Jeff Bezos' rocket company Blue Origins is hitting back at Elon Musk's rocket company SpaceX. Before we get to what Blue Origin is saying about SpaceX, a quick recap. On Tuesday morning, Blue Origin hit an important milestone for it flew a reusable rocket to space and back for the first time. The footage is breathtaking, and it led Musk to tweet out congratulations to Blue Origin and Bezos. But, Musk couldn't leave it alone. Over the next 5 hours, Musk tweeted out more messages, with each getting a bit more denigrating of Blue Origin's accomplishment. Congrats to Jeff Bezos and the BO team for achieving VTOL on their booster — Elon Musk (@elonmusk) November 24, 2015 It is, however, important to clear up the difference between "space" and "orbit", as described well by https://t.co/7PD42m37fZ — Elon Musk (@elonmusk) November 24, 2015 Getting to space needs ~Mach 3, but GTO orbit requires ~Mach 30.