Once the Roton has been slowed sufficiently by atmospheric drag, however, the pilot will change the blade-angles so that the blades are set spinning by the airflow, slowing the craft still further. (This technique, called auto-rotation, is used by helicopter pilots in emergency landings.) Small thrusters on the side of the Roton will stabilise it, so that it can be steered towards its landing site.
In her workshop at the Limerick Craft Hub, she showed me how the technique just involves a strip of silk, some lengths of spun wool, some water and a couple of hand sanders.