First, we’ll need 3 monoliths…
Voyager is moving at ~17KPS … divided into 300,000 KPS … multiplied by 3600 * 24 * 365.25 … multiplied by 20. ~370,000 years to reach Gliese. To me, a 200-year mission is about what I could imagine our civilization buying into. No way gravity assist can scale; I don’t think solar sails scale; no way we’re putting enough nuclear bombs into space to do an Orion thing. Lessee… Wikipedia says ion drives have exhaust speeds of ~30KPS … And this Wikipedia article seems wildly optimistic about “technologies requiring further research” … Some kind of electromagnetic mass-driver I can imagine (but then, my brother-in-law works at Fermilab, so I’m biased) …
Update: Surely (?) Dan Ciruli is correct in his comments that without friction, you can go much faster than your exhaust … So let’s say ion drive … Lessee … 10^-4 g … d = 1/2 at^2 … turnaround at 10 light years … ~620 years with a peak velocity of 9000 km/sec … now we’re talking … get a little more acceleration and we’re on that planet like locusts on a cornfield.
