Single-pixel PIV measurements of a differential-throttled aerospike nozzle jet in supersonic outer flow

Aerospike nozzles are promising for future launch vehicles because they provide enhanced thrust performance by passive altitude adaptation. However, their complex flow behavior, especially under off-design and thrust-vectoring conditions, remains insufficiently understood due to limited experimental data. This paper presents PIV measurements of the mean flow field of a clustered, truncated linear aerospike nozzle at full differential throttling, in interaction with a supersonic outer flow. The study shows that single-pixel PIV can robustly resolve key features of the flow when image pre-processing and correlation function post-processing are systematically evaluated and selected carefully. The measurements reveal asymmetric shock structures and distinct recirculation regions behind the upper shroud and in the plug-base wake extending over the deactivated nozzle half. A consistent deflection of the jet core under full differential throttling is observed, indicating a steering potential, even though the quantitative effect on thrust vector control requires further analysis. The results provide new experimental evidence of how plume structure and nozzle–outer-flow interaction change under asymmetric aerospike nozzle operation. They demonstrate both the potential and the practical limitations of single-pixel PIV for resolving supersonic flows with sharp gradients and smallscale structures.