The aerodynamic design of hypersonic vehicles envisaged for future defence applications, and UK-partnered planetary exploration plans (e.g. ExoMars in ESA's Aurora programme), is a major challenge due to the strong viscous effects (very high local heating rates and shock/shock interactions), the rarefaction phenomena characteristic of mixed-density flowfields, and the real-gas effects of high temperature (vibrational excitation, dissociation and ionization). Conventional fluid dynamics is often unsuitable for many aerothermodynamic situations, while statistical molecular dynamics is computationally too intensive. To address these twin problems we propose deploying extended hydrodynamics alongside a new continuum-fluid description of the non-equilibrium thermochemistry that incorporates both rarefaction and surface-catalycity. Extended hydrodynamics comprises high-order additions to the Navier-Stokes model that correct for rarefaction. It combines the computational efficiency of continuum-flow models with the major advantage that it reduces to the conventional Navier-Stokes model in near-equilibrium conditions.This is a new collaboration between Daresbury Laboratory and Strathclyde and Warwick Universities with the goal of building a new UK capability in high-speed mixed-density aerodynamic modelling. It is a Joint Grant Scheme proposal with the MoD's Defence Science and Technology Laboratory (Dstl), with additional support from MBDA and FGE. Dstl will provide experimental and computational data to help validate our models. They will also co-host with the applicants a one-day open workshop on high-speed flow modelling, which will act as a forum to discuss the future growth and direction of the UK high-speed flow research community.

The aerodynamic design of hypersonic vehicles envisaged for future defence applications, and UK-partnered planetary exploration plans (e.g. ExoMars in ESA's Aurora programme), is a major challenge due to the strong viscous effects (very high local heating rates and shock/shock interactions), the rarefaction phenomena characteristic of mixed-density flowfields, and the real-gas effects of high temperature (vibrational excitation, dissociation and ionization). Conventional fluid dynamics is often unsuitable for many aerothermodynamic situations, while statistical molecular dynamics is computationally too intensive. To address these twin problems we propose deploying extended hydrodynamics alongside a new continuum-fluid description of the non-equilibrium thermochemistry that incorporates both rarefaction and surface-catalycity. Extended hydrodynamics comprises high-order additions to the Navier-Stokes model that correct for rarefaction. It combines the computational efficiency of continuum-flow models with the major advantage that it reduces to the conventional Navier-Stokes model in near-equilibrium conditions.This is a new collaboration between Daresbury Laboratory and Strathclyde and Warwick Universities with the goal of building a new UK capability in high-speed mixed-density aerodynamic modelling. It is a Joint Grant Scheme proposal with the MoD's Defence Science and Technology Laboratory (Dstl), with additional support from MBDA and FGE. Dstl will provide experimental and computational data to help validate our models. They will also co-host with the applicants a one-day open workshop on high-speed flow modelling, which will act as a forum to discuss the future growth and direction of the UK high-speed flow research community.

The aerodynamic design of hypersonic vehicles envisaged for future defence applications, and UK-partnered planetary exploration plans (e.g. ExoMars in ESA's Aurora programme), is a major challenge due to the strong viscous effects (very high local heating rates and shock/shock interactions), the rarefaction phenomena characteristic of mixed-density flowfields, and the real-gas effects of high temperature (vibrational excitation, dissociation and ionization). Conventional fluid dynamics is often unsuitable for many aerothermodynamic situations, while statistical molecular dynamics is computationally too intensive. To address these twin problems we propose deploying extended hydrodynamics alongside a new continuum-fluid description of the non-equilibrium thermochemistry that incorporates both rarefaction and surface-catalycity. Extended hydrodynamics comprises high-order additions to the Navier-Stokes model that correct for rarefaction. It combines the computational efficiency of continuum-flow models with the major advantage that it reduces to the conventional Navier-Stokes model in near-equilibrium conditions.This is a new collaboration between Daresbury Laboratory and Strathclyde and Warwick Universities with the goal of building a new UK capability in high-speed mixed-density aerodynamic modelling. It is a Joint Grant Scheme proposal with the MoD's Defence Science and Technology Laboratory (Dstl), with additional support from MBDA and FGE. Dstl will provide experimental and computational data to help validate our models. They will also co-host with the applicants a one-day open workshop on high-speed flow modelling, which will act as a forum to discuss the future growth and direction of the UK high-speed flow research community.

