its a very easy way.
you just need a strider :D
you go with your character very close to the door and summon your strider.
it will takes you some tries but the strider will be in the door and cant move, the you mount on him .. and you will be stuck so nvm about that point, now use arrow keys to move s bit further into the Door.
If you think you're far enough unmount and you'll be in the Ship witha closed door.
But like i described it will takes you some tries.