A major part of Naval Group's public presentation was that Australia would benefit from stealth technology from France's nuclear submarine program. This was to be specifically in the shape of the winning French design having
"pump jet propulsion that replaces obsolete propeller technology".
See the pump jet offer 15 seconds into to Naval Group's (was DCNS) winning 2016 promotional Youtube.
At Pacific 17 reported by AAP via Australia's SBS (October 4, 2017) is a presentation by Naval Group executive director of the Australian submarine program Jean-Michel Billig: "The vessels may end up with conventional propellers...Mr Billig said." [Comment - Such propellers are what Naval Group previously described as "obsolete"]
Mr Billig dismissed fears about engineering difficulties. "We are not converting a nuclear-powered submarine
into a conventional submarine, we are starting from scratch," he said.
[Comment - This is a big step back from the original major selling point of the French winner - that the French design would benefit from stealth technology from the French nuclear submarine program!]
[Comment - This is a big step back from the original major selling point of the French winner - that the French design would benefit from stealth technology from the French nuclear submarine program!]
On a another tack - did Australia criticise the German TKMS Type 216 entrant (in 2016) on high modelled noise because it did not have that vital French pump jet?
What Naval Group (then DCNS) offered Australia in its winning presentation, at the point of competition decision in 2016. Note the pump jet promise 16 seconds in. Beware this Youtube is likely to be taken down in the next few days.
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Details courtesy Naval Group (was DCNS) - via Sydney Morning Herald, April 26, 2016. Note "Super-quiet pump jet propulsion instead of propellor" is featured.
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Pete
24 comments:
Hi Pete
Vice-admiral Masao Kabayashi pointed out that efficiency of the pumpjet system was low and suggested that adoption of this system was wrong for convensional submarine. Many key proposals by Nabal Group were withdrawn or changed. Nabal Group seems to steal the contract by fake proposal. Turnbull administration is unfaithful for other two contenders, because it permits this kind of behavior. As RAN criticized TKMS and JMSDF based on fake propoal, RAN should explain the situation to them.
Regards
This was obvious with a glance of the photo of the SMX3.0 you posted below.
Do you see a bell surrounding the propeller ?
The pump jet concept only works with speed above 15knts or more SSK's normal patrol speed is far lower then that so how should it work?
Basically the Australians took it hook, line and sinker or more precise they just ignored the fact even if they knew it to make it a big pork barrel project to develop construction jobs in SA.
I would like to elaborate, this had been debated at other sites but with a pump jet to gain the same mass/weight, the propeller and bell for a pump jet you'll need to shrink the propeller, in doing so the propeller requires to spin faster to maintain equal speed even if the bell resonates the flush as thrust at the tip of the propeller since the propeller spin rate for conventional SSKs patrol speed were too slow you don't gain much extra thrust.
On the other hand a propeller spinning faster means cavitation which sub operators want to suppress, meaning the bell requires to absorb more sound oscillation then conventional propellers.
At the end with precise calculation of benefit vs cost they reached the verdict that pump jet technology did not match conventional SSK's operational parameters as had been speculated.
Pump jets cost you drag. In a nuke that doesn't matter. In a D/E, it has *never* been adopted before except for a Kilo class boat that was used as a test bed. I assumed that the RAN decided running four diesels with a large number of batteries offset this inefficiency enough to allow for a pump jet to be retained for higher quiet transit speed. My understanding is that the pump jet doesn't offer a huge quieting effect at 5knt patrol speeds and that its primary quieting effect was raising the top speed at which cavitation occurs for a given depth - ie, speeds above 5knts used in transit or a particularly fast patrol speed that would require towed arrays to avoid total blindness due to 'wash out' of the sonar.
The idea that this is a brand new submarine does seem like a 180 for the RAN, and was my original criticism of the project in the first place: the French nuke boat hasn't hit the water and the D/E version would have a different combat system, propulsion, CG, drop the external cooling loop, etc and as such had high technical risk as an almost entirely new platform.
Cheers,
Josh
Dear Pete,
as I remember Type 212A uses a bubble screen or "bell" to damp the noise. You may remember the "wires" going from one X-ruder to the next one.