This project is intended to enable future space exploration missions into our Solar System that have not been possible before. Re-entering spacecraft are exposed to extreme heat loads, which are mitigated by heat shields that continuously burn-up during flight. However, the physical processes of the extreme high-speed flow around the vehicle, and the influence of the ablating heat shield on the flow are still not well understood and result in exorbitant safety margins for the heat shield mass. Heat shields become too heavy and prevent missions that suffer from high heat loads like planet exploration or sample return scenarios. The project will utilise a newly developed ground-testing architecture to re-create this flight situation in a laboratory. A plasma-generator will heat sub-scaled models of re-entry capsules to extreme temperatures, as experienced in flight. After this phase, the model will start to decompose due to pyrolysis reactions inside the heat shield material. As a final step, the model will be exposed to a hypervelocity flow. This retains the characteristics of an ablation-flow coupling and allows for the first time a real ablating scaled model in an aerodynamically similar flow, enabling the investigation of physical effects that were previously inaccessible. The so created laboratory experiment allows us to investigate the flow and material response and therefore gives us insight into the physical and chemical effects occurring during re-entry. Several of these experiments are planned with varying test model size, temperature, material, and external flow condition. The flow around the models will be investigated using laser absorption spectroscopy and optical emission spectroscopy. The former of these techniques allows the measurement of temperature and concentration of the nitric oxide molecule, which is a strong indicator for the thermal and chemical state of the flow. The latter technique gives insight into various species and enables the measurement of excitation temperatures of different molecules and atoms. The combination of these approaches results a highly detailed characterisation of the flow around ablating test models. These data are extremely valuable for developing physical models of high-temperature flows, which in turn allows a better design of spacecraft and hypersonic vehicles. I will target flow conditions that replicate high-speed Earth re-entry, such as encountered during the re-entry of the US Space Shuttle or the European IXV mission. The final step in this programme is to use the gathered data of sub-scaled spacecraft models to develop a new theory relating ground-tests to flight scenarios. This endeavor will be accomplished by three interlinked methods. 1) A formulation of an analytical description of the problem utilising first principles of heat and mass transfer, fluid mechanics, and chemical kinetics. 2) The utilisation of the created experimental data spanning a large range of different conditions faced by spacecraft re-entry to ensure generality of the developed scaling approach. 3) A set of detailed numerical simulations rebuilding the experiments and beyond. These simulations will furthermore provide insight into flow physics not captured by the optical diagnostics, complementing the holistic methodology. This methodology will be used to identify dominating physical mechanisms, non-dimensionalise the problem, and generate a new ground-to-flight extrapolation theory that allows us to relate the ablating boundary layer flows directly to flight scenarios.

With my proposed research, I intend to enable future space exploration missions into our Solar System that have not been possible before. Re-entering spacecraft are exposed to extreme heat loads, which are mitigated by ablative heat shields. However, the physical processes of the extreme high speed flow around the vehicle, and the influence of the ablating heat shield on the flow are still not well understood and result in exorbitant safety margins for the heat shield mass. Heat shields become too heavy and prevent missions that suffer from high heat loads like planet exploration or sample return scenarios. I will use our new high-speed wind tunnel T6 to investigate these high-enthalpy flows experimentally, and upgrade T6 to a novel hybrid facility that enables hyper-velocity testing of models at flight temperatures that are made of real heat shield materials. T6 is newly built, commissioned in 2018, and is Europe's only facility to achieve the relevant high-speed flow conditions of up to 18 km/s. A plasma-generator will be integrated into the architecture of T6 to pre-heat models before they are exposed to the high-speed flow. This retains the characteristics of an ablation-flow coupling and allows for the first time a real ablating scaled model in an aerodynamically similar flow and enables the investigation of effects that were previously inaccessible and would make T6 the first of its kind world-wide. I plan to conduct three different types of experiments that target hypervelocity Earth re-entry: Shock layer radiation studies in a shock tube, sub-scale model testing of a re-entry capsule in a hypersonic flow field, and the upgrade of T6 to an entirely novel hybrid plasma-impulse facility. The normal shock formed in front of an entry capsule will be experimentally simulated through an equivalent shock travelling through a shock tube. The shock passes a window in the tube where it is interrogated by emission and absorption spectroscopy. This allows the spatially resolved measurement of temperatures, particle densities, and radiative heat flux. Emission measurements will be conducted with an experimental setup that is already in place, which I will extend to also include absorption spectroscopy. The Aluminium shock tube of T6 has the largest tube-diameter of current comparable facilities, which leads to a significant increase of measurement signal enabling new high accuracy data. I will target flow conditions that replicate high-speed Earth re-entry, such as encountered during the re-entry of the Japanese capsule Hayabusa. In addition, I will explore next generation mission scenarios for a Mars sample return case. The next step after the fundamental experiments of shock tube testing is moving to a full flow field around a model. The model will be equipped with surface heat transfer and pressure sensors, as well as ports for optical fibres coupled into a spectrograph. This experiment will allow the investigation of the chemically reacting flow around a real geometry and therefore represents an additional increase in complexity from the shock tube experiments. This will allow the direct comparison to a wealth of numerical simulations and direct measurements of the real flight that were captured during an observation mission. The final step in the methodology of this proposal is to bring high enthalpy ground testing to a new level. A plasma is generated and is expanded through a nozzle into the test section where the model is located. After sufficient plasma heating the model has reached flight temperature and starts to decompose. At this moment, the hyper-velocity flow is started, the plasma generator is switched off simultaneously, and the remaining plasma is flushed out by the incoming shock of the diaphragm burst. The subsequent flow now faces a model at flight temperature that reproduces important previously inaccessible effects like blowing of heat shield products, surface oxidation and surface recombination.