We can do 7-8 AU per year right now using tech we have. Voy 1 and Voy 2 are moving at 3.59 and 3.25. A starship sized rocket could also possibly get a small payload that separates to 15 AU. This is all using conventual propellent. If you consider using nuclear explosive as a prepulsion technique the math starts to change substantially and you can achieve even 25 AU / year.

https://ntrs.nasa.gov/api/citations/20140013260/downloads/20...