I think for the Voyager launches the planets and the sun were aligned in such a way that the probes could be slingshotted around them to gain speed. I think such an alignment is quite rare?

[–] [email protected] 16 points 3 weeks ago

It's a bit more complicated than that. New Horizons actually went way faster than the Voyager probes, getting to Pluto in only 9.5 years. It took Voyager 2 just slightly longer than 12 years to reach Neptune for comparison. The planetary alignment you are thinking about was due to relative proximity. Obviously you can't use Saturn to slingshot you to Uranus if they are on opposite sides of the solar system. All the outer planets were going to be on the same side of the solar system, allowing the Voyager probes to visit them all in succession.

[–] [email protected] 3 points 2 weeks ago

It only happens every 400 years or so.

It's pretty crazy to think about. The Voyager mission isn't just a big thing for the current generations, but also for many future generations, who will not have as good an opportunity.