We'll need even bigger[1] breakthroughs in propulsion if it's going to be self-propelling itself back to Sol at relativistic speeds.
1. A "simpler" sci-fi solution foe a 1-way trip that's still out of our reach is a large light sail and huge Earth-based laser, but his required "smaller" breakthroughs in material science
Well if you can propel something forward you can propel it backwards as well.
I'm assuming some sort of fixed laser type propulsion mechanism would leverage a type of solar sail technology. Maybe you could send a phased laser signal that "vibrates" a solar sail towards the source of energy instead of away.
> Well if you can propel something forward you can propel it backwards as well
Not necessarily - at least with currently known science. Light sails work ok transferring momentum from photons, allowing positive acceleration from a giant laser Earth. Return trip requires a giant laser on the other side.
I meant to say the "simpler" (but still very complicated) solar sail approach was for a one-way trip. On paper, our civilization can muster the energy required to accelerate tiny masses to relativistic speeds. A return trip at those speeds would require a nee type of science to concentrate that amount of energy in a small mass and use it for controlled propulsion.
1. A "simpler" sci-fi solution foe a 1-way trip that's still out of our reach is a large light sail and huge Earth-based laser, but his required "smaller" breakthroughs in material science