Abstract:
Electrical machines, for example motors or generators, based on superconducting technology, in particular based on high-temperature superconducting technology, with the machines having a rotor with superconductors, in particular high-temperature superconductors, a rotor cryostat, a rotor shaft and a cryogenic connection to a cryogenic conductor between the cryostat and a cold generator, and having a stator which is not based on superconducting technology, and in which these electrical machines are designed to be capable of being immersed and to be shock-resistant for navy vessels, with the stator ( 13, 29 ), the rotor ( 18, 28 ) and the cryostat ( 15 ) being decoupled in terms of movement from an outer machine housing ( 4, 23 ) and from the rotor shaft ( 12 ) by means of elastic elements ( 17, 25 ), and in which, in one embodiment, the machine housing is in the form of a steering propeller housing and is elastically connected to the vessel stern.

Description:
[0001]    This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/DE02/03239 which has an International filing date of Aug. 30, 2002, which designated the United States of America and which claims priority on German Patent Application numbers DE 101 43 713.7 filed Aug. 30, 2001, and DE 102 24 014.0 filed May 29, 2002, the entire contents of which are hereby incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present application generally relates to the field of electrical machines, for example motors or generators, based on superconducting technology; in particular based on high-temperature superconducting technology.  
         BACKGROUND OF THE INVENTION  
         [0003]    In the past, it has already been proposed for conventional electrical machines, for example motors or generators, to be designed using superconducting technology, in order to improve the efficiency of these machines and to make it possible to implement space-saving concepts. Corresponding laboratory machines have also already been developed and have been introduced to the public in the USA and Germany. However, they have not yet been implemented for practical operation on vessels, since the technical difficulties, particularly in the case of navy vessels with their particularly stringent requirements for shock resistance, resistance to vibration etc., mean that they have not yet been considered to be feasible.  
         SUMMARY OF THE INVENTION  
         [0004]    An object of an embodiment of the invention is to specify electrical machines based on superconducting technology, in particular based on high-temperature superconducting technology, which are designed to be suitable for practical use and may be used without any problems in navy vessels. One object in particular is to specify an electrical propulsion motor based on superconducting technology for steering propellers, in which the specific advantages of superconducting technology can lead to a particularly lightweight propulsion system, which allows a streamlined stern shape and leads to a slim vessel configuration.  
           [0005]    Suitable electrical machines for navy vessels are already known. These machines are large and heavy. In terms of movement, they are not integrated in the vessels. The same applies to electrical steering propeller motors, as are disclosed in WO 02/30742 A1 and in DE 196 47 948 A1. Although these motors are decoupled from their housing in terms of vibration, they are, however, large and heavy owing to the air cooling which is normally provided.  
           [0006]    One particular object of an embodiment of the invention is to specify the individual components of an electrical machine based on superconducting technology and which is suitable for a navy vessel and can withstand accelerations of the part of the vessel in which it is arranged up to more than 100 g. A superconducting machine can thus also be used without any restrictions for the navy.  
           [0007]    The electrical machine according to an embodiment of the invention, irrespective of whether it is a motor, for example an electric motor for an electrical steering propeller, or a motor for a conventional propeller or water jet which is arranged in the navy vessel in order to increase the flank speed, or whether it is a generator for generating electrical power for any desired electrical loads, always has the specific advantages of the high efficiency, the small dimensions and the low weight of a superconducting electric motor or generator.  
           [0008]    Detailed information for the major elements of the super conducting motor or generator, in particular based on a high-temperature superconductor configuration, is already available, for example about the cryogenic distributor in WO 00/13296. The same information relating to the coupling between the cold rotor shaft part and the shaft part which is passed to the exterior is available in German Patent Application document 101 10 674.2 and information about cold heads is available from European document EP 0 865 595 B1. Details about compressor units and about accessories for cryogenic refrigerators are known, for example, from the descriptions and operating instructions from the Leybold Company for their RGS or Coolpak types.  
