A MICRO high-temperature superconductor-magnet flywheels with dual function of energy storage and attitude control

Abstract

This paper proposes to develop energy storage and power generation system for spacecraft using high-temperature superconductor (HTS)- magnet bearing system. This system consists of an HTS-magnet flywheel energy storage system and a brushless motor/generator. The switching between the modes, the motor commutation and generated voltage rectification will be done by cryogenic HTS PWM power electronics, which will be integrated into the same Si substrate near the HTS disk. The system is ideally suited for energy storage, power generation and attitude control of spacecraft such as micro/nano satellites in low earth orbit (LEO), where the HTS flywheel can last 100,000-150,000 charge/discharge cycles. Recently, there have been various kinds of micropower supplies such as Li ion batteries, chemical fuel cell and microthrusters. However none of them are quite ideal for nano satellites in LEO, where missions require more than 40,000 charge/discharge cycles. It can be also be used for power supply and energy storage during solar nights. The rationale lies bin the unique capability of the HTS to adapt to low temperatures, radiation, and vacuum environments in space and to enhance system stability passively without power consumption. The HTS flywheel has high angular momentum storage since its drag torque is nearly velocity-independent and extremely small, enabling high-speed rotation. The HTS-magnet bearing system can also provide very accurate attitude control because it avoids the detrimental effect of friction in MEMS device by levitating system without power dissipation. It does not suffer from static friction, which makes the motion discontinuous or jerky at near zero velocity. Moreover, it can reject disturbances efficiently with fast responses owing to its high rotational speed. It also isolates vibration from other parts of spacecraft. Therefore, the microHTS bearing system can be used as momentum wheels, which serve as an attitude control system for nanosatellites and microspacecraft. It makes a high bandwidth attitude control system with better disturbance rejection. Thus, it can perform the dual function of a power/attitude control system using flywheel elements for both power storage and attitude control. This dual function capability further reduces the mass of the spacecraft. It has energy storage capacity of about 50 Whr/kg rotating at 530 krpm. The system is ideally suited for low earth orbit (LEO) energy storage, power generation and attitude control of spacecraft such as nanosatellites. The micropower supply/energy storage system can supply about 10-100 mW.