DAAM IP

[SeaRat]

If you’ve read Cousteau’s The Silent World, you’ll note tha Frédérick Dumas survived an underwater explosion by dynamite fishermen in the early 1950s.

No, it was not for other divers to use the regulator, but that the regulator would still function after a diver was exposed to either gunfire, shelling or explosions.

SeaRat

[SeaRat]

Aug 29, 2023 12:37:59 GMT -8 luis said:

Aug 28, 2023 17:20:18 GMT -8 SeaRat said:

Okay, let me give some perspective on the twisting on the ears of the of the horseshoe "Support, Lock" (left and right). This is not mentioned in the U.S. Navy Diving Manual, March of 1970. However, it was a practice I saw during our instruction at the U.S. Naval School for Underwater Swimmers. Under normal conditions, the twisting does not need to be done. But the U.S. Navy divers did not alway work under normal conditions. They sometimes worked under combat conditions, and the equipment was potentially subjected to rather rigorous trauma (like explosions underwater) which could really rattly the regulator. To prevent the horseshoe from being dislodged under these conditions, the instructors recommended the twisting of the ears of this support after assembly. Because the diaphragm holds the horseshoe in position on the extreme end, and the nut holding seat on the other, there is little possibility of the horseshoe coming out from the ears of the Lock Support. But under combat conditions, all bets are off. So far as making things worse, if done correctly the twist doesn't affect the movement of the horseshoe; but not all people did it correctly.

John

Hi John,

I am not sure I am following this concept.

I am sure that you are aware that any underwater explosion capable of rattling a regulator that much, will more than certainly kill the diver.

There are lots of information about the effects of underwater explosion on the human body, without needing to dig deep (no pun intended) ... This is not classified information...
science.howstuffworks.com/explosion-land-water1.htm

So, what was the idea? that under combat condition, if they recover the body, another diver could use that same regulator without first servicing it?


Maybe the instructor was being way too optimistic...

Luis,

I just went to J.Y. Cousteau and Frédérick Dumas' book, The Silent World to refresh my memory about their experiments with underwater explosions. My reference above was accurate, and my memory intact. I'll get to that in a moment.

Before I do, we had USAF Pararescueman in the water under combat conditions, rescueing downed pilots from the HU-16B Albatross amphibian in the mid-1960s. They were inside Haiphong Harbor, in what then was known as North Vietnam, and under shell and small arms fire. Usually they were not is scuba gear, but had the scuba gear available on-board the aircraft. Under those conditions, the equipment was potentially exposed to the shock wave of a shell landing near the aircraft (which happened a lot). We also lost at least one Albatross to shell fire, along with some of the crew. So under these conditions, the Aquamaster regulator would be subjected to these blast forces. We had progressed to single hose, usually Calypso regulators by that time, but this is what the U.S. Navy Underwater Swimmers School instructors were thinking about when we crimped those ears on the holder.
HU-16B dropping package-A by John Ratliff, on Flickr
Now, back to Cousteau's experiments. Here's what he wrote:

The Group* established liaison with oceanographic and diving establishments in Britain, Germany, Sweden and Italy. The Royal Navy, during the war, had made some valuable studies in the resistance of divers to underwater explosions. Professor J.B.S. Haldane who worked on some of the investigations had written, "Now you must be a very brave man indeed to hunt for magnetic mines in muddy water, especially if you have seen some of your comrades go up. You must be a man of super-human courage if you know that, if you hear a mine beginning to tick, and go up to the surface quickly, you may be paralyze for life if you are not blown to pieces." Domas got us into this unappetizing game, because of his incorribible curiosity about odd effects under water.

On Sunday, at Sanary he threw an Italian hand grenade into the water to kill some fish. A few bogues floated up on their sides. Tailliez dived and brought up ten times as many fish he had found lying on the bottom, proof that dynamiting is an excessively wasteful method of fishing unless one can dive to recover the full catch.

Dumas tossed another grenade. It did not explode. Didi waited several minutes and went in to inquire. The grenade lay in fifteen feet of water. As he submerged, Dumas saw tiny bubbles fizzing from it. He did not comprehend what was taking place. The grenade went off directly below him, the worst tangent of an underwater explosion, which blasts vertically through the lighter water layers.

Dumas was in no danger of being hit by shrapnel, which die out in a dribble a few feet from the burst, such is the resistance of water to flying objects. Death comes from shock waves slamming against the body. Yet Tailliez saw Dumas stagger out of the surf. He was racked to his bones, but actually un-injured. The striking incident set off brain waves. We looked at the British tables on underwater explosions and found that Dumas had been in a radius supposed to cause certain death. We postulated that the shock resistance for a naked man was several times greater than the most advanced study indicated.

Dumas and Tailliez thereupon set out to test the hypothesis. Haldane had said, "Experiments on animals are useful to show the kind of danger to be expected, but they do not tell exactly what a man can stand. This can only be done on human beings whose courage or curiosity will keep them going until they drop."

We went under water in pairs while one-pound TNT charges were exploded at progressively nearer distances. When a burst caused too much discomfort, we stopped. The danger factor was that one might sustain internal lesions without feeling them. The program was concluded witout internal injuries, however.

