

Satellite Solar Power Problem
Given a satellite having solar cells wrapped around a cylindrical drum with a diameter of
2.38 meters and a height of 2.92 meters, that is rotating at approximately 60 revolutions
per minuet (rpm) in order to provide spin stabilization to the spacecraft. This drum satellite
is designed to deliver 708 watts of electrical power from its solar cells at the end of the
satellites life. Use these parameters in the following calculations:
Solution:
a) The solar cells efficiency at the end of life is:
P = (Incident Solar Power) (Projected Cell Area) (Efficiency)
P = (1.39kW/m^{2})(2.38m)(2.92m)( η )
Where η = 708 / (1390)(6.95) = 7.33%
b) Define:
Power End of Life = P_{EOL}
Power Beginning of Life = P_{BOL}
Therefore, P_{EOL} = P_{BOL} x 0.85
Solve for P_{BOL}, and P_{BOL} = 708 / 0.85 = 832.9 watts
c) At P_{EOL} the satellite will deliver 708watts, with an 80watt margin.
Therefore, the satellite requires 628watts for the satellite systems. So if at the
beginning of the satellite’s life the power provided was 832.9watts and 628watts
needed to operate the satellite; a total of 204.9watts was dumped into the load
resistors when the spacecraft was initially turnedon.
d) Solar Sails Power = P_{SS} = P_{spinner} / 0.9
So, P_{SS} = 786.7watts
The Area of the Sails = (P_{SS}) / (Incident Solar Power)(Efficiency)
P_{SS} = (786.7watts) / (1390 w/m^{2})(0.0733)
P_{SS} = 7.72m^{2}
Satellite key words: satellite spinner design, twoaxis design, rotating, revolving, spin stabilize,
satellite drum, load resistors, heat dissipation, lifecycle, operational temperature, lifespan, solar
cells, solar power, power generation, status, health, telemetry, satcom, electrical, computation,
dimensions, capture area.
