Page 191 - Intro to Space Sciences Spacecraft Applications

Introduction to Space Sciences and Spacecraji Applications
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storage device during times when power cannot be generated, such as dur-
ing launch, eclipse times, or malfunctions. Fuel cells represent more
power availability than batteries as the quantity depends only on the
amount of fuel elements carried. The Space Shuttle cells have an interest-
ing benefit, as the by-product of the power generation is pure, potable
water used by the astronauts for drinking. The disadvantage of both sys-
tems is their greater weight versus the amount of power produced com-
pared to other methods.

Magnetic. It is also possible to produce power in other ways. One of these
could use the process by which a current is produced when a loop of wire
is moved through a magnetic field. The earth’s geomagnetic field and a
spacecraft’s motion through it represents a possible future space power
source. This potential was demonstrated on a Space Shuttle flight by
deploying a payload on the end of a 12.5-mile-long tether, however, it has
not been used operationally in space as have the other sources of power
discussed above.

Solar Cell Power Systems Design

The power subsystem takes the stabilization method as an input cue
from the ARC subsystem to determine the area and mass scaling factors
that will be used for power subsystem calculations. Solar panel area and
mass scaling factor dependency on the selected stabilization method is
approximately:

Stabilization Method AredMass Scaling Factor
3-axis, zero momentum 1
3-axis, bias momentum 1
Spin and dual-spin 3.14 1593
Gravity gradient 4

Using these values as the foundation for the calculation of the design for
the power subsystem, the design is a complex, interactive process that
proceeds based on a multitude of mission and payload inputs.
The electrical power subsystem (EPS) supplies electrical power to the
satellite, then stores, regulates, and distributes the power as shown in the
block diagram of a typical power subsystem depicted in Figure 8-9. Power
subsystems designers calculate the subsystem mass by determining the