Navy Experimental Diving Unit | |
---|---|
Active | 1927 |
Country | United States of America |
Branch | United States Navy |
Role | NEDU is the primary source of diving and hyperbaric operational guidance for the US Navy. |
Size | 120+ |
Part of | U.S. Naval Sea Systems Command (NAVSEA) |
Garrison/HQ | US Naval Support Activity, Panama City Beach, Florida |
Commanders | |
Current commander | Commander Dustin Cunningham |
The United States Navy Experimental Diving Unit (NEDU or NAVXDIVINGU) is the primary source of diving and hyperbaric operational guidance for the US Navy. [1] [2] [3] It is located within the Naval Support Activity Panama City in Panama City Beach, Bay County, Florida. [3]
The functions of the Navy Experimental Diving Unit are to test and evaluate diving, hyperbaric, and other life-support systems and procedures, and to conduct research and development in biomedical and environmental physiology. NEDU also provides technical recommendations to the Naval Sea Systems Command to support operational requirements of the US armed forces. [3]
Experimental diving in the US Navy started in 1912 at the Brooklyn Navy Yard under the leadership of Chief Gunner George D. Stillson. [1] Stillson's research program ultimately led to increasing diver capabilities from 60 feet (18 m) to over 300 feet (91 m) of depth based on Haldane's decompression work with the Royal Navy. This resulted in the first publication of the United States Navy Diving Manual and established the need for a facility dedicated to research and development of diving procedures. [1] [4] [5]
In 1915, Stillson's team was sent to salvage the F-4 submarine. On these deep dives, the divers experienced the debilitating effects of nitrogen narcosis leading them to try the addition of helium to their breathing mix. [2] The navy salvage operations then came under the direction of Warrant Gunner C. L. Tibbals who led teams through the salvage of the S-51 in 1925 and S-4 in 1927 further establishing the naval need for equipment, training, and procedures for rescue operations. [2]
NEDU was established in 1927 at the Washington Navy Yard. [1] [2]
Early developments for the unit involved evaluation and testing of the Submarine Escape Lung (Momsen lung) and the McCann Rescue Bell. [2] This work was done by Charles Momsen and Allan McCann. In 1929, Momsen received the Navy Distinguished Service Medal for personally testing the device at a depth of 200 feet (61 m). Techniques used for the rescue of submariners aboard the USS Squalus were developed by Momsen and McCann in their time at NEDU. [2] [6] [7] This work lead to the rescue and recovery of 33 crewmen. [6] Momsen and McCann received a Letter of Commendation from President of the United States Franklin D. Roosevelt for the Squalus effort. [6]
The first medical staff were introduced to the facility in the mid-1930s when Charles W Shilling, Albert R Behnke, and OE Van der Aue began work. Their early work improved the prevention and treatment of decompression sickness with the inclusion of oxygen rather than air. [1] [8] [9]
Through World War II, work continued on decompression and oxygen toxicity. [10] [11]
Through the 1950s NEDU tested equipment and further refined procedures for divers including the US Navy 1953 decompression table. [12] [13]
From 1957 to 1962 was the beginnings of saturation diving under the leadership of Captain George F. Bond of the Naval Submarine Medical Research Laboratory and the Genesis Project. [1] [14] Genesis D was performed at NEDU in 1963. [1] [15] Bond then went on to head the SEALAB I saturation project in 1964. [16]
Robert D. Workman published a novel method to calculate decompression schedules in 1965 that involved estimating the limiting values of excess tissue supersaturation. [17]
Work continued in deep saturation dives, equipment testing as well as thermal protection and physiology research throughout the 1960s and early 1970s.
