Dynamic Inversion Heat-Flux Tracking for Hypersonic Entry

To limit the mass of the vehicle's thermal protection system, an optimal trajectory that minimises the total integrated heat load should be flown. This means that the maximum heat-flux 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 flight system under consideration is a hypersonic test vehicle of which the stagnation heat-flux should not exceed 1,700 kW/m^2, with a limit of the mechanical load of 4.8 g. The preliminary results show that the tracking system extends the duration of heat-flux tracking and is able to tightly track the heat-flux constraint, but reduces the flight range because of that. A simultaneous optimisation of these two conflicting objectives should be pursued to refine 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.