If you were travelling through space, how do you know if you are right side up or upside down?

It's all arbitrary -- who is to say north is up and south is down? The fact that we draw north as "up" is purely cultural.

Hi. That's a relative question.

You don't.

There is no universal up or down; any directions are conventions for your local circumstances.

The only sense we have of up or down is gravity. What happens if you get the same gravitational force between two planets? which one are you rightside up or upside down on?

It is arbitrary, just depends on what your reference.

I imagine that the shuttle has something on its user interface to show what degree your at. Or something that keeps the ship from going over a certain degree to steady itself out

You choose a reference point and call it UP. the opposite, you call DOWN.
Simple, eh.
Dr Antony

There's no such thing as "upside-down" in space - motions are universally equal in all directions.

You have to be standing on a planet, affected by gravity, in order to have a "right-side-up". Things are only "up" or "down" in relation to a planet.

Well duh! Since you're an Earthling, down is wherever Earth is, which I hope you can see, and up is towards the sun... which one doesn't matter. Pick one, any one.

well, that's according to what or when or how are you travelling.
in space one cannot know the north, south, east, west and all other directions as one cannot keep a deciding factor or machine or device in hand(like a magnet which indicates the respective directions).