Solar panels are very effective on clear days but less efficient on cloudy days although they do still work contrary to popular belief.
Rtgs vs solar panels.
Two alternatives rtg or solar were investigated in the mars science laboratory environmental impact statement.
The panasonic n series of panels are a good quality solar panel with a top efficiency on their 330 watt monocrystalline system of 19 7 and a very impressive temperature coefficient of 0 29 a figure which is equal best with the market leader sunpower.
If you re using more than 26 3 charge minute a probe unit uses 3 c min the batteries you d have to add to your ship make it lighter to opt for thermos.
Rtgs are used on nasa missions where other options such as solar power are impractical or incapable of providing the power that a mission may need to accomplish its scientific or operational goals.
Rtgs are usually the most desirable power source for unmaintained situations that need a few hundred watts or less of power for durations too long for fuel cells batteries or generators to provide economically and in places where solar cells are not practical.
A thermoelectric generator puts out almost twice as much power as a solar panel does over the entire orbit 4 275 c vs 2 850 c.
1 solar panels can be made with safe readily available materials while rtgs require fuels that are difficult to safely handle and which are in limited and highly regulated supply.
Sometimes referred to as nuclear batteries rtgs are not fission reactors nor is the plutonium the type that is used for nuclear weapons.
In summary solar arrays would limit the msl to operate between 5 n and 20 n and for one martian year only if at exactly 15 n whereas rtgs would permit it to operate for at least one martian year anywhere from 60 s to 60 n.
Rtgs or even reactors whch have more power solar is useless in comparsion for deep space at current tech levels or if a mission needs a lot of power.
Radioisotope thermoelectric generators rtgs the rtg systems are ideal for applications where solar panels cannot supply adequate power such as for spacecraft surveying planets far from the sun.