Designing a boat that can cross an ocean autonomously is no easy task. There are two main components, the electronic control systems, and the overall structure of the vessel. With nobody around to fix problems, small issues such as a wrap of seaweed around the propeller or a loose electrical connection can spell an end to the voyage. To maximize our chances, we have spent a huge amount of time envisioning all potential problems, and incorporating advance solutions to these issues in the way of redundancy and protective mechanisms.
The vessel is a solar electric design, having two inline propellers powered by a 1200 watt solar array. A lithium ion battery bank allows for the motors to run continuously through the night. With this system, we anticipate a continuous supply of 80-130 watts.
We are striving to create a vessel that moves at 4 knots with 100 watts input. A multihull (trimaran) configuration is the ideal way of creating a broad surface area to place the solar array, while having an overall hull profile that moves easily through the water. Length is 7.5 meters (24 feet) and the vessel (including all gear) will weigh approximately 150 kg (300 lbs). The boat will track well in contrary conditions, and is seaworthy enough (and self righting) to endure hurricane conditions. The underwater profile has been created with the intent of protecting vulnerable appendages (rudder and propellers), while being as hydrodynamic as possible.
A series of micro-controllers will control the electronics systems. Some of these systems will include a navigation system, speed controller, active collision avoidance systems, data collection/streaming systems, and tracking system. The boat will be continually updating its position (along with relaying data collected) using two separate satellite tracking units.
Our primary goal is to cross the Atlantic Ocean, however, we also wish to demonstrate the capabilities of this design for autonomous open ocean research. Offshore autonomous research is an industry in its infancy, and there are a number of companies that have developed boats for this purpose. Most of these vessels have low speeds (1-2 knots), and are often hindered by ocean currents. We are striving to have an average indefinite speed of 4 knots (in typical spring/summer/fall solar conditions) with a top speed of six knots. Payload will be 100 kg, and the solar array will provide abundant electricity for powering instruments. Another huge benefit of an electric motorized boat is its ability to stay precisely on the spot – ideal for many types of data collection, in particular for lowering sensors to specified ocean depths.
Long-range small autonomous boats need to gather energy from the surrounding environment. While our vessel uses exclusively solar energy for propulsion, other autonomous boats have been using novel technology to draw energy from waves, wind, and even the thermal gradient in the top layer of the ocean. One of the reasons why primary solar propulsion has not been commonly used is due to the challenge in creating enough surface area to place a large solar array. A large flat deck, ideal for placing solar panels, is typically not good for making a small boat self-righting and seaworthy. The greatest design challenge we faced was creating a vessel that is seaworthy, efficient, and capable of supporting a large solar deck.