           [0009]    In summary, it can be stated that the components which are intended to be used in a new combination and in a modified form which is significant to the invention for the motors and generators for navy vessels, are in principle already known from various fields of technology, for example from nuclear magnetic resonant imaging, from superconducting current limiters, or from similar products.  
           [0010]    A further object of an embodiment of the invention relates to the specific field of propulsion devices for vessels and is applicable to the design configuration of an electric motor which includes a stator and a rotor and is arranged in a streamlined housing which can be arranged like a gondola on the lower surface of the hull of a vessel, and in which the rotor is supported by a shaft which is mounted in the housing and to which at least one propeller is coupled.  
           [0011]    In one known propulsion device of this type, the rotor is in the form of a rotor with permanent-magnet excitation and includes a supporting structure with a tube-like mounting body and a magnetically active part. The rotor is arranged on a propulsion shaft to which at least one propeller is fitted and which is mounted in the housing of the propulsion device. The stator, has an electrically and magnetically active part, is fitted into the housing of the propulsion device such that power can be transmitted.  
           [0012]    The electric motor is in this case cooled by heat dissipation via the housing to the surrounding water. In order to cool the end windings of the stator, air or an insulating oil can be circulated in the interior of the housing (WO 97/49605). Alternatively, it is possible to use a special thermal bridge (DE 199 02 837 A1). Additional cooling measures may comprise the use of closed-cycle coolers which are arranged in the casing-like mount part of the propulsion device (DE 198 26 229 A1).  
           [0013]    In another known propulsion device with an electric motor that is arranged like a gondola, the stator is arranged with a radial gap in the housing, in order to make it possible to cool the stator and the rotor with a gaseous coolant which is supplied from the hull of the vessel via specific cooling channels (U.S. Pat. No. 5,403,216).  
           [0014]    Against the background of a propulsion device, an embodiment of the invention is based on an object of designing the propulsion device such that it can withstand shock loads and is thus also suitable for applications in fields of operation in which severe underwater pressure waves may occur. This embodiment is in this case intended to be suitable for high-temperature superconducting propulsion devices.  
           [0015]    In order to achieve this object, an embodiment of the invention provides for the stator to be fixed on the rotor via rotating bearings, and for the unit which is formed from the stator and rotor to be supported both on the housing and on the. propulsion shaft.  
           [0016]    In a refinement of the propulsion device such as this, the electrically and magnetically active parts of the propulsion motor, which have a high mass, form a unit which is mounted within the housing and in a “damped” manner on the propulsion shaft. In the event of sudden pressure effects acting on the housing and the propulsion shaft of the propulsion device from the outside, these pressure effects act with a time delay and thus with a reduced shock effect on the. electrically and magnetically active parts of the motor. The mechanical forces which act on the hull of the vessel via the suspension of the propulsion, device (which is arranged like a gondola), in particular bending moments, are thus reduced.  
           [0017]    The elastic and damped arrangement of the electrically and magnetically active parts of the electric propulsion motor also results in a reduction in the structure-borne sound which originates from the propulsion device, thus making it harder to use sonar to locate a vessel which is equipped with a propulsion device such as this. The rigid mechanical coupling between the rotor and the stator of the electric propulsion motor has the further advantage in the case of motors in which the rotor is fitted with permanent magnets for excitation purposes that the air gap between the rotor and the stator remains constant even in the event of shock loads on the propulsion device, and can thus be chosen to be very small.  
           [0018]    In one refinement of an embodiment of the invention, the rotor includes a tube-like mounting body and an active part which is fitted to the mounting body and is elastically supported on the propulsion shaft, while the stator is mounted on the mounting body of the rotor and is elastically supported on the housing. In this case, it is expedient for the rotor to be mounted softly on the propulsion shaft both in the axial direction and in the radial direction, but to be designed to be torsionally stiff in the circumferential direction.  
