Inside a single casing the turbopump comprises a main shaft driven by a turbine, a secondary shaft coaxial with the main shaft, at least one low pressure boost impeller mounted on the secondary shaft. The LP fluid flow is brought parallel to the axis of the turbopump by a baffle and after being deflected through 180.degree. in a return channel it is returned parallel to the axis of the turbopump toward a high pressure impeller mounted on the main shaft inside the secondary shaft. The entire HP flow formed by the HP impeller is delivered axially to a boost turbine secured to the secondary shaft and to the LP boost impeller and disposed between the main shaft and the secondary shaft. Through orifices and an axial channel are formed in the main shaft to pass the flow of HP fluid leaving the boost turbine inside the main shaft and then to exhaust the HP fluid to a delivery channel secured to the casing through the radial arms situated at the inlet to the turbopump.