请你以space为题写一篇作文,不少于60字的英语作文.

请你以space为题写一篇作文,不少于60字的英语作文.

Space travel bets on a dream. To design and build a spacecraft for space travel, you need to be able to figure out how big to make it, how heavy it can be, how fast it will have to go, how much fuel it needs and so forth. For that, you need a theory of how objects move in space and how to make the calculations. Over a period of nearly three centuries (from 1600 to 1900), three brilliant men - Johannes Kepler, Isaac Newton and Konstantin Tsiolkovsky, who said "the Earth is the cradle of mankind - one cannot remain in the cradle forever", worked out almost all the theories of space flight.

By 1951 space travel plans had become more grandiose. Famed rocket scientist Wernher von Braun predicted that a successful Mars mission could be accomplished with as few as 46 rockets in a round trip that would take three years. In a later interview with TIME, von Braun affirmed, "Man belongs wherever he wants to go - and he'll do plenty well when he gets there."