           [0019]    The radially rigid mounting of the stator on the mounting body of the rotor is expediently achieved by commercially available radial and axial bearings, which are preferably in the form of roller bearings. Sliding bearings are in contrast expediently used for the bearings for the rotor shaft, preferably those with hydrostatic oil circulation.  
           [0020]    Commercially available damping elements may be used for the elastic support of the rotor on the shaft, such as those which are normally used, for example, for elastic couplings in a shaft run. The essential feature of damping elements such as these is that they are designed to be elastic in the radial and axial directions of the rotor and to be torsionally stiff in the circumferential direction of the rotor.  
           [0021]    The same types of damping elements can be used for the elastic support of the stator on the housing of the propulsion device as for supporting the rotor on the shaft.  
           [0022]    Since the elastic support of the stator on the housing of the propulsion device results in a space being formed between the stator and the housing, the stator cannot be cooled solely by heat dissipation via the housing to the surrounding water. Additional cooling measures must therefore be provided. This could be done by the use of closed-cycle coolers, which are arranged in the area of the wall of the supporting casing which connects the propulsion device to the hull of the vessel, or in the hull of the vessel, with a liquid coolant, in particular water, flowing through this closed-cycle cooler as well as through corresponding holes in the laminated stator core and in a cooling ring which surrounds the laminated core. Cooling such as this may also be used for the end windings of the stator.  
           [0023]    Apart from this, circulating air flow can also be produced, which flows around the end windings of the stator and is cooled down in the area of the supporting casing for the propulsion device. If required, the bilge areas of the propulsion device, that is to say the housing parts which are arranged at the ends of the propulsion shaft, can also be used for cooling-down purposes.  
           [0024]    An electrical steering propeller which can be rotated is known from Canadian Patent 1,311,657. This steering propeller is arranged under the stern of an icebreaker. The casing and its connection to the stern of the vessel are designed especially for icebreaking tasks.  
           [0025]    A further object of an embodiment of the invention is to specify an electrical steering propeller which is likewise specifically designed for a task, namely for propulsion of a navy vessel. One necessary feature for this object is for the electrical steering propeller to be able to withstand high accelerations caused by underwater explosions. In this case, it must be designed to be light, in order to take account of the slim stern configuration of navy vessels.  
           [0026]    The main object is achieved in that the vessel stern casing connection, the casing and the motor are designed such that the vessel stern, the casing and the motor can withstand underwater explosion pressure waves without being damaged, for which purpose the casing is itself designed to be elastically deformable, the vessel stern casing connection is designed to allow movements of the casing with respect to the vessel stern, and the electric motor is designed to absorb accelerations of more than 10 g. Features according to the solution result in the electrical steering propeller being designed appropriately for its object and having the capability to be used for navy vessels which are subject during operation to the risk of a torpedo hit or of a torpedo or a mine exploding underneath the vessel. The resistance is better than that of conventional rudders.  
           [0027]    The configuration of a modern navy vessel is described in the article by Karl Otto Sadler, “Trends im Überwasser-Marineschiffbau” [Trends in the construction of surface navy vessels] in the Journal “Marineforum” [Navy Forum], Issue 6, 1999, pages 8 to 29. The electrical steering propeller according to an embodiment of the invention is intended in particular to be suitable for modern navy vessels such as these.  
           [0028]    One refinement of an embodiment of the invention provides for the casing of the electrical steering propeller to have at least one elastic articulation point, for example a joint, between individual parts of the casing. The joint advantageously has flanges with a screw connection, which is designed to flex elastically and, for example, has cup springs. An elastic joint intermediate layer composed of an elastomer material preferably in a multilayer and reinforced form, for example silicone rubber, is advantageously arranged in the joint.  
           [0029]    These joints that are provided according to an embodiment of the invention result in articulation points for the casing, so that it can behave elastically. This makes it possible to dissipate explosion pressure wave forces which act on the motor at the lower end of the casing and on the junction point between the casing and the stern. The solution according to an embodiment of the invention is in this case sufficiently robust to satisfy the requirements and is very advantageously effective for dissipation of explosion pressure waves.  