The MK 1 lightweight mask was a modification of the commercial Kirby Morgan band mask, which NEDU tested in the early 1970s, and which was suitable for both air and mixed gas operations to 300 feet, and provided voice communications. It was adopted for Navy service after modifications recommended by NEDU were implemented. [18]
In 1975, NEDU relocated to its current location in Panama City, Florida. [1]
NEDU began a project to modernize Stillson's MK V surface supplied diving system which had been in service since 1916 in the early 1970s, and developed, tested, and certified the replacement Mark 12 Surface Supplied Diving System which was taken into service in 1985, and eventually its replacement the Mark 21/ Superlight 17 in the 1970s and 1980s, [1] [19] [20] adopted in 1993. [18]
NEDU developed the MK 14 Closed-Circuit Saturation Diving System in the 1970s. This system is used for diving operations from a closed divin bell and a saturation system. [18]
NEDU comprehensively tested and evaluated the MK 11 rebreather in the 1970s. [18]
NEDU conducts at least one saturation dive per year. These dives were used, amongst other things, to evaluate decompression and recompression procedures, equipment, carbon dioxide absorbents, as well as active and passive thermal protection. [21] [22] [23] Many of these tests included ongoing evaluations of commercially available diving equipment. [24] [25] [26]
NEDU evaluated the Jack Browne lightweight mask for shallow water diving on several occasions. The mask was in service from World War II through the late 1970s. By 1978 NEDU determined the mask was no longer suitable for intensive diving operations and it was phased out in the 1980s. [18]
NEDU tested and certified the commercially produced Mk 15 rebreather for use by Navy Special Forces in 1980, and developed new constant oxygen partial pressure decompression tables to use with the it, as standard open circuit tables could not be used. This was followed by evaluation of the Mk 16 rebreather, an upgrade of the Mk 15 with a low magnetic signal suitable for explosive ordnance disposal (EOD) operations. [18]
In 1998, the Naval Medical Research Center's diving biomedical and development group was transferred to NEDU. [1] [27]
In response to the overseas military needs, NEDU focused on warm water diving from 1999 to 2002. [28] This guidance to the Naval Special Warfare community influences operational needs on an ongoing basis. [1]
NEDU divers were essential to the recovery of artifacts from the wreck of the USS Monitor in 2001 and 2002. [1] [29]
In 2002, certification of the Mark 16 Mod 1 rebreather was completed following improvement of systems including, extension of the working limit to 300 feet (91 m), new decompression tables for both nitrogen-oxygen and helium-oxygen diving including new repetitive diving capabilities for helium-oxygen, test of an Emergency Breathing System with communications, the addition of an integrated buoyancy compensation device, and an improved full face mask. [1] [30]
In 2004, NEDU contributed to operational guidance for diving in harsh contaminated environments. [31]
NEDU has continued research into oxygen toxicity utilizing the US Navy Mark 16 Mod 1. [32] [33]
Development of breathing systems, thermal protection, and decompression procedures for SEAL Delivery Vehicles and the Advanced SEAL Delivery System is ongoing. [34] [35]
In 2011, divers completed a 1,000 fsw saturation dive to evaluate the new Navy's Saturation Fly-Away Diving System (SAT FADS). [36] The SAT FADS was designed in 2006 as a portable replacement of two decommissioned Pigeon-class submarine rescue vessels. [36]
In March 2022, CDR Dustin Cunningham took up his appointment as Commanding Officer of NEDU. [37]
The Ocean Simulation Facility (OSF) simulates ocean conditions to a maximum pressure equivalent of 2,250 feet (690 m) seawater at any salinity level. The chamber complex consists of a 55,000- US-gallon (210,000 L) wet chamber and five interconnected dry living/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 latest data acquisition capability, the OSF can accommodate 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 chamber. 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 quarters, 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 (46,000 m). [38]
The Experimental Test Pool is a 50,000-US-gallon (190,000 L) capacity freshwater tank measuring 15 ft (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 water 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 monitored. The facility can accommodate a wide range of experiments, 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 and analysis, and pressure and gas monitoring. [38]
The depth is sufficient to allow divers to maintain an oxygen partial pressure of 1.3 bar on their breathing apparatus while immersed and riding a bicycle ergometer. [32] [33]
The Environmental Chamber is capable of simulating a broad range of temperatures from 0 to 130 °F (−18 to 54 °C), humidity from 5 to 95%, and wind velocity from 0 to 20 mph (0 to 32 km/h). The chamber is instrumented to conduct physiological studies and to test various types of equipment. [38]
The Experimental Diving Facility (EDF) simulates unmanned pressure conditions to 1,640 feet (500 m) sea water and temperatures can be set from 28 to 110 °F (−2 to 43 °C). As a complement to the Ocean Simulation Facility, the EDF is used to conduct unmanned testing and evaluation of diving and hyperbaric chamber systems and components. All diving practices and procedures are tested to determine their safety, conformance to established standards, and operational suitability and limits. [38] [39]
Operated by certified technicians, the Class 100,000 Clean Room performs a variety of cleaning and testing tasks: oxygen cleaning of piping, valves, regulators, tanks, and filters, as well as hydrostatic testing up to 10,000 psi (69,000 kPa). All components used in diving life-support systems are cleaned and certified to meet military standards. [38] [40] [41]
