US Navy Experimental Diving Unit

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Akimbo

Just a diver
Staff member
ScubaBoard Supporter
Messages
12,517
Reaction score
11,006
Location
Mendocino, CA USA
It's hard to overstate the profound impact that NEDU has had on recreational Scuba diving. NEDU stands for the US Navy Experimental Diving Unit and is often referred to as EDU or just "The Unit". Everything from diving physiology, equipment, testing, and safety is influenced by their work.

It helps to understand
how little was known about
diving in the early 1900s

In the Beginning
NEDU's roots were pretty humble. Chief Warrant Officer George D. Stillson is credited with the Navy's first experimental diving work at the Brooklyn Navy Yard in 1912. That effort produced:
full.jpg

Mysterious symptoms of what we now realize is Decompression sickness or the "bends" were observed soon after Augustus Siebe began manufacturing his surface-supplied diving dress in the 1830s. Greek sponge divers, caisson workers or "Sand Hogs", and salvage divers all noted debilitating effects of deep and long duration dives. Unfortunately decompression tables to avoid DCS were not developed until Haldane and Stillson so these divers had little to depend on besides sea stories handed down by old and often injured divers.

Haldane's work was built on Sir Robert Boyle's experiments that observed bubbles in eyes during animal experiments in 1670 and Paul Bert's work that described the cause of DCS and the benefits of breathing pure Oxygen in 1878. Stillson, who was not a physiologist or physician, improved and extended Haldane's tables through animal and human testing.

Chief Stillson's assignment coincided with the development of early submarines, and the tragic accidents that accompanied them. Stillson and his divers were sent to salvage the submarine F-4 after she sank off Pearl Harbor Hawaii with all hands in 1915. She was in 306'/93M of water. Divers experienced severe impairment caused by Nitrogen Narcosis which prompted the US Bureau of Mines to suggest Helium-Oxygen as a breathing mixture.

Testing of HeO2 mixtures and decompression table development began at the Bureau of Mines Experiment Station in Pittsburgh, Pennsylvania in conjunction with U.S. Navy Bureau of Construction and Repair. There are reports in 1924 that suggest than manned chamber dives were conducted after animal testing. The first operational use of HeO2 was on the private salvage the Steamship Lakeland that sank in more than 200' of water in Lake Michigan.

The submarine S-51 was lost in 1925 at a depth of 130'/40M of water off Block Island (Rhode Island, USA). Three of the 36 man crew survived. Salvage was led by Lieutenant Commander (later Rear Admiral) Edward Ellsberg and was chronicled in his book, On the Bottom (highly recommended). The S-4 sank in 1927 with all hands and was salvaged by Ellsberg's divers in 1928.

Establishing the Experimental Diving Unit
Submarine and crew losses dictated the need for trained divers and submarine rescue systems. NEDU was established in 1927 at the Navy Gun Factory in Washington DC and the Naval School of Diving and Salvage was authorized soon after. The gun factory later became the Washington Navy Yard.

full.jpg

EDU and the school were housed in a two-story brick building with near mirror-image floor plans. Each had two matching chamber complexes rated for 785'/239M of sea water. Each of the four complexes consisted of a horizontal double-lock decompression chamber connected to a vertical double-lock "wet pot" on the second deck. The wet pot was about 9'/2.7M in diameter and extended through the deck and rested on the first deck. The upper section was dry with a center access to water-filled space below. It was the largest hyperbaric facility at the time. EDU's chambers were constantly modified over the years to increase their pressure/depth ratings and support increasingly sophisticated environmental controls, instrumentation, and equipment testing.

full.jpg

Personal Sidebar
EDU was legendary to me in 1970 when I started First Class Diving School. I learned about it from my SCUBA instructor in 1962 who encouraged me to buy a Navy Diving Manual. Countless articles in Skin Diver Magazine elevated it to mythical proportions in my teenage mind. I was 20 by then but was still awed by the place.

These chambers didn’t look much different at the diving school when I was there, but you could barely see them on the EDU side of the building because of all the instrumentation, environmental control systems, calibration gas bottles, control consoles, and support for saturation diving experiments. I was able to get a few invitations when classified gear was out of view. Buying a few drinks in the Green Derby across the Anacostia River also helped. :wink:

The Navy Yard was an odd mix of junk and history. The Bathyscaph Trieste that made the record setting 35,797'/10,911M dive in the Mariana Trench in 1960 was mothballed across the street. It is now displayed at the National Museum of the United States Navy . A few vintage naval guns were strewn around and Franklin Roosevelt's presidential yacht, the USS Sequoia, was moored in the Anacostia next the school's diving stations. We were told that a fully-restored white PT boat moored next to her was used as a presidential escape boat. As the story goes, it would take the president out to open sea to transfer to a nuclear sub that was always on station during a crisis. EDU's goat pens for animal studies seemed to fit right in.

