21 July: Space shuttles

The final Space Shuttle mission ended on this date in 2011. Here are 10 things you may not know about Space Shuttles:

1. The six shuttles were named after vessels of exploration. The prototype, which never went into space, was called Enterprise, not after any of the US Navy vessels of that name but after the Starship Enterprise. Columbia was named after a U.S. Navy ship launched in 1836 that was one of the first vessels to circle the world; Challenger was named after an American Naval research ship that explored the Atlantic and Pacific oceans in the 1870s. Discovery was named after the two ships that discovered the Hawaiian Islands, looked for a northwest passage between the Atlantic and Pacific oceans, and explored southern Alaska and western Canada. Atlantis was named after a science vessel that, from 1930-1966, travelled all around the world on research expeditions. Endeavour, the final one, which was built to replace Challenger, was named by schoolchildren in a contest. If you've ever wondered why an American space ship's name has a British spelling, it's because it was named after a British ship - the one James Cook travelled in when he discovered Australia.
2. Columbia was heavier than the rest of the space shuttles. It was the first spacegoing one, and by the time the rest were built, they had found lighter materials to build them from. It weighed as much, we are told, as 13 African Elephants.
3. The numbering system of missions may appear complicated. The original plan was to number each mission sequentially, but after the first ten, the then-NASA administrator James Beggs, who suffered from triskaidekaphobia (the fear of the number 13) wanted to avoid associations with Apollo 13, so instead, for the next few missions, they used the last digit of the year and a number for the launch site and a letter. After the Challenger disaster (mission STS-51-L) they went back to sequential numbers, starting with STS-26. STS stands for Space Transportation System.
4. In orbit, a shuttle's speed is 17,500 miles per hour, or five miles a second, or nine times faster than a rifle bullet. This means a full orbit of the Earth would take just 90 minutes and every 45 minutes the crew can witness a sunrise or sunset.
5. Only one US President has ever witnessed a Space Shuttle launch in person. Whether or not, despite the fact they no longer fly, this figure could increase to two depends on the result of next year's Presidential election - for the President in question was Bill Clinton, and his wife Hillary, who has announced she is making a bid for President herself, was with him.
6. Altogether a shuttle has more than 2.5 million parts, including almost 230 miles of wiring, more than 1000 valves, over 1400 circuit breakers and 30,000 tiles made of sand: the shuttle's heat shield, or Thermal Protection System, heats up to over 3,000 degrees F, during re-entry while the inside the shuttle, the temperature is maintained at about 70 degrees F. Amazingly, a minute after landing, they will have cooled sufficiently for someone to hold one in their hand.
7. Inspecting the tiles is just a tiny part of the 1.3 million different jobs that needed to be done to get a shuttle ready for launch. This would take 16,000 people 3-4 months of constant work.
8. So a Space Shuttle must have had a pretty powerful flight computer, right? Nope. Actually, you probably have more computing power at home, as an X-Box 360 is over 100 times more powerful. The astronauts actually had to load the programs they needed, ie. lift-off, orbit and landing, into the computer one at a time, removing the previous one. It proved to be a reliable system, which is why it wasn't upgraded. However, there would have been five such computers on board, not to mention laptops belonging to the crew.
9. All space travel is risky, but thanks to the two disasters, statistically, the Space Shuttle is the most dangerous. Fourteen people have lost their lives in Space Shuttle accidents compared to three during the Apollo missions, none during Mercury and Gemini, and four in the Soyuz program. The failure rate for shuttle flights was 1.5%, which would have permanently grounded any other aircraft. Statisticians worked out that the chance of a fatal accident occurring on a Space Shuttle mission was one in 256. The comparable figure for passenger planes is 1 in 12 million.
10. The combined mileage of all five Shuttles is 513.7 million miles (826.7 million km), or 1.3 times the distance between Earth and Jupiter. Each orbiter, except for Challenger, travelled farther than the distance between Earth and the Sun.