Development of High Speed Hybrid Bearings for Reusable Pump-Fed Liquid Rocket Engines

For truly reusable rocket propulsion systems, the next generation first-stage engines have to ensure reusability with a reduced maintenance effort to optimize turnover time and costs. This goal can be better achieved by developing long-life turbopumps with a lifetime requirement of several hours. Specifically, the replacement of rolling bearings with lubricated journal bearings is one of the most promising solution to increase bearing lifetime and reliability. In the framework of the European Space Agency project “Long Life Journal Bearings for Turbopumps,” the Department of Civil and Industrial Engineering of the University of Pisa has selected and designed two promising high-speed journal bearings geometries: a square-recessed journal bearing with 45° orifices and a radial-orifice compensated bearing. Both configurations will be manufactured and tested with a Inconel 718 material, whereas an innovative solution based on ceramic matrix composite, CMC, will be tested with the simpler configuration without recesses. With the goal of implementing such bearings in future pump-fed LOX-CH4 rocket engines, the configurations will be tested in a cryogenic test facility suitably developed to assess the performance with methane in a representative pump environment. In this paper the design bearing choices will be presented and justified, alongside the ongoing test facility development activities.