Low-propulsion vessels can take advantage of powerful ocean currents to navigate towards a destination. Recent results demonstrated that vessels can reach their destination with high probability despite forecast errors. However, these results do not consider the critical aspect of safety of such vessels: because of their low propulsion which is much smaller than the magnitude of currents, they might end up in currents that inevitably push them into unsafe areas such as shallow areas, garbage patches, and shipping lanes. In this work, we first investigate the risk of stranding for free-floating vessels in the Northeast Pacific. We find that at least 5.04% would strand within 90 days. Next, we encode the unsafe sets as hard constraints into Hamilton-Jacobi Multi-Time Reachability (HJ-MTR) to synthesize a feedback policy that is equivalent to re-planning at each time step at low computational cost. While applying this policy closed-loop guarantees safe operation when the currents are known, in realistic situations only imperfect forecasts are available. We demonstrate the safety of our approach in such realistic situations empirically with large-scale simulations of a vessel navigating in high-risk regions in the Northeast Pacific. We find that applying our policy closed-loop with daily re-planning on new forecasts can ensure safety with high probability even under forecast errors that exceed the maximal propulsion. Our method significantly improves safety over the baselines and still achieves a timely arrival of the vessel at the destination.

A 600-meter plastic-sweeper set to head to the Pacific Ocean to clean up the notorious floating Great Garbage Patch is finally ready for launch, its makers have revealed. The gigantic'pac man' system consists of a 600-meter-long floating tube that sits at the surface of the water, with a tapered 3-meter-deep skirt attached below to catch plastic waste. It harnesses the power of wind and surface waves to autonomously sweep through the area, gathering up plastic waste as it goes. The gigantic'pac man' system consists of a 600-meter-long floating tube that sits at the surface of the water, with a tapered 3-meter-deep skirt attached below to catch plastic waste'On September 8, we will launch the world's first ocean cleanup system from our assembly yard in Alameda, through the San Francisco Bay, toward the infamous Great Pacific Garbage Patch,' organisers revealed. The team has spent six months building the contraption.

Researchers hoping to deploy a 600-meter plastic-sweeper to the Pacific Ocean to clean up the notorious floating Great Garbage Patch have revealed the final design for their contraption. The gigantic'pac man' system consists of a 600-meter-long floating tube that sits at the surface of the water, with a tapered 3-meter-deep skirt attached below to catch plastic waste. It harnesses the power of wind and surface waves to autonomously sweep through the area, gathering up plastic waste as it goes. The gigantic'pac man' system consists of a 600-meter-long floater that sits at the surface of the water, with a tapered 3-meter-deep skirt attached below to catch plastic waste. In the water, the'pac man' will catch plastic in a skirt, which will be emptired by a boat every few weeks Ocean Cleanup Project was forced to radically redesign the system after tests of their original system found it moved too much due to waves.