We don't have beds in the space shuttle, but we do have sleeping bags. During the day, when we are working, we leave the bags tied to the wall, out of the way. At bedtime we untie them and take them wherever we've chosen to sleep. On most space shuttle flights everyone sleeps at the same time. No one has to stay awake to watch over the space plane: the shuttle's computers and the enginers at the Control Office do that. If anything goes wrong. The computers ring a warning bell and the engineers call us on the radio.   On the space shuttle, sleep-time doesn't mean nighttime. During each ninety-minute flight around the earth, the sun "rises" and shines through our windows for about fifty minutes: then it "sets" as our flight takes us around the dark side of the Earth. To keep the sun out of our eyes, we wear black sleep masks. It is surprisingly easy to get comfortable and fall asleep in space, and we sleep differently. Some sleep upside down, some sideways, some right side up. When it's time to sleep, I take my bag, my sleep mask, and my tape player with earphones and float up to the flight platform. Then I get into the bag, and float into a sitting position just above a seat, right next to a window. Before I pull the mask down over my eyes, I relax for a while, listening to music and watching the Earth go by under me. When I'm in space I don't need as much sleep as I do on Earth Maybe that's because when I am weightless, I don't feel as tired. Or maybe it's because I'm excited to be in space and don't want to waste time sleeping. How often does the sun rise to people in the space shuttle?
Every 140 minutes. Every 90 minutes. Every 50 minutes. Every 40 minutes.