The dynamite explosions boxed our ears disagreeably and dealt a sort of dry smake against the body. With one-pound tablets of German tolite explosive, the effect was different. We took heavy sandbag blows on the chest, receiving a profound shaking. The astonishing thing was how close we could get and bear it. Sometimes, when two of us were hanging in our stations waiting for the explosion, we would look at each other and wince at the lunatic idea.

A third type of explosive I cannot mention gave Tailliez and Dumas such a bad time that we decided we had better things to do. There had been instructive results. Our first conclusions was that a naked man had better resistance to explosion than a helmet diver. This apparent paradox arises from the fact that pressure waves have nearly the same propagation speed in human tissue as in water, another affirmation of the physical likeness of flesh and the sea mother. For the helmet dive his casque was the weakness. Although it protected his head from the blow, shock waves striking the flexibel suit would shudder in his flesh and through his collar and meet no counter pressure inside the helmet.
Cousteau, J.Y., Captain, with Frédérick Dumas, The SILENT WORLD, Harper & Brothers Publishers, New York, Copyright 1953, pages 54-56.
*The Undersea Research Group

In addition, I have done a google scholar search and found a more recent publication on underwater explosions. Here is the abstract:

Underwater blast injury: a review of standards Rachel M Lance and Cameron R Bass
Abstract
(Lance RM, Bass CR. Underwater blast injury: a review of standards. Diving and Hyperbaric Medicine. 2015 September;45(3):190-199.)
The first cases of underwater blast injury appeared in the scientific literature in 1917, and thousands of service members and civilians were injured or killed by underwater blast during WWII. The prevalence of underwater blast injuries and occupational blasting needs led to the development of many safety standards to prevent injury or death. Most of these standards were not supported by experimental data or testing. In this review, we describe existing standards, discuss their origins, and we comprehensively compare their prescriptions across standards. Surprisingly, we found that most safety standards had little or no scientific basis, and prescriptions across standards often varied by at least an order of magnitude. Many published standards traced back to a US Navy 500 psi guideline, which was intended to provide a peak pressure at which injuries were likely to occur. This standard itself seems to have been based upon a completely unfounded assertion that has propagated throughout the literature in subsequent years. Based on the limitations of the standards discussed, we outline future directions for underwater blast injury research, such as the compilation of epidemiological data to examine actual injury risk by human beings subjected to underwater blasts. (emphasis added, JCR)

It turns out that there is no good scientific documentation about underwater blast injuries. This was confirmed in the body of this article:

Diving and Hyperbaric Medicine
Volume 45, Number 3, September 2015
Pages 190-199
Discussion
Forty-two guidelines for underwater blast exposure were found, only six of which were linked to documented experimental data. However, even these six guidelines are based on non-ideal experimental designs. Corey et al. used strips of beef intestine inside a model of a human torso to try to determine the exposure levels required to create abdominal perforations.34 The experimenters ignored the hundreds of available medical reports that document the overwhelming location of abdominal perforations near the ileocaecal junction.17 It is probable that the structure of the junction and attachment to the abdominal wall contribute stresses that lead to perforations at much lower blast exposure levels, as they do in blunt force trauma.58

Wright et al. conducted extensive human experiments to find a deterrent blast level, but operated under the assumption that
peak pressure was the crucial factor in determining exposure levels and therefore only occasionally reported impulse values.42 This omission was despite the researchers’ own admission in the paper that impulse was a critical predictive factor. Also, it was found later that many of the pressure gauges used by this research group at that time were possibly inaccurate by 25% or more, meaning that while the ‘safe/ deterrent’ levels established are probably approximately accurate, higher-exposure values may not be correct.60...

...Conclusions
The current guidelines for injuries from underwater blast are grossly inconsistent, poorly experimentally founded, and vary by orders of magnitude. Researchers have been declaring the need for valid standards since the original cases of underwater blast in 1916, and the need still exists. It is impossible to predict safe operational distances or to design protective equipment without valid standards for the risk of injury or fatality from underwater blasts.

The field of underwater blast injury needs solid, data-based guidelines that can be used by operators and medical personnel while in the field. An important next step should be the compilation of available injury data and a realistic, quantitatively validated evaluation of the blast exposure levels that cause human injuries, similar to the injury risk curves available for air blast. This evaluation could be performed using either human historical data and epidemiological exposure data or may be developed using animal data in experimental series designed to provide realistic underwater blast exposures scaled to human values. The underwater blast community would benefit from a standard that has been developed using experimental methods that are comparably systematic to those used in the air blast community. (Emphasis added, JCR)
www.dhmjournal.com/images/Journals/45/DHM_Vol45_No3.pdf#page=48

John

PS, I actually found Elmer Jacob Artist’s original paper on blast injuries, from 1943. The portion about underwater explosions starts on page 47. This is some of what Cousteau was talking about when they did their experiments on diver reactions to underwater explosions.
digitalcommons.unmc.edu/cgi/viewcontent.cgi?article=2055&=&context=mdtheses&=&sei-redir=1&referer=https%253A%252F%252Fscholar.google.com%252Fscholar%253Fstart%253D30%2526q%253DHaldane%252Band%252Bunderwater%252Bexplosion%2526hl%253Den%2526as_sdt%253D0%252C38#search=%22Haldane%20underwater%20explosion%22