Improved Modelling of Radiative Heating Effects for Hypersonic Planetary Entry Vehicles
Lead Research Organisation:
University of Oxford
Department Name: Engineering Science
Abstract
A greater understanding of the physics involved in atmospheric entry is required before a manned mission to Mars is viable from an engineering perspective.
An outstanding problem relevant to this goal is the accurate modelling of radiative heating due to high-temperature CO2. This has recently been identified as a significant source of heat load on an entry vehicle in a flow regime where traditionally radiative heating is not an issue. However, current predictive models have been shown to disagree with experiment on several fronts.
The work completed to date to develop an experimental facility allows the simulation of the aerothermodynamic flow conditions present during atmospheric entry. The proposed facility is shown to be capable of achieving the desired flow conditions, of producing high-quality results, and of demonstrating unique research potential for shock-layer radiation studies.
The main aim of the thesis is to experimentally investigate radiative heating due to mid-wave infrared (MWIR) radiation in Martian-simulant gas mixtures. As will be discussed, significant uncertainties - with relevance for future missions - exist in this area. The work will confirm previous results, produce new data of interest and, finally, propose improvements to existing modelling tools which will enable prediction of vehicle radiative heating with greater confidence.
In support of these aims time has been spent on the development of the new T6 aluminium shock tube (AST). This facility will be the highest enthalpy ground test facility in Europe when complete, providing a unique capability for the study of aerothermodynamic effects. To ensure that the potential of this resource is fully realised a series of modelling exercises have been carried out, confirming the required performance is achievable. Developing a more in-depth understanding of the eventual capabilities of the facility has in turn allowed a more pragmatic review of current literature in the field, with future work being planned to exploit the shock tube's strengths.
An outstanding problem relevant to this goal is the accurate modelling of radiative heating due to high-temperature CO2. This has recently been identified as a significant source of heat load on an entry vehicle in a flow regime where traditionally radiative heating is not an issue. However, current predictive models have been shown to disagree with experiment on several fronts.
The work completed to date to develop an experimental facility allows the simulation of the aerothermodynamic flow conditions present during atmospheric entry. The proposed facility is shown to be capable of achieving the desired flow conditions, of producing high-quality results, and of demonstrating unique research potential for shock-layer radiation studies.
The main aim of the thesis is to experimentally investigate radiative heating due to mid-wave infrared (MWIR) radiation in Martian-simulant gas mixtures. As will be discussed, significant uncertainties - with relevance for future missions - exist in this area. The work will confirm previous results, produce new data of interest and, finally, propose improvements to existing modelling tools which will enable prediction of vehicle radiative heating with greater confidence.
In support of these aims time has been spent on the development of the new T6 aluminium shock tube (AST). This facility will be the highest enthalpy ground test facility in Europe when complete, providing a unique capability for the study of aerothermodynamic effects. To ensure that the potential of this resource is fully realised a series of modelling exercises have been carried out, confirming the required performance is achievable. Developing a more in-depth understanding of the eventual capabilities of the facility has in turn allowed a more pragmatic review of current literature in the field, with future work being planned to exploit the shock tube's strengths.
Organisations
People |
ORCID iD |
| Matthew McGilvray (Primary Supervisor) | |
| Peter Collen (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509711/1 | 01/10/2016 | 30/09/2021 | |||
| 2135006 | Studentship | EP/N509711/1 | 01/10/2016 | 30/09/2019 | Peter Collen |
| Description | Four major outcomes from this work are as follows: 1) Development & Commissioning of the T6 Free-Piston Tunnel: The first phase of this work involved the development and commissioning of T6, a multi-mode high-enthalpy ground test facility for hypersonic (greater than Mach 5) flows. This is the only such tunnel in the UK and is now the fastest wind tunnel in Europe - possibly the world. Depending on the configuration used, it can produce test conditions suitable for investigation of: i) Air-breathing atmospheric flight at hypersonic speeds, with applications such as single stage access-to-space vehicles and future civil aircraft. Currently flight-matched conditions at Mach 7 & 8 can be attained. ii) Atmospheric re-entry in a range of planetary atmospheres, at velocities up to 15 km/s. These experiments are performed with a scaled model of a re-entry capsule and can be used to quantify the heating environment for the design of thermal protection systems to protect the spacecraft. iii) Shock Layer Radiation: At many mission-relevant trajectory points, the heat flux on a re-entry vehicle due to radiative effects can be the dominant source of heating. However, this is poorly understood. In T6, the exact conditions behind the bow shock ahead of an entry vehicle can be reproduced, allowing investigation of the aerothermodynamic, chemical and radiative effects using a range of non-intrusive optical techniques. 2) Construction of Aluminium Shock Tube: For the study of shock layer radiation (iii above) there is currently one facility in the world (at NASA Ames) which produces the majority of data to inform mission planning and computational code development. This award has contributed to the development of the T6 Aluminium Shock Tube, a bespoke facility for undertaking comparable experiments. This will allow validation of results produced at NASA, as well as attainment of test conditions which cannot currently be achieved there or in other facilities. 3) Aluminium Shock Tube Benchmarking: Studies of shock layer radiation have been undertaken. This has been performed at conditions previously tested in other facilities which have been the focus of extensive simulation effort. Results have compared favourably to those in the literature. This has resulted in a new UK facility with demonstrated capability to produce comparable data to national space agencies. 4) New Experimental Shock Layer Radiation Data: Data relevant for lunar return trajectories has been generated in T6. The low speed (approximately 7.5 km/s) data in particular compares very closely to computational results and to plasma torch experiments at similar conditions. Of interest is that the NASA facility data does not compare as closely - investigation of the source of this difference is an on-going work. This result highlights the need for a second facility to enable cross-comparison of directly mission-relevant experimental data and hence the value added through this award. |
| Exploitation Route | The development of T6 was funded through the National Wind Tunnel Facility EPSRC grant. Hence, 25% of its time is open to external customers from either academia or industry. As previously discussed, the facility itself has unique capability in the UK, Europe and the world for investigation of high-speed flight, and so test campaigns for a range of aerospace projects can be undertaken. The shock layer radiation data from the testing undertaken during this award can be directly used to inform development of computational models for re-entry vehicles as well as design margins for thermal protection systems. Finally, similar facilities have found applications in other industries e.g. fusion energy. This can be through development of measurement techniques for plasmas or the generation of specific high-temperature test flows for investigation of fundamental physics. |
| Sectors | Aerospace, Defence and Marine,Energy |