Either there will need to be a charger on board, or very strict usage so the phone isn't draining the battery trying to connect to a cell, wifi, bluetooth etc when turned on.
This isn't Apollo with a 2048 byte RAM ferrite core onboard computer :)
How sweet. Can they come with their Tesla™ ? And bring food from McDonalds™ or BurgerKing™ ? /s
Is NASA now an advertising company ?