Setting is standard space opera.
I am writing a story in which 2 characters are crewing a spaceship. The characters are:
(1) the captain, a female in her early 20s, who has grown up on the ship and recently taken it over from her parents.
(2) a crewman, a male of indeterminate age, who represented himself as an itinerant spacefarer and hired on for the voyage.
The spaceship is a commercial vessel in woeful state of repair (in fact it is a coffin ship which the owners want to fail to claim insurance). The ship actually requires a crew of 4, but is undercrewed because of lack of money.
The characters are on alternating 4-hour watches, so at all times one is on the flight-deck, while the other is doing all other necessary work, and eating, sleeping, etc where possible.
For reasons of plot, it is necessary for the characters to trust each other and form a rapport by the end of the 15-day voyage.
However, neither character is likely to "open up" to the other.
For her part, the captain has lived most of her life on the ship, and does not have much experience with strangers. She is curious about the other character, but her instinct is to observe and speculate rather than to make conversation. She is also aware that should the crewman become troublesome, her options for escape or getting help would be limited, trapped as she is on a spaceship with him in deep space.
For his part, the crewman is taciturn and monosyllabic when he speaks at all, to the point that the captain once asks him "can you understand me?" when she talks to him. He shows no interest in the captain's personal life, nor shares any details of his own.
How can I get two self-contained, uncommunicative characters working at different times but in a relatively confined space to build a rapport?