Great point. But wouldn't it pose a power concern as the distance increases? The intensity of light decreases with respect to the distance (r) as 1/r². Let's go with the 'easy numbers' approach. Solar panel the size of 1 m² gives output of 500 W (give or take, in the end it's the ratio of solar panel area that I'm concerned about), Earth is 1 AU from the Sun, Mars is about 1.5 AU from the Sun. Formula in plain words: Power * Area of solar panel / distance ² That would mean that the power output on Mars would be about 500 * 1 / (3/2)² ~= 220 W I know that it's not unfeasible to simply stack a lot more solar panels onto the ship. But the above relationship shows that to produce same 500 W we had at around Earth's distance, on Mars we would need 2.25 m² of solar panels. Although having said that, I am aware of making a silent assumption that all of the power would be provided via solar panels. I have no idea how viable would be some form of thermal generator that uses radioisotopes (as in most satellites)… or maybe I should stop thinking in such limited terms and look for ways to put a full nuclear reactor on the ship. :D