Abstract
This paper presents a novel method for multi-objective optimisation under uncertainty developed to study a range of mission trade-offs, and the impact of uncertainties on the evaluation of launch system mission designs. A memetic multi-objective optimisation algorithm, named MODHOC, which combines the Direct Finite Elements in Time transcription method with Multi Agent Collaborative Search, is extended to account for model uncertainties. An Unscented Transformation is used to capture the first two statistical moments of the quantities of interest. A quantification model of the uncertainty was developed for the atmospheric model parameters. An optimisation under uncertainty was run for the design of descent trajectories for a spaceplane-based two-stage launch system.
Highlights
This paper presents a novel method for multi-objective optimisation under uncertainty, developed to study a range of mission trade-offs and the impact of uncertainties on system models for space launch systems
Each agent is associated with a different weight vector, allowing the agent to converge to a different part of the Pareto-optimal set
The dependence of the aerodynamic coefficients on the Mach number is stronger around Mach 1 and weaker for high Mach numbers, it is not easy to foresee the effect of these variations
Summary
This paper presents a novel method for multi-objective optimisation under uncertainty, developed to study a range of mission trade-offs and the impact of uncertainties on system models for space launch systems. This is applied to the analysis and design of descent trajectories for a two-stage, partially re-usable launch system based on the Orbital-500R, a commercial system developed by Orbital Access Ltd. Ross et al [4] introduced unscented optimal control as the combination of the unscented transform by Julier and Uhlmann [5] combined with deterministic optimal control theory to directly manage uncertainties within an open-loop control framework This has been applied to single objective optimisation problems mainly in the field of guidance and attitude control [6,7], using pseudospectral optimal control methods [8] with the common.
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