Why can’t we fly planes into space? © Getty Images

Why can’t we fly planes into space?

Asked by: Dennis Robertson, Sheffield

Planes can and have flown into space for over 50 years – though not the kind you see at the airport. That’s because conventional planes need air for both propulsion and lift, and space is essentially a vacuum.

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The first plane to reach space was the X-15, designed in the mid-1950s for the US National Advisory Committee for Aeronautics (NACA), forerunner of NASA. It made its first flight in June 1959, using thin, stubby wings for generating lift and stability while travelling at over five times the speed of sound, plus a revolutionary form of rocket motor whose power output could be varied like a conventional aircraft engine.

In 1963, an X-15 using a propellant of oxygen and ethyl alcohol reached an altitude of over 100km, widely recognised as the altitude at which space begins. The lessons learned were fed into the Space Shuttle programme and today’s commercial spaceplane ventures like Virgin Galactic.

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