Today I done some experiments with an old solar balloon of 3.1 kg, 2.7 m diameter and 10 m span, then 7 m, then 4 m as it deflated. In the end a swivel which was not too useful. I rotated the balloon on a half rotation, sometimes a whole rotation. With my arms I obtained a maximal tangential speed of about 4 m/s with 7 m span, and as expected more with 4 m span, less with 10 m span. So the power consumption is a real concern, above all with inflatable balloons with low internal pressure that are subject to deformation due to air friction and also real wind.