Future-proofing icebreaker science
How do you build an Antarctic science and resupply ship that retains its leading-edge status into the future? It’s a question the Australian Antarctic Division’s Modernisation Taskforce has been grappling with during the design of Australia’s new Antarctic icebreaker, which has an expected life span of 30 years.
The new multipurpose ship, which will replace the Aurora Australis in the 2020-21 season, will have an icebreaking capability of 1.65 metres at three knots, a 1200 tonne solid cargo capacity, and the ability to meet changing scientific requirements.
It is this last capability that is particularly sensitive to future-proofing, and the demands for ongoing scientific capability have a big impact on the whole structure.
As the Icebreaker Project Manager, Nick Browne, explained, an important part of the ship’s scientific capability will be its acoustic instruments. These will be used to conduct seafloor and habitat mapping, visualise and measure the biomass of marine organisms in the water column, and measure ocean currents. To do this the instruments, mounted in the ship’s hull, send pings of sound out into the environment and listen to the returning echo to create images of their surroundings. But to work effectively they need a degree of hush.
“A major design challenge for the ship is the requirement for low acoustic noise, so as not to interfere with the quality and detection range of these scientific instruments,” Mr Browne said.
“Noise radiated away from the ship can also affect the behaviour of fish and other marine organisms.
“So the ship will be built to a ‘Silent R’ rating at speeds up to eight knots, ensuring very quiet operations during scientific surveys.”
To achieve this rating a significant amount of work has gone into the design of the ship’s hull and propulsion system, to reduce noise associated with the engines, gear boxes and propellers, and bubble formation and movement, while still maintaining the required icebreaking capacity and efficiencies in ocean transit. Big diesel engines directly drive the propellers when icebreaking, while quiet electric motors, powered by diesel generators on flexible mounting systems, power the ship for silent research operations.
To get the hull and propeller system right, hydrodynamic consultants used numerical modelling (computational fluid dynamics) to optimise the design. They then built a six-metre model to conduct a range of physical tests – icebreaking, propeller cavitation (generation of air bubbles in areas of low pressure) and sea-keeping (response to waves).
As an added level of precaution the ship also has two drop keels, packed with acoustic sensors, which drop below the bubble layer formed by ocean waves. These duplicate some of the multibeam and bioacoustic capabilities installed in the hull, but include other instruments and an “expansion space” for future equipment.
Flexible science platform
With the fundamental performance requirements bedded down, the ship design is now focused on delivering a flexible scientific platform that can react to changing scientific needs.
Scientific Research Systems Lead, Mr Jono Reeve, is responsible for channelling the needs, wants and dreams of scientists into the final design. The process has involved many months of workshops with scientists, the development of position papers by experts in oceanography, atmospheric science, marine geoscience, glaciology and biological science, and ongoing consultation with key parties as plans for work spaces and equipment interfaces are drawn up.
The process has also drawn heavily on the work done for CSIRO’s Marine National Facility, RV Investigator; the new icebreaker will match Investigator’s scientific capabilities in blue water, but will extend them into the ice.
“We looked at best practice around the world and asked what the future directions were for science and what capabilities would be important,” Mr Reeve said of the process.
“Scientific research voyages often require a unique combination of activities and sometimes activities not previously undertaken. So you need a platform that’s flexible enough to support the new activities that come up.
“The fundamentals of that platform are low noise, good deck handling equipment such as winches and cranes built into the ship, and an open deck that gives you the space and flexibility to do new things.” (see boxed text below).
Many of the scientific design considerations aim to improve efficiencies in operation and reduce the amount of time the ship has to stop for science. The moon pool inside the ship, for example, is a 13 m vertical shaft, four meters square, which runs from the science deck through the hull to the ocean. When its hatches are open, the moon pool allows instruments that were previously deployed only in open water, to be deployed in bad weather and sea ice.
“Once the ship is surrounded by sea ice we can use the moon pool to drop nets and deploy remotely operated vehicles and CTDs (conductivity, temperature and depth rosettes),” Mr Reeve said.
“The moon pool will also allow us to deploy equipment at the same time as we’re running nets or other equipment off the stern, so that we can make the most of the ship’s time.”
One possible addition to the ship’s scientific capability is a “wet well sampling space”, centred in the hull, below the water line (see New ways to catch krill). Large volumes of water would gravity feed into the wet well via observation tanks and filter tables designed to catch krill and more fragile life forms such as jellyfish and salps.
The brainchild of krill researcher Rob King, the wet well idea solves a major conflict between scientific and resupply needs, by allowing some science activities to be undertaken independently of other ship priorities.
“To catch krill we usually deploy a trawl net, which involves slowing and stopping the ship for a few hours. If you haven’t got time to stop, or there’s ice in the way, bad luck,” Mr King said.
“The wet well will allow us to capture live krill and other planktonic organisms, in the open ocean and the ice, without stopping the ship or interfering with other activities.”
For the Modernisation Taskforce, the design development process (conducted in consultation with Serco (or DMS Maritime) and vessel designer Damen) has largely been about finding synergies between the three non-negotiable ship functions – icebreaking, science and station resupply (see Icebreaker at a glance). There’s a long way to go yet before the blueprints for internal spaces, fixtures and fittings are finalised, but the team is confident they’re on a winner.
“This ship will open up new opportunities for Australian scientists and international collaborators,” Mr Reeve said.
“Science will continue developing new questions, and this ship will be flexible enough to support answering them. In fact, I can’t think of any ship that will be able to combine icebreaking, science and logistics better than this.”
Australian Antarctic Division
To meet changing scientific needs the new icebreaker will have:
- state-of-the-art scientific equipment, including a moon pool;
- space for up to 30 science containers on the aft deck, above the heli-hanger and at the front of the heli-deck;
- a range of power and water supplies for containerised laboratories;
- overhead cranes, specialist winches and a 30 tonne A-frame to lift and position containers and equipment, sediment coring systems and rock drills;
- a range of towing points to deploy nets and other equipment;
- fibre optic cables with bandwidth suitable for real-time video for underwater sensors;
- three small boats (‘tenders’) and a science tender for nearshore surveys, to take samples or retrieve equipment, and to deploy personnel from ship to shore.