Development of a ultrathin reaction wheel for modular nanosatellites

CubeSats are particular kinds of miniaturized satellites. This standard has been developed by Professor Robert Twiggs at Stanford University’s Space Systems Development Laboratory in 1998. The standard defined the 1U CubeSat, which shall have a maximum mass of 1:33 kg and a cubic shape with 10 cm edges, and thus is a nanosatellite. Further standards have been defined, from 2U to 6U CubeSats, having maximum masses and
dimensions multiples of the 1U standard.
This thesis concerns the development of part of the Attitude Determination and Control System (ADCS) of the
AraMiS nanosatellite (acronym for modular architecture for satellites). The AraMiS project started in 2006 at
Politecnico di Torino, after conclusion of the PICPOT project, which took its name from a previously developed
nanosatellite.
The objective of the project is to design, produce, test and operate nanosatellites, whose development cost and
time are strongly reduced with respect to traditional nanosatellites. The current version of AraMiS is a 1U
CubeSat. Thus the main obstacle to space access for universities and small companies would be downsized. To
achieve this result, the following strategies are adopted:
– Use of a highly modular architecture, for mechanical and electronic components and for testing. It allows
to spread costs among a remarkable number of space missions, to reduce design cost, which represents
90% of total cost and to reduce testing and production time. In addition, modularity allows to easily
implement satellite components redundancy;
– Use of Commercial Off-The-Shelf (COTS) components. These commercial level components allow components
cost reduction, although their generally low reliability requires particular care during subsystem design. Components redundancy is employed to increase fault tolerance and keep performances decay at an acceptable level.
As a result, AraMiS bus is composed of small, distributed, intercommunicating units mounted on CubeSat structure external faces, called smart tiles or tiles, whose prototypes are shown in gure 1(a). Tile functions include all bus functions, although each subsystem components are normally distributed between two or more tiles. For example, the reaction wheel tile, object of the present thesis, contains the reaction wheel, its motor, a magnetic torquer and their electronic components, which are part of the ADCS system, and two solar cells with their electronic components and power conduits, which are part of the electrical power system. Hence subsystems components are distributed among CubeSat tiles.
While AraMiS payload has a different design for each mission and lies in the AraMis CubeSat interior, AraMiS bus (whose prototype is shown in figure 1(b)) is mounted on CubeSat structure external faces and is composed by a set of tiles that satises payload and mission requirements. The most appropriate tiles are chosen from a broader set which has previously been designed, produced and tested.