> This is all predicated on 25 km/s being very fast, which in this case it really isn't. Man made objects like the ISS travel at 7 km/s, so these are relatively achievable speeds, even for humanity.
Quite a few spacecraft have reached this speed. Off the top of my head, I think Juno reached something like 70 km/s when approaching Jupiter.
That's pretty meaningless though, the speed of interest is the heliocentric velocity. Juno was accelerating toward the largest planet in the solar system and orbiting it, not doing a gravitational slingshot.
The current record is Voyager 1, which got its speed from a flyby tour of the outer solar system. It is going 17 km/s.
Quite a few spacecraft have reached this speed. Off the top of my head, I think Juno reached something like 70 km/s when approaching Jupiter.