           [0030]    A joint collar is advantageously provided on the outside around the joint, is composed of elastic, in particular elastomeric material, and prevents water from entering the joint during movement of the casing parts.  
           [0031]    Provision is also advantageously made not only for the housing of the electric motor to be formed from two or more parts, with individual parts of the housing preferably being composed of aluminum, but also for the casing to be formed from more than two parts, with aluminum, or else fiber-reinforced plastics, in some cases also with steel or aluminum flanges preferably also being provided in this case. This results in considerable saving in weight, or else an increase in the elasticity of the casing.  
           [0032]    A further refinement of an embodiment of the invention provides for the electric motor to have an elastic rotor bearing and a large air gap which is, for example, between 5 and 50 mm. This makes it possible to reliably prevent the rotor from striking the stator part, of the electric motor even when very high accelerations occur (accelerations may be more than 100 g). The large air gap in conjunction with an elastic rotor bearing and the use of sliding bearings instead of roller bearings achieves the surprisingly high capability for the electric motor to. withstand acceleration, according to an embodiment of the invention.  
           [0033]    The large air gap can be achieved particularly advantageously without any reduction in efficiency by using HTS (high-temperature superconductor) rotors. An air gap three-phase winding is particularly advantageous for this purpose. The use of an HTS rotor in this case has the particular advantage that it can be designed to be particularly small, and the stator windings are also correspondingly small. Thus, this may result in a very small electrical machine which can be designed to be explosion-proof and shock-proof without in the process being less efficient than conventional machines. The measures as described above (use of a motor with HTS technology, use of aluminum or plastic instead of steel) and the further measures mentioned in the following text make it possible, for example, to reduce the weight of a 7 MW steering propeller highly advantageously from about 120 t to about 65 t.  
           [0034]    A further advantageous refinement of an embodiment of the invention includes the vessel stern casing connection in the vessel stern having elastically deformable structural elements, for example highly flexible metal sheets, which form elastically deformable mount cells. This makes it possible to dissipate not only the explosion pressure forces which act on the stern of the vessel via the casing but also the explosion pressure waves which act directly on the stern of the vessel.  
           [0035]    A further refinement of an embodiment of the invention provides for the power supply lines for the electric motor to be designed without sliprings, for example in the form of a rotationally elastic cable run or a helical spread cable. The lack of a slipring body saves a considerable amount of weight on the steering propeller and, furthermore, this removes one possible fault source which should not be ignored in the event of severe movements, for example in the event of an explosion pressure wave. The lack of a slipring body admittedly restricts the capability to rotate the electrical steering propeller to 120 to 180°, but this is acceptable because the electrical steering propeller can be rotated back from extreme positions again and does not need to be rotated any further in the same rotation direction.  
           [0036]    A further refinement of an embodiment of the invention provides for the electrical steering propeller to have an auxiliary rudder, which can move independently of the position of the casing. Thus, in normal conditions, the casing can be fixed, with minor vessel direction changes being carried out by way of the auxiliary rudder.  
           [0037]    The auxiliary rudder may be arranged on the trailing edge of the casing in the same way as the elevator on an aircraft tailplane. However, its effect here is restricted since it is located in the vortex train behind the casing. It is particularly advantageous for the auxiliary rudder to be in the form of a side or leading-edge vane, particularly in conjunction with an asymmetric profile corresponding, in particular, to an airfoil profile. This results in the effect of the side or leading-edge vane being particularly good.  
           [0038]    A particularly resistant embodiment of the electric motor provides for the electric motor to be in two parts and to have two parts which can be operated independently of one another, in particular are supplied with power independently of one another, and for which open-loop and closed-loop control can be provided independently of one another. Each of these two electric motor parts may drive a propeller, thus resulting in redundantly operating electric motors and the capability to provide contrarotating propellers easily. This leads to an improvement in the efficiency of the propulsion system. An electric motor configuration such as this is particularly advantageous for relatively small navy vessels, such as high-speed boats.  
