Magellan Spacecraft Venus Orbiter Example

Spacecraft Systems

Power Systems

• Batteries: what they had on Sputnik, but they run down after a while. Rechargeable batteries are used as a backup for solar cells, for when the spacecraft passes through a planet's shadow or during maneuvers, when the panels aren't pointed toward the sun.
• Solar Cells: like on your calculator. These are the method of choice for most satellites and probes, because space is real sunny and they last forever. They look like big wings on the satellite, and can put out a few thousand watts. Not so good for deep-space probes like those that go to Jupiter, which get too far from the sun to be any good.
• Fuel Cells: burn hydrogen & oxygen to produce electricity. Good for manned vehicles like Apollo or the Space Shuttle, where you have to carry a bunch of oxygen anyway. Not as good for unmanned probes, since like batteries they will run out .
• Radioisotope Thermoelectric Generators (RTG's): fancy name for itty-bitty nuclear reactors. Used on unmanned deep-space probes (which get far from the sun), since they don't need the sun to operate and the nuclear fuel lasts a long long time.