An Overview of Electric Motors for Space Applications

Spacecrafts rely on electric motors for Important functions such as attitude control, deployment mechanisms, throttle valve control, etc. Electric motors for space applications must have long life and high reliability, under high vacuum, radiation, and wide operating temperature environments. Although various types of motors are available, all of them are not suitable. Limitations of ac synchronous motors and brushes and commutators of conventional dc motors are given. Brushless dc motors and stepper motors, which are widely used, are discussed in detail. Problems of conventional lubrication and bearings and the advantages of magnetic bearings are also discussed. In a totally noncontacting system, such as a brushless dc motor/stepper motor with magnetic bearing, life and reliability are functions of only electronic components, and they can be improved to the desired level. Thus this paper gives the problems and prospects of electric motors for space applications.