From: Marshall Space Flight Center
Posted: Wednesday, April 23, 2003
Credit: The crew of ISS Expedition 6, NASA
Explanation: Somebody up there is a comedian. In the Unity node of the International Space Station (ISS), just above the head of ISS Flight Engineer Nikolai Budarin, hangs a sign: "Space Station Construction: Speed Limit 17,500 mph." In metric units: 28,000 km/h.
Seriously, folks, the space station is a construction zone. Since the first module (Zarya) was launched in 1998, spacewalking astronauts have added to the station a science laboratory, living quarters, a robotic arm, an airlock, solar arrays spanning 125 feet from tip to tip ... fifteen major elements in all. The habitable volume has increased to 15,000 cubic feet, and the outside surface area of the station is now so great that it catches enough sunlight to flare like a supernova when it flies over backyards on Earth.
Somehow the busy crew also find time to do scientific research. They must be moving quickly!
And they are. The ISS circles Earth once every 90 minutes; each hour the crew travels 17,500 miles or 28,000 km--hence the sign. It's... well... you know... astronaut humor.
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