This paper presents a novelexperimental technique where infra-red thermography is employed to directly measure the surface heat transfer of a transpiration cooled porous material in transient hypersonic flow. Experiments were conducted in the Oxford High Density Tunnel on a flat faced hemispherical probe at a single Mach 7 free-stream condition (𝑅𝑒 𝑢 = 3.84•10 6 1/m) with Nitrogen, Air, Argon, Krypton and Helium injection gases and mass flow rates ranging from 0.01-0.235 kg s −1 m −2 . Surface heat transfer measurements were extracted by imaging directly on the porous material using a FLIR A6751 high-speed long-wave infra-red camera. Porous alumina was chosen due to its favourable thermal properties for infra-red analysis and its very small pore sizes (≈ 2 𝜇m) enabling a uniform outflow. It was found that the Stanton number reduction matched to within 10% of both CFD results and correlations. Nomenclature 𝐵 ℎ Blowing parameter 𝑐 𝑝 Specific heat capacity, J kg −1 K −1 CFD Computational fluid dynamics 𝐼 Radiant intensity, W m −2 sr −1 GIS Gas injection system 𝐻 Enthalpy, J ℎ Planck's constant, m 2 kg s −1

Laser-induced grating spectroscopy (LIGS) is an optical diagnostic technique for gas-phase thermometry in challenging environments where physical probes are undesirable. The Portable In-line LIGS for Optical Thermometry (PILOT) instrument is a novel self-contained, compact device capable of tracer-free LIGS measurements at 400 Hz. It can be mounted in any orientation and includes internal alignment capability, adjustable path length matching for the pump beams, and an energy/power attenuation mechanism for the pump/probe beams. Characterization of the instrument demonstrated that it can produce accurate (<0.37% in ambient air) and precise (±0.7% in ambient air) spatially- and temporally-resolved temperature measurements, and is now ready to be deployed in research facilities.

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