Alston Lee-Van Gu

Liquid hydrogen foil-bearing turbopump

The testing and performance evaluation of a liquid hydrogen turbopump with the rotor supported by foil bearings is discussed. The objectives of the program were to demonstrate the long-life feature of a foil-bearing turbopump and to evaluate its operational characteristics. The demonstration has successfully shown the reliability, long life, and robust nature of foil-bearing turbopumps by operating for long periods of time, with many start and stop cycles and a wide speed range. It has also proven that foil-bearing turbopumps can start without total chilldown of the foil bearing, offering operational simplicity.

Foil bearing performance in liquid nitrogen and liquid oxygen

Space transfer vehicles and other power and propulsion systems require long-life turbopumps. Rolling-element bearings used in current turbopumps do not have sufficient life for these applications. Process fluid foil bearings have established long life, with exceptional reliability, over a wide range of temperatures and fluids in many high-speed turbomachinery applications. However, actual data on bearing performance in cryogenic fluids has been minimal. The National Aeronautics and Space Administration (NASA) and AlliedSignal Aerospace Systems and Equipment (ASE) have attempted to characterize the leaf-type compliant foil bearing in oxygen and nitrogen. The work performed under a joint internal research and development program between Marshall Space Flight Center (MSFC) and ASE demonstrated that the foil bearing has load capacities of at least 266 psi in liquid oxygen and 352 psi in liquid nitrogen. In addition, the bearing demonstrated a direct damping coefficient of 40 to 50 lb-sec/in. with a damping ratio of .7 to 1.4 in. liquid nitrogen using a bearing sized for upper-stage turbopumps. With the results from this testing and the years of successful use in air cycle machines and other applications, leaf-type compliant foil bearings are ready for testing in liquid oxygen turbopumps.