Abstract: Techniques are disclosed for providing retractable control fins on an underwater vehicle. The retractable control fins can be extended away from a main hull portion of the underwater vehicle and retracted inwards to a stowage region within the hull portion to protect the fins from damage and reduce an overall outer diameter (e.g., in the case of a cylindrical body) of the underwater vehicle. In some embodiments, the control fins are folded inwards to reduce the vehicle diameter. In other embodiments, the control fins are pulled inwards using a rotating structure designed to slide the control fins through an opening and into an inner portion of the hull to reduce the vehicle diameter. The retraction of the fins through the various retraction mechanisms reduces the envelope diameter of the underwater vehicle.

Abstract: Techniques are disclosed for providing retractable control fins on an underwater vehicle. The retractable control fins can be extended away from a main hull portion of the underwater vehicle and retracted inwards to a stowage region within the hull portion to protect the fins from damage and reduce an overall outer diameter (e.g., in the case of a cylindrical body) of the underwater vehicle. In some embodiments, the control fins are folded inwards to reduce the vehicle diameter. In other embodiments, the control fins are pulled inwards using a rotating structure designed to slide the control fins through an opening and into an inner portion of the hull to reduce the vehicle diameter. The retraction of the fins through the various retraction mechanisms reduces the envelope diameter of the underwater vehicle.

Abstract: In one embodiment, a return flux linear alternator employs a magnet assembly that includes a pair of permanent ring magnets with opposing polarity and a pair of air gaps. The additional permanent ring and air gap complete a magnetic flux loop of the alternator rather than the magnet pole, as in traditional designs. An alternator coil assembly includes a pair of oppositely wound coil sections that each linearly move through a respective one of the pair of air gaps. In addition, the return flux linear alternator may employ a variety of structures to increase mechanical strength, including a reinforcement fabric, and a variety of structures to increase electrical efficiency, including a thermally conductive but electrically nonconductive spacer between the coil sections and multiple pairs of electrical leads.