In the correctly gradual process, since 2014, to select Netherlands' 4 Walrus replacement subs the shortlist (3 contenders: Sweden, France and Germany) are fighting it out on many levels. One level is the relatively arcane choice of less magnetic pressure hull
steel.
By contrast Australia only gave itself less than 18 months (for political vote reasons) from shortlist stage to picking the winner.
Below the article of January 19, 2021 two particular comments were:
A. Anonymous's (for the French or Swedish contender?) comment of January 29, 2021
at 6:01 PM:
[Germany’s? ] Regarding "Non-magnetic stainless [steel] Nitronic 50,
well for it to be truly ‘non-magnetic’ it needs to be annealed which means no strength, which means...nope,
not useful for the application at hand. Incredible hard to weld, solidification
cracks. And there are other ways to manage magnetism too; degaussing.
Wonder why Nitronic,
which I think is inherently an American steel is offered by the Germans?"
__________________________
Against which Anonymous B. countered:
__________________________
B. Another Anonymous (for Germany?) at January 31, 2021 at 12:17 PM:
(1) 1.3964 is material number and Nitronic 50 is bland name [that hyperlink explaining]:
“1.3964 is the Werkstoff number for a more highly alloyed austenitic stainless steel most commonly known as Nitronic 50. The Werstoff designation was developed by the German standards body DIN, with the term Werkstoff translating approximately to ‘material’. It is also known as XM19, as used in ASTM A182, ASTM A276 and ASTM A479, alongside the unified numbering system caption of UNS S20910. Nitronic 50 is a trademark of AK Steel Corporation.”
(2) Magnetism of 1.3964 is extremely small and annealing is not needed.
[See this link] page 2/2, figure of “Magnetic permeability”
(Relative) magnetic
permeability (ur) is 1.0033, while ur for iron is 200000 as shown in wikipedia.
(3) Effect of annealing on magnetism of Nitronic 50 is neglectable.
[See this link] ,
page2/2, table of “PHYSICAL PROPERTIES”, Magnetic Permeability: (@ RT, 200
oersted):
(Relative) Magnetic
Permeability of Annealed or “Super” High Strength (of Nitronic 50) is ca.1.004”
ibid MAGNETIC PERMEABILITY: Nitronic® 50 does not become magnetic when cold worked. The magnetic permeability of the alloy remains low even at cryogenic temperatures to below -400˚F.
Pete Comment
So there you have it. After 6 years the Dutch future submarine selectors thoroughly continue the mage task deciding the $Multi-Billion merits of the 3 contenders – maybe by 2022.
If only Australia's future submarine selectors had also been allowed 8 years (instead of less than 18 months) by their political masters to coolly select the winner of 3 contenders.
Note what I wrote on April 25, 2016. But the selection milestone in Australia was the 2016 Federal Election. Racing towards selection of France was essential for the ruling Coalition to win votes in South Australia. So Australia's Prime Minister cut the selection from a shortlist of 3 to just one winner, on April 26, 2016.
Pete
6 comments:
Dear Pete,
magnetic signature is an interesting topic. Germans always put a focus here because of the mine threat in the Baltic Sea and the shallowness of it.
Lots of places and opportunities there to hide from active sonar. Not so many to hide from magnetometers. And magnetometers are likely to get more powerful and so small that they even can be used from fairly small unmanned aerial vehicles. (link e.g. https://www.aspistrategist.org.au/prospects-for-game-changers-in-submarine-detection-technology/ - SQUID sensors)
Smart design of the submarine's degaussing system mitigates the problem to a certain extent. However, this systems continously nibbles on your (limited) amount of energy. Not so cool for the captain when his sub is in a high threat environment. Best way to avoid a high magnetic signature is to dramatically reduce the magnetic field of the steel structure. The rest can be reduced with a much smaller degaussing system.
As always... it's some kind of philosophy question and guess what your future opponents capabilities might be during the life cycle of your submarine.
Hi pete
Concerning the use of austenitic stainless steel(non magnetic) versus the use of dedicated low carbon steel (extra high yield stress ) in sub construction I did understand that the choice had to do more with the compromise selection relevant to the expected missions ;I might be wrong however
For a coastal sub ( operating in the baltic a must for instance) magnetic signature is very relevant (magnetic anomality signal decrease at the cube with depth and the sensor has to be very close , may be a fraction of a mile) while the need to operate at great depth (250 /400 m)and endure the associated cycling fatigue /cracks is not the prerequisite.
AIP for short distance , low speed makes also sense . (Israeli Dolphin really in the "parking lot " off Haifa or the syrian coast for a second N strike..)
