How long do the astronauts stay at a time when they're manning the International Space Station? -- Jacob F., 14, from Great Bend Middle School in Great Bend, Kansas

Having just entered its third year of continuous habitation, the International Space Station is on its sixth crew, known as Expedition Six. The crew is rotated approximately every four to six months. The Expedition Four crew spent 196 days in space, giving two astronauts -- Carl Walz and Dan Bursch -- the U.S. space flight endurance record. The current crew moved into the ISS on Nov. 23, 2002.