In Starbound, when in admin mode you not only have access to admin commands, but you become invinicible and don't lose energy.
To enter god mode, all you have to do is enter /admin into the chat. To toggle god mode off, simply type /admin again.
On some servers, admin mode is restricted to those who have been "whitelisted" and therefore this command will only work on single player and on servers that grant you access to the command.