Underwater autonomous vehicles, or drones, have been in operation – and in the public eye – for decades. One of the earliest and most well-known remotely operated, deep-sea vehicles is Argo. Towed along the sea-bed and bristling with cameras, Argo was responsible for revealing the first glimpses of RMS Titanic in 1985, 73 years after her fateful maiden voyage.

More recently, submersible drones have been employed for other such expeditions; the hunt for missing Malaysian Airlines ‘MH370’ is noted as the largest and most expensive underwater search effort in history. Undertaking ‘deadly, dangerous and dull’ tasks across the oceans, drones help reduce the risk to human lives and extend research capabilities beneath the waves. Unfortunately, however, this much technology doesn’t come cheap.

Sampriti Bhattacharyya, a roboticist and engineer at MIT, thinks she may have found a solution to costly unmanned missions.

Working with her PhD advisor, Harry Asada, Sampriti has developed ‘Hydroswarm’, a powerful, affordable, underwater drone platform, complete with ‘swarm’ capabilities. Puttering through the sea, Hydroswarm’s autonomous bots, dubbed ‘Eve’, leave no visible wake behind them and can make themselves almost invisible against the ocean floor. Working together in teams of twenty or more, Sampriti envisions the drones will be cheap and easy to run, making them ideal for routine studies and lower-priority government uses.

Football shaped robots

Coming in at roughly the same size and shape as an American football, the rounded bodies of the robots feature a flattened panel, allowing them to glide across flat surfaces.

Originally designed to emit ultrasounds and scan for cracks in the water tanks of nuclear reactors, they robots could also be used to inspect ships for contraband goods, map areas of the ocean floor, monitor underwater pollution levels and even scout out new sources of oil.

One of the key objectives of the project is to keep the robots affordable, while making them as manoeuvrable as possible. The main structural components of the robot can be 3D printed, and only half of the bot must be kept watertight. The electronics are housed in the bottom half of the bulbous robot, while the top half is permeable to water.

In order to propel itself through the water, the top half of the drone contains six pumps, pushing water through specially designed rubber tubes. Two tubes vent on the top of the drone, keeping the flat panel pressed against the underwater surface, whether it’s the hull of a ship, an undersea pipe, or even the ocean floor. The other four pipes vent in pairs down the robot’s sides, and are used to control locomotion.

Jet-fighter precision

The oval shape of the robots may make them a bit wobbly, but that’s all in the design. Just like jet fighters, the robots are engineered to be unstable, allowing them to manoeuvre quickly and easily. To keep the bots travelling in a straight line, the four locomotive vents must exit its body at specific angles, all calculated by Sampriti to give the robots maximum control.

Housed inside the bottom half of the drones are the electronic circuits, a communications antenna allowing the drones to keep in touch with each other and the people on the surface, and an ‘inertial measurement unit’. This is a series of accelerometers and gyroscopes, making sure the robots always know which way is up. An algorithm controls the speed of water pumped through each of the six jets, keeping it on course.

While still in the prototype and testing phase, Eve currently runs on rechargeable lithium batteries. Travelling between a 50cm and a metre each second, the batteries give each robot around 40 minutes of dive time. In the future, the team envision the robots will work on rotation, with fresh bots subbing in for those with drained batteries.

Image by Woodym555, CC BY-SA 3.0, Link