New Delhi, July 22 -- TO CHANNEL ONE of Elon Musk's favourite science-fiction authors, SpaceX is a product of infinite improbability. When Mr Musk began, few would have predicted that a startup could design a liquid-fuelled rocket and put it in orbit. Nor that an engineer would be able to get a rocket's booster to return to Earth, land upright on its own tail and be re-used. And no one has yet recovered a rocket's second stage, which must withstand 1,500degC or so during atmospheric re-entry.

Having pulled off the first unlikely feat in 2008, six short years after its founding, and the second in 2015, SpaceX will try to use a launch due on May 21st to show that it can carry off the third, too. If the test fails by the time you read this,...