A Test Facility for the Lifetime Characterization of Cryogenic High-Speed Bearings

Currently, reusable rockets are the most promising design solution to reduce launcher costs. A truly reusable rocket engine to be economically viable should ensure the increase of frequency launch with virtually no maintenance effort. The rocket engine reusability can be reached by developing long-life turbopumps with a lifetime requirement of several hours. The replacement of rolling bearing, which represents a critical component for reusability, with journal bearing has been considered the most promising solution to increase turbopump lifetime. The propulsion team of the Department of Civil and Industrial Engineering of the University of Pisa, UniPi, is currently pursuing the development of high-speed hybrid bearings for reusable pump-fed liquid rocket engines in the framework of the ESA’s project “Long Life Journal Bearings for Turbopumps.” UniPi’s team selected the two most promising candidate journal bearings: a square-recessed journal bearing with 45° orifices, a radial-orifice compensated bearing. Inconel 718 and ceramic matrix composite, CMC, are the chosen materials that minimize the possible surface wear of the bearings and ensure the material compatibility with LCH4. The geometry and material configurations will be tested in a cryogenic test facility suitably developed to characterize the performance of journal bearings employing liquid methane in a representative turbopump environment of future pump-fed LOX-CH4 rocket engines. This paper illustrates the selection of the test journal bearings and presents the novel test apparatus, and a facility designed for the bearing experimental lifetime characterization