Nope, none. Because George Lucas said so.

From the Erotic Mad Science tumblr:

Carrie Fisher, in her memoir Wishful Drinking reports the following exchange with George Lucas about her Princess Leia dress:

Anyway. George comes up to me on the first day of filming and he takes one look at the dress and says “You can’t wear a bra under that dress.”

So, I say, “Okay, I’ll bite. Why?”

And he says, “Because…there’s no underwear in space.”

I promise you this is true, and he said it with such conviction too! Like he had been to space and looked around and he didn’t see any bras or panties or briefs anywhere.

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