When solar panels are functional in a satellite why is the satellite life limited by fuel?
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Answer:
The Fuel are are talking about is explosive material used to create thrust. In space there is no gravity. The satelite can't simply "kick its legs" to move from point A to point B. Remember that bodies in motion stay in motion unless acted on by another force. When the satelite runs out of fuel to create thrust we lose the ability to manuever the satelite. Usually what happens is that it's orbit decays and they fall to earth and burn up in our atmosphere. If they didn't their solar cells would continue to power the internal systems. So to answer your question. The fuel supply determines the life span of the satelite by determining the point at which operators can no longer keep the satelite in orbit.
On-board fuel is used for positioning, not operations.
Solar panels provide some power, but what fuel do you speak of? Propulsion? Rocket fuel? You still need that. Also, some satellites have a small nuclear power source.
S-U-N.
When u want to position a satalite, u need to give it a velosity.
if not will fall down to the earth or may be to the sun, because their gravity.
If it's positioned in Azimuth Zone (up to the Equator by 30000km s) u need to give it a velosity, same as the rotating speed of earth.
u need to give that velosity by a timely manner, because the earth's gravitional force, depreesing the satalite's speed.
So because of that, after the fuel is over. satalite's life is over.
Now the scientists are considering about this matter to increase the lifetime of a satalite by using other options on fuel. (ion streaming, nuclear power)
Spacecraft solar arrays are used to provide power to the onboard electronics. Spacecraft fuel (typically hydrazine) is not used to provide power, it is used to control the orientation of the spacecraft or to perform "delta-Vs" which are changes in velocity. Onboard fuel is used in the Attitude Control Subsystem (ACS) or in the propulsion subsystem. Many satellites use reaction wheels to control their attitude. These wheels can become saturated and ineffective. One method to desaturate the reaction wheels is to provide thrust (via the fuel) in an opposing velocity. Once onboard fuel is expended, the solar arrays may still function but if the spacecraft can not control its attitude and keep the solar arrays pointed at the sun then it won't really matter if they work or not.
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