Going down to ocean depths needs specialised platforms for instruments. Some platforms are tethered, and are towed or lowered from the ship, collecting real-time data; others are stand-alone, to be deployed and then recovered several months later.
Remotely Operated Vehicle
A remotely operated vehicle (ROV) is a tethered underwater robot that is unmanned, highly manoeuvrable and controlled by an operator(s) aboard a vessel. They are linked to the ship by the umbilical – a group of cables that carry electrical power, video and data signals back and forth between the operator and the vehicle.
ROVs vary in shape, size and capability, depending on their task. They are a complex array of electrical, electronic, hydraulic and mechanical systems, comprising monitoring and control equipment, launch and recovery systems, umbilical controls and winches.
The NOC currently operates one ROV, called Isis, the UK’s deepest diving ROV dedicated to science. Isis collects samples, drills sediment cores and shoots high definition video and stills at ocean depths of up to 6,500 metres (four miles). The vehicle is supported with containerised control room, workshop and spares storage, with a launch and recovery system.
Isis technical specification
Weighing 4000kg laden in air with dimensions 2m × 2m × 2.5m, the vehicle is equipped with cameras, lights, thrusters, manipulators and numerous scientific sensors. Isis is connected to the ship with an 18mm umbilical cable; this is steel armoured with three electrical and three fibre optic passes. A hydraulic power pack allows for hydraulic functions, e.g., manipulators, cable cutter, tool drawer.
The lower half of the vehicle is designed as a detachable tool sled so it is feasible to have a number of units preconfigured for specific tasks. Suitably sized and dynamically positioned (DP) ships of opportunity enable the system to be freighted and operated around the world.
ROVs enable intricate surveys of the seabed enabling the collection of precision samples from the seafloor. Experiments at extreme water depths unreachable by human divers, due to the water pressure, are also possible with the ROV. Although manned submersibles exist that can transport humans to extreme depths, ROVs are a more compact, portable and practical alternative, without the human risk element. An ROV can be manoeuvred precisely with its thrusters (propellers). Through its eyes (cameras), the manipulators (hands) can recover small, delicate objects more precisely than any other sampling system. Scientists can see the undisturbed area from where samples are selectively taken, providing them with a better understanding of habitats and structures. Complex in situ experiments can be achieved maintaining the environmental conditions and minimising sample damage caused by recovery to the surface.
Hydraulic Benthic Interactive Sampler (HyBIS) is a modular, versatile, robotic underwater vehicle (RUV) capable of reaching depths of 6000 metres, developed and operated by the NOC. Controlled via fibre optic cable connected to the ship, HyBIS is equipped with sampling grab, cameras and equipment used to record conditions in the deep sea.
The main module consists of the steering unit represented by two propellers as well as the energy supply, the cameras, the light, the hydraulic systems and the telemetry. Depending on the sampling requirements, different modules can be mounted under the main module.
In contrast to a conventional remotely operated vehicle (ROV), HyBis is not neutrally buoyant. Both the descent and the ascent of the HyBIS, as well as the operating depth are controlled from the ship by the fibre optical cable. Therefore, HyBis can deploy and recover a net load up to 700kg (sampling equipment and sampling material), which is several times the payload of an ROV. As well as sampling the ocean it has also been used to help to recover two different seabed landers containing scientific equipment worth over £300k.
In its first four years HyBIS has dived over a hundred times, recorded more than 450 hours of HD video footage and taken 1,000s of HD photographs. It has undertaken complex sampling missions at over 40 different sites.