           [0039]    In order to save weight, an embodiment of the invention provides for the capability to rotate the casing and/or to move the auxiliary rudder by means of electric servomotors. This particularly advantageously results not only in the casing rotation apparatus being lightweight, but also in a particularly quiet casing rotation apparatus since there is no need for the hydraulic motors which otherwise run continuously. In this case, it is particularly advantageous that the electric servomotors allow specific ramp forms to be achieved easily during start-up and during swiveling to a desired nominal position. The turning movement of the vessel can thus be completed particularly quickly and controlled in a suitable manner.  
           [0040]    One particularly advantageous embodiment of an embodiment of the invention provides for the vessel stern casing connection to be designed to be elastic in a specific manner. A semi-universal-joint suspension for the casing or the use of spherical segments, in particular sprung spherical segments, to support the casing are advantageous for this purpose. Mounting the casing upper part in spherical segments in this case has the particular advantage that it is both robust and allows large flexing movements for the casing. Both semi-universal-joint suspension and the support of the casing via spherical segments are in this case achieved with the assistance of spring elements, for example elastomer or hydraulic cushions. These are advantageously supported horizontally and vertically on a moving mount structure, which also advantageously has steering elements. A defined movement can thus be achieved, with large flexing movements for the casing.  
           [0041]    Finally, one refinement of an embodiment of the invention also provides for the electric motor to be provided with windings which are shrunk in the motor housing, and with external wall cooling. This results in the motor gondola having a particularly small volume, with a small area for shockwaves to act on. In conjunction with the capability of the casing to move elastically, this thus results in an optimum configuration for the electrical steering propeller, which satisfies the requirements for an electrical steering propeller—lightweight, small, resistant to shocks—in a manner which has not been achieved in the past. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0042]    Further advantages, features and details of the invention will become evident from the description of illustrated embodiments given hereinbelow and the accompanying drawings, which are given by way of illustration only and thus are not limitative of the present invention, wherein:  
         [0043]    [0043]FIG. 1 shows an outline section through an HTS version of an electrical steering propeller,  
         [0044]    [0044]FIG. 2 shows an outline section through an electrical steering propeller with simplified movement decoupling,  
         [0045]    [0045]FIG. 3 shows an elastic coolant line in the motor,  
         [0046]    [0046]FIG. 4 shows a propulsion device, illustrated schematically in the form of a longitudinal section,  
         [0047]    [0047]FIG. 5 and FIG. 6 show a design refinement of the arrangement as shown in FIG. 4,  
         [0048]    [0048]FIG. 7 shows an overall view of an electrical steering propeller for a navy vessel from the side,  
         [0049]    [0049]FIG. 8 shows two steering propellers, as shown in FIG. 7, from astern,  
         [0050]    [0050]FIG. 9 shows the principle of spherical segment suspension for the electrical steering propeller,  
         [0051]    [0051]FIG. 10 shows the principle of universal-joint suspension of the electrical steering propeller;  
         [0052]    [0052]FIG. 11 shows the embodiment of a dividing joint between two casing parts, and  
         [0053]    [0053]FIG. 12 shows the embodiment of the electric motor in the form of an HTS motor. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0054]    In FIG. 1, 1 denotes the contour of the hull of the vessel, in which a steering propeller casing  2  is arranged such that it can rotate and can flex elastically. The propeller of the electrical steering propeller is annotated  3 , in this case being single traction or pusher propeller. One shaft end therefore advantageously remains free in the housing for the introduction of the coolant. The housing of the electrical steering propeller is annotated  4 , and rotor shaft  12  (which acts as the propulsion shaft at the same time) is arranged centrally in it, with bearings  5  and  7 .  
