Abstract: Aiming at the new task for POGO stability analysis of liquid strap on launch vehicle with redundant propulsion system and crossfeed, three different working modes of liquid bundled vehicle, i.e. independent work(Mode 1), tanks of the booster supply the propellants to the core stage engines in case of one booster failing(Mode 2), and two boosters feed propellants to the core stage engines at the same time(Mode 3), are taken into account, and the dynamic model is established by utilizing the improved Rubin’s method. The effects of the parameters of propulsion system on the POGO stability are analyzed by the numerical method. The results show that the POGO stability is more sensitive to the accumulator energy value of booster than that of core stage for modes 1 and 3. Reducing the pump gain can improve the POGO stability, in which the effect of oxygen pump is stronger than that of fuel pump, and the effect of pump of booster is larger than that of pump of core stage. The increase of the pump flexibility of booster reduces the frequency of fuel system, which may induce POGO vibration, in addition, the influence is the largest for mode 2. It provides the theoretical basis for further optimizing the redundant propulsion system of liquid strap on launch vehicle and restraining POGO vibration.

Key words: Liquid strap on vehicle, Redundant propulsion system, Improved Rubin’s method, POGO stability