Lieutenant (later Vice Admiral) Charles "Swede" Momsen was among the first officers assigned to EDU. He qualified on Submarines in 1922 and later commanded the refurbished S-1, which was assigned to sub-rescue testing duty. He led the development of the Momsen lung for submarine escape and the McCann Submarine Rescue Chamber. The McCann bell was still standard equipment on ASRs (submarine rescue ships) when I was in school and was included in our training.

EDU had a lot of basic questions to answer. Nobody knew how long a submariner could be exposed to pressure and how fast he could shoot to the surface without getting bent or suffer an embolism. Exhaustive human testing was conducted which ultimately lead to No Decompression Tables used by Scuba divers for decades.

The first Navy Medical Doctors didn't begin working with NEDU until mid-1930. They included Charles Shilling and Albert Behnke. Dr. Behnke did pioneering research on nitrogen (and inert gas) narcosis, recompression treatment and the use of Oxygen, Helium-Oxygen gas mixtures, and decompression theory to name a few. On a personal note, I had the opportunity to hear Dr. Behnke speak in 1967 at the UCSF's Applied Diving Physiology extension course. It seems like his name appeared in the footnotes on everything I read on diving physiology after that. The first Behnke Award was issued in 1969 by the Undersea and Hyperbaric Medical Society.

Edit: Corrected and updated Helium-Oxygen history with the assistance of @Oceanaut

Continued in the next post
 
OP
Akimbo

Akimbo

Just a diver
Staff member
ScubaBoard Supporter
Messages
12,517
Reaction score
11,006
Location
Mendocino, CA USA
Continued from previous post

EDU was called on in 1939 to aid in the rescue of the crew and to later salvage the USS Squalus. She sank during a test dive on 12 May 1939 when the main air induction valve failed to close. She sank to the bottom off Portsmouth, New Hampshire in 243'/74M of water. They rescued 33 survivors of the 59 man crew. Unfortunately the rest of the crew perished soon after the sinking in flooded compartments. I remember watching this on TV with my family in the 1950s.


Four divers were awarded the Medal of Honor for their work during the rescue and salvage. The Squalus was extensively overhauled and recommissioned as the USS Sailfish in February of 1940. She performed 12 patrols in the Pacific during World War II. I recommend The Terrible Hours: The Greatest Submarine Rescue in History by Peter Maas for anyone interested in learning more.


World War II
The prospect of war increased EDU's focus on support for combat swimmers. The units that would become the UDT or Underwater Demolition Team had not been formed yet. Christian Lambertsen designed a series of pure Oxygen rebreathers starting in 1940 as a medical student. He named them Laru for Lambertsen Amphibious Respiratory Unit which became a standard for the UDT and SEALs for decades.

Lambertson coined the acronym
SCUBA in 1952* to describe all
Self-Contained Underwater
Breathing Apparatus

* some accounts indicate that Lambertson used the term in the 1940s... either way, he is universally credited.


Breathing apparatus wasn't EDU's only concern. Oxygen tolerance and thermal protection were also problems that limited combat swimmers' ability to operate. Oxygen Toxicity was generally defined in medical literature but figuring out operational limits needed a lot of work.

Dramatic improvements in aircraft technology was causing aviators to suffer closely related symptoms to divers including low PPO2 (Partial Pressures of Oxygen), barotrauma, and DCS. Aviation pioneers didn’t always connect the dots just like the divers 30 years before. Solving these problems naturally fell on EDU. Other unusual tasks like developing an improved life jacket were assigned to EDU because of their expertise in submersion physiology.

Post-War EDU
The end of the war allowed EDU to return their primary focus to submarine rescue and diving R&D, although support for the UDT (later SEALs) and high-altitude physiology was included. Some of the notable projects included:
  • Time-depth oxygen limits
  • Improved air decompression tables
  • Repetitive air decompression tables
  • Multigas decompression theory
  • Decompression treatment tables that are still the standard of care
  • Diver thermal tolerance and protection
Hugh Bradner was a physicist at UC Berkeley when he invented the wetsuit in 1952. EDU quickly began testing the new suit to understand the limits for the UDT and the evolving EOD (Explosive Ordnance Disposal) divers. Navy salvage divers weren't very interested in any form of SCUBA or the wetsuit largely because their work required communications, long bottom times, heavy-lifting support, power for cutting tools, and was usually in a relatively small area. The Mark V dominated Navy diving and was augmented by the surface-supplied Jack Browne mask.

EDU was also a minor sponsor of Hannes Keller and Dr. Albert Bühlmann's revolutionary work. Keller's dive to 1,010'/308M in 1962 smashed all human depth records. Unfortunately Keller barely survived while his dive-mate Peter Small and safety diver Chris Whittaker died.

Project Genesis
Captain George Bond started a series of "off-the-clock" experiments based on Dr. Behnke's proposition in 1942 that divers could be exposed to greater depths until tissue become fully saturated and eliminate further increases in decompression. Captain Bond began animal studies at the Naval Medical Research Laboratory in 1957, aided by Walter F. Mazzone. The success of animal studies led to human testing at EDU in 1962. There is a fascinating back-story of politics, dedication, and diving history described in the books Papa Topside and SeaLab by SEALAB Author Ben H.. Highly recommended.

