NASA testing underwater robots to explore ocean worlds

• When NASA’s Europa Clipper reaches Jupiter in 2030, it’ll study the ocean that lies beneath the moon Europa’s icy crust from orbit.
• NASA is already preparing for a possible follow-up mission, in which swimming robots could explore the watery depths of Europa and other ocean moons.
• These engineers and scientists recently tested an autonomous prototype robot, which successfully explored a swimming pool.

NASA published this original story on November 20, 2024. Edits by EarthSky.

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Underwater robots under development

When NASA’s Europa Clipper reaches Jupiter in 2030, it will aim an array of powerful instruments toward Jupiter’s moon Europa. During 49 flybys, it’ll look down from orbit, hoping to spot any signs that the ocean beneath the moon’s icy crust might sustain life. But teams are already developing the next generation of spacecraft technology, which could potentially send underwater robots plunging into the watery depths of Europa and other ocean worlds.

In September 2024, a team at NASA’s Jet Propulsion Laboratory tested a series of underwater robot prototypes in a swimming pool at Caltech, Pasadena. And they say the results were encouraging.

The mission concept is called SWIM, short for Sensing With Independent Micro-Swimmers. The project envisions a swarm of dozens of self-propelled, cellphone-size swimming robots that, once delivered to a subsurface ocean by an ice-melting cryobot, would zoom off, looking for chemical and temperature signals that could indicate life.

Ethan Schaler, principal investigator for SWIM, said:

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.

See the underwater robots in action in this video, via NASA/ JPL-Caltech.

SWIM practice

The SWIM team’s latest version is a 3D-printed plastic prototype that relies on low-cost, commercially made motors and electronics. Pushed along by two propellers, with four flaps for steering, the prototype demonstrated controlled maneuvering, the ability to stay on and correct its course, and a back-and-forth “lawnmower” exploration pattern. It managed all of this autonomously, without the team’s direct intervention. The robot even spelled out “J-P-L.”

Just in case the robot needed rescuing, it was attached to a fishing line, and an engineer toting a fishing rod trotted alongside the pool during each test. Nearby, a colleague reviewed the robot’s actions and sensor data on a laptop. The team completed more than 20 rounds of testing various prototypes at the pool and in a pair of tanks at JPL.

Schaler said:

It’s awesome to build a robot from scratch and see it successfully operate in a relevant environment. 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.

Tiny underwater robots

The wedge-shaped prototype used in most of the pool tests was about 16.5 inches (42 centimeters) long, weighing 5 pounds (2.3 kilograms). When ready for spaceflight, the robots would have dimensions about three times smaller. That’s tiny, compared to existing remotely operated and autonomous underwater scientific vehicles.

The palm-size swimmers would feature miniaturized, purpose-built parts. And they’d employ a novel sound-based communication system for transmitting data and triangulating their positions underwater.

Swarm science

Digital versions of these little robots got their own test, not in a pool but in a computer simulation. In an environment with the same pressure and gravity they would likely encounter on Europa, a virtual swarm of 5-inch-long (12-centimeter-long) robots repeatedly went looking for potential signs of life.

The computer simulations helped determine the limits of the robots’ abilities to collect science data in an unknown environment. And they led to the development of algorithms that would enable the swarm to explore more efficiently.

The simulations also helped the team better understand how to maximize science return while accounting for tradeoffs between battery life (up to two hours), the volume of water the swimmers could explore (about 3 million cubic feet, or 86,000 cubic meters), and the number of robots in a single swarm (a dozen, sent in four to five waves).

In addition, a team of collaborators at Georgia Tech in Atlanta fabricated and tested an ocean composition sensor that would enable each robot to simultaneously measure temperature, pressure, acidity or alkalinity, conductivity, and chemical makeup. Just a few millimeters square, the chip is the first to combine all those sensors in one tiny package.

More testing to come

Such an advanced concept would require several more years of work to be ready for a possible future flight mission to an icy moon. In the meantime, Schaler imagines SWIM robots potentially being further developed to do science work right here at home. They could be used to support oceanographic research, or take critical measurements underneath polar ice.

Bottom line: NASA is testing prototypes for underwater robots that could one day explore our solar system’s subsurface oceans.

Source: NASA Ocean World Explorers Have to Swim Before They Can Fly

Read more: Underwater robots to explore beneath Antarctic ice

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