Question: is there a name for the time when all the stars lie up in a straight line so when you launch a rocket you can use the "sling shot" to get the rocket further without useing more fuel than you need?
I’m assuming you mean when all the planets line up? We have never used the stars to get a slingshot, we can’t get that far!
There isn’t a proper name for it, but the two Voyager probes used this fact to be the first manmade objects to be able to escape the gravity of the sun (nothing else has gone fast enough).
However, the planets didn’t really ‘line up’ as such, more that they were in the right place at the right time. When we sent spacecraft between planets they generally take so long that by the time they get there, the planet has moved!
The ‘Grand Tour’ that the Voyager probes managed looked a bit like this
When all the planets line up, it’s called an ‘alignment’ and the last time that happened with six of the planets in our solar system was in May 2000. People then predicted the end of the world, but there’s no reason why planets all being in a line should have any effect on the earth at all, because everything is so far away!
So the world didn’t end, and we are all still here today. Phew!
When planets line up its called an alignment (stars don’t move from our point of view as they’re so far away).
What I’ve always thought was interesting/challenging about planning space craft flights is that it doesn’t matter where the planets are when you launch – only where they are when the space craft reaches them. So the people at NASA (and elsewhere) doing this have to make quite complicated and accurate predictions of the motion. So spacecraft like New Horizons which is on its way to Pluto always impress me that they can get it right so accurately years in advance. 🙂