This Torpedo-Style Autonomous Submarine Will Travel 10 Leagues Under the Sea

Jules Verne’s science fiction classic Twewnty Thousand Leagues Under the Sea has a title that misleads many. It doesn’t mean the Nautilus dove to a depth of 20,000 leagues (about 96,000 kilometers), but rather that Captain Nemo and crew traveled for a great distance while submersed. For all we know, based on the title alone, they could have been just a meter below the surface. Luckily, CPSdrone’s requirements were a little more modest when they built this torpedo-style autonomous submarine for undersea exploration.

While the planned voyage might not be of Vernian proportions, it is still quite an expedition. The CPSdrone team wants the sub to travel from Gdańsk, Poland to the Hel Peninsula, which is a round trip of about 46.5km. That is just under 10 leagues, for the ancient mariners among our readers (the literature buffs are loving this article, trust me). Such a long distance requires both a lot of battery capacity and strong reliability. A fault along the way would very likely result in the expensive craft being lost at sea, like the SS Poseidon.

The torpedo shape of the drone solved the problem of battery capacity. CPSdrone was able to fit a bunch of 18650 lithium batteries into the hull, while keeping the shape hydrodynamic and efficient. The bigger challenge was reliability, starting with positioning. To work autonomously, the sub needs to know exactly where it is. But GPS signals barely penetrate water at all, so the sub needed a floating GPS receiver tethered to the drone. A Raspberry Pi single-board computer monitors the GPS location and controls the sub’s motors through a Pixhawk 6C controller, which also has IMU and gyroscope sensors to maintain a sense of orientation.

The sub has four motors in total: the main thruster and three waterproof servos that rotate fins for steering. Those attach to the hull, which is a combination of aluminum tube and 3D-printed parts.

But like Ahab chasing his white whale, the CPSdrone team found success to be quite elusive. There were numerous problems, from higher-than-expected buoyancy, to a failed servo, to poor steering performance. But quite unlike Ahab chasing his white whale, perseverance didn’t prove to be fatal — at least not in this video.

This video is the first in a series and it ends with a promising short distance test. In the following videos, CPSdrone will perform more extensive tests and will then hopefully travel 10 leagues under the sea to go to Hel and back.