Thanks!
I made it specifically so that you can theoretically reach your goal by burning all of your remaining fuel to reach the space station without considering the gravitation of the astroids in the first missions.
However, the less fuel remains the lower your score will be. I implemented it this way so the player is encouraged to use as little fuel as possible.
The score is calculated by this formula:
So basically in order to get the highest score you have to complete the mission as quickly as possible with as much fuel left as possible.
But I think I'm gonna mention this ingame at some point in future updates, so thank you for the comment. It was really helpful.