SpaceX has successfully completed six major iterations and is on its seventh rocket version iteration. SpaceX has existed for eighteen years and has shortened its development time from six years to about two years.

These problems are fundamentally intertwined. Building many rockets allows for successive approximation. Progress in any given technology is simply # of iterations * progress between iterations.

— Elon Musk (@elonmusk) February 20, 2020

This is why SpaceX is crushing all of its competitors like United Launch Alliance, China, Russia, Ariane and Blue Origin.

Here is the pace of SpaceX progress. SpaceX is doubling and tripling launch capacity every three years and has almost completed its journey to full reusability. The Starship could further evolve from reusable once month to once a week to three times per week to daily.

Iteration 1- SpaceX Falcon 1 was the first rocket. It had a payload capacity of 670 kilograms (1,480 lbs.). It flew from 2006 and 2009. Three launch failures, successful dummy payload in 2008 and a commercial launch in 2009. It took six years to get to the first successful dummy payload launch.