Editing Turbopump (section)

=== 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.<ref name=nasahistory>{{cite web |url=https://history.nasa.gov/SP-4404/ch3-18.htm |title=Liquid Hydrogen as a Propulsion Fuel, 1945-1959 |publisher=[[NASA]] |access-date=2017-07-12 |archive-date=2017-12-25 |archive-url=https://web.archive.org/web/20171225233143/https://history.nasa.gov/SP-4404/ch3-18.htm |url-status=live }}</ref>

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.<ref name=nasahistory/>

By the end of 1948, Aerojet had designed, built, and tested a liquid hydrogen pump (15&nbsp;cm diameter). Initially, it used [[ball bearing]]s that were run clean and dry, because the low temperature made conventional lubrication impractical. The pump was first operated at low speeds to allow its parts to cool down to [[operating temperature]]. When temperature gauges showed that liquid hydrogen had reached the pump, an attempt was made to accelerate from 5000 to 35 000 revolutions per minute. The pump failed and examination of the pieces pointed to a failure of the bearing, as well as the [[impeller]]. After some testing, super-precision bearings, lubricated by oil that was atomized and directed by a stream of gaseous nitrogen, were used. On the next run, the bearings worked satisfactorily but the stresses were too great for the [[brazing|brazed]] impeller and it flew apart. A new one was made by milling from a solid block of [[aluminum]]. The next two runs with the new pump were a great disappointment; the instruments showed no significant flow or pressure rise. The problem was traced to the exit [[Diffuser (thermodynamics)|diffuser]] of the pump, which was too small and insufficiently cooled during the cool-down cycle so that it limited the flow. This was corrected by adding vent holes in the pump housing; the vents were opened during cool down and closed when the pump was cold. With this fix, two additional runs were made in March 1949 and both were successful. Flow rate and pressure were found to be in approximate agreement with theoretical predictions. The maximum pressure was 26 atmospheres ({{cvt|26|atm|MPa psi}}) and the flow was 0.25 kilogram per second.<ref name=nasahistory/>