Abstract: The hull of a submerged sea craft adjacent its stern end is provided with auxiliary facilities for controlled maneuvering operations under low speed conditions, including steering, stopping and negative thrust backing performed independently of main propulsion of the craft. The auxiliary maneuvering control facilities include a curved channel pipe connected to two angularly related sub-channel pipe sections for selectively controlled outflow of fluid which is pressurized by a maneuvering control pump within the curved channel pipe before outflow through exit openings in the hull in different directions, as negative angle thrust jets and as steering control jets perpendicular to the hull centerline. By use of a sub-channel flow diverting flapper and gate valves at the inlet and exit outlet openings in the hull, all of the maneuvering operations may be performed under selective control.

Abstract: Forward underwater movement of a sea craft at a high speed induced by propulsion thereof is decelerated and stopped by projection of drag devices, mounted on a fully submerged underwater sea craft hull, from retracted positions within said sea craft hull or the steering rudders positioned thereon. Each of the drag devices has an elongated drag plate with an end surface cap flush with the outer surface of the hull or the steering rudder in the retracted position of the drag device.

Abstract: A movable ramp, forming part of the inlet flow channel of a water jet prosion system, is adjustable to provide variable inlet area for various speed and propulsion requirements. In this flush or semi-flush type inlet, the lower lip is stationary and an upper ramp, forming an extension of the base-line shell, directs the flow into the inlet. If the baseline shell is not suited to the inlet installation, (for example, if a high deadrise angle exists) a forebody fairing is provided to make the baseline shell geometry suitable. The ramp is flexible, has a smooth surface, and is backed up by bell cranks and pusher bars that can move the ramp position to change the inlet area. The ramp position or inlet area may be adjusted manually or automatically to meet the requirements of speed and propulsion. If the centerline of the lip leading edge radius falls below the normal baseline (semi-flush inlet) suitably shaped "sideplates" are provided to avoid inlet cavitation or ventilation at yawed conditions.