyancy system for propulsion Buoyed along December/January 2020 | Unmanned Systems Technology