         [0055]    The compressor for a cooling unit  8  is arranged in the steering propeller casing  2 , for example on the upper part of the motor housing  23 , and is connected by way of a closed-cycle cooling system, which is not shown in any more detail, to the cooling system of the vessel or of the electrical steering propeller. A flexible compressed-gas feed and return line  9  is arranged between the compressor  8  and a cold head  10 , and feeds compressed gas to the cold head  10 . The cold head  10  is connected to a cryogenic coupling  11 , which is known per se and passes the coolant (which has been cooled down in the cold head) to the rotating cryogenic distributor  20 , from which it is passed via the flexible line  21  to the cryostat  15 .  
         [0056]    The superconducting winding  14 , in particular a high-temperature superconducting winding, is located in the vacuum-insulated rotor cryostat  15  and is connected to the hot rotor cryostat  15  via a torque transmission coupling  16  with low thermal conductivity. The rotor tube  24  is connected via damping elements  17  to the shaft  12  of the electrical steering propeller, and is supported via bearings  19  on the end flange of the housing  23 . The stator  13  is located externally in the housing  23 , and a relatively large air gap  22  is formed between it and the rotor  18 .  
         [0057]    The air gap is of such a size as to ensure that elastic deformation of the rotor  18  and/or of the stator  13  as well as the bearing plate of the bearing  19  remain less, overall, than their movements under the influence of shock. This therefore ensures correct operation even in the event of an underwater explosion, for example directly underneath the electrical steering propeller.  
         [0058]    The rotor tube  24  is connected to the rotor shaft  12  via damper  17 , with the same dampers as those between the rotor tube and the housing advantageously being used here. Overall, this results in a solution with very low cold losses, and with good shock resistance at the same time.  
         [0059]    The high ampere-turns figure which can be achieved with superconducting windings is utilized in FIG. 2, which shows a simplified embodiment, in which individual parts of the machine correspond to those in FIG. 1 and are therefore not shown again. The rotor requires only a small conductor mass and can be designed with little iron, or no iron. Shock forces on the small mass of the rotor are then small, or comparable with forces that occur during operation.  
         [0060]    The rotor is connected to the shaft without any damping; the cryogenic coupling is connected to the coolant area via a rigid, vacuum-insulated line. The heavy stator and the cryogenic cooler are suspended via dampers  25 , with only one flexible connection  26  being required for the cold head-cryogenic coupling. The air gap  27  between the rotor and the air gap stator winding is in this case chosen to be sufficiently large, up to 50 mm, that the rotor and the stator  28 ,  29  do not touch even in the event of the maximum shock load. This results in a particularly lightweight, simple embodiment of the superconducting machine.  
         [0061]    [0061]FIG. 3 shows a flexible coolant line as is required, for example, for the machine. There is a vacuum  31  in a double-walled housing  30 , and this continues between the two flexible coolant line parts  33  and  34 . These flexible coolant parts are connected via flanges  35 ,  36  to the walls which enclose the coolant  32 . Overall, this results in a simple embodiment, which allows only minor heat losses, for a coolant line.  
         [0062]    [0062]FIG. 4 shows the propulsion shaft  101  of an electric-motor propulsion device  100  for a vessel, with the propulsion shaft being fitted with one propeller  102  and  103  at each end. Only the upper half of the electric motor which drives the propulsion shaft  101  is illustrated, in the form of a section. This electric motor comprises a rotor  104  and a stator  105 , with the rotor having an electrically active layer  106  in the form of permanent magnets, and being arranged on a tube-like mounting body  107 . The stator  105  has a mounting housing  108  with two or more parts and which is fixed via rotating bearings  109  on the mounting body  107  of the rotor.  
         [0063]    The unit including the rotor  105  and the stator  106  is supported by means of elastic damping elements  110  and  111  firstly on the propulsion shaft  101  and secondly on a housing  112  which holds the electric motor and the propulsion shaft. The propulsion shaft  101  is in this case mounted in the housing  112  via rotating bearings  113 .  
