Syzygy

At the dawn of humanity's leap into space, already having colonized most of the solar system, it set its sights on becoming an interstellar civilization. Right then it was dealt a fatal blow. In the year 2461 an insectoid alien species, known as the Dulotics, invaded the solar system and occupied all planets. They enslaved all humans to work for their purpose of creating a dyson-sphere, to harvest all of the suns energy that the Formic queen needs to procreate. 

Only a very small colony of brave frontier-expanding settlers on Pluto managed to evade the initial attack, though only by sheer luck since the Dulotics didn't know Pluto existed. With their very limited resources they couldn't really do anything and just decided to keep on surviving for all of humanity. However after 31 years of just getting by and trying to remain under the Dulotics radar, a once in a lifetime opportunity was presented to them. On May, 6th of the year 2492 all planets in the solar system aligned, giving them a chance to travel from planet to planet to refuel and repair their ships at each stop. With this, they might just make it to the sun and defeat the queen, which they hope will cause all other Dulotics to become disoriented and docile.

The two bravest pilots under the settlers took their only two ships that are capable of inter-planetary travel and set off on this hail mary mission towards the sun.