The hoverboard runs on manure, but the saucer requires a new green Fuel Rod. The only place you can get one is the robot invader in the castle dungeon. You can only get to him by opening the rear gate in his cell, then entering through the tunnel Mordred dug to escape. (see related question)
The saucer Excalibur is crashed in the mud swamp to the right of the Mill.
It is half-buried in the mud swamp right of the mill. (see related questions)
The saucer Excalibur, one of the attacking craft, has crashed in the mud swamp to the right of the Mill.
The fuel rod powers the saucer Excalibur. The hovercraft runs on manure.
The crashed saucer Excalibur is in the mud swamp. To reach it, get the hovercraft from the attic of the mill. You will need to replace the fuel rod of the Excalibur, and there is another one powering the robot in the castle dungeon. (see related questions)
When you get a replacement for it, it automatically snaps into place. (see the related question)
On the saucer Excalibur, you must enter coordinates before the ship will launch. (see related question)
Reach and repair the saucer Excalibur in the mud swamp past the mill. (see related questions)
The hovercraft will carry you over the mud swamp to reach the crashed saucer Excalibur. (see related question)
You will use the saucer Excalibur to reach space, then build a spaceship on the Pewter Moon. (see related questions for how)
You can reach space by fixing the crashed saucer Excalibur, and get a new spaceship at the Pewter Moon. (see related questions)
You have to fix the saucer by obtaining a new fuel rod. There is one in the robot invader held in the dungeon. Once it is replaced, you can dial in the coordinates to launch the saucer. (see related questions)