SpaceX may be a rocket company, but lately it feels more like a roller coaster. This past week alone, Chief Executive Elon Musk watched as SpaceX shares plummeted almost 14% in one day — which wasn't even the worst performance in the company's short tenure as a publicly traded entity. By Friday, the shares had soared more than 20% from where they began the week. Put another way, that was a more than $300 billion market-value swing.

For most CEOs, that would be a vomit-inducing ride. For Musk, it's a nagging reminder that he's back in grind mode, having to deliver on all of his highflying promises for SpaceX's performance. He made those earlier this year to launch the biggest IPO ever in June, a headier period that has now given way to the more down-to-earth reality of executing on the strategy.