Sleep Compartments: The Habitation Module will have space for four sleep compartments like this one. (The three others will be located in bays "in the ceiling.") Personal space aboard the Station will be small but comfortable, as each crewmember will have his or her own small refuge. Like the rest of the International Space Station, the sleep compartments will be used for research as crewmembers become subjects of sleep experiments. Space travelers often report that they enjoy the sensation of sleeping in microgravity.