As Elon Musk wrote [1]: It is, however, important to clear up the difference between "space" and "orbit", as described well by https://what-if.xkcd.com/58/

As Elon Musk wrote [1]: It is, however, important to clear up the difference between "space" and "orbit", as described well by https://what-if.xkcd.com/58/ Getting to space needs ~Mach 3, but GTO orbit requires ~Mach 30. The energy needed is the square, i.e. 9 units for space and 900 for orbit. 1 - https://twitter.com/elonmusk/status/669129655597731841 https://twitter.com/elonmusk/status/669129655597731841