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Special Operation Forces must be able to launch and recover quickly and covertly. When launching from larger ships, these ships must stop and conduct launch operations using on board davits, cranes or similar systems. This launch approach; exposes forces to enemy detection, alerts the enemy that potential forces are being deployed, takes valuable time and can be extremely dependent on sea states for safety. Recovery, while not as essential does require speed and should not expose forces to enemy action. The problem being addressed in this proposal is to provide a methodology to launch and recover craft and personnel quickly, safely and easily while underway in heavy sea conditions. It will also address the system potential payload limits. The primary technical issue for large ships is deployment off a high deck when dead in the water (DIW). This exposes deployment to the ships motions which are exaggerated when the ship is DIW.
The Soft Rail system operates under two basic rail configurations, a single cable and a double cable design. The single rail configuration is designed primarily for launching small UUVs, jet skis or smaller sized payloads. Most combatant-type launches of vessels greater than 10,000 lbs would likely require the heavier lifting capacity of the double cable configuration. The launch and recovery scenario described in this report will focus on the double rail configuration, since it has more widespread application and will prove both system concepts. The basic approach and methodology of Soft Rail applies to both systems with some distinctive changes in the drogue depressor design.
In a Soft Rail launch and recovery operation, the combat support craft is launched from the ship using cables trailing from the fantail. These cables are constructed of high-strength polyethylene rope approximately 2 inches in diameter. Tension is developed in the cables by the ship’s forward movement or thrust by towing a specially designed drogue device underwater by the two soft rail cables. The drogue is a small-modified trawl net that is easy to deploy and retrieve but yet will achieve high drag forces and high tension in the Soft Rail Cables.
The Drogue is fabricated of netting material and is attached to dive wing. The Drogue is depressed by a specially designed steel wing. This steel wing or depressor provides stability to the drogue and causes it to maintain a prescribed depth to avoid the turbulence of the ocean surface and the ship’s propeller. The drag on the net creates high tension in the cable causing the cables to become extremely rigid and rail-like. The Soft Rail system takes advantage of the rail-like characteristic of the cable to provide a means of transferring equipment from the decks of ships to the water. Combat or other types of craft can be launched from ships simply by sliding down the rails on specially designed slings. For the single rail system there are two small drogues each with a depressor/ deflector. These split at a rail location yoke above the water line and one drogue deploys to the starboard and one to the port. This keeps the launch vessel clear from the Soft Rail cable during water entry.
The Soft Rail launch and recovery system using a 2-rail approach is shown. The combat support craft is placed in a sling-ride cradle that traverses the cables and carries the craft to the water. Once at the water surface, the vessel automatically releases itself as the sling ride goes underwater. This is similar to the action that occurs when launching a boat from a trailer. The Sling ride stops on the rails when it is underwater by stops on the cable rails themselves. Upon release, the craft operates under its own power. The Sling ride is then retrieved by the launch ship by hauling in on a messenger line sent down with the sling ride unit.
For a detailed presentation on Soft Rail, please click through to the location below (SlideShare.net):