SUMMARY

The development of hypersonic vehicles has been an active area of research for several decades with implications for both defense and space travel. The current state-of-the-art of hypersonics has shown the need to address two major design challenges before sustained hypersonic flight can be realized: managing the extreme heat loads of high-speed flight and storing energy in the absence of in-flight energy generation. The exterior of a hypersonic vehicle is subject to extreme aerothermodynamic heating, which traditionally must be rejected from the vehicle by way of some combination of radiation, ablation, and active heat rejection, such as by circulating a cryogenic fuel before combusting it and expelling it from the rear of the aircraft. Additionally, large batteries must be stored on-board the vehicle to provide energy, occupying a significant portion of the vehicles total mass. This work will address both of these challenges by developing a methodology for the design and modeling of advanced thermophotovoltaic (TPV) cells for hypersonic applications to mitigate both the heat management requirements and energy storage requirements for future vehicles.
A traditional TPV cell includes a burner as a heat source for an emitter, a method of capturing waste heat, and cooling for the TPV converter. In a hypersonic application, however, assuming thermodynamic equilibrium for sustained flight, energy entering the vehicle skin as heat must either be converted into electrical energy or removed via active cooling. This study will focus on the methodology for the design and optimization of the emitter and converter of advanced TPV skins for hypersonic vehicles. The proposed approach will involve 1) A first principles approach to the governing equations for this novel application of TPV cells in a closed system, 2) Optimization of such a system with the aid of optical metamaterials, and 3) The testing and evaluation of a representative TPV cell structure inside a representative environment.
The developed methodology will allow the designer of such a vehicle to increase the available design space for these highly constrained designs, and the tools developed in this research will be of immediate utility to various defense research organizations, as well as NASA and private space-access-oriented entities. Furthermore, the methodology of tailoring metamaterials to a specific TPV environment will have broad applications in the energy sector.