So last night, I dreamed about Helcaraxe.
Helcaraxe is from Tolkien's Silmarillion, which is the holy book of the Ruins setting. It means the Grinding Ice, and it was the means for those Noldor who couldn't leave Valinor to return to Middle Earth.
In my dream, Helcaraxe was a rogue gas giant - that is without a sun. It was hot, but that was not enough to heat its moons which were all covered in ice. It had eight moons, and four of them had space stations orbiting them. the stations were mining ice and breaking it into hydrogen and oxygen, and mining minerals for their stations.
And that was the solution to my problem. Going into and out of Helcaraxe would be easy - no big ass solar gravity well to fight! - and with the stations to refuel them, they could, by stopping at Helkaraxe, reach the other system with enough reaction mass to brake in.