Regards,
MHalblaub
Heres a bit of info on Russian sub propellers with a good rear view photo in dock of the Russian Navys pump jet equipped Kilo , the Alrosa. One picture shows part of the the rear shroud removed showing the rotor.-the term used for the propeller. Scroll down to the end.
http://www.subsim.com/radioroom/showthread.php?t=229242
I think the discussion of the tactical patrol low speed, misses the point. For conventional submarines its the quietest speed, with a pump jet you can have a higher quietest speed. Thats all. To say its not needed at the low speeds assumes theres something immutable about the speeds.
With a pump jet you can have higher efficiency ( accelerating duct) or reduced noise(decelerating duct) or a bit of both. Advances in use of carbon fibre and 3D design for large aircraft fans may have spilled over into reduction of weight and or maintenance for the submarine pumpjet components.
The original reasearch was done by the UK Admiralrt Resercah Laboaratory Teddington
Sorry but wrong, the low speed for SSK is dictated by the batteries. Basically SSK can only make short sprints at high speed before depleting the batteries.
'the Australians took it hook, line and sinker or more precise they just ignored the fact'
Ignored the fact. We call them waterjets not pump jets, it's an Australasian invention - the NZ Hamilton Jet - the strengths and weaknesses of the technology are understood here better than anywhere.
Hi Anonymous [at 5/10/17 3:56 PM]
If only small "water" jets for speed boats less than 5 tons or even Waterjet Bow Thrusters [1] were useful for large submarines.
The reality of $Billions in research on highly specialised submarine pump jets (by the US and Russia over 2 decades) is more accurate.
[1] https://en.wikipedia.org/wiki/Manoeuvring_thruster#Waterjet_bow_thrusters
Pete
Tri-ring is correct. I got around the wrong way, I meant the pump jet optimized for efficiency will allow a higher speed for the same propulsive effort.
What Australasian invention ? It was a Nzer, Australia had nothing to do with it. The water jets were designed for use shallow water, having a small tunnel in the hull in which the water was accelerated out the rear.
Latest aerospace designs: open rotor!
http://www.aero.de/news-27613/Safran-Open-Rotor-im-Test.html (German)
About 20% more efficient than a comparable fan engine.
The problem: open rotor produces more noise...
Thrust is created by overspeed of mass pushed behind. With a smaller fan less mass could be moved so the overspeed has to be higher. Higher speeds are always related to more energy losses through friction.
So RAN choose higher transit speeds but less economic ones.
A duct may be necessary for SSN but I am not sure about that in case of an SSK. A different propeller design could solve the problem with less energy required and less noise.
Regards,
MHalblaub
The shrouded propulsor only made sense if the RAN was willing to accept an increased indiscretion rate in exchange for a faster patrol or transit speed. For a transit, that might be a perfectly acceptable trade off, and since four diesels are to be carried the recharge rate might have allowed for a faster rate of advance with lower noise (while using more charge than a regular screw for a given speed). I had assumed that was the desired advantage.
My understanding is that subs of all types, nuke or otherwise, are top speed limited on patrol due to sonar wash out. That is, a nuke might do 20 knots and a Virginia might even do it relatively quietly at depth, but it largely won't hear anything (hull mounted hydrophones apparently suffer more dramatically form the flow noise than towed arrays due to being inside the hull's turbulence). That said I suspect nukes benefit from the option of a faster patrol speed should sonar conditions or opponent systems make it advantageous. More area could be searched and TMA would come more quickly. Its possible the Short Fin was envisioned as operating at patrol speed greater than a regular D/E and offsetting the higher electrical discharge and increased drag with more batteries and generation capability, but this again would be at the cost of indiscretion rate.
Cheers,
Josh
The counter rotating open rotors have been around a long time, back in the mid 1980s.
Given Shortfin is a new design from scratch, that triggers all sort of alarm bells. May be Australia should just move straight to Suffren SSN to minimize program risks. Why have taxpayers pay twice?
KQN
"For a transit, that might be a perfectly acceptable trade off, and since four diesels are to be carried the recharge rate might have allowed for a faster rate of advance with lower noise (while using more charge than a regular screw for a given speed). I had assumed that was the desired advantage."
Unfortunately no matter how many diesel engines are installed on the sub, under Peukert Law the LABs would need to be charged under 14.4V per cell to get them fully recharged. Any higher and the battery plates charge only near the interface between the plates and the electrolyte. In this case the battery voltage might rise to a value near the interface between the plates and the electrolyte. In which case the battery voltage might rise to a value near that of the charger voltage; this causes the charging current to decrease significantly.
In other words, the sub will be snorkeling most of the way.
