(DE19647948-A1)      The gondola (1) suspended in a vertical tunnel (4) through the hull (3) contains a polyphase induction motor whose rotor (8) and stator (15) drive the respective propellers (7,12) in opposite directions. The axis of the stator is a hollow shaft (11) centred in a supporting bearing (16) with a sealing disc (13) at the other end. The rotor axis (6) rotates in a thrust bearing (9) with a supporting bearing (10) at the other end within the hollow shaft.    Diameter and pitch of the propellers are chosen so that at nominal flow rate in the forward direction they co-operate at equal torque with optimal efficiency of propulsion.    ADVANTAGE -   Torque and weight can be halved with higher electrical and hydrodynamic efficiencies, better streamlining, little cavitation noise and no influence of harmonics on the ship.    (DE19637146-A1)      The system has a gondola (1) fixed or rotatably mounted in a vertical tunnel and attached via a flow dynamically coated strut (2) to the underside of a ship or to a windmill tower. It contains a synchronous machine. Each end of the gondola carries a contrarotating propeller. One propeller is attached with the rotor to a rotor axle (6) and the other with a stator to a coaxial stator shaft.    The rotor axle is mounted in the gondola housing by a journal and thrust bearing (9). The second journal bearing is mounted in the hollow stator shaft (11), which is sealed wrt. the propeller, has a journal and thrust bearing (10) wrt. the gondola housing and a force-locking connection to the stator housing. The stator housing is centrally attached on the rotor propeller side to the rotor axis via the second journal bearing. Each axle is sealed wrt. the housing against water ingress by a stop bush (17).    ADVANTAGE -   The system enables increased manoeuvrability to be achieved.    (EP786402-B1)      The system has a gondola (1) fixed or rotatably mounted in a vertical tunnel and attached via a flow dynamically coated strut (2) to the underside of a ship or to a windmill tower. It contains a synchronous machine. Each end of the gondola carries a contrarotating propeller. One propeller is attached with the rotor to a rotor axle (6) and the other with a stator to a coaxial stator shaft.    The rotor axle is mounted in the gondola housing by a journal and thrust bearing (9). The second journal bearing is mounted in the hollow stator shaft (11), which is sealed wrt. the propeller, has a journal and thrust bearing (10) wrt. the gondola housing and a force-locking connection to the stator housing. The stator housing is centrally attached on the rotor propeller side to the rotor axis via the second journal bearing. Each axle is sealed wrt. the housing against water ingress by a stop bush (17).    ADVANTAGE -   The system enables increased manoeuvrability to be achieved.