The gas analysis laboratory is equipped for the precise analysis of gases, and it is used to evaluate diving-related problems such as offgassing and contaminant control. The laboratory's analytical capabilities include gas chromatography, mass spectrometry, and infrared spectroscopy. The facility is currently used to develop reliable and rapid screening methods and analyzers for the Fleet. [38] [40] [41]
The cardiopulmonary laboratory consists of machines that perform a variety of respiratory function tests and aerobic performance measurements that are often recorded before and after pressure and/or thermal exposure. [38]
The NEDU Library contains over 120,000 documents on diving medicine, engineering, and history from around the world. [42] Many of the NEDU publications have been scanned and are available online at the Rubicon Research Repository. [43] Other articles can be found in the Duke University Medical Center Archive finding aids of the Undersea and Hyperbaric Medical Society library collection. [44]
The 120 person NEDU Team includes highly qualified and experienced military divers with a combined 1,000 man-years of diving experience: Sea-Air-Land (SEAL), Explosive Ordnance Disposal (EOD), Salvage, Saturation, Seabee, Diving Officer, and Diving Medical Officer (DMO), Ph.D. scientists, engineers, various science-degreed professionals and support personnel. [45]
Nitrox refers to any gas mixture composed of nitrogen and oxygen that contains less than 78% nitrogen. In the usual application, underwater diving, nitrox is normally distinguished from air and handled differently. The most common use of nitrox mixtures containing oxygen in higher proportions than atmospheric air is in scuba diving, where the reduced partial pressure of nitrogen is advantageous in reducing nitrogen uptake in the body's tissues, thereby extending the practicable underwater dive time by reducing the decompression requirement, or reducing the risk of decompression sickness .The two most common recreational diving nitrox mixes are 32% and 36% oxygen, which have maximum operating depths of about 110 feet and 95 feet (29 meters respectively.
Trimix is a breathing gas consisting of oxygen, helium and nitrogen and is used in deep commercial diving, during the deep phase of dives carried out using technical diving techniques, and in advanced recreational diving.
Heliox is a breathing gas mixture of helium (He) and oxygen (O2). It is used as a medical treatment for patients with difficulty breathing because this mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort by a patient to breathe in and out of the lungs. It is also used as a breathing gas diluent for deep ambient pressure diving as it is not narcotic at high pressure, and for its low work of breathing.
The timeline of underwater diving technology is a chronological list of notable events in the history of the development of underwater diving equipment. With the partial exception of breath-hold diving, the development of underwater diving capacity, scope, and popularity, has been closely linked to available technology, and the physiological constraints of the underwater environment.
Decompression sickness is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompression. DCS most commonly occurs during or soon after a decompression ascent from underwater diving, but can also result from other causes of depressurisation, such as emerging from a caisson, decompression from saturation, flying in an unpressurised aircraft at high altitude, and extravehicular activity from spacecraft. DCS and arterial gas embolism are collectively referred to as decompression illness.
Deep diving is underwater diving to a depth beyond the norm accepted by the associated community. In some cases this is a prescribed limit established by an authority, while in others it is associated with a level of certification or training, and it may vary depending on whether the diving is recreational, technical or commercial. Nitrogen narcosis becomes a hazard below 30 metres (98 ft) and hypoxic breathing gas is required below 60 metres (200 ft) to lessen the risk of oxygen toxicity. At much greater depths, breathing gases become supercritical fluids, making diving with conventional equipment effectively impossible regardless of the physiological effects on the human body. Air, for example, becomes a supercritical fluid below about 400 metres (1,300 ft).
Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen at increased partial pressures. Severe cases can result in cell damage and death, with effects most often seen in the central nervous system, lungs, and eyes. Historically, the central nervous system condition was called the Paul Bert effect, and the pulmonary condition the Lorrain Smith effect, after the researchers who pioneered the discoveries and descriptions in the late 19th century. Oxygen toxicity is a concern for underwater divers, those on high concentrations of supplemental oxygen, and those undergoing hyperbaric oxygen therapy.
A diving chamber is a vessel for human occupation, which may have an entrance that can be sealed to hold an internal pressure significantly higher than ambient pressure, a pressurised gas system to control the internal pressure, and a supply of breathing gas for the occupants.
Artificial gills are unproven conceptualised devices to allow a human to be able to take in oxygen from surrounding water. This is speculative technology that has not been demonstrated in a documented fashion. Natural gills work because nearly all animals with gills are thermoconformers (cold-blooded), so they need much less oxygen than a thermoregulator (warm-blood) of the same size. As a practical matter, it is unclear that a usable artificial gill could be created because of the large amount of oxygen a human would need extracted from the water.
