Robotic underwater glider sets out to circumnavigate the globe

A small robotic submarine is set to make its first trip around the globe. Teledyne Marine, in collaboration with Rutgers University New Brunswick in New Jersey, will launch an underwater glider known as Redwing on its Sentinel Mission from Martha’s Vineyard, Massachusetts, on October 11.

Underwater gliders have been in use since the 1990s. Unlike traditional submarines which utilize propellers, gliders operate with a buoyancy engine. This device comprises a gas-filled piston that slightly alters the glider’s overall buoyancy. When the electric motor pushes the piston in, the glider becomes denser than water and gradually sinks at a gentle slope. Once it reaches approximately 1000 meters, the piston is retracted, allowing the glider to rise buoyantly. This method generates a slow yet effective sawtooth pattern of movement. Auxiliary propellers can be used if necessary, but the intention is to minimize their use.

As noted by Shea Quinn from Teledyne Marine, leading the Sentinel Mission, “Redwing will utilize ocean currents to glide rather than combat them, achieving an average speed of 0.75 knots” – slightly under 1 mile per hour.

Measuring 2.57 meters long, Redwing is about the size of a surfboard but weighs a substantial 171 kilograms. Previous gliders have endured missions lasting several months, but Redwing is designed with ample battery storage, enhancing its endurance capabilities.

According to Brian Maguire at Teledyne Marine, “The goal of this historic Sentinel Mission is to complete the circumnavigation in approximately five years.” The glider will operate autonomously while being monitored by engineers from Teledyne Webb Research and students from Rutgers University; it will communicate via satellite upon surfacing. Every day, mission control will adjust Redwing’s course to maintain its intended path. It is anticipated that the glider may require a battery replacement midway through its five-year mission, as indicated by Maguire.

Redwing aims to retrace explorer Ferdinand Magellan’s route from 1519-1522, with planned stops at Gran Canaria, Cape Town, Western Australia, New Zealand, the Falkland Islands in the South Atlantic, and potentially Brazil, culminating in a journey spanning approximately 73,000 kilometers back to Cape Cod.

Gliders are capable of conducting extensive, long-endurance research missions without the need for costly support vessels, making them essential for tracking vital data related to climate change. Redwing will collect information on ocean currents and sea temperature from previously uncharted areas using a range of instruments.

“We believe this is the most extended open ocean sampling effort ever conducted,” states Maguire.

Past glider missions crossed the Atlantic in 2009 and the Pacific in 2011, successfully traversing regions beneath the Ross ice shelf and other inaccessible locations. According to Karen Heywood from the University of East Anglia in the UK, “Gliders are excellent tools for gathering data in areas too risky for ships to navigate, such as during storms or hurricanes, or near calving glaciers.” The primary challenges during this mission will likely stem from fishing gear and busy shipping lanes rather than weather conditions. “Gliders are surprisingly durable and can handle strong winds and rough seas,” she adds.

Alexander Phillips at the National Oceanography Centre in the UK notes that the glider will also face potential dangers such as sharks and biofouling, where marine growth can impair the vessel’s function. “Biofouling can render a glider inoperable due to algae and plant accumulation on its outer shell. In some oceanic regions, gliders have been lost because of shark interactions. Damage from shipping and fishing activities can also lead to the loss of gliders,” Phillips explains.

Data collected during this mission will be accessible to universities, schools, and various global institutions, but the primary objective is to showcase the potential of gliders and to inspire future exploratory missions.