A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The purpose of a turbopump is to produce a high-pressure fluid for feeding a combustion chamber or other use. There are two types of turbopumps: a centrifugal pump, where the pumping is done by throwing fluid outward at high speed, or an axial-flow pump, where alternating rotating and static blades progressively raise the pressure of a fluid. Axial-flow pumps have small diameters but give relatively modest pressure increases. Although multiple compression stages are needed, axial flow pumps work well with low-density fluids. Centrifugal pumps are far more powerful for high-density fluids but require large diameters for low-density fluids. History Early development High-pressure pumps for larger missiles had been discussed by rocket pioneers such as Hermann Oberth. In mid-1935 Wernher von Braun initiated a fuel pump project at the southwest German firm Klein, Schanzlin & Becker that was experienced in building large fire-fighting pumps. The V-2 rocket design used hydrogen peroxide decomposed through a Walter steam generator to power the uncontrolled turbopump produced at the Heinkel plant at Jenbach, so V-2 turbopumps and combustion chamber were tested and matched to prevent the pump from overpressurizing the chamber. The first engine fired successfully in September, and on August 16, 1942, a trial rocket stopped in mid-air and crashed due to a failure in the turbopump. The first successful V-2 launch was on October 3, 1942. Development from 1947 to 1949 The principal engineer for turbopump development at Aerojet was George Bosco. During the second half of 1947, Bosco and his group learned about the pump work of others and made preliminary design studies. Aerojet representatives visited Ohio State University where Florant was working on hydrogen pumps, and consulted Dietrich Singelmann, a German pump expert at Wright Field. Bosco subsequently used Singelmann's data in designing Aerojet's first hydrogen pump. By mid-1948, Aerojet had selected centrifugal pumps for both liquid hydrogen and liquid oxygen. They obtained some German radial-vane pumps from the Navy and tested them during the second half of the year. By the end of 1948, Aerojet had designed, built, and tested a liquid hydrogen pump (15 cm diameter). Initially, it used ball bearings that were run clean and dry, because the low