This achievement could be classed as 'double missable.'
There's an achievement for giving Aled the wrong tea, which will make this completely missable. If you infact give Aled his correct mug, you'll be entered into a first person mini-game where you have to press random buttons at the front of the space ship. After hitting random buttons on the right side, you'll 'eject the fuel cell'. You'll know this because an onscreen prompt will tell you so.
With your left hand, look for the throttle and quickly push it forward once the floating 'fuel cell' comes into view. Easy when you know how.