sous marins dans le monde

Citation :

Sous-marins : des conditions de vie extrêmes

A bord des sous-marins américains, l'équipage commence une nouvelle journée toutes les 18 heures. Un rythme « anti-physiologique » qui est amené à évoluer.

La marine américaine est prête à modifier le temps de travail de ses sous-mariniers. Actuellement, leur journée de travail est de 18 heures par jour. Or, des études menées par l'U.S. Navy ont montré que répartir le travail sur 24 heures était moins éprouvant pour les marins et plus respectueux du rythme biologique.
«Cette journée de travail extrêmement longue est due au faible nombre de marins à bord», explique au Figaro Dr Nita Lewis Shattuck de l'Université Navale de Monterey (Californie). En effet, dans un sous-marin, l'équipage compte une centaine d'hommes, divisée en trois équipes, qui doivent 24/24 heures et 7/7 jours se relayer à un même poste. Dans la marine américaine, la journée de 18 heures se répartit en deux périodes: six heures où ils occupent leur poste et les douze heures restantes sont consacrées aux repas, au sport, à leur formation continue et au sommeil. En place depuis les années 1960, cette organisation était censée réduire le temps de travail à 6 heures afin de limiter la fatigue des sous-mariniers. Pourtant, ce rythme «est anti-physiologique et perturbe le cycle biologique veille-sommeil», affirme au Figaro le médecin en chef Patrice Baert, instructeur à l'école des applications militaires de l'énergie atomique à Cherbourg, qui a étudié l'impact de ces perturbations à bord des sous-marins français.
Un rythme de travail épuisant
Dans un article publié en janvier 2013 dans le magazine Proceedings , le Capitaine John Cordle de l'U.S. Navy déclarait qu'un marin dormait 4 heures par nuit voire moins alors que «nous avons besoin de dormir au moins huit heures par nuit et aux mêmes heures chaque nuit», rappelle Dr Nita Lewis Shattuck. D'autant que «nos performances physiques et mentales, notre productivité mais aussi nos relations souffrent si nous ne respectons pas les rythmes circadiens», explique-t-elle.
Un premier sous-marin a testé pendant un déploiement de sept mois la nouvelle organisation. Le commandant Seth Burton, un ancien malade du cancer, avait pris conscience lors de sa maladie des bénéfices pour la santé de garder un rythme de sommeil régulier. Il a déclaré à l'agence AP que «l'équipage avait apprécié l'organisation sur 24 heures et qu'il avait observé de bons retours».
En adoptant ce nouveau rythme, «l'armée américaine se rapproche des quarts français organisés sur 24 heures», note le médecin en chef Patrice Baert. Dans la marine française, chaque «tiers» ou équipe effectue deux quarts par jour. Ces derniers sont répartis au cours de la journée - un poste peut être occupé pendant 4,3 ou 2 heures - et d'une journée à l'autre les marins ne travaillent pas aux mêmes heures. «Ce rythme de travail irrégulier a pour particularité de ne pas spécialiser les personnels sur certaines tranches horaires tout en préservant une durée minimum de sommeil de quelques heures», explique le médecin en chef Patrice Baert dans son étude. Ainsi, «tous les trois jours, un tiers à l'opportunité de dormir 8 heures d'affilées», explique Patrice Baert. Mais malgré le respect du rythme circadien, «ce système est source de fatigue chronique», ajoute-t-il.
Absence de lumière naturelle
A cela s'ajoute une privation totale de lumière naturelle durant une dizaine de semaines. Or, c'est en partie l'alternance jour-nuit qui synchronise le cycle veille-sommeil. Pour mimer ce changement au cours de la journée, l'environnement lumineux est adapté à bord d'un sous-marin: ampoules claires ou fluorescentes pour le jour et rouge pour la nuit. Cependant, lors de son étude à bord, le médecin en chef Patrice Bert a observé des perturbations du cycle du sommeil en l'absence de lumière naturelle et de réelle alternance jour-nuit. L'horloge interne adopte alors une périodicité d'environ 25 heures. On parle de «désynchronisation» ou d' «horloge en libre cours». Modifier l'éclairage à bord des sous-marins permettrait de réduire l'impact de ce phénomène, d'après le médecin en chef.
A bord d'un sous-marin, «dormir est un luxe et rester éveillé est un honneur», déplore le Capitaine John Cordle dans son article. Pourtant, respecter le rythme circadien pour diminuer l'état de fatigue de l'équipage permettrait d'améliorer leur vigilance et leur efficacité lors des opérations mais réduirait aussi les accidents.

http://sante.lefigaro.fr/actualite/2014/04/30/22284-sous-marins-conditions-vie-extremes

Citation :

Exclusive: DCNS will unveil the SMX OCEAN at Euronaval 2014: A Conventional (SSK) Barracuda
Navy Recognition learned that DCNS will introduce a new submarine concept at Euronaval 2014 which be held from October 27th to 31st at Paris Le Bourget in France. The SMX OCEAN is based on a Barracuda hull, the next generation SSN of the French Navy, fitted with a conventional propulsion system (SSK) with AIP technology.

