Modeling and Analysis of Tethered System Dynamics for Venus Aerobots and Towed Probes

Venus, the Earth’s nearest planetary neighbor, provides a unique natural laboratory for studying plan- etary and climate processes. Despite sharing similarities with Earth, an out-of-control greenhouse effect has made it the hottest planet in the solar system. Because of its corrosive atmosphere, high temperatures, and pressures, Venus’s atmosphere represents an extreme and challenging environment for scientific explo- ration. One of the most promising approaches to studying the Venusian atmosphere and its surface is using an autonomous scientific balloon, also called “aerobot”, which could navigate the atmosphere using buoy- ancy force to maintain a certain altitude (around 52 km), where temperatures and pressures are comparable to Earth’s. NASA’s Jet Propulsion Laboratory is developing missions to explore and survive the Venusian harsh environment. The paper describe modeling and simulation developed to support the technology de- velopment of the Venus Aerobot mission, demonstrating how an efficient and user-friendly flight mechanics simulator could be extremely helpful in capturing and testing various systems architectures with different purposes. The simulator implemented two different, but complementary, modeling approaches of the tether dynamics, specifically a Lumped Mass approach and the DeNOC (Decoupled Natural Orthogonal Matrix) recursive approach. In addition, a stochastic wind model was included. The simulator can also reproduce and analyze the behavior of towed atmospheric probes and assess their ability to change the trajectory of the entire system by exploiting aerodynamic forces acting on the towed body, which could be trailing at kilometers of distance below the balloon. The models used in the simulator demonstrated the feasibility of tracking the trajectory of a towed body using a micro aerial vehicle capable of flying autonomously. These mission architectures would allow the collection of samples from Venus’s surface and their return to the lofting system. The simulator described in this paper enables preliminary system-level analysis and the understanding of the entire flight chain dynamics, encompassing inflated balloons, gondolas suspended by tethers, and bodies towed with long tethers. Future studies will explore balloon and body aerodynamics in more detail, focusing on controlling the aerobot trajectory vertically and laterally using aerodynamic forces on towed bodies.