Computational analysis of effect of spiked reentry capsules on reduction in temperature

In the present study, experiments and computations were performed to understand the flow field around a scaled down model of Apollo re-entry capsule at Mach 6. Temperature distribution measurements were made for various aero spikes added to the model. Computations using the commercially available software FLUENT, were carried out for two dimensional axisymmetric flow. Three different types of aero spikes, namely: arrow head, aerospike, aerodisk were used in front of the re-entry capsule to increase the distance between the body and the shock wave and hence decreasing the temperature. The effects of the three different types of aero spikes on the flow with various dimensional variations are analysed as well. From the analysis, it was found that the aerodisk yield a rise in reattachment temperature at the shoulder of the Apollo capsule. It is also found that the role of the spike length is more dominant in dictating the aeroheating than that of the aerodisk size. Analysis for two different lengths, that is, L=1.5D and L=2D, where D is the diameter of the capsule, were carried out for all the three models. In case of the pointed spike, the boundary layer remains attached to the spike surface and an expansion wave is created downstream if the till shoulder to turn the flow outside the shear layer in a direction parallel to it. It was investigated that the arrowdisk and the aerodisk also create vortices over the length of the spike which redirects the flow in order to reduce the heating levels on the fore body. It was noticed that the aerospike produces lesser temperature than the Apollo capsule without an aerospike and at the same time is much more efficient than the aerodisk. The maximum temperature reaches a peak while using aerodisk which shows that the aerodisk is ineffective in reducing aeroheating levels.