Randall Munroe explains this very nicely in his piece on Orbital Speed[1]:<p>&gt; But getting to space is easy. The problem is staying there.<p>&gt; To avoid falling back into the atmosphere, you have to go sideways really, really fast…The speed you need to stay in orbit is about 8 kilometers per second. Only a fraction of a rocket&#x27;s energy is used to lift up out of the atmosphere; the vast majority of it is used to gain orbital (sideways) speed.<p>Highly recommended.<p>1: <a href="https:&#x2F;&#x2F;what-if.xkcd.com&#x2F;58&#x2F;" rel="nofollow">https:&#x2F;&#x2F;what-if.xkcd.com&#x2F;58&#x2F;</a>