Solar has a few problems for spacecraft, especially when talking about objects not in an earth-centric orbit. 1. The further the spacecraft is from the sun the

Solar has a few problems for spacecraft, especially when talking about objects not in an earth-centric orbit. 1. The further the spacecraft is from the sun the less efficient solar panels are. 2. Solar panels are a pretty heavy thing to launch. 3. Solar panels have a tendency to degrade in performance over decades.