Dynamic Inversion Heat-Flux Tracking for Hypersonic Entry
Erwin Mooij (Astrodynamics & Space Missions)
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Abstract
To limit the mass of the vehicle's thermal protection system, an optimal trajectory that minimises the total integrated heat load should be own. This means that the maximum heat-ux constraint is followed for as long as possible, until the maximum mechanical load is encountered. Flying as close to this load as possible contributes to minimising the heat load as well. The guidance system to track the path constraints includes two components: a semi-analytical guidance that produces nominal bank-angle commands and a tracking system based on non-linear dynamic inversion. The ight system under consideration is a hypersonic test vehicle of which the stagnation heat-ux should not exceed 1,700 kW/m2, with a limit of the mechanical load of 4.8 g. The preliminary results show that the tracking system extends the duration of heat-ux tracking and is able to tightly track the heat-ux constraint, but reduces the ight range because of that. A simultaneous optimisation of these two con icting objectives should be pursued to rene the guidance-system design in case both have requirements to be met. In none of the cases considered, the g-load constraint was violated, although a more detailed analysis is required to make this part of the guidance more robust.