Global Reachability and Path Planning for Planetary Exploration with Montgolfiere Balloons

Abstract — Aerial vehicles are appealing systems for possible future exploration of planets and moons such as Venus and Titan, because they combine extensive coverage with highresolution data collection and in-situ science capabilities. Recent studies have proposed the use of a montgolfiere balloon, which controls its altitude by changing the heating rate or venting gas from the balloon, but has no actuation capability in the horizontal plane. A montgolfiere can use the variation in wind with altitude to guide itself to a desired location. This paper considers the problems of determining the altitude profile that the montgolfiere should follow in order to reach its target most quickly. We provide a new method that solves this path planning problem for all possible target locations, thereby providing a reachability analysis for the entire globe. The key idea is to perform a principled simplification and decoupling of the dynamics of the montgolfiere. We then discretize the search space, converting the planning problem into a graph search problem, and use Dijkstra’s algorithm to calculate the minimum-time path from the start location to every possible location in the graph. We demonstrate the approach on a possible Titan mission scenario. I