Of course, two rotate in one direction and two in the opposite direction.
You must use a very light hydraulic oil. If it were not frozen in winter.
Hydraulic pump in the balloon has the best power to weight ratio. All the airlines are working on the hydraulic actuators.
Of course, all of the balloon must be tested in the wind tunnel aerodynamic, in order to fully match the efficiency of the 21st century.
Some pictures of how to create a balloon from the inside
and NASCAR wind tunnel
Regards Andrew
