Thrust enhancement in aerospike nozzles through the generation of a compression corner

Kurzfassung

The aerospike nozzle has long been recognised as a promising alternative to conventional bell-shaped nozzles due to its altitude-compensating capability. Classical design methods, such as the Angelino and Lee–Thomson techniques, use the method of characteristics and expansion fan theory to generate smooth, shock-free plug contours at design conditions. Thrust-optimised approaches, like Rao’s method, build on these principles by employing the calculus of variations to generate contours that maximise thrust performance. This study investigates the modification of the Rao method by introducing greater concavity in the initial plug section, creating a compression corner that generates a local recompression and a shock–expansion system. Computational simulations predicted a thrust gain of up to 18% compared with the baseline Angelino (ideal) contour. To validate these findings, a cold-flow test campaign was conducted in the high-altitude simulation chamber (HASC) P6.2 at DLR Lampoldshausen. Two nozzle models, based on Angelino's and a modified Rao's contour, were tested across a range of nozzle pressure ratios. The experimental results show good agreement with CFD predictions, confirming the thrust enhancement of the modified contour. However, RANS-based models consistently overestimated the wall pressure immediately downstream of the compression corner. These results demonstrate that aerospike nozzle performance can be further enhanced by introducing a compression corner in the initial contour section.