         [0064]    The housing  112  has an associated mounting casing  114  for attaching the propulsion device  100  to the hull of the vessel. The mounting casing  114  may have a double-walled configuration or may be provided with cooling channels  16  which surround it vertically, for example in order to carry cooling air.  
         [0065]    In order to cool the stator  105 , in particular the end windings  115 , cooling air, for example, may be fed from the mounting casing  114  at one end of the electric motor into the internal space between the mounting housing  108  and the mounting body  107 , and can be carried away at the other end of the electric motor. The cooling air could flow within the electric motor between the electrically active layer  106  of the rotor and the mounting body  107  in the axial direction. The stator housing  108  could have flow channels for cooling the stator and the stator windings, through which cooling water that is supplied from the mounting casing  114  flows.  
         [0066]    As is illustrated in FIG. 5 and in the somewhat enlarged detail in FIG. 6, the electric motor including the rotor  124  and stator  125  is arranged in a streamlined housing  132 , which can be positioned by means of the mounting casing  139  like a gondola underneath the hull of a vessel. The mounting housing  128  for the stator is fixed to the mounting body  127  for the rotor  124  via rotating bearings  129  which are in the form of inclined roller bearings. This supporting body is elastically supported via damping elements  130  on the propulsion shaft  121 . The damping elements  130  are in this case fixed axially on annular flanges  118  and  119 .  
         [0067]    The mounting housing  128  for the stator is supported via damping elements  131  on the housing  132 . These damping elements each comprise a rubber body  117 , which is mechanically coupled via bolts  135 ,  136  to the mounting body  128  and to the housing  132 .  
         [0068]    The propulsion shaft  121 , to which the rotor is fitted, is mounted in the housing  132  by way of sliding bearings  133  and  134 . The sliding bearings are in this case sealed from the surrounding water by way of sealing devices  137 ,  138 .  
         [0069]    In FIG. 7, 201,  202  and  203  respectively denote the propeller end, the center part and the stern end of the motor gondola which forms the housing for the electric motor. The propeller is annotated  204 , and is preferably in the form of a traction propeller. The stator winding  205  as well as the rotor winding  206  are located in the motor gondola preferably being designed for direct heat dissipation via the surface. This is preferably composed of HTS material.  
         [0070]    There is a large air gap  207  between the stator winding  205  and the rotor winding  206 . The bearings which are provided for the rotor shaft, preferably sliding bearings which absorb the radial and axial forces of the rotor and of the propeller, are not shown, for the sake of simplicity; this also applies to other components in the motor gondola.  
         [0071]    The bottom of the hull section of the vessel is annotated  208  and  209 . The bottom of the hull structure in the areas  208  and  209  is designed conventionally. An elastically flexible structure  211 ,  212  is located between the parts  208  and  209  and, in its center, has a hollow body  210  which forms the extension of the uppermost casing part  215 .  
         [0072]    The hollow body  210  is mounted elastically and such that it can move with respect to the elastic structural parts  211 ,  212  via springs, for example rubber buffers  215 . A sprung structure  213  is arranged on its upper face, is preferably composed of metal and allows a long spring movement. Thus, if a torpedo explodes under the electrical steering propeller, the steering propeller can move vertically to a considerable extent, dissipating the acceleration caused by the explosion pressure waves. The illustrated design allows both vertical and horizontal/vertical flexing with considerable flexing movements.  
         [0073]    The mounting casing for the motor gondola is designed in at least two parts and has the parts  216  and  217 . An elastic flange connection  218  is arranged between them and can act as an articulated joint. In this example, the casing including the parts  216  and  217  is shown as having only two parts. However, it may likewise also have further parts.  
