On Monday history was made. Returning to flight after six months on the ground in the wake of the failure of the CRS-7 mission, Elon Musk and SpaceX accomplished something most people in the industry thought was impossible. For the first time ever a rocket stage that delivered a payload to orbit turned around and returned, landing safely on its tail.
To get into orbit your rocket must overcome both gravity and drag. To do that it’s important to understand how the design of a rocket affects its flight, and why landing it again is so hard.