Aerospace and Electronic Systems Magazine June 2017 - 42

Design of The 3U
Table 1.

LituanicaSAT-2 Model Parameters
Mass, kg

3.6

Satellite dimensions, m

0.1 × 0.1 × 0.34

Center of mass coordinates [x;y;z], m

[0.05; 0.05; 0.19]

Fin length, m

0.30

Principal moments of Inertia, kg*m

Px = 0.00646;

2

Py = 0.0435;
Pz = 0.0439.
Magnetic dipole moment of magnetorquers (per axis), A*m

0.05

Orbit altitude, km

380

2

Inclination, degrees
Residual magnetic dipole moment, A*m

98
0.01

2

can be seen by comparing e.g. Figure 13 and Figure 14 where two
different B-dot controller types are simulated using the same model configuration. For proportional B-dot controller with gain value
of 6000, the steady state error and detumbling time are almost three
times higher than for the bang-bang B-dot controller. However this
comes with power penalty for the satellite operations since average bang-bang B-dot torque is twice over the proportional B-dot
torque [15].
Off nominal tip-off rates of 90 deg/s have been considered additionally to nominal conditions. Again it was found that detumble
time is not influenced by fin angle. In this case the bang-bang
mode B-dot controller detumbles the satellite in about 48 orbits
which corresponds to the 3 day commissioning requirement of
QB50. The simulated time response for 90 deg initial tip-off rate

and 10 deg fin angle case is shown in Figure 17. The satellite again
obtains a steady state condition with an error of 3.6 deg and 2 deg
standard deviation which is within QB50 requirements [5].

CONCLUSIONS
A 3U in orbit technology demonstration CubeSat based on space
dart geometrical configuration has been designed and verified for
the QB50 mission scenario. For lower (<400 km) altitudes it is
suggested to use 30 cm length aerodynamic fins deployed at 10
degrees relative to longitudinal (Z) axes of the spacecraft. This
configuration demonstrated the best trade-off between velocity
vector pointing accuracy within 10 deg (3 sigma) and orbital lifetime expectancy, which is approximately 6 months as worst case

Figure 12.

Simulated time response of 3U CubeSat with 30 cm fins deployed at 20° and B-dot damping gain 18000, with gravity gradient but without magnetic
residual disturbance torque. Initial tumble rate 10 °/s, altitude 380 km. Model parameters same as in [11].

42

IEEE A&E SYSTEMS MAGAZINE

JUNE 2017



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