A little-noticed but historic milestone will be reached this week when the 500th person ever to fly in space blasts off. The moment will come whenever NASA’s shuttle Endeavour finally launches to continue building the international space station.

Endeavour’s crew of seven will include four rookie astronauts, making their first trip into orbit. But the crew agreed that former naval commander Chris Cassidy, 39, who has led combat missions in Afghanistan, will take the honour.

Space website collectSpace reports the reaching of the 500 milestone and includes a list of all 500 brave spacemen and women.

There is some debate about which of the rookies will actually cross the space boundary first, considering their seating position and the roll of the spacecraft, but at the speed Endeavour will be going, it is probably academic.

First human in space was Russian Yuri Gagarin, in 1961. (First woman in space was another Russian, Valentina Tereshkova, in 1963).

Interestingly, the 250th person in space was Britain’s first astronaut, Helen Sharman. A food chemist who helped invent Mars ice cream, Helen, now 46, flew a Russian Soyuz ship to the Mir space station in 1991.

The 26th man in space, Neil Armstrong, later became the first man on the Moon.

The shuttle Endeavour was due to launch on Saturday but that was scrubbed due to a hydrogen leak. It is now set to fly between Wednesday and Saturday.

Shuttle commander Mark Polansky will continue his Twitter updates – although he has admitted that they will be uploaded for him by a PR person back on Earth.

• Discover space for yourself and do fun science with a telescope. Here is Skymania’s advice on how to choose a telescope. We also have a guide to the different types of telescope available.

Picture: NASA astronaut Chris Cassidy (Photo: NASA).

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