Sea creature-inspired robots could swim in extra-terrestrial oceans

Underwater robots inspired by the shape and movement of a jellyfish-like creature could operate in unknown and extreme environments, their creators have said – even exploring the depths of extra-terrestrial oceans.

Known as RoboSalps after their natural namesake, the devices were developed at the University of Bristol. Salps have translucent barrel-shaped bodies and a complex lifecycle, changing between solitary and aggregate generations – living as individuals at some points, and combining into chain-like colonies at others.

Like their biological counterparts, RoboSalps have light, tubular bodies and can link together to form ‘colonies’, giving them new capabilities.

“RoboSalp is the first modular salp-inspired robot,” said research leader Valentina Lo Gatto of Bristol’s Department of Aerospace Engineering.

“Each module is made of a very lightweight soft tubular structure and a drone propeller which enables them to swim. These simple modules can be combined into ‘colonies’ that are much more robust and have the potential to carry out complex tasks.

“Because of their low weight and their robustness, they are ideal for extra-terrestrial underwater exploration missions, for example in the subsurface ocean on the Jupiter moon Europa.”

Using a small motor with rotor blades, the RoboSalps can swim on their own. They are difficult to control as individuals, however.

After joining together to form colonies, their movement becomes more stable and sophisticated. Joining multiple units together also adds redundancy to the system, making it more robust against failure. If one module breaks, the whole colony can still move.

A colony of soft robots is a relatively novel concept with a wide range of interesting applications, the researchers said. The devices are soft, potentially quite energy efficient, and robust. This could make them suitable for autonomous missions where a direct and immediate human control is not feasible.

“These include the exploration of remote submarine environments, sewage tunnels, and industrial cooling systems,” said Dr Helmut Hauser of Bristol’s Department of Engineering Maths. “They can easily be stored in a reduced volume, ideal for reducing… space mission payloads.” 

The soft materials enable gentler interaction with potentially delicate ecosystems, both on Earth and in extra-terrestrial applications, reducing the risk of environmental damage. The possibility to detach and rearrange units gives the system adaptability – once the target environment is reached, the colony could be deployed to start exploration, before splitting into multiple segments heading in different directions. They could then reassemble in a new configuration to achieve a different objective, such as sample collection.

Professor Jonathan Rossiter said: “We are also developing control approaches that are able to exploit the compliance of the modules, with the goal of achieving energy efficient movements close to those observed in biological salps.”