Decentralized Bi-Level Optimization for Cooperative Orbital Transportation of a Rigid Payload

The paper presents a decentralized bi-level optimization framework for swarms of small spacecraft transporting a rigid payload. It separates convex thrust allocation from an outer search over payload torque trajectories, using exact gradients to find fuel-efficient solutions without requiring full nonlinear-program convergence. The authors report theoretical convergence guarantees and validate the method in extensive Monte Carlo simulations, including closed-loop recovery from in-flight faults; short-timescale performance scales with the number of agents.