 It was controlled from a small cab placed just forward of the cylindrical centre piece set into the middle of the deck which contained the craft's engine and horizontally mounted fan.For aerodynamic efficiency, the fan and the wall of the centre piece had very little clearance, while the exterior wall of the centre piece itself was heavily reinforced so that the crew would be protected in the event of a catastrophic engine failure.The core of the vehicle was a rivetted aircraft-grade aluminium alloy sheet buoyancy tank, which had been coated with a thin layer of pure aluminium to protect against corrosion.