Electrical Motors

An electric motor is the combination of an electromechanical converter and its controller. It performs the function of providing elementary motion within a mechanism. The following types of motors are mainly used for Space Mechanism Applications:

Electromagnetic motors

  • Brushed DC motors (incl. brush equivalent concepts)
  • Brushless DC motors
  • Stepper motors
  • Voice Coil motors

Non electromagnetic motors

  • Piezo-electric motors

Between these two main families of electric motors and actuators, the most important and most familiar is the electromagnetic group of devices. However the rapid development in piezo systems into several terrestrial applications means that they must be considered as well, especially as some of their characteristics make them attractive for space applications.

Looking more specifically at space applications, the electromagnetic electrical motor technology landscape can be divided in two main industrial categories:

  • Category 1: Custom design and special-purpose motors for key spacecraft equipment, often in mission critical applications (e.g. solar array drive mechanisms, antenna and electric propulsion thrusters pointing, SAR antenna deployment mechanisms, etc.) on which previous R&D efforts were focused in priority
  • Category 2: Adapted general-purpose (industrial/commercial) motors in local and decentralized applications, often for actuation tasks in scientific instruments and other payloads (e.g. for miniature rovers and robotic arms, instrument mirror and aperture door actuation, internal scanning motion, etc.)

Regarding this first category, continuous efforts is being dedicated to maintaining, re-establishing and extending European capabilities. However, the spectrum of space qualified motors presently available in Europe is limited.

On the other side, there is a steadily growing interest in the second category of electric motors. The use of industrial electric motors for space implies a series of dedicated investigations relating to the general compatibility with the relevant space environment, with emphasis on vacuum and extended temperature range, as well as adequate performance of potentially life limiting components like e.g. shaft bearings, and commutators in brushed DC motors.

The Mechanisms Section has been providing a continuous support to industry for many years in order to improve the performance of electric motors in Europe. Several activities have been initiated or will be started soon to enlarge the catalogue of space qualified European electric motors. Special attention in this process is given to the Technical Harmonization Dossier Road Map (for further information and updated harmonization documents version, please contact: harmo @ esa.int).

Last update: 18 January 2011

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