Design
| Enviro |
Astro | Propulsion
| Power | Thermal
| Structures | AD&C
| CDHS |
Test
Sunlight
is abundant for the inner planets
and provides a relatively
constant source of clean energy.
Solar
Arrays
Photovoltaic
cells
convert
light into electricity. Incident photons transmit
energy to atoms in the cell, which frees electrons
to flow and creates an electrical current. Solar
cells are semiconductor crystals made of silicon
or more expensive gallium-arsenide. Silicon cell
efficiency is around 15% whereas gallium-arsenide
cells approach 20%. This means that 20% of the solar
energy is converted into electricity and the rest
is reflected or lost as heat.
Eclipse
time is that period when a
satellite is shadowed by the Earth and varies for
every orbit. It is a design parameter used to size
batteries that take over when solar arrays are eclipsed.
Concentrators
are essentially mirrors that direct sunlight onto
solar arrays to increase electrical energy production.
The NASA/Caltech JPL DS1
mission demonstrated this
technology.
