Stealth ship sees deep

Australia’s Antarctic icebreaker RSV Nuyina uses sound to ‘see’ into the deep ocean and seafloor below.

The capability is critical to measuring the distribution and abundance of marine organisms – particularly krill – to inform conservation and fisheries management measures, to understand the glaciological and geological history of an area, and to map the seafloor to understand habitat or produce navigational charts.

To do this a range of acoustic instruments are mounted in the hull, and in two drop keels that can be lowered up to three metres beneath the ship.

In the hull, a large low frequency multibeam echosounder is used to map a swath of the seafloor and continental shelf up to 25 kilometres wide in one pass, and work at depths of 11,000 metres.

In the hull and drop keels, a higher frequency multibeam provides measurements on the continental shelves, while a sideways looking multibeam 'sees' schools of fish and krill, to help scientists understand their movements.

The ship also has hydrophones to listen for marine mammals, and a fisheries sonar that allows scientists to find schools of fish or krill.

The drop keels get the acoustic instruments past the noisy bubble layer, which can interfere with the instruments’ ability to detect their targets.

But the ship has another clever noise cancelling system – called ‘Silent R’.

RSV Nuyina Science Coordination Manager, Jono Reeve, said Silent R provides a range of scientific capabilities.

“If you’re silent you can hear really well and you can hear what’s out there,” he said.

“And if you’re silent you can be stealthy; so that means that the fish don’t go ‘what’s that?’. They don’t know you’re there, so they keep on doing what they’re doing and you don’t affect them.

“That’s important when you’re trying to understand their behaviour or how many are there, because you can observe them without influence.”

To achieve this level of stealth the ship has a hybrid drive system. Silent electric drives coupled with diesel generators provide propulsion during scientific research, and flexible mounts on all equipment in the engine room absorb vibrations within the ship.

Learn more in the video below.