If everything goes as planned, the Discovery will launch Oct. 23 from the Kennedy Space Center in Florida.
Why Florida? No, it's not the warm temperatures or great beaches that make Florida a prime shuttle launch location. It's speed.
The Earth rotates the fastest at the equator, so it's more efficient to launch eastward from there than from anywhere else on the globe. The closer to Earth's middle, the less thrust and fuel is needed to send a spacecraft into orbit.
Think about a basketball spinning on the fingertip of a Harlem Globetrotter. The ball spins fastest at the middle, its "equator," with very little rotational speed at the top and bottom, its "poles." The globe is just like that basketball.
Launching near the equator gives shuttles extra speed.
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In theory, natural rotational speed could give rockets an additional 1,000-plus mph of orbital speed. That's 6% of the 17,000 to 18,000 mph they need to be propelled into orbit.
This "speed bonus" explains why the United States, Russia and the European Space Agency have situated their launch sites as close to the equator within their national boundaries as is practical. In the United States, Cape Canaveral, Fla., is the southernmost launch site. Rockets launched there get an additional 911 mph of boost. At the launch site in Kourou, French Guiana, which is just 5 degrees from the equator, the extra push can exceed 1,000 mph.
-- By Ellen Ruppel Shell
