In the years following her return, Princess Luna oversaw the revival of Equestria's Space Program. She, along with the mane six, are on a mission to construct a colony on a moon orbiting a neighbouring planet, Sigma-6.
What they don't know is that they are not alone in the vast reaches of space - and in space, nopony can hear you whinny.
[A story inspired by a picture. Credits to hereticofdune.]