Pointing lasers at solar sails on small probes is theorized to get to 15-25% c: https://en.wikipedia.org/wiki/Breakthrough_Starshot https://en.wikipedia.org/wik

Pointing lasers at solar sails on small probes is theorized to get to 15-25% c: https://en.wikipedia.org/wiki/Breakthrough_Starshot https://en.wikipedia.org/wiki/Breakthrough_Starshot To me this seems like the logical next step after using chemical rockets to populate a moonbase. Plop some big lasers on the moon and use them to push things really fast. No weird physics needed, just improvements on what we already have.