A mathematical model was presented for the priming process of propellant lines with moving boundary conditions based on one-dimensional fluid transient theory.The nonlinear hyperbolic partial differential equations governing the unsteady motion of fluid were solved by the Fourier spectral method.A coordinate transformation technique was employed to reduce fluid motion in time-dependent domains to ones in time-independent domains.The results obtained from the Fourier spectral method exhibit greater consistency with method of characteristics.In addition

spectral method requires less computer calculation time with less numerical error

which shows that the method is more suitable to solve fluids motions in such a complex system.The analysis shows that initial gas pressure

tank pressure and ploytropic exponent all have vital effects on surge pressure.