Abstract: A turbopump pumps a fluid of high viscosity. The pump has an inlet and an outlet. The pump is disposed on a shaft. A turbine has a separate inlet and a separate outlet from those of the pump. The turbine is disposed on the same shaft as the pump. A vehicle liquid has a viscosity less than that of the fluid and is miscible with the fluid. The vehicle liquid is conducted under pressure to the inlet of the turbine, such that a portion of the partially pressure-relieved vehicle liquid exits from the turbine as solvent liquid and is admixed to the fluid in a chamber disposed before the inlet to the pump. Thus, the viscosity of the mixture is reduced. Such that the mixture of solvent liquid and fluid is suctioned from the inlet of the pump. A plurality of injection channels are disposed in the chamber.