         [0074]    The casing part  216 , to which an auxiliary rudder  219  can also be attached, is preferably composed of fiber-reinforced plastic material, while the casing part  217  is composed of aluminum, for example in the same way as the center part  202  of the motor gondola. The gondola part  201  is preferably composed of steel in order to make it possible to absorb the considerable bearing forces that occur there, while the end part  203  may likewise advantageously be composed of fiber-reinforced plastic, in order to save weight. Cooling channels are in this case advantageously incorporated in this part, through which a cooling liquid flows.  
         [0075]    In FIG. 8, which shows two steering propellers arranged alongside one another (that is to say the propulsion units for a two-screw vessel) from astern,  222  and  223  denote the propellers of the two propulsion systems. The casings on which the two propulsion systems are suspended have at least one flange arrangement  224 , which is used as an articulated joint, on the upper part. In principle, the electrical steering propellers are suspended in the same way as that shown in FIG. 7, with a hollow body  221  in the center which can move axially and horizontally between rubber buffers and steel spring structure  220 . The structural unit  225 , which can move elastically, in this case increases the movement capability.  
         [0076]    The design configuration of the steering propellers, which can move horizontally and vertically and are suspended such that they can absorb shocks, as shown in FIGS. 7 and 8 is only schematic and by way of example. It is self-evident that appropriate variations matched to specific requirements are possible here. FIGS. 9 and 10 show two further possible solutions, with FIG. 9 showing the upper part of the electrical steering propeller casing being suspended in spherical sections, and FIG. 10 showing a corresponding suspension based on a universal joint.  
         [0077]    In FIG. 9, 226 denotes the casing that is shown for the electrical steering propeller, which is mounted in a frame  227  and is located in the stern of the vessel and is connected to the structural elements of the stern. Spherical section parts  229  are arranged between the frame  227  and the casing head  226  and are mounted in spring elements  228 , for example cup springs. The frame  227  is likewise advantageously mounted in a sprung manner in the structural elements of the stern. This results in the casing being suspended in such a way that it can flex equally in all directions. The capability to flex equally in all directions is also provided by the design in FIG. 10.  
         [0078]    In this case, the casing head  232  is connected via bolts  231 ,  233  to the frame  230 , which is mounted in the structural elements of the stern. This is also advantageously sprung. For longitudinal and lateral guidance, the casing for the stern propellers (which are suspended in accordance with the principle illustrated in FIG. 9 and FIG. 10) also has supporting guides, although these are not illustrated.  
         [0079]    [0079]FIG. 11 shows the principle of an elastic joint, which is in the form of an articulated joint, between two casing parts. The two flanges  236 ,  237  have a layer between them formed, for example, from a multilayer and fiber-reinforced elastomer material. On the outside, the flange area is protected by elastic bellows elements  239 , which also extend over the screw heads  234  and are advantageously attached to the casing, which is not illustrated, by way of flexible sleeves.  
         [0080]    In addition, underneath the screw heads  234 , there are also, for example, cup springs  235  so that the joint can “give” briefly when a shock wave occurs. This results from the fact that the collars  239  are arranged externally, without water being able to enter the interior of the casing. In the same way that the collars  239  are arranged externally, they can also be arranged internally, thus producing a double seal.  
         [0081]    [0081]FIG. 12 shows an example of how an HTS motor is accommodated in a steering propeller.  240  in this case denotes the HTS winding, and  41  the rotor cryostat.  242  denotes the air gap winding and  243  the iron yoke.  246  denotes the cooling compressor with its coolant. Liquid coolant passes from the coolant compressor  246  to the cold head  245 . The so-called “cryogenic heatpipe”  244  leads from here to the rotor cryostat  241 . The electrical lines to the stator  242  are annotated  247 .  
         [0082]    The suspension systems that are shown in FIGS.  4  to  10  are only one possibility from a large number of possible designs. These designs always have the common feature that the casing can flex in response to explosion pressure waves in order in this way to compensate for the considerable pressure waves that are caused by an exploding torpedo or a mine and produce accelerations of more than 100 g for parts of the vessel, and to dissipate the pressure waves without any adverse effect on operation.  
         [0083]    Exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.