United States Navy Experimental Diving Unit The United States Navy Experimental Diving Unit dures for rescue operations.[2] (NEDU or NAVXDIVINGU) is the primary source of diving and hyperbaric operational guidance for the US [1][2][3] Navy. It is located within the Naval Support Ac- 2.2 Washington Navy Yard tivity Panama City in Panama City Beach, Bay County, Florida.[3] NEDU was established in 1927 at the Washington Navy Yard.[1][2] 1 Mission and vision NEDU describes its mission as: “The Navy Experimen- tal Diving Unit tests and evaluates diving, hyperbaric, and other life-support systems and procedures, and con- ducts research and development in biomedical and en- vironmental physiology. NEDU provides technical rec- ommendations based upon knowledge and experience, to Commander, Naval Sea Systems Command to support operational requirements of our armed forces.”[3] The vision for NEDU is stated to be: “The Navy Ex- perimental Diving Unit will be the most credible and re- spected research, development, and test and evaluation center for diving as well as the focal point of leadership for biomedical and bioengineering solutions for undersea military operations.”[3] 2 History A Momsen lung in use during training 2.1 Brooklyn Navy Yard Early developments for the unit involved evaluation and Experimental diving in the US Navy started in 1912 at testing of the Submarine Escape Lung (Momsen lung) the Brooklyn Navy Yard under the leadership of Chief and the McCann Rescue Bell.[2] This work was done by Gunner George D. Stillson.[1] Stillson’s research program Charles Momsen and Allan McCann. In 1929, Momsen ultimately led to increasing diver capabilities from 60 received the Navy Distinguished Service Medal for per- feet (18 m) to over 300 feet (91 m) of depth based sonally testing the device at a depth of 200 feet (61 m). on Haldane’s decompression work with the Royal Navy. Techniques used for the rescue of submariners aboard the This resulted in the first publication of the United States USS Squalus were developed by Momsen and McCann in Navy Diving Manual and established the need for a fa- their time at NEDU.[2][6][7] This work lead to the rescue cility dedicated to research and development of diving and recovery of 33 crewmen.[6] Momsen and McCann procedures.[1][4][5] received a Letter of Commendation from President of the United States Franklin D. Roosevelt for the Squalus In 1915, Stillson’s team was sent to salvage the F-4 sub- [6] marine. On these deep dives, the divers experienced the effort. debilitating effects of nitrogen narcosis leading them to The first medical staff were introduced to the facil- try the addition of helium to their breathing mix.[2] The ity in the mid-1930s when Charles W Shilling, Albert navy salvage operations then came under the direction of R Behnke, and OE Van der Aue began work. Their Warrant Gunner C. L. Tibbals who led teams through the early work improved the prevention and treatment of salvage of the S-51 in 1925 and S-4 in 1927 further estab- decompression sickness with the inclusion of oxygen lishing the naval need for equipment, training, and proce- rather than air.[1][8][9] 1 2 3 FACILITIES Through World War II, work continued on decompres- biomedical and development group was transferred to sion and oxygen toxicity.[10][11] NEDU.[1][26] Through the 1950s NEDU tested equipment and further In response to the overseas military needs, NEDU fo- refined procedures for divers including the US Navy 1953 cused on warm water diving from 1999 to 2002.[27] This decompression table.[12][13] guidance to the Naval Special Warfare community influ- [1] From 1957 to 1962 was the beginnings of saturation div- ences operational needs on an ongoing basis. ing under the leadership of Captain George F. Bond of NEDU divers were essential to the recovery of artifacts the Naval Submarine Medical Research Laboratory and from the ex-USS Monitor in 2001 and 2002.[1][28] [1][14] the Genesis Project. Genesis D was performed at In 2002, certification of the Mark 16 Mod 1 rebreather NEDU in 1963.[1][15] Bond then went on to head the [16] was completed following improvement of systems in- SEALAB I saturation project in 1964. cluding, extension of the working limit to 300 feet (91 Robert D. Workman published a novel method to m), new decompression tables for both nitrogen-oxygen calculate decompression schedules in 1965 that in- and helium-oxygen diving including new repetitive div- volved estimating the limiting values of excess tissue ing capabilities for helium-oxygen, test of an Emergency supersaturation.[17] Breathing System with communications, the addition of an integrated buoyancy compensation device, and an im- Work continued in deep saturation dives, equipment test- [1][29] ing as well as thermal protection and physiology research proved full face mask. throughout the 1960s and early 1970s. 2.3 Naval Support Activity Panama City In 1975, NEDU relocated to its current location in Panama City, Florida.