Human spaceflight

How many people have been to space? That all depends on your definition of space. The Earth's atmosphere doesn't have a fixed boundary. It just gets thinner and thinner. The closest to an international standard we have is an altitude of 100 km. This suspiciously round number is close to the Karman Line - a place where the speed needed for a craft to be controllable by aerodynamic forces equals the orbital speed. It is a cut-off between aeronautics and astronautics.

As is often the case, the United States chooses a different definition to the rest of the world. The US prefers to use 50 miles (~80km). The practical difference from using the lower altitude is that six US Air Force pilots are then included as astronauts. I stick to 100km as it has some kind of physical justification.

Using a 100 km definition of space, there have been 545 astronauts so far but expect that to increase by December 2015 when the next Soyuz goes up to the ISS. These split into 331 from the US (NASA), 120 Russians, 10 Chinese, 9 space tourists, and 75 from a range of other countries.

For my recent book, I collated data on all 545 astronauts and made visualisations of various aspects. On the website, I've created a human spaceflight timeline which lets you see when every mission was along with key moments.



There are a few things that become obvious when it is presented like this. The first is how we've increased the duration of spaceflights over the years. You can see how short the Shuttle missions were (roughly 8-12 days long) compared to those on space stations such as Mir or the ISS. It is also easy to see the pauses in the human spaceflight programmes of the Soviets and the Americans following the disasters of Soyuz 11, Challenger, and Columbia.

I've also created a graph of astronaut data, a map of astronaut birthplaces, a page which shows who is in space and who was in space (just change the date in the URL), and a breakdown of astronaut stats and records. - taken from Astronomy Blog (http://ift.tt/1g8FhhM)

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