Turbopump with actine suspension for a propulsion system

Turbopump with active suspension for a propulsive system comprising a fixed casing, a rotary shaft fast with at least one turbine wheel, an axial active inside the casing, axial sensing means including detectors for detecting the axial position of the rotary shaft, two radial active magnetic bearings for the radial positioning of the rotary shaft inside the casing, at least two radial sensing means including detectors for detecting the radial position of the rotary shaft, and a control system receiving signals delivered by all the detectors in order to control, via said radial and axial active magnetic bearings, axial and radial play between the components of the machine fast with the casing and the components of the machine fast with the rotary shaft, wherein

• said turbopump further comprises at least two back-up bearings, each constituted by a first ring fast with the rotary shaft, and a second ring fast with the casing, said second ring being concentric with the first ring and defining with said first ring a free space the length of which in the radial direction is about one half the length of the mean air gap of the radial magnetic bearings, said first and second rings being made of a composite material or a fluorinated thermoplastic resin,
• said turbopump further comprising channels formed in the stator ferromagnetic cores of the radial active magnetic bearings so as to bring a fluid pressurized by the pump into the air gaps of said bearings, said air gaps of the radial magnetic bearings being defined by surfaces of geometrical shape varying slightly from one to the other in order to create significant hydrodynamic effects at the level of each of the radial active magnetic bearings.