[1] SEALs using SEAL Delivery Vehicle In 2004, NEDU contributed to operational guidance for diving in harsh contaminated environments.[30] NEDU has continued research into oxygen toxicity uti- lizing the US Navy Mark 16 Mod 1.[31][32] Development of breathing systems, thermal protection, and decompression procedures for SEAL Delivery Ve- hicles and the Advanced SEAL Delivery System is US Navy Diver using Kirby Morgan 37 diving helmet ongoing.[33][34] In 2011, divers completed a 1,000 fsw saturation dive to NEDU tested and evaluated the replacement of Stillson’s evaluate the new Navy’s Saturation Fly-Away Diving Sys- Mark V as the US Navy standard diving dress, the Mark tem (SAT FADS).[35] The SAT FADS was designed in 12 Surface Supplied Diving System, and eventually its re- 2006 as a portable replacement of two decommissioned placement the Mark 21/ Superlight 17 in the 1970s and Pigeon-class submarine rescue vessels.[35] 1980s.[1][18][19] Evaluation and testing of new breathing apparatus and ap- NEDU conducts at least one saturation dive per year. plication of other technologies for diving is key to their These dives were used, amongst other things, to evalu- mission.[36][37] ate decompression and recompression procedures, equip- ment, carbon dioxide absorbents, as well as active and passive thermal protection.[20][21][22] Many of these tests included ongoing evaluations of commercially available diving equipment.[23][24][25] 3 Facilities In 1998, the Naval Medical Research Center’s diving 3.3 Environmental chamber 3 NEDU experimental test pool (4.6 m) by 30 ft (9.1 m) by 15 ft (4.6 m) deep, capable of sustaining temperatures from 34 to 105 °F (1 to 41 °C). It is designed and constructed for manned, shallow wa- ter testing and for supporting workup dives for the Ocean Simulation Facility. The test pool is supported by a fully instrumented medical and engineering deck, from which the safety of both divers and test equipment can be moni- tored. The facility can accommodate a wide range of ex- periments, from biomedical studies of diver thermal and workload conditions to equipment studies of submersible devices. The test pool has a communications suite, full video capability, real-time computerized data acquisition NEDU Ocean Simulation Facility and analysis, and pressure and gas monitoring.[39] The depth is sufficient to allow divers to maintain an oxy- 3.1 Ocean simulation facility gen partial pressure of 1.3 bar on their breathing appara- tus while immersed and riding a bicycle ergometer.[31][32] The Ocean Simulation Facility (OSF) simulates ocean conditions to a maximum pressure equivalent of 2,250 feet (690 m) seawater (fsw) at any salinity level. 3.3 Environmental chamber The chamber complex consists of a 55,000-US-gallon (210,000 L) wet chamber and five interconnected dry liv- ing/working chambers totaling 3,300 cubic feet (93 m3) of space. Wet and dry chamber temperatures can be set from 28 to 104 °F (−2 to 40 °C). Equipped with the lat- est data acquisition capability, the OSF can accommo- date a wide range of complex experiments including diver biomedical studies and testing of humans as well as small submersible vehicles and other machines in the wet cham- ber. Saturation dives can be performed for more than 30 days of continuous exposure in the OSF. For human and equipment testing underwater over extended periods, divers use the dry chambers as comfortable living quar- ters, from which they can make diving excursions into the wet chamber. The dry chambers are also capable of altitude simulation studies to heights of 150,000 feet NEDU environmental chamber (46,000 m).[38] The Environmental Chamber is capable of simulating a broad range of temperatures from 0 to 130 °F (−18 to 54 3.2 Experimental test pool °C), humidity from 5 to 95%, and wind velocity from 0 to 20 mph (0 to 32 km/h). The chamber is instrumented The Experimental Test Pool is a 50,000-US-gallon to conduct physiological studies and to test various types (190,000 L) capacity freshwater tank measuring 15 ft of equipment.[40] 4 4 PERSONNEL 3.4 Experimental diving facility NEDU gas analysis lab 3.6 Gas analysis lab NEDU experimental diving facility The gas analysis laboratory is equipped for the pre- cise analysis of gases, and it is used to evaluate diving- The Experimental Diving Facility (EDF) simulates un- related problems such as offgassing and contaminant con- manned pressure conditions to 1,640 feet (500 m) sea trol. The laboratory’s analytical capabilities include gas water and temperatures can be set from 28 to 110 °F chromatography, mass spectrometry, and infrared spec- (−2 to 43 °C).