SUBMERSIBLE JOHNSON-SEA-LINK (JSL) I AND II
The Johnson-Sea-Link (JSL) I and II are owned and operated by HARBOR BRANCH Oceanographic Institution (HARBOR BRANCH). At 23.6 ft long, 10.9 ft high and 8.3 ft wide, these highly maneuverable submersibles can dive to a depth of 3,000 ft and travel at a maximum speed of one knot. Edwin Albert Link, engineer, inventor, and friend of HARBOR BRANCH founder Seward Johnson, working at HARBOR BRANCH, designed and built the JSL in 1971, at Mr. Johnson's request. HARBOR BRANCH constructed the JSL II, which is virtually identical to the JSL I, in 1975.
The JSL has two separate pressure hulls and can accommodate four people. Aft compartment occupants enter the sub through a bottom-facing 20 inch-wide hatch. The front chamber, which contains the sub's controls, is a 5-ft-diameter sphere made of five-in thick, clear acrylic. It provides a panoramic view for the pilot and one observer. Because acrylic is a good insulator and hampers conductivity of cold ocean temperatures, the front compartment actually requires air conditioning. The second chamber, the stern compartment, houses another crewmember and a second observer. The occupants have access to two side view ports and a video monitor.
Deployment and Utility
The JSL is deployed from HARBOR BRANCH's R/V Seward Johnson, which is equipped with an A-frame crane on the stern. In the span of five minutes, three crewmembers can launch the sub. The A-frame operator lifts the sub from deck and places it into the water, a process supervised by the submersible operations coordinator, who remains in contact with the crewmember operating the ship. Another crewmember handles the crane's lines. Recovering the sub requires the help of one additional crewmember - a swimmer, who attaches the towline to the emerged sub - but generally takes the same amount of time as deployment.
The JSL can be deployed even in moderately rough sea conditions with 3- to 6-ft waves, but the decision to deploy can be subjective. For instance, the submersible operations coordinator may decide not to deploy the sub if waves are coming in both directions, which is known as a "confused sea," or if swells are detected under the surface. The ship's captain is responsible for making the final decision.
The JSL is highly flexible and adaptable. It is used to study both the mid- and deep-water realms, inspect dump sites, perform search and recovery tasks, and conduct underwater archeological missions. A typical dive lasts for about 4 hours. The sub can hover in midwater and rest on the sea floor to allow researchers to make observations and collect samples. It is highly maneuverable and can navigate around underwater slopes and other tricky bottom typography.
The JSL is equipped with an active sonar system and HARBOR BRANCH-developed xenon arc lights. The lights illuminate underwater scenes in "true color," resembling daylight conditions. In addition to its permanent equipment, the JSL can be fitted with other equipment that a researcher may need. It takes time, however, to install the equipment and ensure that it will interact properly with other aspects of the sub. Alternative equipment also must be tested and certified to withstand the pressure of the deep sea.
Researchers vary in their choices of additional equipment, depending on their specific research goals. For instance, alternative sampling devices can collect tube worms, hydrate samples, jellyfish or other creatures. Researchers also may choose to install an insulated sample basket to protect a sample from rising water temperature as it is brought to the surface (in some areas the water temperature differential between 3,000 ft and the surface can be more than 35 F). Also, in many cases, HARBOR BRANCH engineers are often called upon to custom design, fabricate and install new tools and equipment for scientific investigators.
Notable Submersible Missions
In 1977 NOAA and the Navy began the first of several surveys of the wreck of the Civil War ironclad USS Monitor using the HARBOR BRANCH submersible Johnson-Sea-Link. The Monitor, which sank about 16 miles south southeast of Cape Hatteras, NC, was located in 1974 but it wasn't until the JSLs were used in 1977 that artifacts from the ship could begin to be recovered. At that time, the JSL subs were equipped for lockout diving, which allowed divers to exit the sub to examine and survey the wreck up close. Submersible-based surveys have been repeated numerous times since then under the auspices of NOAA's National Marine Sanctuary program. These surveys contributed the foundational work that is now making possible the recovery of the principal components of the Monitor, such as the engine, the main gun turret and numerous other artifacts.
Space Shuttle Challenger
The image remains etched in the minds of most people who saw the tragedy unfold on live television: the trail of smoke interrupted and ended by the flash of the explosion that consumed the Space Shuttle Challenger.
Soon after the tragedy, HARBOR BRANCH's highly capable subs and pilots were enlisted in the mission to recover any and all pieces that could help the investigating authorities determine what had caused the explosion. The superior panoramic view afforded from the clear, acrylic passenger compartment, along with the sub crew's experience operating a vehicle that was designed to overcome the formidable Florida Current, gave the JSL submersibles distinct advantages over other deployed salvage assets. These advantages were immediately demonstrated, when on its second dive, the JSL found the booster rocket containing a faulty seal. This early find enabled the disaster investigators to quickly establish the probable cause of the explosion.