Design of the life-ring drone delivery system for rip current rescue

Over 40% of the United States population visit the beach each year. For the 10 year period between 2003 and 2012, lifeguards made on average 67,700 rescues per year. Rip currents account for 80% of annual beach rescues and fatalities. When a lifeguard spots the victim, the lifeguards must reach the victim before a mean time of 102 seconds (σ = 30s). This paper presents the design of the Life-ring Delivery Drone System, which delivers life-rings to victims faster than a lifeguard. Once victims have a life-ring, they can survive long enough until the lifeguard reaches them. A stochastic simulation of rip-current victim's location and time-to-drown was used to determine the optimal drone launch location of near a lifeguard tower, and operational range covering one lifeguard section while using a flight path avoiding overhead flight of beach goers. An Analytical Hierarchy Process determined that a tethered life ring is the best flotation device for this application. The drone size-weight-power design space was analyzed with a system dynamics model to determine that an octocopter with a 1000 mm wheelbase, 10.2 kg total weight, using a battery with 20000 mAh energy capacity provided the optimal size, power, and endurance. The Life-ring Delivery Drone System results in a reduction in mean time to reach a victim of 39% (reducing standard deviation by 66%), increasing the probability of a successful rescue from 92.3% to 99.4%.