中国志愿者加入火星-500试验计划：the volunteers will have eight hours of ____,eight hours of work

中国志愿者加入火星-500试验计划：the volunteers will have eight hours of ____,eight hours of work
and eight hours of free time
the volunteers will have eight hours of ____,eight hours of work and eight hours of free time,空应该填什么，差不多像宇航员的工作：一天二十四个小时，八个小时用来工作，八个小时用来睡觉，还有八个小时干什么？