I recently read about an idea to power rockets with solar energy, also known as “solar sails”. It made me wonder how practical this idea was given that solar thermal energy plants are in the experimental phase in Las Vegas. They basically use thousands of parabolic mirrors to focus sunlight on a central tower, which then runs a rankine power cycle.
Keplar originally proposed the idea of solar sails to navigate the solar system. In this idea, light from the sun basically propells a object without any need for external power. The math is somewhat theoretical, and with little practical data, but the sun can produce about 1.4 kW of power at a distance of 93 million miles away.