The SMX OCEAN concept to be unveiled at Euronaval 2014. Picture: DCNS

The focus of DCNS engineers in developing this concept was put on endurance and high sustained speed. We learned that the 4,700 tons SSK was designed for an endurance of 14,000 nautical miles (3 months autonomy) and a continuous transit speed of 14 knots for 1 week thanks to its Air Independent Propulsion (AIP) system fitted with two fuel cells. The original nuclear propulsion system of the Barracuda design was also replaced with six diesel engines and three sets of Li Ion batteries.

Two thruster pods are deployable at the bottom of the hull to allow the submarine to maneuver while the main screw is not in action (full stop). The X rudder design is the same as on the Barracuda and allows increased maneuverability.

The SMX OCEAN concept is fitted with an impressive load of up to 34 weapons for action in the four domains: anti-air, anti-surface, anti-submarine & action against land targets.

The SMX OCEAN SSK is fitted with one large modular VLS tube that may launch up to six MdCN vertically (much like the Virginia payload module developed by GDEB for the US Navy’s Virginia class of SSN). The submarine may also deploy F21 heavy torpedoes, SM39 Block 2 anti-ship missiles and a submarine launched version of the Mica missile (A3SM Underwater Vehicle Version) for self protection against air threats.

Finally a DCNS representative told Navy Recognition that the SMX OCEAN may deploy and recover a new UUV DCNS is working on, as well as deploy a UAV acting as remote sensor for intelligence gathering.
http://www.navyrecognition.com/index.php?option=com_content&task=view&id=2029

JOSEPH TREVITHICK - The Drive a écrit:

Royal Navy Submarine Appears In Gibraltar Equipped With Enhanced Wake Detection System

These somewhat exotic non-acoustic sensors that were once mainly found on Soviet submarines would help supplement sonar when searching for other subs.

The U.K. Royal Navy's Trafalgar class attack submarine HMS Talent has arrived in the British territory of Gibraltar sporting curious new sensors on either side of its sail. We can say with near certainty that these are additions to an existing system designed to detect enemy submarines without the use of sonar that first appeared on the boat in 2019.

Photographer David Parody grabbed the pictures of Talent in this new configuration as it sailed into Gibraltar today and was kind enough to share them with The War Zone. In addition to the sensor suite, the submarine also has a pair of 7.62mm FN MAG machine guns, known as L7 General Purpose Machine Guns (GPMG) in British military service, mounted on pintles on top of the sail. The fitting of machine guns in this manner, together with arming individual sailors with small arms and non-lethal weapons, are common force protection measures employed by the crews of Royal Navy submarines, as well as those belonging to other navies, especially when entering or exiting ports.


A close up of the new sensor arrays on the sail of HMS Talent, as well as the two L7 machine guns.


HMS Talent in its latest configuration in Gibraltar.

It's not clear how long Talent has had all three of these sensor arrays installed together. The boat is one of just three remaining Royal Navy Trafalgar class submarines, which have been steadily retired as new Astute class attack submarines have entered service. Talent is scheduled to be decommissioned later this year.

As for what these sensors actually do, they are designed to detect other submarines beneath the waves via the changes in water density that they leave in their wake. These systems have historically been almost exclusively associated with Soviet and now Russian submarines. In that country, they are most commonly referred to collectively as examples of a System Obnarujenia Kilvaternovo Sleda (SOKS), or Wake Object Detection System.

There have also been reports in the past suggesting that certain SOKS variants could be able to detect trace amounts of certain chemicals in a submarine's wake, including from temporary anti-corrosive coatings flaking off or byproducts from oxygen generation systems. Detecting minute increases in radiation levels from the reactors on nuclear-powered boats, such as the Trafalgar class, or elevated water temperatures from a submarine passing by, may also be among their capabilities.


SOKS gear fitted to an early Soviet Akula class submarine

In principle, such a system would be a valuable additional passive sensor for a submarine when hunting for other boats underwater. While modern sonar systems have passive, as well as active functionality, in the former mode, operators have to pick out the sounds of another submarine from a host of background noises, ranging from sea life to the simple movement of the ocean itself. These issues are even more pronounced in shallower littoral areas. You can read more about how all of this works in this previous War Zone story.

Using active sonar "pings" could help them find a target faster, but would also greatly expose the boat sending out those signals. In submarine warfare, staying as quiet as possible is critical to staying alive.



At the same time, there have long been debates about just how effective SOKS variants, which appear to have first emerged in the late 1960s, might actually be, with now-declassified U.S. intelligence documents hinting at potential limitations in range and sensitivity. At the same time, the continued Russian use of such systems would indicate that they provide at least some level of additional sensing capability.


