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Satellite Battery Capacity Problem
Batteries make up a significant part of the in-orbit weight of a communications satellite but are needed to keep
the communications system operating during eclipses. This question looks at some trade-offs in battery capacity.
Therefore, given a satellite carrying batteries that weigh 65kg of a total in-orbit weight of 1130kg at start of
life; the communication system weighs 167kg, and the station keeping fuel and propellant weigh 189kg. The solar
array and power system weigh 77kg. The satellite requires 140 watts of housekeeping power at all times, and the
communication system draws 875 watts of electrical power. During an eclipse of 70 minuets, the batteries discharge
to 50 percent of their capacity.
If a power system operates at 50 volts, what is the capacity of the batteries in ampere-hours? Note, one ampere-hour
means the battery supplies a current of one ampere for one hour.
Satellite key words: electrical battery power, battery capacity, discharge rate, battery life,
housekeeping, current draw, ampere, amps, communication system, supplied power, spacecraft
batteries, weight and configuration, solar power, DC generation, SATCOM, power consumption.
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