foil bearing assemblies 30 a and 30 b can be of a conventional type where during operation when the shaft 18 is rotating the shaft 18 is supported by the fluid pressure of a working fluid e g xenon gas present between the shaft 18 and metallic structures of the foil bearing assemblies 30 a and 30 b during operation the rotating shaft 18 generally does not contact the metal components of foil bearing assemblies 30 a and 30 b this means that generally no wear occurs due to direct physical contact between the rotating shaft 18 and the metallic structures of the foil bearing assemblies 30 a and 30 b during operation although some incidental contact may occur the turboalternator 10 can be installed in a space shuttle or other aerospace vehicle not shown that typically will undertake a flight cycle that includes a launch phase where the turboalternator 10 is not operational and an orbital phase where the turboalternator 10 is activated and operated the restraint system 32 helps to secure the rotatable shaft 18 of the turboalternator 10 when not operational such as during the launch phase in order to help reduce the possibility of damage to the foil bearing assemblies 30 a and 30 b due to undesired movement of the shaft 18 fig2 is a perspective view of the restraint system 32 and the shaft 18 shown in isolation for clarity as shown in fig2 the shaft 18 defines a first end 18 a and an opposite second end 18 b and further defines an axis of rotation a the first restraint assembly 32 a is positioned relative to the first end 18 a of.