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The US space agency’s Swim (Sensing With Independent Micro-swimmers) project hopes to one day explore beneath the surface of Jupiter’s icy moon using ‘swarms’ of small robots. Delivered to the subsurface ocean by an ice-melting ‘cryobot’, dozens of mobile-phone sized bots would zoom off, searching for chemical and temperature signals that could indicate life.
“People might ask, why is NASA developing an underwater robot for space exploration? It’s because there are places we want to go in the solar system to look for life, and we think life needs water. So we need robots that can explore those environments – autonomously, hundreds of millions of miles from home,” said Ethan Schaler, principal investigator for Swim at NASA’s Jet Propulsion Laboratory in Southern California.
NASA has now tested prototype machines that could provide vital engineering knowledge for the ambitious future expedition, it announced yesterday (20 November), with “encouraging” results.
Relying on low-cost, commercially-made motors and electronics, the 3D-printed prototypes were tested in a 23m swimming pool at Caltech in Pasadena. Pushed along by two propellers and with four flaps for steering, the prototypes demonstrated controlled manoeuvring, the ability to stay on and correct course, and a back-and-forth ‘lawnmower’ exploration pattern. Working completely autonomously during more than 20 rounds of testing, they also spelled out ‘JPL’ with their movements.
“It’s awesome to build a robot from scratch and see it successfully operate in a relevant environment,” Schaler said. “Underwater robots in general are very hard, and this is just the first in a series of designs we’d have to work through to prepare for a trip to an ocean world. But it’s proof that we can build these robots with the necessary capabilities and begin to understand what challenges they would face on a subsurface mission.”
The wedge-shaped prototype used in most of the pool tests was 42cm-long and weighed 2.3kg. With mass extremely limited on any spaceflight, NASA envisions any deployed robots would be about three-times smaller, with miniaturised, purpose-built parts. The swimmers would also use a novel acoustic communication system to transmit data and triangulate positions.
Digital versions of the miniature robots were also tested in computer simulations, which replicated the same pressure and gravity they would likely encounter on Europa. A virtual swarm of 12cm-long robots was sent on repeated missions to look for signs of life, helping determine the limits of their abilities to collect science data in unknown environments. The work also led to the development of algorithms that would enable the swarm to explore more efficiently, and helped the team understand how to maximise useful findings with predicted battery life of up to two hours.
Collaborators at Georgia Tech in Atlanta also built and tested an ocean composition sensor, which would enable each robot to simultaneously measure temperature, pressure, acidity or alkalinity, conductivity, and chemical makeup. The tiny millimetre-scale chip is the first to combine all those sensors into one, NASA said.
The agency’s Europa Clipper spacecraft will reach the moon in 2030, and will use 49 ‘flybys’ to scan for signs of life below. The Swim project will continue developing its robots for possible future missions in the meantime. Schaler also suggested that the robots could be used for oceanographic research on Earth, including under polar ice.
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