Submarine Escape Immersion Equipment (SEIE), also known as Submarine Escape and Immersion Equipment, is a whole-body suit and one-man life raft that was first produced in 1952. It was designed by British company RFD Beaufort Limited and allows submariners to escape from a sunken submarine. The suit also provides protection against hypothermia and has replaced the Steinke hood rescue device. The suit allows survivors to escape a disabled submarine at depths down to 600 feet (183 m), with an ascent speed of 2–3 meters/second, at a rate of eight or more sailors per hour.
Capt. Edward Deforest Thalmann, USN (ret.) was an American hyperbaric medicine specialist who was principally responsible for developing the current United States Navy dive tables for mixed-gas diving, which are based on his eponymous Thalmann Algorithm (VVAL18). At the time of his death, Thalmann was serving as assistant medical director of the Divers Alert Network (DAN) and an assistant clinical professor in anesthesiology at Duke University's Center for Hyperbaric Medicine and Environmental Physiology.
The Thalmann Algorithm is a deterministic decompression model originally designed in 1980 to produce a decompression schedule for divers using the US Navy Mk15 rebreather. It was developed by Capt. Edward D. Thalmann, MD, USN, who did research into decompression theory at the Naval Medical Research Institute, Navy Experimental Diving Unit, State University of New York at Buffalo, and Duke University. The algorithm forms the basis for the current US Navy mixed gas and standard air dive tables. The decompression model is also referred to as the Linear–Exponential model or the Exponential–Linear model.
A task load indicates the degree of difficulty experienced when performing a task, and task loading describes the accumulation of tasks that are necessary to perform an operation. A light task loading can be managed by the operator with capacity to spare in case of contingencies. Task loads are primarily associated with underwater diving. They are also associated with workloads in other environments, such as aircraft cockpits and command and control stations.
Hydrox, a gas mixture of hydrogen and oxygen, is occasionally used as an experimental breathing gas in very deep diving. It allows divers to descend several hundred metres. Hydrox has been used experimentally in surface supplied, saturation, and scuba diving, both on open circuit and with closed circuit rebreathers.
Captain Albert Richard Behnke Jr. USN (ret.) was an American physician, who was principally responsible for developing the U.S. Naval Medical Research Institute. Behnke separated the symptoms of Arterial Gas Embolism (AGE) from those of decompression sickness and suggested the use of oxygen in recompression therapy.
Albert Alois Bühlmann was a Swiss physician who was principally responsible for a number of important contributions to decompression science at the Laboratory of Hyperbaric Physiology at the University Hospital in Zürich, Switzerland. His impact on diving ranged from complex commercial and military diving to the occasional recreational diver. He is held in high regard for his professional ethics and attention to his research subjects.
Captain George Foote Bond was a United States Navy physician who was known as a leader in the field of undersea and hyperbaric medicine and the "Father of Saturation Diving".
The decompression of a diver is the reduction in ambient pressure experienced during ascent from depth. It is also the process of elimination of dissolved inert gases from the diver's body which accumulate during ascent, largely during pauses in the ascent known as decompression stops, and after surfacing, until the gas concentrations reach equilibrium. Divers breathing gas at ambient pressure need to ascend at a rate determined by their exposure to pressure and the breathing gas in use. A diver who only breathes gas at atmospheric pressure when free-diving or snorkelling will not usually need to decompress. Divers using an atmospheric diving suit do not need to decompress as they are never exposed to high ambient pressure.
John R. Clarke is an American scientist, private pilot and author. He is currently the Scientific Director at the United States Navy Experimental Diving Unit (NEDU). Clarke is recognized as a leading authority on underwater breathing apparatus engineering.
The US Navy has used several decompression models from which their published decompression tables and authorized diving computer algorithms have been derived. The original C&R tables used a classic multiple independent parallel compartment model based on the work of J.S.Haldane in England in the early 20th century, using a critical ratio exponential ingassing and outgassing model. Later they were modified by O.D. Yarborough and published in 1937. A version developed by Des Granges was published in 1956. Further developments by M.W. Goodman and Robert D. Workman using a critical supersaturation approach to incorporate M-values, and expressed as an algorithm suitable for programming were published in 1965, and later again a significantly different model, the VVAL 18 exponential/linear model was developed by Edward D. Thalmann, using an exponential ingassing model and a combined exponential and linear outgassing model, which was further developed by Gerth and Doolette and published in Revision 6 of the US Navy Diving Manual as the 2008 tables.
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