The manure is used up in the hovercraft. The saucer needs a different power source. You might find the same kind of green Fuel Rod in the captured robot invader. (To reach the dungeon : see related question)
It is on tp of the castle roof in astro knight island
Yes, anytime you are back on the Pewter Moon.
To return to space on Astro Knights Island after completing the mission there, you can head back to the rocket ship in the observatory and select the option to launch it again. This will take you back to space where you can explore further or complete any remaining tasks.
You can't, although it will be back on once you finish the game and save the Princess.
You can't. That only happens at the end of the game.
You use the manure to power the hovercraft. The saucer Excalibur uses green fuel rods. There is a replacement you can get: inside the captured robot invader in the dungeon. To get it you have to enter Mordred's secret underground lab and enter the cell from the back way. (see related question)
The mouse will get surprised, run around, then run back to you.
you go to the top of the castle and there it is :D just found out;)
There's a lock under the hay in Astro Knights
If you land back on Poptropica, your spaceship is parked atop the castle. This is also its location when you have beaten the island.
If you log off while in space, you will be on the planet you last left.
The rocket is on top of the castle of Arturus.