Elon Musk can’t sell a single SpaceX share for a year—and then all the locks crack open at once

Unless you’ve been on the moon, you know that Elon Musk’s SpaceX just pulled off the biggest IPO of all time and raised about $86 billion in its public stock offering last month. 

The reusable rocket maker did it while selling only a tiny sliver—between 4% and 5%—of its stock. The other 95%—which consists of about 12.5 billion shares—is being kept behind bars in one of the most byzantine, complicated lock-up schedules in history.

To level set, lock-up periods are standard fare following an IPO; founders, top executives, and early venture investors usually agree not to sell their shares for 180 days. The point, as IPO advisor Lise Buyer of Class V Group explains, is twofold. First, it forces the people who know the company best to hold through at least one earnings report, so they can’t dump stock on the public right before a bad quarter. Second, it sends a soothing signal during what could otherwise be a volatile and tenuous time in the life of a newly public company. 

“It’s a message to the new buyers that the people who know the company best still believe in it and are going to hang on,”  said Buyer.

But when the lock-up expires, usually right after 180 days, a glut of stock typically hits the market a...