Prediction of Nozzle Side Forces Which Occur During Staging

Large asymmetric nozzle flow separation side forces have been observed during staging of some operational missiles. Because of the proposed use of extendible exit cones in advanced launch vehicles, the available staging clearances are small. Therefore, a need exists for a reliable nozzle side force prediction methodology during the missile design phase. Existing methodologies rely on unobstructed nozzle test data, which could be deficient for staging analysis due to nozzle blockage by the lower-stage dome. This paper presents an empirical procedure that takes nozzle blockage into account. Predicted results are compared with flight (Minuteman I/II and II/III staging) and subscale test (Trident I/II staging) side force data with reasonably good agreement.