Thank you so much for your great questions! Check out the complete interview with the shuttle astronauts below.
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.
How long does it normally take for messages from space to get to earth? -- Chris P., 15, from Woodford County High School in Versailles, Kentucky
The crew on the International Space Station must communicate with flight controllers on the ground every day for routine operation of the station. NASA's Mission Control uses a 60-ft radio antenna to send signals to two satellites orbiting the earth. Using these satellites and radio antennas attached to the space station, astronauts can communicate via ham radio, video link and text messaging. Since the signals are sent via satellite, the time it takes to transmit messages is similar to when you see two people talking via satellite on the ground -- there's a brief, seconds-long delay like you might see on the nightly news.
What is it like being completely weightless? -- Jacob M., 14, from Bellevue Middle School in Bellevue, Michigan
Weightlessness is more correctly described as microgravity. The earth's gravity still maintains a hold while you are in space, but the reason you appear weightless is because you are actually in freefall while orbiting the earth. It's as if you jumped off a cliff but never hit the ground, so you -- and everything around you -- are constantly floating. When people first experience microgravity, they usually get spacesick -- that is, they feel nauseous, disoriented, lose their appetite and get headaches and congested. It's like that sinking feeling in your stomach when you hit a dip in a roller coaster ride, but it lasts for days. After a few days in space, however, your body adjusts. NASA issues anti-nausea patches for astronauts to get through the first few days in space.
How do you keep papers in place when you have to do paperwork in space? -- Alyssa S., 14 from Union Middle School in Sandy, Utah
Thanks to microgravity, astronauts have to make sure everything is tied down. Papers are kept in regular three-ring binders and clipboards. Elastic bands, binder clips and Velcro straps keep those binders and clipboards in place. For jotting down notes, small pads of paper can be placed in Velcro holders that are strapped to the astronaut's thigh.
What does the Great Wall of China look like from space? Can you really see it? -- Janna L., 14, from Clarke High School in Clarke, Arkansa
Contrary to popular belief, the Great Wall of China cannot be seen from space. In fact, no man-made object is visible with the naked eye from space. At a low orbit, such as that of a space shuttle, large man-made features, such as highways, bridges and the Great Wall can barely be seen. All that is visible once you leave the earth's orbit and gain a few thousand miles of altitude are geographic features.