Mass- and Momentum-Conserved Secondary Injection Model (MMC-SIM) for Thrust Vector Control Analysis
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A mass- and momentum-conserved secondary injection model (MMC-SIM) is presented for thrust vector control (TVC) analysis in axisymmetric nozzles. TVC modelling provides fast thrust vector predictions for control design, preliminary nozzle sizing, and integration into flight simulation frameworks. Existing low-order models rely on simplifying assumptions regarding the secondary jet exit state, which limits reproducibility and can compromise predictive accuracy. MMC-SIM addresses this limitation by reformulating the equivalent obstruction height problem. Mass conservation and momentum conservation provide two independent constraints that are solved simultaneously to determine both the effective injection height and the secondary jet exit state, eliminating the need to prescribe downstream jet conditions a priori. These constraints are embedded within a blunt-body framework to predict boundary layer separation, wall pressure distribution and thrust vector characteristics. Computational fluid dynamics (CFD) simulations are used to assess the modelling assumptions and examine the flow structures. MMC-SIM shows strong agreement with experimental results, yielding average and maximum lateral force prediction errors of 3.3% and 4.8%, respectively. Compared to current leading models, MMC-SIM substantially improves the prediction of the pressure-driven lateral force while providing a transparent and reproducible modelling framework suitable for engineering design applications.
Recommended citation: Abdelwahab N, Johansen C. Mass- and momentum-conserved secondary injection model (MMC-SIM) for thrust vector control analysis. *The Aeronautical Journal*. Published online 2026:1-27. doi:10.1017/aer.2026.10203
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