A three-stage H-l rocket has been developed, the second stage of which has a LOX/LH 2 engine, LE-5. Regarding the POGO phenomenon of the second stage of the H-l rocket, analyses are being conducted in order to determine whether or not a POGO suppression device is necessary for the LE-5 engine. In this study, the dynamic characteristics of the liquid oxygen pump of the LE-5 engine were examined by artificially creating periodical perturbations in the pump flow in order to obtain the data necessary for POGO analysis of the H-l rocket. /or g h H A// = j L = M h = TV = c -•R = S = «, = Vc -z,-,. = Nomenclature : pump inlet cross-sectional area = cavitation compliance • • resonant frequency • • gravitational acceleration • • dimensionless head, H/(u 2 t /g) = head = pump delivery head fluctuation, h 2 -h l • -imaginary index = inertance = mass flow gain factor = rotational speed = flow rate, dimensionless for fluctuating quantity, Q/(NQ d /N d ) • • resistance = suction specific speed, NQ°-5 /(NPSH)°-75 • • impeller tip velocity cavity volume pump transfer matrix component pump dynamic gain factor angular velocity Superscripts Q = fluctuating quantity ( ) = mean quantity ( )* = cavitation breakdown point value Subscripts 1 = pump inlet 2 = pump outlet d = design point ij = component number p = pump