I believe this is also the reason why the JMSDF have such a elaborate battery management protocol for the present LAB Soryu class, if you only use part of the whole battery banks then you need less time to snorkel to recharge resulting to less possibility to being detected.
Once LIBs are installed I believe the management protocols will be less stringent since LIB does not suffer from Peukert law and can be quickly recharged unlike LABs.
Hi Tri-ring [at 6/10/17 10:39 AM]
Your description of Peukert's Law is very useful - on LABs needing to be charged under 14.4V per cell.
On "Once LIBs are installed I believe the management protocols will be less stringent since LIB does not suffer from Peukert law and can be quickly recharged unlike LAB."
I think Japan will maintain the management protocols stringency - on account of the thermal runaway risks.
Regards
Pete
Thanks KQN [at 6/10/17 6:30 AM]
Re "Given Shortfin is a new design from scratch, that triggers all sort of alarm bells."
I've responded in the next SubMatt article - at http://gentleseas.blogspot.com.au/2017/10/mainstream-media-misses-naval-groups.html
Regards
Pete
The Russian Tu-95 Bear has counter rotating props since 1950s. The problem since than was related to noise issues for civil aviation.
Also turboprops were a rather long time more fuel efficient than jet engines. The jet engines provided higher speeds and made the aircraft more efficient through more turn arounds per day. That changed rather late with more and more higher bypass ratios.
A big fan engine also adds a big so called wetted surface an open rotor doesn’t has. More surface more drag.
So the need for a ducted propeller is related to a load propeller. In case a sophisticated propeller is quite much is gained.
Regards,
MHalblaub
I dont think you can directly compare a slow moving submarine in water with a much higher speed plane with turboprops in air. If you wanted to exceed 40kts in a sub, which the Russians did with the K-162 Papa class (44.7Kts, nearly 83 km/hr) you wouldnt be using a shrouded propeller.
Dear Ztev Konrad,
the basic physics stay the same:
- thrust is created through overspeed of mass.
- with less surface you need more overspeed to reach the same speed - higher speed => more friction
- a shrouded propeller means more "wetted" surface. In case of a submarine the surface is really wet. More surface => more friction
Regards,
MHalblaub
Hi Pete
Russian Navy has a pump-jet convensional submarine, B-871 Alrosa commissioned in 1990 [1,2]. But, Russia has not built other pump-jet convensional submarine, suggesting lower performance of B-871 than expected.
[1] https://en.wikipedia.org/wiki/Russian_submarine_B-871
[2] http://rusnavy.com/nowadays/strength/submarines/b-871/
Regards
I would note however, it will be more than 20 years between Alrosa & Shortfin. Since Alrosa is still in commission, it must not have been a complete failure. Hopefully DCNS can make it work. Otherwise, you can always fit a prop.
As to batteries, LIB is the way to go eventually. But no current sub is using them. Japan is about to & everyone in the industry will be watching. Its smarter at this stage to plan for LAB, but keep your eye on whats happening in the LIB space. The one thing you don't want is to design for LIB & then be forced to LAB, as you may find yourself short of what you need. The two Japanese subs currently being built with LIB's is a design that was originally LAB. The two technologies have different charging, weight & size specs (as well as performance), so its not a simple one for one replacement.
Regards
Regarding Naval Group possibly packpedalling on its Australian future submarine pump jet proposal, the Australian Defence Department now asserts (via Defence Connect):
"Defence intends to use the pump jet propulsion system for the Future Submarine that was offered by Naval Group as part of their Competitive Evaluation Process proposal, and remains on offer to Australia."
see https://www.defenceconnect.com.au/maritime-antisub/1410-defence-commits-to-pump-jet-propulsion-for-sea-1000
Pete
Hi Pete
Alrosa commissioned in 1990 is still active, but stayed in dock for 8 years.
In building plan of Soryu-class, Soryu No5 (SS505 Zuiryu, raid down in 2009) was going to equip with LIBs and related research using prototype LIB had finished in 2006. But, raid down of LIBs sub delayed to 2015 due to budget constraints. Currently, LIBs are manufactured in GS Yuasa factrory, and they are delivered in 2018. Dimensions and weight of LIBs are resembled to those of LABs. One of biggest difference between two batteries is votage of battery module which is 36V and 2V for (NCA-) LIB and LAB, respectively. As a result, connection of batteries is perfectly different from each other.
By the way, did Naval Group rearly submit proper simulation or data to CEP?
Regards
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