A turbopump with active magnetic suspension comprises at least two back-up bearings, each constituted by a first ring fast with a rotary shaft and a second ring fast with a casing, the rings being concentric and defining a free space whose length in the radial direction is about half the length of the...http://www.google.de/patents/US4929158?utm_source=gb-gplus-sharePatent US4929158 - Turbopump with actine suspension for a propulsion system
