Commercial off the Shelf Components in Reaction Wheels

This paper presents the approach adopted by Surrey Satellite Technology Ltd (SSTL) for development of reaction wheels incorporating commercial components and the accelerated life test / qualification philosophy. The paper focuses on the mechanical development and re-qualification of reaction wheel which has flown successfully on many missions having conducted years of in orbit operation. The scope of the requalification was to verify the wheels performance with ground testing for new missions where an increased life was required, with some re-design where applicable. Introduction The Microsat Reaction Wheel (MRW) or Micro Wheel was developed at SSTL in the mid-nineties and is unique in its design from the simple drive electronics which are enclosed in the base of the wheel to the commercial brushless DC motor using dry lubrication, to the wheel volume at approximately 100*100*100 mm3 all weighing in at under 1 kg, this wheel was succeeded by the Enhanced Microsat Reaction Wheel (EMRW) in the year 2000. The aim of the new Superior Microsat Reaction Wheel (SMRW) was to build on the heritage and success of the MRW and EMRW increasing the performance and extending the life in terms of revolutions of the wheel. Figure 1 shows the MRW, EMRW and SMRW wheels. At the time of writing this paper the SMRW is integrated onto the protoflight model of 5 imaging micro satellites currently being built at SSTL and due for launch towards the end of 2006. The Microsat wheels have led the way forward for the development of the next generation of larger more powerful wheels which use similar electronics and lubrication systems. Although this wheel is not discussed here in the paper, four smallsat reaction wheels also incorporating dry lubricated bearings have been integrated onto the GIOVE A spacecraft ready for launch at the end of December 2005. Figure 1. SSTL Microsat reaction wheels Background The small satellite market (400 kg) is particularly demanding not only for the small budgets involved or the mass and power requirements but also for the fact that a typical program for SSTL from contract to in orbit operation is normally from 18 24 months which leaves a very short period of time for development and qualification. ' Surrey Satellite Technology Ltd., Surrey Space Centre, Guildford, Surrey, U.K. Proceedings of the 3d' Aerospace Mechanisms Symposium, Langley Research Center, May 1719,2006