You’re right. Solar sails need to be massive to move anything heavy, and they take a long time to build up speed. Stopping is another big hurdle. But they’re no

You’re right. Solar sails need to be massive to move anything heavy, and they take a long time to build up speed. Stopping is another big hurdle. But they’re not supposed to replace everything. They’re useful when you can’t carry fuel, like on really long missions. They’re slow, but they work for what they’re designed to do: keep going without needing fuel.