Dynamics of Ultralight Flexible Spacecraft During Slew Maneuvers

Citation

Marshall, Michael Aaron (2022) Dynamics of Ultralight Flexible Spacecraft During Slew Maneuvers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/w6na-w476. https://resolver.caltech.edu/CaltechTHESIS:05262022-221946560

Abstract

Traditional spacecraft design paradigms rely on stiff structures with comparatively flexible appendages. More recent trends, however, trade deployed stiffness for packaging efficiency to stow increasingly large-area apertures inside existing launch vehicles. By leveraging recent advances in materials and structures, these ultralight, packageable, and deployable spacecraft, hereafter referred to as ultralight flexible spacecraft, are up to several orders of magnitude lighter and more flexible than the current state-of-the-art. They promise to deliver higher performance for a wide range of applications, but this comes at a cost, in this case, due to their very low-frequency structural dynamics. Structural dynamics can negatively interact with spacecraft attitude control systems and degrade pointing performance.

These developments motivate the main objective of this thesis: to demonstrate the feasibility and limitations of maneuvering next-generation ultralight flexible spacecraft. To that end, the thesis proposes a quantitative method for determining structure-based performance limits for flexible spacecraft slew maneuvers using reduced-order modal models. It then develops a geometrically nonlinear flexible multibody dynamics finite element model of a representative ultralight flexible spacecraft based on the Caltech Space Solar Power Project architecture to validate this method. The results demonstrate that contrary to common assumptions, other constraints impose more restrictive limits on slew maneuver performance than the dynamics of the structure. In particular, they show that the available attitude control system momentum and torque are often significantly more limiting than the structure. Consequently, these results suggest that spacecraft structures can either be (i) maneuvered significantly faster, assuming suitable actuators are available, or (ii) built using lighter-weight, less-stiff, and lower-cost construction that moves the structure-based performance limits closer to those of the rest of the system. Thus, there is a significant opportunity to design less-conservative, higher-performance space systems.

Thesis Files