Autonomous sailing boat: Unmanned 7000 kilometers against the forces of nature

"Students at the Technical University of Darmstadt (Germany) want to create something that no one has ever managed to do: have an unmanned, self-propelled sailing boat cross the Atlantic.

Microtransat Challenge” is the name of the competition and its track record so far is not very encouraging. In the early 2000s, a computer scientist from Aberystwyth University in Wales and a colleague at the Institut Supérieur de l'Aéronautique et de l'Espace in Toulouse came up with the idea of using boats and sailboats up to a length of 2.40 meters autonomously for scientific and competitive purposes to send through the ocean. A handful of teams from around the world have competed since then, but most boats didn't get very far. The previous attempts always ended the same: lost at sea, washed ashore, missing, stopped by a fishing boat or fishing net. Autonomous sailing appears to be even more difficult than autonomous driving.

This does not deter the students of the Sailing University Group at the TU Darmstadt. Perhaps it is precisely this challenge that particularly excites them. A few of them are in the “Makerspace” this evening, an open workshop founded by citizens in Darmstadt. They meet there regularly. The white hull of the prototype, on which the team has been working for eight years now, sits enthroned on trestles. Just 2.2 meters long, with the mast 3.5 meters above the water, the boat looks like a nutshell in the face of the huge ocean and the forces of nature that it has to face on a two-month microtransat journey across the Atlantic from Europe to Florida. However, the TU students are self-confident. "As far as we know, we are the only German team working on a boat for the Microtransat," says Lucas Herfurth.

Each team member brings specialist knowledge with them

"Technology learns to sail" is their motto. The saying goes well with a technical university, and all disciplines are represented in the team. Herfurth, for example, is studying mechatronics and information systems technology, while Ben-Jasper Kettlitz is studying mathematics. He is also studying IT security for a master’s degree, a subject that Moritz Dafelmaier also chose. Simon Kohaut is writing his doctoral thesis in computer science and has never set foot on a sailing boat in “real life”, as he explains with a grin.

Only Lucas Herfurth knows how to handle tillers, sails and winches. That helps immensely, but everyone in the ten to fifteen-strong team has their own specialist knowledge that they bring to the construction of the boat. For example, one group takes care of the on-board electronics, while others deal with robotics, mechanics or the software. These individual components have to mesh perfectly so that the boat later actually sails unmanned and energy self-sufficient, survives meter-high waves and storms and does not collide with an obstacle.

The prototype is called “roBooter”, and the students developed, designed and built each component themselves. You won't get very far with such extreme requirements with ready-made elements from model construction. "Everything has to be robust, waterproof and, above all, resilient, which means it has to be able to set itself up or repair itself," says Herfurth. "In an emergency, nobody can intervene," Kettlitz points out. For example, the solar panel for the energy supply of the on-board electronics is specially designed for maritime use, so that salt water does not form a crust on the surface, which reduces the electrical energy generation.

Everything on board is designed to save energy. If the batteries have to be recharged, the mainsail can also be rolled up for a short time to ensure optimal solar radiation for the solar cells. The two sails - a mainsail and a self-tacking jib - can be adjusted depending on the wind and weather conditions and reefed if necessary. The boat is fast up to three knots. The students have constructed a special chamber inside the hull so that the lines on deck do not get caught when hauling in or in a storm.

The boat weighs around 250 kilograms, most of the weight is made up of a so-called bomb on the keel: a metal weight that ensures that the ship capsizes in heavy weather and gets right again. The students also designed two rudders in case one gets stuck. Using the earth's magnetic field, a magnet on the mast and a special wind vane, sensors determine the position of the boat and also where the wind is currently blowing.

No intervention possible

Weather or navigation data, position and course determination, all this information comes together in a tiny computer below deck. The on-board computer, an energy-saving Raspberry Pi, consists of a single-board processor, explains Dafelmaier. The software team is developing the artificial intelligence that will be used to steer the boat autonomously for months. This includes an internal communication system on board, report Dafelmaier and Kohaut. It is used, among other things, to receive and analyze weather data. Information that people would otherwise read and interpret "and that now has to be translated into computer language," they explain.

And how would the students know where and in what condition their boat is on the Atlantic? The boat sends data over the cell phone network and receives information over the long wave radio network, says Dafelmaier. However, the team cannot and must not intervene.

The model has already survived the first test drives on the Langener Waldsee, and a trip on the Baltic Sea or the IJsselmeer is coming up. With the smaller predecessor ship Estelle, the team took part in the 2013 World Championships in robotic sailing in Brest in Brittany and received the prize for the "Most Professional Student Team". At that time, the Estelle sailed seven kilometers autonomously across the Atlantic. With the Microtransat it would be a thousand times as many.

The team has not yet set a date for the start. "There are still opportunities for optimization," says Kettlitz. Everything should be perfect. The team wants to minimize the risk. "After all, a lot of time, effort and sponsorship money went into the sailing boat," says Herfurth. And you don't want to end up on the list of failed attempts as just another example."