Stable Platforms for the Launch and recovery of Submersibles

Abstract A new type of platoon has been developed from which submersible vehicles can be safely launched, recovered, and transported in heavy seas. An unpowered catamaran, this platoon offers unique advantages over conventional techniques by performing its functions while submerged below surface disturbances. To date, two such systems have been successfully operated with various submersibles in the Hawaiian Islands and off the coast of Southern California. Additional applications for this concept are seen in such areas as salvage, construction, and offshore oil recovery. Introduction Launching and recovering submersibles through the ocean interface has historically been a serious problem, particularly in rough seas. The lack of a safe, efficient, and economical means of handling these fragile vehicles is one of the reasons that the majority of them are currently not in use. Characteristically, the methods commonly employed for launching and recovering submersibles fall into three categories; (1) cranes on board a mother ship, (2) special purpose ships, and (3) towing directly to and from dive sites. While it is not the purpose of this paper to evaluate these methods, it can safely be stated that as seas approach state 3, all of the currently employed techniques begin to break down with resulting hazards to equipment and personnel or cancellation of operations altogether. A seemingly ideal solution to most of the problems associated with current handling techniques would be to use a large submarine which could travel great distances to and from a dive site if necessary, sink below all surface turbulence, and launch and recover a deep submersible vehicle (DSV) while underwater. Although this does not eliminate the very real problem of recovering a disabled submersible on the surface, it is mainly the economics of such a vessel which precludes any serious consideration of the method at present. An attractive compromise to this "solution" is the use of a simple, un powered platfonn which can act as a stable base for transporting submersibles and which can hover below the surface for their safe launch and recovery. Such a launch and recovery platform has been developed in Hawaii and utilized successfully for over 2 years in rough Hawaiian waters. Called the LRT for "Launch, Recovery, and Transport," it not only reduces the cost of handling deep submersibles, but also improves the reliability of operation in high sea states, thereby making the submersible, itself, more cost effective. Design Requirements A number of essential design requirements were initially established for the LRT platoon and may be summarized as follows:(available in full paper)