Is squid-inspired propulsion all it’s kraken up to be?

The “jet age” began either in 1939, with the first flight of the Heinkel He 178, or over 500 million years ago, with the evolution of cephalopods powered by jet propulsion. Under water, jets are a less efficient means of locomotion than fin-based propulsion, but it does offer great advantages in maneuverability, as bursts enable the fast approaches of predator and the hasty escapes of prey.

Now a study, “Fluid-structure investigation of a squid-inspired swimmer” — published Oct. 1, 2019, in the journal Physics of Fluids — looks at how squid-like propulsive systems can be modeled and, in theory, designed for future underwater vehicles.

“The existing experiments, simulations and prototypes are concentrated on the imitation of fish swimming. In contrast, cephalopods (i.e., squids, octopuses and cuttlefish) have been mostly neglected,” write authors Xiaobo Bi and Qiang Zhu, both of the Department of Structural Engineering at the University of California San Diego. “These animals are also capable of highly effective swimming, especially when escaping from predators.”

While squid-inspired robots have been built before, the authors are specifically looking for a “cephalopodlike design that is capable of long-distance locomotion through repeated deflation-inflation cycles of its compression chamber.”

Could it someday be a long-range strategic blotter?

Novel aquatic propulsion methods are of interest to military planners and designers as autonomy and uncrewed vehicles expand the domains into which sensors can go. Biomimicry can yield both exciting new capabilities and lends itself well to a sort of ambient camouflage. Sonar that listens for the ping of metal hulls and the distinctive rotations of rotors may find itself unable to see the soft robotics and jet-propelled motion of a future robot squid.

Putting a sensor on a platform with squid-like jets and fins could enable it to sip power as it travels through the sea, navigating depths or shallows as needed, and then sprint through the water when needed, gliding and squirting under large vehicles, into docks or coastal outlets, or wherever else a squid robot might want to go.

The research outlined is useful, but don’t expect to see it lead to squidbots anytime soon. For starters, the modeling done only proved the usefulness of repeated squid-jet propulsion in two-dimensional space.

Still, as planners look to the seas of the 2040s and beyond, novel propulsion and advanced autonomy could lead to a whole new jet age.

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