Humans' exploration of solar system brings one of the most challenging engineering feats, the design of spacecraft which can survive extreme heat loads while re-entering Earth's atmosphere, such as recent asteroid sample return mission Hyabusa, and to enter other planets atmospheres such as the Mars Science Laboratory. Currently, large uncertainties exist in the expected flight heat loads leading to spacecraft heat shields which are much heavier than necessary when every gram is critical. This projects aims to build a novel high response diamond based heat transfer sensor which can be used to accurately measure the heat transfer on subscale spacecraft models in high speed wind tunnels. To slow a spacecraft to either enter into planetary orbit or land on the surface, aerodynamic braking in the planet's atmosphere causes a conversion of the vehicles kinetic energy to thermal energy, generating gas temperatures hotter than the surface of the sun (6000 degrees C) in front of the vehicle. This results in enormous heat transfer to the vehicle, in excess of 100's MW/m2. This requires the vehicle to use thermal protection systems (TPS), which apply advanced ablating materials which limits the heat conduction to the spacecraft's structure. As the TPS adds significantly to the lift-off mass, any reduction in TPS will result in an increase in available payload to achieve mission objectives or reduce launch costs while increasing reliability. To directly replicate the flow conditions experienced in spacecraft entry in a ground based wind tunnel is extremely difficult due to the high energy and pressures involved. This has led to engineers developing impulsive wind tunnels, which generate appropriate flow conditions for periods on the order of milliseconds by a cascade of high energy processes. Current heat transfer measurement techniques for impulsive high speed wind tunnels have been shown to be inadequate in measuring the heat fluxes in the front of subscale models in these tunnels due to slow time response (thermocouples, IR) or are damaged by particulates and have interference from the ionised flow field (thin film heat transfer and atomic layer thermopiles). Diamond is an incredible material, and has unique combination of thermal properties allow it to be used as a very fast acting calorimeter up to 1 MHz. The gauge measures the temperature rise of a thin piece of diamond (50-500 micrometres), and by measuring the temperature rise on the rear side of the diamond using thin film gauges, this protects the electronics from particle debris and the ionised gas, and also high accuracy. For the high heat transfer rates seen on spacecraft, the temperature rise achieved would be appropriate for reliable measurement using current thin film resistive gauge technology. In summary, this project will develop and test diamond based heat transfer gauges for application in accurately measuring heat transfer rates on spacecraft models. This aligns with the EPSRC research areas of both Sensor development and Fluid Dynamics research, with the proposed research both having direct impact, as well as facilitating research into the future.

This grant will deliver a step change in the understanding and predictability of next generation cooling systems to enable the UK to establish a global lead in jet engine and hypersonic vehicle cooling technology. We aim to make transpiration cooling, recognised as the ultimate convective cooling system, a reality in UK produced jet engines and European hypersonic vehicles. Coolant has the potential to enable higher cycle temperatures (improving efficiency following the 2nd law of thermodynamics) but invariably introduces turbine stage losses (reducing efficiency). Cooling system improvement must enable higher Turbine Entry Temperature (TET) while using the minimum amount of coolant flow to achieve the required component life. For high speed flight, heat transfer is dominated by aerodynamic heating with gas temperatures on re-entry exceeding those at the surface of the sun. Any reduction in heat transfer to the Thermal Protection System will ultimately lead to lower mass, allowing for decreased launch costs Furthermore, the lower temperatures could serve as an enabler for higher performance technologies which are currently temperature limited. The highest temperatures achievable for both jet engines and hypersonic flight are limited by the materials and cooling technology used. The cooling benefits of transpiration flows are well established, but the application of this technology to aerospace in the UK has been prevented by the lack of suitable porous materials and the challenge of accurately modelling both the aerothermal and mechanical stress fields. Our approach will enale the coupling between the flow, thermal and stress fields to be researched simultaneously in an interdisciplinary approach which we believe is essential to arrive at the best transpiration systems. This Progreamme Grant will enable world leaders in their respective fields to work together to solve the combination of cross-disciplinary problems that arise from the application of transpiration cooling, leading to rapid innovations in this technology. The application is timely since the proposed research would enable the UK aerospace industry to capitalise on recent developments in materials, manufacturing capability, experimental facilities/measurement techniques and computational methods to develop the science for the application of transpiration cooling. The High Temperature Research Centre at Birmingham University will provide the means to cast super alloy turbine aerofoils with porosity. The proposed grant would allow innovation in the cast systems arising from combining casting expertise with aerothermal and stress modelling in recent EPSRC funded research programmes. It also builds upon material development of ultra-high temperature ceramics and carbon composites undertaken in EPSRC funded research, by use of controlled porosity and multilayer composites. It will also provide the first opportunity to undertake direct coupling of the flow with the materials (porous and non-porous) at true flight conditions and material temperatures. Recent investment in the UK's wind tunnels under the NWTF programme (EPSRC/ATI funded) at both Oxford University and at Imperial College will allow for direct replication of temperatures and heat fluxes seen in flight and interrogated using advanced laser techniques. Recent development of Fourier superposition in CFD grids for modelling film cooling can now be extended to provide a breakthrough method to predict cooling flow and metal effectiveness for high porosity/transpiration cooling systems. The European Space Agency has recently identified the pressing requirement for alternatives to one-shot ablative Thermal Protection Systems for hypersonic flight. Investment in this area is significant and transpiration cooling has been identified as a promising cooling technology. Rolls-Royce has embarked upon accelerated investment in new technologies for future jet engines including the ADVANCE