Why isn’t nuclear power used in space as?
Nuclear power is too dangerous to use. Before the satellites and Orbiters are launched, the very first thing to be calculated is the safety of humans from departure to going home. If the space agencies will use nuclear power instead of Solar Cells, they will cost much and putting the whole Orbiter and Satellites in danger because nuclear power is so hard to control, one wrong move destroys all. They prioritize the cost it will have and the safety of lives.
Because nuclear power needs fuel. Rovers and the ISS run on solar power because it means they only need a few solar tiles for enegy, rather than getting supplies every so often. For a Mars rover that has to last 7/8 years cannot run on a fuel based power source so the easiest option is solar power. The same is with the ISS, it would require a lot of space shuttle missions to refuel it, costing too much money and time.