Diving pioneers including Jacques Cousteau and Edwin Link quickly began open-sea saturation experiments with underwater habitats. The US Navy also began their open-sea experiments with the Sealab habitats. Habitat-based saturation systems were soon replaced by surface-based chambers with diving bells (PTC or Personnel Transfer Capsule in Navy parlance) outside of shallow and limited scientific projects.


The Cold War
Nuclear powered submarines and ballistic missiles convinced Navy decision makers to reevaluate their priorities. That rapidly pushed submarine development to #1. That and loss of the submarine USS Thresher in 1963 at a depth of 8,400'/2,600M changed everything.


Government and industrial R&D funding for deep diving, manned and robot vehicles, and ocean science exploded. The fledgling offshore oil industry was also moving into deep water off California and augmented the demand. A lot of industries believed that government sponsored undersea R&D would soon rival NASA in funding.

Naval Support Activity Panama City
There were a lot of moving parts in those days, and many involved security clearances at the highest levels and secret budgets in the billions. Some of this came to light when the book Blind Man's Bluff The Untold Story of American Submarine Espionage was published.

EDU and the diving school had long outgrown facilities in Washington DC. NEDU (now the preferred moniker) moved to Panama City, Florida in 1975 and the school followed several years later. NEDU's new facility included the massive Ocean Simulation Facility (OSF) with an operating depth of 2,250'/690M. Five interconnected living and transfer chambers on the second deck attached to the 7,352 Ft³/210M³ horizontal wet chamber on the deck below. The entire end of the wet chamber opens for access so small submersible vehicles can be tested.

full.jpg

This image is courtesy of Stephen Frink from the excellent article Deep in the Science of Diving
by Michael Menduno that was published in Alert Diver Magazine. It gives you a sense of the wetpot's massive scale.

18953.jpg

NEDU’s Executive Officer LCDR Steve Duba stands in the open wet pot of the Ocean Simulation Facility.

OSF's chamber temperatures can be controlled between 28-104° F/-2-40° C. Living chambers can also simulation altitudes up to 150,000'/46Km. It is still the largest hypobaric and hyperbaric research facility in the world.


full.jpg

The new NEDU logo reflects their R&D work for SEALs in addition to Navy divers.

I will let other Scubaboard members continue the saga because I don't have direct experience at the Panama City facility. I look forward to reading their experiences and the sea stories.

Scubaboard Footnotes

Oxygen Toxicity

Rubicon Research Repository

Deadly helmet squeeze

What do you call this gear?


End of Multipart Post
Edit: Added Stephen Frink's photo and updated text.
Edit: Fixed broken video link.
 
Last edited:

USMC CPL.

Contributor
Messages
202
Reaction score
51
Location
Lake Havasu city
# of dives
I'm a Fish!
Great read. Would have loved to have been a Navy Diver. Thanks for all the effort you put into your article.
 
OP
Akimbo

Akimbo

Just a diver
Staff member
ScubaBoard Supporter
Messages
12,517
Reaction score
11,006
Location
Mendocino, CA USA
I just updated Post #2 above with a new image and video that might be interesting.

... Would have loved to have been a Navy Diver...

Here is a thread that might be helpful for anyone who is interested in becoming a Navy Diver: Any ex navy divers out there?

It would be great if someone with more recent experience could add to it.
 
Last edited:

abnfrog

Contributor
Scuba Instructor
Messages
1,960
Reaction score
1,650
Location
great white north
# of dives
2500 - 4999
sorry not a navy diver army CD but did a couple of courses with ND great group of guys .....tough as nails
 

flyboy08

ScubaBoard Supporter
ScubaBoard Supporter
Messages
4,047
Reaction score
2,974
Location
NYC
# of dives
500 - 999
Thank you, this was very educational and interesting.
 

John C. Ratliff

Contributor
Scuba Instructor
Messages
3,193
Reaction score
2,010
Location
Beaverton, Oregon
# of dives
I'm a Fish!
I have now watched both videos, and enjoyed seeing the actual facilities. I have read a lot of the NEDU reports on diving regulators, and enjoyed seeing how some were made. If I had been allowed o enlist in the U.S. Navy in 1966, this may have been where I ended up. But, there were no slots, so. I enlisted in the USAF instead.

SeaRat
 

DEEPLOU

Contributor
Messages
766
Reaction score
14
Location
Boynton Beach/ former Long Island, NY (THE ISLAND)
# of dives
1000 - 2499
back around 1969 I thought I might want to become a Navy diver. But, I would have had to commit to another 4 or 6 years of active duty (don't remember), plus I didn't think I had the "metal" to make it thru the program.
as a result, it was another 25 years before I got certified.
 
https://www.shearwater.com/products/swift/

Top Bottom