Bairdmaritime provides a review of Australia’s new icebreaking research and supply vessel.
Looking for more information, I found a very extensive description here (click on the menu tab on the upper right). This is a big, powerful, very versitile ship, but I wonder about the choice of propulsion and hope our resident icebreaker expert, Tups, will comment.
First, at 25,500 tons, it is much larger than either Healy (16,000) or Polar Star (13,623 tons). It is way longer as well at 160.3 m (526 ft), compared to Healy (420 ft / 128 meters) and Polar Star (399 ft / 122 meters). She is even larger than the Polar Security Cutter PSC (22,900 tons and 460 ft / 140 meters in length).
A good part of the ship’s size is due to the fact that this ship is more than an icebreaker. While a typical US support mission to Antarctic would envolve three ships, an icebreaker, a supply ship, and a tanker, this ship is a combined icebreaker, dry cargo ship, tanker, and research vessel. The crew is small, 32, but there are accommodations for an additional 117 expeditioners plus 1200 tonnes of cargo and 1.9 million litres of fuel.
Aviation facilities are generous. The hangar can accommodate four small AS350 B3 helicopters or two Sikorsky S-92 that are larger than the H-60s.
It has a large number of boats including a pair of barges. Each barge has two 448 kilowatt (600 horsepower) engines and a water jet propulsion system that provides greater manoeuvrability than propellers. The barges carry general cargo from ship to shore in Antarctica.
On the cargo hatch covers near the bow of RSV Nuyina are two 16.3 metre-long, 6.2 metre-wide barges, each capable of carrying more than 45 tonnes of cargo.
The aluminium barges can operate in calm seas and up to 50 knots of wind, at a speed of eight knots.
What I found most surprising was the choice of propulsion systems. This is a seriously powerful icebreaker, but unlike most modern icebreakers, it does not use steerable podded diesel electric systems (such as Azipods). Instead all power goes through two shafts to controlable pitch propellers. Both the sources reported power comes from two V16 diesel engines (19,200 kW each) geared diesels and 4 diesel generators (7,400 kW each) powered by diesel generators. From the https://www.antarctica.gov.au/ site which Bairdmaritime seems to have copied.
RSV Nuyina can cruise efficiently in open water, operate silently (in ‘Silent R’ mode) during scientific operations, or continuously break ice up to 1.65 metres thick.
RSV Nuyina has a diesel-electric propulsion system that provides different levels of power depending on the task.
In icebreaking mode RSV Nuyina uses its full propulsion system – two V16 diesel engines (19,200 kW each), and 4 electric motors (7,400 kW each) powered by diesel generators.
In its 12–14 knot cruising mode, the ship relies on the electric motors.
There are two engine rooms to provide an enhanced level of safety and redundancy. Each room houses a V16 diesel engine and two diesel generators.
That seemed like an awful lot of power for the modest maximum and cruising speed reported. The descrtiption sounded like a total of 68,000 KW total (about 92,000 HP) but that seemed unlikely.
Wikipedia indicates they max total power is a still very respectable 26,600 KW or 35,657 HP (confirmed here). This would make her slightly more powerful than Healy (2 × 11.2 MW (15,000 hp).
Something did not sound right.
Looking up the MAN 16V32/44CR engines reportely installed I found that they were rated at 9600 KW not 19,200 each, rather that would be the total for the two. Given a total output in the icebreaking mode, of 26,600 KW, 19,200 of which comes from the two main diesels, that means the electric motors would provide an additional 7400 KW total, or probably 3700 KW each which be enough for a 12 knot cruise. That makes sense.
It appears that pod propulsion is not as robust as required versus the shaft and variable props.
Chuck, you did your due diligence! Great report! She still seems like a competent icebreaker/research ship, which should serve Australia for decades to come.
Yes, If anything, she seems more capable than I would have expected.
I still feel direct drive and controlable pitch props may be a mistake for an icebreaker. Look forward to comment from our more knowledgable readers.
The Australians are no strangers to geared propulsion: their previous Antarctic research and supply vessel, Aurora Australis, had a single shaft with controllable pitch propeller. Given Nuyina’s operational profile which includes long open water transits and only limited ice operation, adopting mechanical transmission with better fuel economy makes sense. The reliability issues of early geared power plants, including those of the USCG Polar class, were largely solved during the 1980s. The hybrid “combined diesel-electric and diesel” drivetrain also addresses the inherent poor low-end torque of diesel engines, an issue previously solved with oversized “ice flywheels” that would increase shaftline inertia.
That being said, combining mechanical geared and electrical drivetrains increases the complexity of the propulsion system particularly in “icebreaker scale”. I know of a few small ice class “eco-freighters” that feature a shaft generator that can double as an electric booster motor during ice operation, but even at full power those ships put less than a megawatt of power to the water. For the most powerful icebreaker permanently stationed in the southern hemisphere, I would have proposed a fully-integrated diesel-electric powerplant which has remained as the industry standard for icebreaking ships since the 1930s whereas geared diesel icebreakers have largely remained one-offs.
However, I would probably still have kept the twin-shaft layout instead of azimuthing propulsion because, frankly speaking, I would have had hard time justifying expensive Azipod units for this ship given its operational profile in the Antarctic summer season. Despite its “Polar Class 3 Icebreaker(+)” classification, Nuyina is first and foremost a cargo/resupply ship and a research vessel; it does not “need” the added capabilities of azimuthing propulsion.
@Tups, thanks for you comment.
Chuck, as always a solid post and I was enjoying the reading a lot. And in regard to the chosen concept: Tups nailed it already. However the high cost of Azipod propulsors were certainly not the only factor to go with CPPs and hybrid propulsion system. Our PSI team supported the shipbuilder in the phase of preliminary ship design, so we may deliver some insight into the design criteria being relevant to selection of the propulsion system
The propulsion system architecture was subject to a combination of various, sometimes contradicting requirements, such as low underwater radiated noise level satisfying DNV Silent R notation but also high ice loads capability to obtain the Icebreaker (+) notation according to Polar Code 3 accompanied with the requirements for high redundancy level and economical operation on long transits.
This combination of requirements resulted in the selection of a hybrid combined diesel and electric propulsion system with CPPs.
The low noise mode of operation performed by the electric propulsion motors (RENK AED 37-T), each one connected to the respective shaft line by a flexible coupling. This is the sole interface, which enables for quick disconnection of EPM from the shaft line in case of emergency. The propeller clutches allows for disconnection of the remaining part of the propulsion system reducing the number of propulsion equipment involved in this particular mode of operation.
The medium speed main diesel engines, dynamically engaged by the propeller clutch, cater for economical operation during the transits including the possibility of using the AED as shaft generators in DE-PTO mode.
The redundancy requirements are effectively covered by distribution of total propulsion power into multiple propulsion engines (EPMs and MDEs) located in separate watertight compartments.
Finally, in the icebreaking mode the total propulsion power is available on CODLAD mode and the mass moment of inertia of the propulsion system is increased by clutchable flywheels connected to main reduction gears preventing the diesel engines from stalling even in the most severe load cases of propeller-ice interaction applicable for PC3 conditions.
Additional information regarding the vessel’ characteristic can be found on shipbuilder’s website: https://archive.damen.com/en/magazines/2017/11/a-state-of-the-art-antarctic-icebreaker-asrv-nuyina
(Please forgive me, as a RENK employee, for mentioning one or the other of our products in my comments as long as this serves to explain the facts)
@Marco, thank you for your comment. Appreciate you input. The link provides a very clear, very complete explanation of the design.