June 13, 2013

Tiny Submarine made of Titanium Alloys Proposed for Exploring Europa

Jonas Jonsson envisions the tiny submarine named Deeper Access, Deeper Understanding (DADU) taking on the Europa challenge in his 2012 Ph.D. thesis for Uppsala University in Sweden. The submarine could first get its feet wet by exploring similar watery environments on Earth where its small size could prove exceptionally useful.

The DADU submersible would use eight small thrusters to maneuver around the underwater world. A fiber optic tether would connect DADU to a surface lander or station — a way to recharge the submersible's lithium-ion batteries and allow for remote control by a human operator. On-board software would allow the submersible to automatically dodge obstacles or stay at a certain depth underwater.

The Swedish team created a series of miniaturized instruments and sensors for the dream submersible. DADU has a forward-looking camera with a small laser to capture high-resolution video and to gauge the distance, size and shape of underwater objects.

But a huge challenge came from shrinking everything down to incredibly small sizes. The sensor for measuring the conductivity, temperature and depth of water is smaller than a fingernail.

The submersible's sonar device alone could fit within a matchstick box, Jonsson said. Such a device uses piezoelectric material that can vibrate to create acoustic sonar pulses and read reflected pulses or vibrations as electrical signals.

Jonsson also tested the idea for the submersible's sampling device for collecting tiny life forms on Europa — a microfluidic device smaller than a human thumb with a special filter to trap tiny microorganisms.

The first prototypes of the DADU submersible were made of plastic from 3D printers that allowed the team to quickly "print" the digital designs into real objects. But they envision the real submersible being built from a titanium alloy in order to survive the harsh temperatures and intense pressures of underwater environments.

Next up, the Swedish team hopes to further refine the miniaturized instruments. They also need to build the full integrated systems with all the miniaturized electronics before they can seriously test the submersible's capability to survive in a frigid ocean — whether on Earth or on Europa.

"I don’t think there are any particular technological breakthroughs required," Jonsson said. "There exist possible solutions for the technological barriers; however, further developments and optimizations are required for such a mission to succeed."

Getting down beneath the ice is still far from simple. Any Europa mission designed to penetrate the moon's icy surface would require a mole-like drill to melt its way through the ice. The submersible would also need kilometers of tether connecting it to a surface lander or station in order to communicate with its remote human operator.

Nobody is seriously planning a landing mission on Europa yet. But the European Space Agency aims to launch its JUpiter ICy moons Explorer mission (JUICE) to make the first thickness measurements of Europa's icy crust starting in 2030. NASA also has begun planning a Europa Clipper mission that would study the icy moon while doing flybys in a Jupiter orbit.

A model of Europa's interior, including a global ocean. If a 100 kilometer-deep ocean existed below Europa’s ice shell, it would be 10 times deeper than any ocean on Earth and would contain twice as much water as Earth's oceans and rivers combined. Credit: NASA/JPL

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