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A jet propulsion system for a submersible vehicle, such as a submarine includes a propulsion unit mounted away from the stern of the submersible. Generally, the propulsion system consists of a set of blades secured to a hub within a shroud. Combining such a propulsion system with a surface texture t

A jet propulsion system for a submersible vehicle, such as a submarine includes a propulsion unit mounted away from the stern of the submersible. Generally, the propulsion system consists of a set of blades secured to a hub within a shroud. Combining such a propulsion system with a surface texture treatment greatly reduces overall drag while improving the submersible's efficiency. Further, such an arrangement contributes to the submersibles stealthy characteristics. An additional hub and set of high-speed blades capable of generating a supercavity may be added to achieve supercavitation. The propulsion system can be varied to include a pumpjet and/or a centrifugal force blade system.

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A jet propulsion system for a submersible vehicle, such as a submarine includes a propulsion unit mounted away from the stern of the submersible. Generally, the propulsion system consists of a set of blades secured to a hub within a shroud. Combining such a propulsion system with a surface texture t

A jet propulsion system for a submersible vehicle, such as a submarine includes a propulsion unit mounted away from the stern of the submersible. Generally, the propulsion system consists of a set of blades secured to a hub within a shroud. Combining such a propulsion system with a surface texture treatment greatly reduces overall drag while improving the submersible's efficiency. Further, such an arrangement contributes to the submersibles stealthy characteristics. An additional hub and set of high-speed blades capable of generating a supercavity may be added to achieve supercavitation. The propulsion system can be varied to include a pumpjet and/or a centrifugal force blade system. (3) attached to said valve main body (1), a needle (2), inserted in said needle fit/insert aperture (16), for adjusting the flow path area of said refrigerant flow path (9), and for zoning said refrigerant flow path (9) into a refrigerant introduction portion (11) and a refrigerant withdrawal portion (12), and electrically operated means (X) for driving said needle (2), wherein said valve main body (1) on the other side of said needle fit/insert aperture (16) is positioned in an internal space (30) of said casing (3), while at least a part of said electrically operated means (X) is housed in said internal space (30) of said casing (3); and wherein said valve main body (1) is provided with refrigerant flow amount lowering means (P) that allows a refrigerant to follow between said refrigerant introduction portion (11) of said refrigerant flow path (9) and said internal space (30) in two opposite directions without flowing through a needle fit/insert clearance (17), so as to lower the amount of flow of a refrigerant flowing into said internal space (30) from said refrigerant flow path (9) through said needle fit/insert clearance (17) formed between said needle fit/insert aperture (16) and said needle (2). 2. The refrigerating circuit electrically operated needle valve of claim 1, wherein said refrigerant flow amount lowering means (P) is a refrigerant flow path (41) which is formed in said valve main body (1) so as to establish another communication between said refrigerant flow path (9) and said internal space (30) independently of said needle fit/insert aperture (16). 3. An electrically operated needle valve for a refrigerating circuit, comprising a valve main body (1) having a needle fit/insert aperture (16) and a refrigerant flow path (9) to which one end of said needle fit/insert aperture (16) opens, a casing (3) attached to said valve main body (1), a needle (2), inserted in said needle fit/insert aperture (16), for adjusting the flow path area of said refrigerant flow path (9), and electrically operated means (X) for driving said needle (2), wherein said valve main body (1) on the other side of said needle fit/insert aperture (16) is positioned in an internal space (30) of said casing (3), while at least a part of said electrically operated means (X) is housed in said internal space (30) of said casing (3); wherein said valve main body (1) is provided with refrigerant flow amount lowering means (P) for lowering the amount of flow of a refrigerant flowing into said internal space (30) from said refrigerant flow path (9) through a needle fit/insert clearance (17) formed between said needle fit/insert aperture (16) and said needle (2); wherein said needle fit/insert aperture (16) comprises a larger diameter aperture portion (16A) located nearer to said refrigerant flow path (9) and a smaller diameter aperture portion (16B), located nearer to said electrically operated means (X), for movably supporting said needle (2); and wherein said refrigerant flow amount lowering means (P) comprises a pressure equalization aperture (18) which is formed in said valve main body (1) so as to establish another communication between said larger diameter aperture portion (16A) and said internal space (30) independently of said smaller diameter aperture portion (16B), and said larger diameter aperture portion (16A). 4. The refrigerating circuit electrically operated needle valve of claim 3, wherein said larger diameter aperture portion (16A) is provided with a needle guide member (42) which, while movably supporting said needle (2), allows refrigerant circulation in the axial direction of said larger diameter aperture portion (16A). 5. The refrigerating circuit electrically operated needle valve of claim 3 or claim 4, wherein said valve main body (1) comprises a base portion (1A) including said refrigerant flow path (9) and a secondary portion (1B) which is a separated portion from said base portion (1A); and wherei