Mission Design for the CubeSat OUFTI-1

CHAPTER 77.1 Inertia propertiesBefore proceeding with the estimation of the disturbing torques acting on thesatellite, we need to know its inertia properties. As the position of the elementsinside the structure is still unknown, we will use a totally simplified model. Asshown in figure 7.1 there are four antennas: they are approximately L long = 50cm and l short = 17.5 cm long as they are 1/4 of the wavelength. Made ofaluminium and with a diameter of 2 mm, they have respectively a mass ofm long = 4.15 g and m short = 1.44 g. The mass of the cubic central body istherefore m cube = 0.994 Kg. The longest antennas are directed as the y-axisand the shortest as the z-axis.Figure 7.1: Example of OUFTI-1 configurationWe study the CubeSat as a cube with uniform density, whose gravity centeris situated in the geometrical center, to which we add a mass M on the corner[0.05 0.05 0.05] m respect to the geometrical center of the cube in order to keepinto account all the non-symmetrical components. We calculate it in order todisplaces the gravity center 2 cm away from the geometric center of the cube:this is the maximum allowed by the CubeSat specifications.M = 0.02m cube0.05= 0.3976 Kg (7.1)The mass of the uniform cube is then m unif = 0.5964Kg.We calculate then the inertia moments of all the parts and we place theminto the gravity center of the satellite thanks to the Huygens-Steiner theoremof parallel axis:I P = I GC + md 2 (7.2)Galli Stefania 64 University of Liège