Comparison of Forced and Unforced Rendezvous, Proximity Operations, and Docking Under Model Mismatch
Robert Muldrow, Channing Ludden, Christopher Petersen
TL;DR
The study addresses RPOD fuel optimization under model mismatch between the Clohessy-Wiltshire equations and higher-fidelity two-body dynamics. It compares forced and unforced trajectories for circumnavigation and interception, quantifying how impulse requirements and efficiency shift as maneuver size and model fidelity change. A key finding is that CW-based unforced motion is not inherently more fuel-efficient; as maneuver size grows, model mismatch makes forced motion more favorable, though small-maneuver benefits may arise with frequent impulses. The work informs RPOD mission planning and highlights the need for higher-fidelity analyses to validate trend persistence under realistic perturbations.
Abstract
This paper compares the required fuel usage for forced and unforced motion of a chaser satellite engaged in Rendezvous, Proximity Operations, and Docking (RPOD) maneuvers. Improved RPOD models are vital, particularly as the space industry expands and demands for improved fuel efficiency, cost effectiveness, and mission life span increase. This paper specifically examines the Clohessy- Wiltshire (CW) Equations and the extent of model mismatch by comparing pre- dicted trajectories from this model with a more computationally complex, higher fidelity RPOD model. This paper assesses several test cases of similar mission parameters, in each case comparing natural motion circumnavigation (NMC) with comparable forced motion circumnavigation. The Guidance, Navigation, and Con- trol (GNC) impulse maneuvers required to maintain the supposedly zero fuel CW trajectories is representative of the extent of CW model mismatch. This paper demonstrates that unforced motions are not inherently more fuel efficient than forced motions, thus permitting extended orbital operations given the higher fuel efficiency.