For an oceanic sub which need to hide below the accoustic diopter at 150m+ typically,magnetism becomes secondary versus the need to have a lighter structure allowing more batteries for a conventional sub for instance (we are talking a hundred ton probably for equivalent depth
Magnetic anomality detection is probably not really pertinent for a nuclear attack sub à la sea wolf/astute/barracuda
Within a few min of a datum it can cruise at 30 knots at 350 m ..how long it takes for an helo or plane to be on the spot and launch an attack in the real tactical world ?
The US , UK or french sub use HY100 or equivalent steel. I do not know about the japanese choice..
Hi Pete,
It may happen that the Blekinge class (A26) will get rid of some steel and replace it with composite structure instead (in Swedish) below is the English abstract
"This report is a master thesis performed at The Royal Institute of Technology divisions of Lightweight Structures and Naval Architecture in collaboration with the Swedish defence material administration, FMV. There are several naval submarines used by the Swedish navy and more to be built. The existing submarines have stability problems due to a high centre of gravity. Most parts on the existing vessels are made of steel, despite a position far above the vertical centre of gravity. By replacing the current steel casing covering the top part of the submarines pressure hull and the rudders placed on the tower, to a lighter composite structure it is possible to lower the centre of gravity. In this report the composite structure of the rudder and the casing has been weight optimized to achieve a structure as light as possible, but still able to withstand the forces applied to the structure. An analysis of the applied loads shows that the dimensioning loads vary between 50 and 90 kPa depending on the specified part. The results show that it is possible to decrease the weight of the rudder and casing with over 80 %. This would also give the submarine an increase in initial stability with over 40 % compared to the existing steel construction. "
/Kjell
Pressure hull of Japanese submarine is made of NS80(proof strength 784MPa) and NS110(1078MPa). Welding strength of NS80-NS110 and NS110-NS110 were experimentally proven.
Many talking the Talk, but when start they walking the Walk ?
The official Walrus replacement process started at the beginning of 2013. By signing a MoU about submarine cooperation with Norway and Germany. In this process there are two sides. One side wants to import a cheap MOTS submarine from abroad. The other side wants a Walrus 2.0.
The cheap MOTS side,consists of politicians and civil servants, who are at a quite distance of the defense dept. And are afraid of a repeat of the Walrus troubles. In the eighties, politicians decided to save a large shipyard consortium (RSV). By speeding up the Walrus design phase. Then, the same happened as during the JSF System Development & Demonstration phase. The construction allready started, while many drawings were not ready or made at all. During the development, the specifications also changed because of the increasing Sovjet submarine threat. Costs and timeschedule went through the roof. The navy top made the mistake not to report this to the politicians. The Walrus (troubling) affair was born.
There are not only 2 sides, with totally different views about the Walrus replacement.
Other Departments interfere in this project too. Oh yes in this kind of large defense projects there are financial, economical (trade & jobs), industrialand Foreign Affairs components too. Unfortunately, the Departments of Treasury, Foreign Affairs, Trade, Internal Affairs and the prime minister himself, got a 'too big finger' in this project. And all those Departments have opposing views about the Walrus successor.
Our economy depends a lot at international trade and has an open character.
So the foreign relations are important for The Netherlands. Two contenders are from the most powerful EU members. This plays a significant role in the choice for the new sub.
All those factors have made the Walrus replacement a highly politically sensitive matter.
According to the current time schedule, in 2021, the decision will be made for the Staff Requirements, design and shipyard.
The contract will be signed in 2022. The start of the construction will start in 2023 or 2024. The Walrus successor must hit the water in 2027, and enter service in 2028.
Well, that's a challenge !
Many experts, insiders and other interested people in The Netherlands are following the Attack class project.
Many Dutch do not like the French and do not favour the shortened Barracuda version.
Why?, because the Dutch see the French as too dominant, too selfish and unreliable.
According to the Dutch General Accountability Office (Algemene Rekenkamer) one of the 3 contenders is too expensive for the Dutch budget. But this candidate is also the best performing one. Many Dutch suspect, that this the shortened Barracuda.
Beacause poltical factors play the main role in this project. There is a realistic chance that the Walrus replacement ends up as 'a trainwreck'. In other words: they get, what they don't need.
Locum
Hi Anonymous [at February 6, 2021 at 12:32 AM]
Thanks for your information on the very high yield Japanese pressure hull steel strength. The customer has been very deep diving Japanese submarines operating in the Western Pacific.
In the race to provide future submarines for the Netherlands: France, Germany and Sweden have a sales advantage over Japan because 3 are members of the EU - as is the Netherlands https://europa.eu/european-union/about-eu/countries/member-countries_en
France and Germany also have a NATO membership advantage - Netherlands also being a NATO member.
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