Abstract
Understanding the hypersonic flow around faceted shapes is important in the context of the fragmentation and demise of satellites undergoing uncontrolled atmospheric entry. To better understand the physics of such flows, as well as the satellite demise process, we perform an experimental study of the Mach 5 flow around a cuboid geometry in the University of Manchester High SuperSonic Tunnel. Heat fluxes are measured using infrared thermography and a 3D inverse heat conduction solution, and flow features are imaged using schlieren photography. Measurements are taken at a range of Reynolds numbers from {40.0 times 10^3} to {549 times 10^3}. The schlieren results suggest the presence of a separation bubble at the windward edge of the cube at high Reynolds numbers. High heat fluxes are observed near corners and edges, which are caused by boundary-layer thinning. Additionally, on the side (off-stagnation) faces of the cube, we observe wedge-shaped regions of high heat flux emanating from the windward corners of the cube. We attribute these to vortical structures being generated by the strong expansion around the cube’s corners. We also observe that the stagnation point of the cube is off-centre of the windward face, which we propose is due to sting flex under aerodynamic loading. Finally, we propose a simple method of calculating the stagnation point heat flux to a cube, as well as relations which can be used to predict hypersonic heat fluxes to cuboid geometries such as satellites during atmospheric re-entry.Graphic abstract
Highlights
A half century of human space flight and exploitation has resulted in approximately 6000 satellites being placed in orbit around the Earth
The schlieren images revealed the presence of a separation bubble on the side surface of the cube at certain Reynolds numbers
A detailed error sensitivity analysis of the inverse heat conduction method for heat flux calculation used showed that the Stanton numbers calculated by the data reduction method have an error of 12%, which is dominated by errors in the material emissivity
Summary
A half century of human space flight and exploitation has resulted in approximately 6000 satellites being placed in orbit around the Earth. Due to the limited availability of Earth orbits, the presence of decommissioned satellites in space increases the risk of in-orbit collisions and the associated risks of space debris. To address these problems, satellites must be disposed of at their end-of-life. On the other hand, decommissioned satellites in Low Earth Orbit (LEO) are often left alone at the end of their life, as their low orbits will gradually decay due to the atmospheric drag experienced in LEO This results in an uncontrolled atmospheric re-entry. As the satellite size increases it becomes more and more likely that significant satellite mass will hit the ground
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