Session
Session II: Advanced Concepts I
Location
Utah State University, Logan, UT
Abstract
The history of reaction wheel development at the Technische Universität Berlin (TUB) begins early in the 90s. Since then many of these reaction wheels performed on-orbit without a single failure as a part of six micro- and nanosatellite missions. The last one is the S band Network for co-operating Satellites (S-Net). S-Net is a cluster of four nanosats successfully launched in February 2018. Since then a number of communication experiments using intersatellite links have been performed by the S-Net satellites. This paper is focusing on the design and on the on orbit performance of the reaction wheels for S-Net nanosatellites. The design is based on COTS and differs considerably from the state-of-the-art one. The wheel is pressurized, allowing higher rotation speeds due to a better thermal performance as well as the use of commercial motors without any changes in ball bearings and their lubrication. Due to a better ball bearing friction the performance and, consequently, the failure tolerance have increased significantly. The wheels can run at higher speeds continuously allowing their use within momentum bias platforms. A novel suspension system helped to optimize the misalignment of the rotational axis compared to a simple spiral spring based suspension used for TUB wheels earlier. A further outstanding feature is the implementation of some additional control loops alongside with the standard current, speed and torque control. The use of built-in internal angular velocity sensors makes satellite velocity and satellite angle control modes possible. For some operational scenarios, especially for such with high agility requirements, it can be advantageous because these control loops can be closed with a higher frequency as if would be possible with a centralized external attitude controller. The system is characterized by a low steady-state power consumption of 220 mW at the zero motor speed and under 1.5 W at the maximum speed, has the dimensions of 65 x 65 x 55 mm3 and a weight of less than 320 g. Two wheel modifications for different satellite classes with slightly different rotor geometry exist. The angular momentum can be as high as 45 mNms. The modular design allows a scale-up without significant changes in mechanics and electronics. Finally, future work based on the described design is discussed.
Design and On-Orbit Experience of Reaction Wheels for Small Satellites
Utah State University, Logan, UT
The history of reaction wheel development at the Technische Universität Berlin (TUB) begins early in the 90s. Since then many of these reaction wheels performed on-orbit without a single failure as a part of six micro- and nanosatellite missions. The last one is the S band Network for co-operating Satellites (S-Net). S-Net is a cluster of four nanosats successfully launched in February 2018. Since then a number of communication experiments using intersatellite links have been performed by the S-Net satellites. This paper is focusing on the design and on the on orbit performance of the reaction wheels for S-Net nanosatellites. The design is based on COTS and differs considerably from the state-of-the-art one. The wheel is pressurized, allowing higher rotation speeds due to a better thermal performance as well as the use of commercial motors without any changes in ball bearings and their lubrication. Due to a better ball bearing friction the performance and, consequently, the failure tolerance have increased significantly. The wheels can run at higher speeds continuously allowing their use within momentum bias platforms. A novel suspension system helped to optimize the misalignment of the rotational axis compared to a simple spiral spring based suspension used for TUB wheels earlier. A further outstanding feature is the implementation of some additional control loops alongside with the standard current, speed and torque control. The use of built-in internal angular velocity sensors makes satellite velocity and satellite angle control modes possible. For some operational scenarios, especially for such with high agility requirements, it can be advantageous because these control loops can be closed with a higher frequency as if would be possible with a centralized external attitude controller. The system is characterized by a low steady-state power consumption of 220 mW at the zero motor speed and under 1.5 W at the maximum speed, has the dimensions of 65 x 65 x 55 mm3 and a weight of less than 320 g. Two wheel modifications for different satellite classes with slightly different rotor geometry exist. The angular momentum can be as high as 45 mNms. The modular design allows a scale-up without significant changes in mechanics and electronics. Finally, future work based on the described design is discussed.
