HTS bearings for space applications: reaction wheel with low power consumption for mini-satellites

Superconducting bearings have very low coefficients of friction. It is promising to exploit this feature of HTS bearings in the construction of reaction wheel systems that consume meager power. Reaction wheel systems that consume little power are particularly suitable for use on mini-satellites where both energy and power are scarce resources. Thus, these mini-satellites can still have attitude control capabilities without prohibitive requirements for total volume and weight of hardware, and power consumption. Here, we will present the design and discuss the performance of a prototype with a 1.9 kg stainless steel wheel of diameter 82.5 mm, and height 75 mm, which can store 3.5 J-sec of angular momentum when it rotates at an angular speed of 15000 RPM. We have performed spin down tests from 7000 RPM down and measured the input power required to sustain rotational speed under a vacuum of 0.01 torr. Implications of the results are discussed.