A screengrab showing the Russian Navy Akula II class submarine Vepr, also known as K-157, with SOKS equipment on its sail.

In addition, there continues to be clear interest among other militaries around the world, including elements of the U.S. military, in sonar alternatives. The year before Talent had appeared in Gibraltar with the addition to its bow, another Trafalgar class submarine had arrived there with a similar-looking modification to the front of its sail.

Looks like HMS Talent @RoyalNavy got something rather special fitted for her current Mediterranean deployment - original images by @dparody pic.twitter.com/xaGfTpD6NF

— Joseph Dempsey (@JosephHDempsey) May 8, 2019

The additional arrays on Talent could enable it to collect more data and do so more rapidly, improving its overall capabilities. Putting the additional sensors on either side of the sail might improve the system's ability to determine the range or depth of the target based on the differences between what each of the three arrays detect, broadly akin to how radiofrequency signals can be triangulated.


A frontal view of HMS Talent in its latest configuration showing the two sensor arrays on the sides of the sail, as well as the one on top of the bow.

General technological advances, including increased computing power and artificial intelligence-driven systems to help process data from the sensors faster and more accurately, over the years may well have helped make the general concept more viable, as well. Those same developments could also enable the fusing of the wake-detecting data together with information from the boat's sonar arrays and any other sensor systems onboard to even more precisely spot, categorize, and track hostile submarines, as well as any other objects of interest underwater.

Using an older boat, such as Talent, to help prove all of this out in an operational environment would make good sense, too. The Mediterranean Sea, where Gibraltar is situated, which is a relatively well-understood body of water where Russian submarines are known to prowl, could be a particularly ideal testing ground.

"We've put this submarine right in this area of the eastern portion of the Mediterranean to counterbalance the Russian buildup in Syria," U.S. Navy Rear Admiral William Houston, then-tripled-hatted as Director of Plans and Operations for U.S. Naval Forces Europe/U.S. Sixth Fleet, the Deputy Commander of Sixth Fleet, and the Commander of Submarine Group Eight, told ABC News' "Nightline" in 2019, referring to the deployment of the Ohio class guided-missile submarine USS Florida to that area. "We're watching them [the Russians] very very closely. There's really not a day where we're not watching them, every single day."

Concerns about increases in Russian submarine activity, especially on both sides of the northern Atlantic, have grown among NATO members, including the United States and the United Kingdom, in recent years. Expanding Chinese underwater capabilities present another growing naval challenge. Both of these countries are also increasingly fielding new nuclear and advanced conventionally-powered submarines with features that make them extremely quiet and difficult to detect. All of this would only underscore a desire for additional ways to detect threats beneath the waves, such as a wake-detecting system.

All told, while Talent may be set to sail into retirement later this year, the equipment fitted to the submarine now may well find its way onto other Royal Navy boats in the future.

Citation :

DSME Delivers Key Technology for Air Independent Propulsion (AIP)

29 November 2021


Air-Independent Propulsion (AIP) for submarines, based on the production of hydrogen by reforming methanol mixed with water (photo : maily-so)


DSME Develops Methanol Reforming Plant for Submarine Fuel Cells

Daewoo Shipbuilding & Marine Engineering (DSME) has successfully developed a methanol steam reforming plant for submarine fuel cells and delivered it to the Agency for Defense Development.

The company held a delivery ceremony at its Siheung R&D Campus on Nov. 18.

The plant produces high purity hydrogen using methanol and water. It means DSME has secured a level of competitiveness as high as that of advanced countries in the field of fuel reforming and hydrogen refining technologies.

Fuel cells are highly efficient in power generation and generate no noise and vibration. They do not generate foreign substances other than water in generating electricity.

Submarine fuel reforming technology is a state-of-the-art technology that has been studied for more than 20 years in major advanced energy powers such as Germany, France, and Spain.

Currently, hydrogen is supplied to submarine fuel cells through metal hydrogen storage alloy cylinders. This method is low in storage efficiency per weight and requires space for equipment installation. Its weaknesses are that separate auxiliary facilities are required for hydrogen charging and charging time is long. By contrast, the fuel reforming method using methanol boasts high storage efficiency, which improves submarines’ operation capabilities.

The fuel reforming method requires a smaller space and facilitates fuel supply. It does not require separate facilities for recharging and has short charging time.

(Business Korea)


http://defense-studies.blogspot.com/2021/11/dsme-delivers-key-technology-for-air.html  

[#125YearsOfSubs] 2nd submarine built in Cherbourg in 1899, the Narval was the world’s 1st “attack submarine”.
She was the 1st sub with a double hull and a double propulsion system, and her heritage can be found in the architecture of modern submarines, to this day. pic.twitter.com/qfYGrZ4z1L

— Naval Group (@navalgroup) June 21, 2024