Using sunlight to power up a flywheel in space to fling interstellar objects.
"Kipping began thinking about using sail materials to harvest the energy of solar photons, storing it in what could be considered a battery, and then using that stored energy, transformed into kinetic energy, to hurl a small spacecraft outwards."
https://www.centauri-dreams.org/2025/08/01/a-space-catapult-with-interstellar-potential/