Abstract
Earth’s oceans span a wide range of dynamical environments, with variations in flows, turbulence, and spatial scales imposing different constraints on underwater vehicle design and performance. Here, we develop a framework linking ocean conditions to vehicle specifications of size and speed. Order-of-magnitude scaling of the six-degree-of-freedom equations of motion, combined with constraints from ocean turbulence and transport, energy, and payload requirements, results in five criteria that delimit a feasibility region in the length-speed plane. Boundary slopes follow from dimensional analysis, with environmental parameters including turbulent kinetic energy dissipation rate and buoyancy frequency. Application to the open ocean and surf zone demonstrates how environmental conditions impose distinct limitations on vehicle design. In the open ocean, feasibility is limited by the endurance required to fulfill mission duration requirements. Eleven existing, field-tested platforms fall within the feasibility region, consistent with the framework’s predictions. In the surf zone, the integral length scale limits vehicle size, such that the environment rather than endurance constrains the feasible design space. The feasibility zone, through the Reynolds number (Re), also identifies candidate propulsion modes, including robots in the low-to-intermediate Re regime, which remains unoccupied by field-tested vehicles. The framework provides general design constraints for new vehicles and a means of identifying platforms that are over-or under-specified for their environment. We also consider implications for flow-based navigation and extend the framework to vehicle design for exploration of Europa and other ocean worlds in the outer solar system.