This will require use of admin commands or /suicide to fix. And if you fall out of your ship, you can become potentially stuck floating in 0 G if you are not currently orbiting a planet and able to beam down (or have advanced techs). Gravity can be generated through a ship gravity generator. Be careful, however: if there is no background block behind you, there is no breathable oxygen and no gravity. Once you've selected the Build your ship option, all ship tiles are now unprotected and can be edited with your matter manipulator at will, included hull blocks. Frackin' Universe allows a default ship or vice versa without starting a new character.