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RW4-1.0 GEO Wheels Use Less Power

posted Nov 30, 2019, 9:52 AM by Doug Sinclair
The first RW4-1.0 reaction wheels are getting ready to ship out.  This is an evolution of the earlier RW3-1.0 wheel, built rad-hard and intended for long-duration GEO missions.  Recent vacuum testing confirms that the power consumption of this wheel is greatly reduced compared to its predecessor:
  • At 0.2 Nms momentum, power is 1.4 W instead of 2.4 W
  • At 1.0 Nms momentum, power is 5.3 W instead of 15.1 W
  • Torque is +/- 100 mNm instead of +/- 50 mNm
This wheel will run cooler, and give the satellite greater agility, than ever before.  We can expect that, after successful flight demonstration, the RW4-1.0 will make the older RW3-1.0 model obsolete.

[For those who are interested: in this revision of the motor design I paid careful attention to the fringing magnetic fields from the rotor.  Where possible, aluminum radiation shielding in high field areas was removed and replaced with carbon-loaded PTFE.  Where the aluminum was required for thermal reasons, it was covered with a thin layer of high permeability nickel-iron alloy.  The skin depth in this alloy is very small, and prevents eddy-current formation in the aluminum substrate.  That's all it took to reduce the drag losses to 1/3 of their original values!]