Development of an Ultra Thin Reaction Wheel For Modular Nanosatellites

Space is of important interest for many scientists around the world but due to the enormous costs, for decades remained an unaffordable issue for many of them. The launching costs are still high now days while the use of COTS (Commercial Off The Shelf) components allowed to reduce satellite implementation costs. “A CubeSat is a type of miniaturized satellite for space research” said Wikipedia. One of the most important characteristics of a CubeSat is its dimension that allows to be launched on the orbit with low costs, taking advantage of free space that can be found on the missile of bigger missions or by gathering more nanosatellites to divide launching costs.
Moved by the growing interest of the Universities around the globe in space research at affordable costs in 1999 California Polytechnic State University and Stanford University developed the CubeSat specifications. The main goals of the professors Jordi Puig-Suari and Bob Twings was to enable the graduate students to be able to design, build, test and operate in space a spacecraft with the similar capabilities of Sputnik, the very first spacecraft ever launched. The CubeSat has become a standard over time and lots of satellites have been built following the CubeSat idea.

1.1. PicPoT Project
Many Universities around the world have used CubeSat standard since
then. One of them is Politecnico di Torino, which has realised its first
nanosatellite named PiCPoT (Piccolo Cubo of Politecnico di Torino).
This project was
aimed to build a low
cost satellite, which
must fit within tight
cost constrains for the
launch and the actual
satellite hardware.
The PiCPoT was a
cube of 130 mm side
and 2.5 kg of weight
with the external
faces made by
aluminium alloy type 5000AlMn. The main motivations were to give a
training opportunity for the students and PhD students, create an
interdisciplinary team from different departments of Politecnico,
consolidate the knowledge of the team in the fields of electronic,
aerospace and avionic system design, assessing the feasibility of building
high-reliability satellites with cheap off-the-shelf components and the
intention of building a “constellation of Italian satellites”, together with
other five Italian universities. The mission was transmitting and
receiving data, shoot photos and test the off-the-shelf components, of which was built, in space conditions. The satellite had solar panels (used to power the entire system) on five sides of the cube and the sixth side was populated with antennas and cameras. This nanosatellite was never tested in space because its carrier failed few seconds after the launch.
1.2. Aramis Project
The AraMiS project is a prosecution of the PiCPoT. It’s main goal is, in addition of the first project goals, the modularity. The PiCPoT was realised using an ad-hoc view, which didn’t offered the possibility to reuse the designs. AraMiS project is thought with the use of independent modules, with specific independent functions, perfect interchangeable, reusable in other similar projects. Once standard modules are defined, they can be assembled into the project according with the specification of the mission, resulting in reduced projecting costs and high versatility.
The main modules, called tiles, in addition of the Inertial Attitude Subsystem Tile are the Power Management Tile and Telecommunication Tile.

1.2.1. Power Management Tile
These modules perform different functions, electrical energy generation by converting the solar light by means of the solar panels, charging this energy into the batteries and distribute it to the other systems at suitable parameters. This modules are put on the outside of the satellite because of the solar panels presence, which must be illuminated by the solar light. The Tiles are independent and managed to allow to decide which battery will be charge from which solar panel, in order to optimize the system as well as possible( clearly in a specific moment very few panels will be illuminated so only them will give power in that moment). To do that the power and data bus is used.
1.2.2. Telecommunication Tile
These modules allows the communication between the satellite and University Earth station. Uses 2 channels, the firs, on the 437 MHz band, is dedicated to the radio amateur and allow them to receive the satellite beacon, the second operates on the 2.4 GHz band. The use of two channels allows to increase communication system reliability, allowing to maintain the communications while one of radio channel is out of order.